Poppin' Tilly

[bobpo]

I have a Tilliston Carb and although the engine is running great and I seem to have eliminated all the air leaks, etc. Everything seems to be tight so should I remove the carb and re-adjust the float level?

I still get Poppin' when backing down from a higher speed to a lower speed and between gears.

(P.S. I also get gasoline fume smells when I shut the engine off.)
IT IS DRIVING MY WIFE NUTS.....) I'M AFRAID I'LL LOOSE MY 50+ YEARS ALLOWANCE IF I CAN'T GET THIS FIXED.....

[Jack '29 Sport Coupe]

Since we don't know what all you have done, here's my starter list.

1. Timing
2. Have you experimented with various spark positions?
3. Yes, it could be your float level, so by all means check it.
4. Do you close the fuel valve when you shut the engine off? My garage
used to smell to high heaven until I started closing the valve every time.
5. Could be a condenser

Just my two cents worth, others will chime in.

Jack

[Patrick L.]

I just found a crack in mine, in the venturi area just below the throttle shaft and mixture screw.. I knew they were susceptible to flange warpage but not housing cracking.. I'm thinking that may be the cause for the 'burble' between shifts.. Not sure whether to fix it or spring for a Zenith.. They used to say that Tillys were for go and Zeniths for show, maybe thats just another of those old wives tales..

[dalton]

Jack is on to it. I'd say check the float level and the condition of the needle valve. When decelerating on my Harley, if I open the throttle just a little bit, I can get it to 'pop', just for fun. So, with that being said it makes sense that the float level or needle valve might be the problem. Also, if the float isn't shutting off fuel completely it could certainly cause the fuel smell in the garage.

[Purdy Swoft]

If you are needing to open the gav more than a quarter turn after warm up you have a vacume leak somewhere and this will cause popping. If the float is set so that the carb is starving for fuel, this will cause popping when you try to accelerate. If the initial timing is set retarded or the points gap is too close this will cause popping. Optimum point setting is .022 . I f you are running with the spark lever part the way up this will cause popping when you let off the gas. If you are running with the spark lever part the way up, when it starts popping pull the lever down and see what happens.

[bobpo]

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I started with a rebuilt Zenith and no matter what I did, it leaked when I shut it off and the car just plain ran bad. My brother had an old Tilliston and gave it to me to try. I pulled the Zenith and installed the Tilly, and it's ran great ever since. Just has a gas smell that irritates my wife. I still have the Zenith.

I have tried several different timing positions, and have the point gap at.022. I also think the timing is right on the money.

I have a new distributor housing, cap, rotor and condensor. The plugs are running evenly and clean.

I religiously turn the gas valve (which is also new) off whenever I shut the engine down.

I generally run with the spark lever 3/4 way down and the GAV 1/4 open at speeds of 35-45 mph.

I might add that the car ('30 coupe) runs like a dream, well except for the gas fumes.

When changing the level of the Float for this particular purpose, should I lower it slightly into the bowl...???

[Purdy Swoft]

Lowerin the float in the bowl will cause less gas to enter the bowl. this would cause a lean when under power condition such as climbing hills and trying to accelerate. If the float is set too low in the bowl you would have popping when it was under strain such as climbing hills and tring to accelerate. Unless it is doing this I would probably leave the float alone unless, the carburetor was damp with gas or dripping. I would experiment with idle adjustment and run with the spark fully advanced, except for low speed such as take offs and if it was allowed to get in a strain and begin to buck ping and knock, you would then need to retard the spark as needed to cushion the engine and the bearings from detonation pressures. I have driven and lived with model A's for over 50 years. I completely retard the spark to crank the engine . as soon as it cranks I fairly quickly advance the spark about 3/4 down and advance as I increase speed. I keep the momentum built up so as not to ever strain or lug down the engine. Where the road and speed limits allow I usually keep a speed of 45 -50 mph with the spark fully advanced. There is no advantage of running the spark retarded at all even at 30 mph unless it is in a strain. running at speed with the spark not fully advanced will usually cause popping when letting off the gas. If it can draw the least amount of air into the muffler this will contribute. It is a real pain but it happens.

[bobpo]

Well, that makes sense Purdy. I have been running with the lever about 3/4 down. I'll try it today after warm-up and at speed (40-45) and see what happens with the lever all the way down.

Somehow this makes sense to me, and I've only driven a Model A little over 500 miles in my whole life.

I imagine I'm not the only new/old person in this position.

[Patrick L.]

I just cleaned the outside of the Tillotson with some ether[ to lazy to remove it], mixed up some epoxy and 'slobbered' it around where I thought the split was.. The color even pretty well matched so its hard to see this 'fix'.. The 'hiss' thats been there for the past 35 years is gone and I actually had to adjust the speed and mixture.. Once the weather cooperates I see if the ' bloop' between shifts is gone..

