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Old 10-10-2018, 09:39 PM   #1
Cape Codder
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Default Terriable backfiring

My car has been running badly for quite some time. The latest problem is it is Backfiring! I have changed the condenser which did not help. I tried to take it out for a ride today and as usual, I took it out of the garage to let it warm up. While it was running it Backfired, at idle and then shut down. Any idea's?
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Old 10-10-2018, 09:45 PM   #2
Chuck Sea/Tac
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Default Re: Terriable backfiring

Does it idle smoothly?
Is it hard to get it to idle?
I would look for a leaky intake gasket or cracked manifold
Try shorting each plug, one at a time and see if that changes the idle. That will narrow down a lean cylinder.
Do you have full flow gas feeding the carb?
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Old 10-10-2018, 10:28 PM   #3
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Default Re: Terriable backfiring

Chuck Sea/Tac Thanks for the response and ideas.
Idle seems to be smooth and not hard to get to idle.
I recently changed the intake/exhaust manifold gasket (can't say when).
I will check for the leaky intake gasket or cracked manifold.
The other two suggestions I will try tomorrow.
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Old 10-10-2018, 10:33 PM   #4
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Default Re: Terriable backfiring

Check your GAV. You might be running it too lean. Leaning it out will cause backfiring. Another issue I saw on another person's car was some dirt or something in the distributor causing cross-fire to wrong cylinders. In that case a new distributor body and cap solved the problem.
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Old 10-10-2018, 10:39 PM   #5
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Default Re: Terriable backfiring

Had you remembered to advance the spark after starting?
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Old 10-10-2018, 11:03 PM   #6
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Default Re: Terriable backfiring

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Closing point gap?
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Old 10-10-2018, 11:09 PM   #7
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Default Re: Terriable backfiring

Use a propane torch, unlit. Turn the gas on and direct the gas stream around the intake manifold as the engine is running. If there is a change you have a leak. Can also use WD40 but it makes a bit of a mess.
As previously posted. Check point gap. Usually point gap too close makes for hard starting as well.
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Last edited by eagle; 10-10-2018 at 11:14 PM.
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Old 10-10-2018, 11:58 PM   #8
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Default Re: Terriable backfiring

Have you played with anything lately? If so and it was running OK beforehand, that is the place to start looking.
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Old 10-11-2018, 06:05 AM   #9
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Default Re: Terriable backfiring

Try a condenser that you know is good, not a new one. A bad new one can really fool you.
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Old 10-11-2018, 07:45 AM   #10
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Default Re: Terriable backfiring

Make sure the spring is not broken on the point arm. We had one where it would idle, but at speed, the broken spring would let the arm float. Just feel it to make sure there is guts to spring.
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Old 10-11-2018, 09:00 AM   #11
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Default Re: Terriable backfiring

I had one that would start and idle but when I gave it gas it would backfire. It had been sitting for a little while. Critters crawled into the exhaust and plugged up the muffler.

I removed the muffler and shook all the acorns and nesting out. It stopped backfiring.
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Old 10-11-2018, 09:41 AM   #12
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Default Re: Terriable backfiring

How can I check a new condenser to see it is good?
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Old 10-11-2018, 10:01 AM   #13
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Default Re: Terriable backfiring

Hook both us. They can't both be bad. It won't hurt anything. Just use some jumpers to ground the loose one and to connect it to the passenger side of the coil.
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Old 10-11-2018, 10:10 AM   #14
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Default Re: Terriable backfiring

It is also possible that you have a cracked distributor body or a brake-down in the insulation between the leads in the body. A number of years ago some repo bodies were defective and would crack near where the #4 internal lead went past the #3 plug lead causing the a short between the #3 and #4. This short is very visible if you run at an idle in a dark garage, check along the edges of the body near where the plug leads are close to the body. Try another distributor body. After I found out about this problem we had a tune-up clinic and I found about 1/3 of our clubs cars had bad distributor bodies.
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Old 10-11-2018, 10:58 AM   #15
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Default Re: Terriable backfiring

Good Morning...A few more odd things to check would be the nuts on the back of your amp meter and the nuts on the back of your ignition switch if you have an after market switch instead of the original pop out. Another spot that can be a problem is the little fuse box on the side of the starter. The rivet can work lose and the connection can be lost and it will behave as if you are turning the ignition off and on. Just remove the little box and put things back like Henry had them for an hour or so and see if the problem goes away. Good Luck...Ernie in Arizona
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Old 10-11-2018, 03:28 PM   #16
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Default Re: Terriable backfiring

That's right. If you have a make-break condition in the circuit from the coil to the point arm, it will backfire.
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Old 10-11-2018, 04:23 PM   #17
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Default Re: Terriable backfiring

Quote:
Originally Posted by Jacksonlll View Post
That's right. If you have a make-break condition in the circuit from the coil to the point arm, it will backfire.
Some repro switches have loose terminals at the back. Give them a wiggle (I love these technical terms!) to check. If there is any movement, get back and I'll expain again how to fix it.
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Old 10-13-2018, 06:55 PM   #18
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Default Re: Terriable backfiring

FIRST I want to thank everyone that has responded to my "Terrible backfiring" post.

