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Old 08-23-2017, 11:59 AM   #1
Minn-Tex Lee
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Default I think I found it

I have been fighting a miss for some time. Today while idling the engine, I grounded out #1 and no change. I grounded out #2 and no change. Grounding out #3 and #4 each slowed down the engine speed.
I measured the dynamic pressure at each plug and all were at 90-93 psi.
I do not have the tools to do a leak down test.
I have previously lubed the cylinders with MMO to help in the event it is a valve sticking.
I am guessing a head gasket failure between #1 and #2 cylinders. However wouldn't that keep the pressure from being as high as it is?
I would like to hear some other fixes besides replacing the head gasket.
Your thoughts would be appreciated.
Lee
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Old 08-23-2017, 12:30 PM   #2
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Default Re: I think I found it

Before proceeding further, have you checked to see if you are getting spark to plugs 1 and 2?
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Old 08-23-2017, 12:49 PM   #3
H. L. Chauvin
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Default Re: I think I found it

Hi Lee,

Two (2) Bingo guess tests from miles away:

A. Gap between the rotating metal perimeter tip of the rotor and distributor body's in-side metal lugs at all four (4) distributor body metal contacts measures: and,

B. The height of the (4) lobes on the distributor cam opens points how many thousandths of an inch:

1. _________? _________?
2. _________? _________?
3. _________? _________?
4. _________? _________?

Last edited by H. L. Chauvin; 08-23-2017 at 12:55 PM. Reason: typo
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Old 08-23-2017, 12:51 PM   #4
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Default Re: I think I found it

And are the plugs fouled from the MMO? Stay on point, don't try another fix that is not next thing to verify. You need to verify spark at those 2 plugs, common possible cause: crack in cap causing cross-fire, Wires crossed (may not apply), try swapping the rear plugs with the front plugs. Then consider one intake port feeds #1&#2, vacuum leak at manifold gasket.
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Old 08-23-2017, 12:56 PM   #5
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Default Re: I think I found it

first find out if 1, and 2 are firing. A vacuum leak should not cause the plug to not fire.
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Old 08-23-2017, 01:02 PM   #6
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Default Re: I think I found it

Don't pull the head yet! If the compression is 90-93 on all cylinders it isn't the head gasket. As previously suggested verify a good spark to #1 and #2 cylinders.As 100IH pointed out, it may be an intake leak, I would try spraying some carb. cleaner around the front intake port while idling and see if you get an improvement. Let us know what you find.
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Old 08-23-2017, 01:05 PM   #7
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Default Re: I think I found it

That would be called a lean misfire, very real in today"s cars. Lean won't stop the spark but it will stop the ignition of the fuel and air mix and it will send unburned fuel out to the hot exhaust and often can be a backfire.
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Old 08-23-2017, 02:33 PM   #8
H. L. Chauvin
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Default Re: I think I found it

FWIW: For often reported future Model A problems in general:

Lots of times, Model A owners have a Model A that's been sitting for quite a few years where they were formerly maintained with cheap, foreign Model A parts from the 1950's, (some from J.C. Whitney and others where points and condensers sold for only 00.15 each), prior to today's Model A modern parts suppliers.

If these cheap substandard parts are not removed and provided with some of the better than 1950's new modern Model A parts of today, Model A engine problems will always be a possible mystery.
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Old 08-23-2017, 03:11 PM   #9
Minn-Tex Lee
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Default Re: I think I found it

Thanks for all of the great suggestions. I do have spark at #1 and #2. I will have to get a hand crank to further test point gap etc. I am very encouraged by the comment associated with 90# pressure would negate blown gasket.
I will keep you posted as to my findings.
Lee
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Old 08-23-2017, 03:38 PM   #10
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Default Re: I think I found it

Minn-Tex Lee. I had the same problem. Turned out to be a bad distributor body. It was shorted on the inside. It sparked #1 and #2 at the same time. So as it rotated to #2, it would spark #1 as well.
So when you grounded #1 and # 2 it would not change the engine idle.
Use an olhm's tester to see if you have continuity between 1 and 2 on the dist body.
Good Luck. Jeff
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Old 08-23-2017, 06:54 PM   #11
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Default Re: I think I found it

Minn-Tex Lee...keep us informed on your progress.
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Old 08-23-2017, 07:00 PM   #12
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Default Re: I think I found it

Jeff's got the right idea! It's usually between 3+4 thats shorted!
In one of my modern's , I was going through caps fast, the aluminum contacts would corrode. After about 3 caps@6$ each I asked who makes better caps? He said we have them but there 10$ each :-( Last cap I put on that modern :-)
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Old 08-24-2017, 10:18 AM   #13
Minn-Tex Lee
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Default Re: I think I found it

Good news --I think. Spraying carb cleaner around the manifold reved the engine up considerably. So now I believe the problem to be the manifold gasket. My engine builder insisted on putting the manifold on himself because he felt an novice would damage the glands. So now this is an area where I will be on new ground. I will now dis-assemble inspect and order new gasket etc.
I will keep you all posted with a new thread when I have more info.
WOW- I never thought of intake leak would be the problem. Thanks so much for the great ideas.
Lee
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Old 08-24-2017, 11:56 AM   #14
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Default Re: I think I found it

Square up the manifold surface if necessary.
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Old 08-24-2017, 12:09 PM   #15
Minn-Tex Lee
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Default Re: I think I found it

It was indeed a blown gasket at #1/2 intake.
I am in the process of ordering new glands and gasket.
This is new territory for me so any advice to keep me from messing up will be appreciated. You guys are the greatest!!!
Lee
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Old 08-24-2017, 02:08 PM   #16
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Default Re: I think I found it

ALWAYS dab a bit of anti-seize on the threads!!
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Old 08-24-2017, 02:11 PM   #17
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Default Re: I think I found it

Quote:
Originally Posted by Minn-Tex Lee View Post
It was indeed a blown gasket at #1/2 intake.
I am in the process of ordering new glands and gasket.
This is new territory for me so any advice to keep me from messing up will be appreciated. You guys are the greatest!!!
Lee
some engines were not made for glands. Make sure they go in all the way in the head and manifold.
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Old 08-24-2017, 03:53 PM   #18
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Default Re: I think I found it

Quote:
Originally Posted by George Miller View Post
some engines were not made for glands. Make sure they go in all the way in the head and manifold.
all the way in WITHOUT a gasket... sometimes between the engine being decked and the manifolds being decked the glands no longer fit.
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Old 08-24-2017, 04:00 PM   #19
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Default Re: I think I found it

Quote:
Originally Posted by SeaSlugs View Post
all the way in WITHOUT a gasket... sometimes between the engine being decked and the manifolds being decked the glands no longer fit.
Yes. The other thing is a lot of time the rear of exhaust sags a little. That will keep the rings from going in.

For me I do not use them any more. They really are a good thing if every thing is right. But for my cars they work fine with out them. But every one should do what is best for them.
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Old 08-24-2017, 06:04 PM   #20
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Default Re: I think I found it

Glad you found the problem...instead of needlessly pulling the head.
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