We have tried: changing the distributor body & cap, re-gapped the points, changed the condenser, changed the coil & coil wire, re-timed the engine, checked for vacuum leaks at the intake/exhaust manifolds, did I say retimed the engine cause I forgot to tighten the screw on the cam, used a jumper to check the ignition switch, adjusted the GAV from almost closed to 1/4, 1/2, and maybe as much as 3/4. After these few checks, we still have a Terrible Backfiring.

Soooo.......we are thinking of changing the plugs. We found the washers? on the bottom of plugs crushed and don't seem to be sealing. Don't know for sure about that but they sure are flat. However, the plug tips are a lite tan color with no oil or soot.

I have Champion W16Y plugs in there now but which one do most use looking at the below chart which was posted by someone on this site? Should I have a hotter or colder plug?

Champion (hotter down to colder):

W95D
W89D
W16Y
W20
W18
W14
W10
W85N
W80N

Thanks for any help you can supply because we are at witts end with this problem.
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Old 10-13-2018, 07:16 PM   #19
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Default Re: Terriable backfiring

I think you need to investigate beyond your ignition system. If your sparkplug washers were "crushed" and causing a bad seal, you would hear air rushing out around the plugs when cranking over the motor.

Have you conducted tests to check on the health of your motor?
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Old 10-13-2018, 07:26 PM   #20
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Default Re: Terriable backfiring

With mine it was rust in the tank. Put the filter in the tank and a strong magnet on the outside.
Never has backfired since.
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Old 10-13-2018, 07:52 PM   #21
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Default Re: Terriable backfiring

Similar to what Curtis has mentioned, I've run into fuel blockages due to rust (either in tank or sediment bowl) and with movement of the vehicle it can stir up the sediment and block the fuel flow. Likewise, any sediment that makes it into the carb can also cause this intermittent backfiring but periodic cleanings of these parts may correct it if it's a fuel issue.
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Old 10-13-2018, 07:59 PM   #22
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Default Re: Terriable backfiring

Check to make sure the spring on the moveable arm of the points is strong enough. It was mentioned in an earlier post. Hook a fingernail on it and pull it apart. It should give you a bit of a tussle.

A bad flexible wire under the upper plate can cause the backfire at high rpms too.

Did you recently have your carburetor apart? Leaving out the venturi will cause similar troubles.
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Old 10-13-2018, 09:41 PM   #23
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Default Re: Terriable backfiring

One test we did I failed to put forward was the fact we grounded each plug.
#4 showed a significant change in idle speed, #3 showed very little change, #2 showed a good change and #1 had NO change.

That was really the reason we have considered changing the plugs which have 6-7 thousand miles on them.
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Old 10-13-2018, 10:13 PM   #24
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Default Re: Terriable backfiring

'Sounds as if you are about ready to consider the weird causes of misfires since you've just about exhausted the list of usual culprits. So, odd though it may sound, try this: Take off the terminal box cover and wiggle the bolts sticking out. If either is loose or can be pushed in and out, it's possible that the heads are touching or arcing against the metal firewall and creating a misfire. This will be especially likely when the firewall gets warm and the metal expands to close the gap between itself and the stud heads. In the 1970's, a couple inferior and somewhat shady parts vendors (old-timers know whom I mean!) imported lousy terminal boxes that had bolts with the heads too big to be completely sunk into the plastic body. The holes were not countersunk deep enough, either. In any event, after some use and vibration, the bolts loosened up and moved ever so slightly (but enough!) towards the firewall, causing occasional arcing and misfiring. This happened to me personally in Germany in 1974 in my 1928 roadster. I swapped out EVERYTHING while sitting along side the Autobahn as you have done, but couldn't fix the misfiring. 'Drove me nuts!!! Cutting to the chase, it turned out to be one of those poorly-made reproduction off-shore terminal boxes with the too large head bolts and shallow countersunk holes. I have since diagnosed a couple other instances locally that perplexed the owners because they couldn't find the source of their Model A's misfire. They also had older terminal boxes that had been bought "on the cheap" from the same suppliers. There are probably still hundreds of them out there waiting to ruin some Model A owner's day.
I'm guessing if you have a car that was rebuilt or "restored" in the 1970's or 1980's, one of these timebomb terminal boxes may be at fault. If the two studs are not loose, back off the four mounting screws inside on the firewall, pull the terminal box out a little ways from the firewall and keep it separated by inserting a couple pieces of cardboard. Then start the engine and drive the car. If there is no miss, you can bet that one or both stud slot-head bolts is/are arcing against the firewall. It may be a long shot, but you've tried just about everything else.
Did I miss that you performed a compression check to ensure that a valve isn't stuck or burned out?
Marshall

Last edited by Marshall V. Daut; 10-14-2018 at 08:34 AM.
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Old 10-14-2018, 09:05 AM   #25
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Default Re: Terriable backfiring

Pull the side timing gear cover and check the large timing gear.
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Old 10-14-2018, 10:42 AM   #26
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Default Re: Terriable backfiring

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Quote:
Originally Posted by Cape Codder View Post
One test we did I failed to put forward was the fact we grounded each plug.
#4 showed a significant change in idle speed, #3 showed very little change, #2 showed a good change and #1 had NO change.

That was really the reason we have considered changing the plugs which have 6-7 thousand miles on them.
Change the location of the plugs you have in the car and see if they have the same symptoms in different cylinders.
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Old 10-14-2018, 12:51 PM   #27
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Default Re: Terriable backfiring

You've checked a few likely culprits but not ALL.

Battery terminals tight?


Auxiliary ground strap needed?

Ammeter and connections thereto? check by attaching jumper to junction box lugs.

Pigtail in distributor?

Swap with a good carb?
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Old 10-14-2018, 01:10 PM   #28
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Default Re: Terriable backfiring

Mine was caused by trash in the carb.
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Old 10-14-2018, 05:49 PM   #29
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Default Re: Terriable backfiring

Go ahead and change the plugs, nothing to lose. Put in W-18's NOT 3X's, it will be cheaper to experiment this way.
Have you ck'd compression??
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Old 10-14-2018, 08:19 PM   #30
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Default Re: Terriable backfiring

Soooo……many questions to answer so here goes:
Frank 55a As I have said I have changed out the Distributor body AND Cap along with the Coil wire. Ernie I had checked the nuts on the amp meter and ignition because I was in there to check amps on the back of the meter. Nothing lose at that time so I’m holding off taking the dash down again. As to the fuse box I don’t have one on my car. Synchro909 I’m thinking you meant the ignition switch, see above. Curtis in MA I had drained the gas tank at Gettysburg last year to check the filter and found nothing but a clean filter and not bragging but a very nice clean tank. I think I will hold off on checking this again for awhile. Heneste see previous answer. 1crosscut I have been in there to check the arm of points several times in adjusting points cause I want it perfect at .020” and never felt the spring to be bad. As to the flexible wire under the upper plate I plan on checking this again. No, I haven’t taken the carb. apart and I wouldn’t leave out any parts anyhow HA! HA!
Marshall V. Daut I have to say I had that box apart because the back part of the box was cracked OR I took it off for the same reason you mentioned about the bolts. I remember using RTV on the back of the bolts so I’m hoping it would be good for five years. But this is another suggestion I have to keep in mind if I don’t find anything else. NO, you didn’t check.at I had done a compression check . We actually had a suggestion from a non-fordbarner and non-Model A’er to see if we have a leaking head gasket BECAUSE when I went to short the plugs two of them didn’t really have any change in RPM. Katy now you are talking about something I don’t want to get into especially when I’m trying to find something simple, HOWEVER I will keep it in mind. 1crosscut I’m sorry but I don’t understand your suggestion or I guess what I don’t understand is what would it prove? steve s I actually disconnect my battery for the non-season and when getting it ready to get back on the road I always wire brush the posts, and cables, put electro (sp?) grease on each post then check the battery with a hydrometer done maybe 600-700 miles ago. The pigtail was screwed all the way in so I backed it out about two threads. I just had screwed it in with my fingers, no pliers. 1931 flamingo W18 Y’s are planned. No compression check but see above.

Thanks again to all who have responded and given me advice which I really appreciate. I’m just trying to get the info in some sort of order. By the way sorry for the rambling but trying to talk to everyone.
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Old 10-14-2018, 08:48 PM   #31
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Default Re: Terriable backfiring

a great case study in randomly trying things versus systematic trouble shooting, still playing out.
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Old 10-14-2018, 09:16 PM   #32
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Default Re: Terriable backfiring

What I meant by changing the positions of the plugs was to take
#1 plug to #2 cylinder
#2 plug to #3 cylinder
#3 plug to #4 cylinder
#4 plug to #1 cylinder

Then see if shorting out the plugs has the same result as your first test.
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Old 10-14-2018, 09:29 PM   #33
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Default Re: Terriable backfiring

I understand what you are saying BUT what does it prove? Please explain.
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Old 10-14-2018, 09:37 PM   #34
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Default Re: Terriable backfiring

Check all your electrical connections then do a load test on the battery. Sounds stupid but a friend had the same problem and it turned out to be a bad battery. Who would have thunk it!
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Old 10-14-2018, 09:47 PM   #35
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Default Re: Terriable backfiring

If you switch plug if they miss in the same ones they miss in now you know your plugs are good
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Old 10-14-2018, 10:35 PM   #36
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Default Re: Terriable backfiring

First - 1931flatheadthanks for the response and explanation. I will try that.
PalAl - also thanks for your response and suggestion.

Boy, do I have a lot of work ahead of me in the next couple of days with all the suggestions.

Thanks again!!
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Old 10-14-2018, 10:41 PM   #37
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Default Re: Terriable backfiring

When I get into something like this it sure can be frustrating, I like to eliminate many items at one time, just a thought have you considered "Hot Wiring" to eliminate the key switch, and all other electrical circuits other than the points, condenser and coil. A simple jumper from the starter terminal ...
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Old 10-14-2018, 10:47 PM   #38
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Default Re: Terriable backfiring

holdover Thought I said "used a jumper to check the ignition switch" in post 18 which eliminated the switch, OR so I think. Thanks for your response!
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Old 10-14-2018, 10:59 PM   #39
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Default Re: Terriable backfiring

Just fixed one like yours. Idled great, would run several quarters of a mile then sputter and backfire. Then start right up and repeat as you waited to get back into traffic.

Gas flow to carb was a dribble from disconnected fuel line. Blew air into tank from gas line and found high resistance (~15 psi to overcome). Checked screen in gas sediment bulb = clean. Disconnected interior gas line (was a repro fat one) and found it packed full of rust like coffee grounds.

About 12 weeks ago the leaky fuel shut off valve was replaced with an Ace Hardware ball valve complete with yellow natural gas teflon tape sealant and the stand-up in-tank filter was removed opening the floodgates for years worth of crud to descend into the fuel system and reduce flow to a trickle good enough for idle but not for go.

I have replaced a lot of corroded/dissolved/and as a result plugged in-tank filters and cursed them all the while but they do serve a useful purpose if they are installed AS A CONSUMABLE MAINTENANCE ITEM (around here 3-5 years is pushing it for trouble) and not a permanent fix.
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Old 10-15-2018, 06:46 PM   #40
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Default Re: Terriable backfiring

Quote:
Originally Posted by 1931flathead View Post
If you switch plug if they miss in the same ones they miss in now you know your plugs are good
Thanks, that is what I was getting at.
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Old 10-19-2018, 01:57 PM   #41
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Default Re: Terriable backfiring

Sooo....I have checked a couple things that were suggested. Started the engine and ran for several minutes to warm it up. Grounded each plug and each showed a difference in idle. Don't understand BUT I will be putting in NEW Champion W18 plugs. I think they are a colder running plug but....... I then took the car around town for perhaps 10 miles and it backfired a couple of times, and several times actually quite. At the end of driving the engine was really smooth. I also removed the plugs and did a compression check. 1 - 2 - 4 shoed 60 pounds BUT 3 showed at best 48 pounds. Do I have a head gasket problem? Always thought that a 10% variance in pressure was acceptable but this is 20%.
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Old 10-19-2018, 02:18 PM   #42
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Default Re: Terriable backfiring

I wonder if you have a leaking exhaust valve that is letting raw gas into
the exhaust system when the piston is coming up on compression. I would do a leak down test to see where the compression on #3 is going.



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Old 10-19-2018, 02:25 PM   #43
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Default Re: Terriable backfiring

a 12 LB difference when all other 3 are at 60 looks like a problem. Could be head gasket, could also be a valve issue. Not sure if it would cause backfiring, others may know.


Sticky valve, carbon under valve, bent valve, etc.


Take the plugs out.


Crank the motor with ignition off or hand crank and you may be able to view the valve operation through the spark plug hole


Or take the valve cover off, crank engine and view valve operation


Or use a borescope through the spark plug hole.


Or perform a leak down test.


To see if you have a head gasket leak into the coolant - look for bubbles in the radiator coolant with the engine running, also load the engine down and recheck. As a final check you can purchase a NAPA Block Test and test the coolant for exhaust gas (the test kit is about $45).
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Old 10-19-2018, 04:53 PM   #44
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Default Re: Terriable backfiring

My stock engine has only 50 PSI on all 4 cylinders, but runs strong and smooth.
10 years ago all the bad backfiring was caused by poor contacts in the repro switch.
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Old 10-19-2018, 05:33 PM   #45
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Default Re: Terriable backfiring

Tom Wesenberg like I said in a previous post I installed the jumper for the switch and it still BACKFIRED! So I think the switch is not an issue. Thank You!

Bob C and 30 Closed Cab PU I plan on doing a leak down test tomorrow. I just have to read how it is done. I had done one years ago but will brush up with the instructions. Thanks to your both!!
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Old 10-19-2018, 05:45 PM   #46
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Default Re: Terriable backfiring

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Don’t discount a failed manifold gasket.
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Old 10-19-2018, 06:45 PM   #47
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JacksonIII it was just replaced and then checked with a butane torch that was suggested earlier.
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Old 10-20-2018, 09:46 AM   #48
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Default Re: Terriable backfiring

Take the car out and drive it hard for 20 or 30 miles, and then see how it runs.
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Old 10-20-2018, 02:40 PM   #49
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Default Re: Terriable backfiring

There are many causes to a backing fire on the Model A. The two I recently discovered was a loose coil cable. Be sure the cable from the coil to the distributor is seated tight in the coil. if it is loose it can arc causing a backfire. the second was a badly clogged carburetor. The gas had gone bad for sitting too long and gummed everything up. I cleaned the carburetor and replaced the gasket where it bolts to the intake to make sure I had no leaks. That seamed to solve the problem for me.
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Old 10-20-2018, 04:56 PM   #50
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kathy Thanks for responding. Well, I believe I did that a month ago when I went to Lake George, N.Y. and back! 650-700 miles!
gibbdoHonestly I have changed the COIL WIRE but it didn't seem to seat as well as the old. I attributed that to being new. I will have to revisit my coil wire. I have yet to take the carburetor off because at this point I don't believe I have a fuel problem i.e. dirt in the tank/carburetor because my glass bowl filter is as clear as can be. I would also like to thank you for responding.
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Old 10-20-2018, 06:17 PM   #51
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Default Re: Terriable backfiring

All these things tried and you HAVEN"T CHECKED FOR FUEL FLOW?! You're assuming because the tank looked nice and clean a while ago and the sed bowl was clean, no problemo--right?


A single chunkie can cause your problem.

First, disconnect fuel line at carb and observe fuel stream onto ground or in a can. Stream should look like that of a young man proudly writing his name in the snow; not an old man laboring to keep his shoes dry.

IF stream is good, try another carb OR perform the carburetor Heimlich: momentarily pop palm of hand over carb intake while simultaneously racing motor. release throttle and remove hand before engine dies. Engine vacuum will suck any little poopies that may be blocking carb jets on thru.

Last edited by steve s; 10-20-2018 at 06:27 PM.
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Old 10-20-2018, 08:07 PM   #52
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Default Re: Terriable backfiring

If you happen to have access to another carb, you may replace the one you have on your rig and try another. Also make sure your carb gasket between the carb and intake manifold is not leaking. I had similar problem as you and when I used a different carb, problem went away. I am no expert on things but this worked for me. Or it may have been a leaky gasket between the carb and manifold. I found this gasket "wet" when I took it off.


I also put some MMO in the gas. I thought I may have a stuck valve and the reason for the MMO.


So don't know what solved the problem.
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Old 10-23-2018, 05:48 PM   #53
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steve s - Well you will be happy because I checked for fuel flow!!! It was fine. I also checked the filter in the front of the carburetor. Nothing there either. I'm on another mission trying to get head off but when that is done I will be opening the carburetor up.

After doing a compression check and finding #3 was low I did a leak down test and I could hear air coming from #4 but when I reversed the process the air coming from #3 was not as great as what came from #4. My conclusion is the head gasket is blown so I am trying to remove the head. I don't think it has anything to do with the backfiring.

BUT my question is if the head gasket is blown why did #4 show 60lb. while #3 had only 48lb.
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Old 10-24-2018, 09:29 AM   #54
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Default Re: Terriable backfiring

how can an electrical issue cause a backfire?
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Old 10-24-2018, 11:21 AM   #55
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steve s - Well you will be happy because I checked for fuel flow!!! It was fine. I also checked the filter in the front of the carburetor. Nothing there either. I'm on another mission trying to get head off but when that is done I will be opening the carburetor up.

After doing a compression check and finding #3 was low I did a leak down test and I could hear air coming from #4 but when I reversed the process the air coming from #3 was not as great as what came from #4. My conclusion is the head gasket is blown so I am trying to remove the head. I don't think it has anything to do with the backfiring.

BUT my question is if the head gasket is blown why did #4 show 60lb. while #3 had only 48lb.
Were you able to tell where the air was leaking? Intake Manifold, Exhaust Manifold, Crankcase, etc? - this info would help with diagnosing the issue.


Sorry did not read this thoroughly enough - seems you saying the leak is between cylinders. Is it possible with a slight leak the gap/break in the gasket opens, but in the other direction moves back and provides a seal? Just a guess, do not know if this is possible.

Last edited by 30 Closed Cab PU; 10-24-2018 at 11:29 AM.
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Old 10-24-2018, 11:24 AM   #56
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Default Re: Terriable backfiring

I'm not sure I saw a response to JR1967's comment about a plugged exhaust

I had a very similar condition that you have - and I did the exact same things you did to find the problem. In the end, it was baffles in the later style muffler had collapsed and blocked the exhaust. At idle the pressure is low enough that it could get through the small gaps around the blockage, but at higher RPM, the pressure was too great and caused backfiring.

Here's a link to my discussion thread:

https://www.fordbarn.com/forum/showt...ferrerid=17981

Assuming you exhaust system is welded one piece from manifold to tailpipe, the only way to test it is to disconnect the exhaust pipe from the manifold. That of course has some risks, as any backfire is occurring right in front of the carburetor. And honestly, with NO exhaust back pressure, you may well get some backfiring when you let off the gas. But, when I tested it, I increased idle up as high as I felt comfortable, and had no backfire (that is, until I released the throttle and it felt back to idle - but that was minor).

Good luck! And keep a fire extinguisher handy!
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Old 10-24-2018, 06:11 PM   #57
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Default Re: Terriable backfiring

Good afternoon...If you remove the muffler and tail pipe system, and shake it on the driveway...if it rattles than you can be sure that the baffles are loose. You can also shoot compressed air through it and see what happens. Most of us did not think of the muffler...Ernie in Arizona
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Old 10-24-2018, 09:48 PM   #58
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Default Re: Terriable backfiring

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Originally Posted by daren007 View Post
how can an electrical issue cause a backfire?
Easy, if the spark is momentarily interrupted, raw air/fuel mixture gets into the exhaust. Then, when ignition is restored, and fire goes into the exhaust, boom, as that unburned mix explodes. Anything that causes a misfire can cause a backfire.

Don't believe me? Drive your A along and turn off the key for a second or so, then turn it back on. Boom. I once destroyed a muffler when scaring my neighbor. He had the last laugh on that one, but it occurred when I was in high school, back in the '50s and I have since gotten a tiny bit smarter.
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Old 10-24-2018, 10:49 PM   #59
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Default Re: Terriable backfiring

30 Closed Cab PU Thanks for your response. I was thinking the same thing about the gasket BUT I have to get the head off before I can report how it looks.

saintjoelarry Well I haven't taken the muffler off yet. It is an Aries Stainless Steel (put on new 11,000+ miles ago) although I'm sure that doesn't matter. Thanks for your response also.

Ernie Vitucci Thank you also for the comment and suggestion.

Corley Thanks for your response and also a great explanation!!

I will make comments when I get the head off. I also plan on checking the valve clearances while I'm at it. Then I will see if either the blown gasket? or the valves being out of adjustment caused the backfiring which I'm not really convinced it is. If not I will have to continue on with the trouble shooting.
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Old 10-25-2018, 08:32 AM   #60
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Default Re: Terriable backfiring

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: ... momentarily pop palm of hand over carb intake while simultaneously racing motor. release throttle and remove hand before engine dies. Engine vacuum will suck any little poopies that may be blocking carb jets on thru.

If it's not too late (head already off) do me a personal favor and try this. It will only take 15 seconds. Probably prudent to wear a glove on your left hand, although I've done it a hundred times and never had a problem.
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Old 10-25-2018, 11:00 AM   #61
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steve s It is too late as the engine has been drained of water, water pump is off and all bolts to head are loose. Problem is head won't come off so I have ordered a head puller which hopefully will be here Saturday. When I get it back together I will try your suggestion.
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Old 10-25-2018, 11:12 AM   #62
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Default Re: Terriable backfiring

Start soaking all the studs with Kroil ASAP.
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Old 10-25-2018, 12:09 PM   #63
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Did you try just turning the engine over with the starter after backing off the nuts just a few turns?
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Old 10-25-2018, 12:30 PM   #64
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Default Re: Terriable backfiring

Tom and Steve have great ideas. Even if you have previously tried Steve's suggestion but not Tom's, do Tom's and try again. You can actually run the motor. As the head lifts the distributor/cam shaft should raise with the head, and immediately shuts off the motor.




I had a particularly stubborn head, the mechanic tried this method, did not have a puller, tried using a motor hoist and had the front end off the ground, had to resort to soft wedges. Ends up there was so much rust from sitting for 50 years with a bad gasket he was not sure a puller would have worked.
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Old 10-25-2018, 01:27 PM   #65
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Tom Wesenberg I have been soaking the bolts to no avail. I have had 5 - 6 bolts come out and all are unrusted maybe because they are chrome molly bolts.

steve s that was the first thing I did and the rear lifted just a bit! I'm done using the scraper and waiting for the puller. I also tried some HARD WOOD WEDGES but that also didn't help.

I installed the head gasket myself some 11,000+ miles ago which was the NEW head gasket at the time i.e. with the RED sealant around all the bolt holes etc. and believe the gasket itself is holding the front of the head down.
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Old 10-25-2018, 01:31 PM   #66
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I forgot to acknowledge 30 Closed CabPU for his response. You can see above my response.

Also thanks to Tom Wesenberg and steve s for your suggestions and response.
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Old 10-25-2018, 03:45 PM   #67
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Default Re: Terriable backfiring

The puller will help get the head off. They work pretty well. Once the head is all the way to the top of the head studs it will not be able to lift it any farther. You can then attach a engine lift to the puller and use that to get it the rest of the way off if it still needs help. Be careful though if you do because the head can separate pretty suddenly causing damage the junction box or firewall etc...
Another option is to make spacers out of 1/4' nuts by grinding the tips off making them round. They will then be able to sit on top of the four head studs the puller pushes against and have room to recess into the head. Sometimes several need to be stacked on top of each other to get a head all the way off.
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Old 10-26-2018, 08:32 AM   #68
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Default Re: Terriable backfiring

Quote:
with the RED sealant around all the bolt holes etc
That's probably what's holding the head on.
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Old 10-26-2018, 09:09 AM   #69
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I have not seen additional sealing around the bolts mentioned before in my short time as a Barn member. Is this recommended, and if yes why?
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Old 10-26-2018, 09:44 AM   #70
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I have not seen additional sealing around the bolts mentioned before in my short time as a Barn member. Is this recommended, and if yes why?
Perhaps to keep any water leaks from rusting the studs?
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Old 10-26-2018, 11:06 AM   #71
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Default Re: Terriable backfiring-Another Reason to use antifreeze.

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Perhaps to keep any water leaks from rusting the studs?
Reason number 27 to use antifreeze.

Simple solution to rusted stud problem is to use antifreeze mixed with the water!!

Just sayin ....
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Old 10-26-2018, 01:17 PM   #72
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Default Re: Terriable backfiring

30 Closed Cab PU The gasket that I have on the engine right now is pictured below, hopefully ...........but is listed in Snyders P/N A-6051-M. Sorry didn't work, but check it out in Snyder's catalog online listed under Parts on the home page of this site.

cpf240 That is the reason I used it but............now I have questions because I really think that is what's holding it on.

Benson I have been using antifreeze in the motor ALONG with DISTILLED WATER. As I said the bolts that have come out attached to the nut don't have any rust on them.
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Old 10-26-2018, 01:27 PM   #73
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Quote:
Originally Posted by Cape Codder View Post
30 Closed Cab PU The gasket that I have on the engine right now is pictured below, hopefully ...........but is listed in Snyders P/N A-6051-M. Sorry didn't work, but check it out in Snyder's catalog online listed under Parts on the home page of this site.

cpf240 That is the reason I used it but............now I have questions because I really think that is what's holding it on.

Benson I have been using antifreeze in the motor ALONG with DISTILLED WATER. As I said the bolts that have come out attached to the nut don't have any rust on them.

No need for the picture, I was asking you and the others the purpose of sealing the bolts, and if it is recommended. By the way you do a great job of responding to everyone, I really appreciate that.
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Old 10-26-2018, 01:45 PM   #74
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Default Re: Terriable backfiring

Backfire= fire out the carb usually caused by ignition problems
Afterfire=fire out the exhaust usually caused by valve; timing, leaking or burnt
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Old 11-02-2018, 10:30 AM   #75
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Just an update on my problem. As I had said we opted to pull the head. We bought the head puller from Brattons but to be truthful, I was disappointed in its operation. The #7 bolt which works with the puller was not as accessible as to other three to get a wrench on. The wrench was hitting on the high spot of the head because of the tunnel, for a lack of a better word, that goes forward to the water pump, and also the fitting supplied that goes in the #1 spark plug hole. We, therefore, decided to pull the remaining bolts from the head, with #7 giving us considerable trouble.

After getting the head off we observed that the gasket between #3 & #4 was intact. This was the reason we removed the head as the compression check showed 48lbs. in #3 and #60 in the rest of the cylinders. We also had done a blowdown test which showed air coming from #4 and when we put air to #4 we had air coming from #3. These two tests indicated to me that the head gasket was blown.

I will check the head for straightness today and if needed take it to the machine shop and have it ground. Wonder how much is left to take off?

As always any comments would be welcome relating to this latest event!
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Old 11-02-2018, 11:55 AM   #76
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Default Re: Terriable backfiring

If the head is straight and not the issue with the compression loss, would a poor valve seat, bent valve or sticking valve let air from #3 to #4 and vice versa?
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Old 11-02-2018, 04:28 PM   #77
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30 Closed Cab PU Thanks for the compliment! I try.


heneste Thanks for your response. I just returned from the machinest and he declared that the head is in fact FLAP! However, in the same breath, he said I should have it planned because he saw some spots that were too ruff into the head.

As to determining if there is a poor valve seat or bent valve I don't know how to determine that. After cleaning up from the head removal i.e. cleaning the gasket off I will get into checking the valve clearances sooo...if there is anything wrong I should be able to determine that.
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Old 11-02-2018, 09:59 PM   #78
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Default Re: Terriable backfiring

gonna be a heck of a note if the problem was a plugged jet in the carb.
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Old 11-02-2018, 10:05 PM   #79
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gonna be a heck of a note if the problem was a plugged jet in the carb.
X2. I agree.
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Old 11-03-2018, 01:21 PM   #80
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Default Re: Terriable backfiring

Sure would have changed the carb before I pulled the head. Both times I had backfiring was a carb issue.
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Old 11-03-2018, 08:48 PM   #81
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steve s, Fred K-OR, GPierce I would suggest that you three re-read my #41, #45 and #53 posts. I know I started this entitled "Terrible backfiring" but has gone to low compression. However, I decided that a compression check was in order. When I found #3 having 48lbs. pressure then I decided a "Blow Down Test" was in order. Having found air leaking from #3 that was when I decided to remove the head, NOT for the "Terrible backfiring" but because of the leaking from #3. It was going to have to be done now or later.

Steve s In post #53 second paragraph, last sentence I said: "I don't think it has anything to do with the backfiring". Also in post #53 the last sentence of the first paragraph I said: "I'm on another mission trying to get head off but when that is done I will be opening the carburetor up". I have not because of all the problems I had removing the head.

I appreciate ALL of your responses to my problem and look forward to those of the future.
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Old 04-07-2019, 10:40 AM   #82
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Did you ever get this problem solved?
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Old 04-14-2019, 12:50 PM   #83
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Default Re: Terriable backfiring

Found the cure to my backfiring . The throttle was not closing all the way at the carb ,corrected that problem and no more backfiring.
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Old 04-15-2019, 09:37 AM   #84
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Default Re: Terriable backfiring

Thanks for the update, good info.
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Old 04-15-2019, 10:18 AM   #85
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Default Re: Terriable backfiring

How about internal distributor wiring? If insulation frayed can cause a short and backfire.
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Old 05-12-2019, 04:17 PM   #86
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I have always read on this site to get back to the board when the problem has been resolved and how. Well here I am.

A little background. Engine did a lot of backfiring and rough running. I did a compression check: Cylinders 1, 2 and 4 had 60 lbs. in each. 3 had 48 lbs. I followed this with a blow down test. This showed air being blown from #3 to #4 cylinder. I reversed that process and #4 was now blowing into #3. This indicated to me that the head gasket was blown. WORKED at getting the head off a considerable time but finally accomplished that. Found head gasket intact. Looked at valve adjustment and found #3 exhaust shut. At this point decided to take valves out and lap seats but #3 exhaust didn't look to good after the lapping so had a machinist come and CUT the seats with the engine in the car. Installed all NEW valves because old ones had VERYnarrow margarine's. Now engine didn't run well and thought it was a distributor problem and went on to change a condenser in the second distributor. Still not running well.
Changed with a different carburetor from a engine that ran well but still did not help. Then assembled another carb. from the shop with parts I had on hand. Took car out yesterday for a ride and picnic with my buddy and his wife and of course on to Ice Cream. This car runs well and sure am now a happy Model A Owner!

Thanks to all for your advice and suggestions!!
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Old 05-13-2019, 09:03 PM   #87
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Default Re: Terriable backfiring

So it was the carb?
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Old 05-13-2019, 09:18 PM   #88
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Default Re: Terriable backfiring

My roadster would miss badly when I was on a trip to TX. I had all kinds of help changing gaskets, carbs and distributors. It was so bad I was towed part way and yet we never found the culprit. Then on the way back it somehow seemed okay and I made it home and a year or so later It suddenly did the same thing again and I had two guys helping me sort it out. As I raised the hood on the drivers side one of them saw my alternator and as he said, "Oh, you have an alternator," he reached in and touched it. The wire to the fuse fell out of the crimped holder that holds the wire to the outlet on the alternator. No more problem after I crimped the holder a bit tighter. That was in 2008, Still working well.
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Old 05-14-2019, 05:59 AM   #89
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Default Re: Terriable backfiring

My car had a bad back firing problem , no power. Turned out to be points and the coil.
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Old 05-14-2019, 07:52 AM   #90
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Default Re: Terriable backfiring

I had a similar issue and found that the lower shaft of the distributor had worn and it was causing the issue. The shaft only fits in one way but the groove had so much slop in it that it was wobbling and causing the car to run terribly and back firing like crazy. Cops came by and said they had reports of shots in the neighborhood.
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Old 05-14-2019, 10:23 PM   #91
Cape Codder
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Default Re: Terriable backfiring

Yes that's what I said. When the carb. I had was put together and float set it seems to run fine. I have only driven it maybe 30---35 miles but feel good about it.
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