[bobpo]

Patrick,

I guess now we can add Epoxy to the list of Duct Tape and Baling Wire.
AND, that ain't a bad idea.

I did take "Ms. Tillie" to the local rural coffee shop this morning (MacDonalds) and by leaving the spark lever all the way down, it eliminated the "POPPIN' " I have been experiencing. I even opened it up to 55 mph and backed off and guess what,," NO POPPIN'."

I am so tickled...........................

[Purdy Swoft]

Thanks bobpo for posting. I have tried many times to give helpful information about timing, use of the spark lever and lots of things that is just common sense to me, after years of living with model A's. I really have no agenda. Most you just can't help. I'm glad that the popping problem is solved.

[bobpo]

I really appreciate all your help Purdy. And I mean it.......And I need it......Really...

[Purdy Swoft]

Thanks bobpo, I'll be glad to try and help whenever you ask. Sounds like ms. Tillie is really performing well. I bet you can notice an improvement in power with full advance at speed.

[RJ]

HI I had the same problem with my 1930 , the car ran good put would get a popping when decelerating. its been doing this for awhile. Last night I was getting ready for a weekend trip and I found the vacuum line was broken at the intake manifold, you couldnt see the brake it was inside fitting. Fixed the line no more popping.

[Purdy Swoft]

Vacume leaks can cause popping usually between gear shifts and deceleration. With a vacume leak usually the most noticed problem is that the engine will run so lean that the gav may have to be opened way up, maybe a couple of turns to get it to idle or run, even sort of smooth. The reason being with loss of vacume the engine will struggle to draw the mix into the cylinders and it will be drawing more air from the source of the leak causeing the mix to be very lean. This is why the gav must be opened farther to compensate for the lean condition caused by the vacume leak. Usually people will have vacume leaks more often with the pot metal carburetors such as the Tillotson or Marvel. Warpage of these fine little carburetors is usually caused by overtightening at the flange or from overheating caused by retarded timing or improper use of the spark advance. Retarded timing for which ever reason will cause the manifolds to overheat and contribute to the problem. I've seen them running with the exhaust manifold dark red and you can really feel the heat radiating.

[bobpo]

Purdy, I had her up to 55 this morning on the way to the Barber and that was with the GPS. She purrs like a kitten when I'm on the road. When I got to the barber shop and shut 'er off, there was a hesitation and then a pop.....Not real loud tho. The attorney crossing the street in front of the bank a hundred feet away told me later that he didn't hear it. Good thing I wasn't in a bigger town. The Swat Team would have surrounded me.

I have a feeling that it may be related to "Tillie" carb. It's an old one, never rebuilt. I'm also wondering if that may be where the gas fumes are coming from. The ones my wife complains about. I think I may need to get a re-build kit. I've also been running with the spark lever all the way down and the GAV open about 1/4 turn.

Gotta take 'er in tomorrow morning to have the paint guy re-touch the fender scratch I put on it last winter.

The biggest thing now is the Belt is too loose with the Alternator. The standard belt is too loose.

Is there a way (or size) of belt that is shorter that most guys use with the alternator? I got a new belt from Snyders and the adjustment bracket is extended all the way and there is still too much slack....!

KEEP THAT HELP A' COMIN AS I HAVE A SHOW THAT I WANT TO GO TO LATER THIS MONTH..:rol leyes:

[Purdy Swoft]

bobpo,

Sounds like its running too good to mess with the tilly. Steve S and I had a good discussion on another thread about a week ago about the backfire after cut off phenomenon. We pretty much agreed that it is an exhaust leak that causes it. Brent also brought up some good points earlier this week that makes a lot of sense. The carburetor will breath in the carbon monoxide and effect the mix. The gas needs air instead or the mix won't burn properly, gas will enter the muffler. after cut off it will be able to draw air through the exhaust leak and the backfire after cut off will occur. As a test I would remove the fan belt so air wouldn't be blown to confuse the test. I would crank the engine when it was cold and stand on the manifold side of the engine while reving it up and feeling around for hot exhaust leaks.

My 31 tudor had been sitting in the garage for several months without being cranked up or driven. Our grand daughter was over for the week end and we decided to take the tudor out for a ride on model A day. The tudor had been running good when parked and cranked right up and was ready to go. When we got up town and stopped at the gas station for gas, I was very embarrased when it was cut off and gave a loud back fire. It also had the raw gas smell that you mention. The last time that I had the manifolds off, the only gasket that I had on hand was one of the one piece steel clad on one side gaskets.
I'm thinking that the steel cladding on only one side of the gasket has probably rusted or burned through causeing the problem. I'm dreading having to go into it but I recommend the late 31 two piece copper clad gaskets. part number A-9433-C2 listed on page A134 of the new Snyders catalog. as you can see in the picture, this gasket covers more area and has a better chance of solving the problem. If you end up removeing the manifold assy. be sure and lay a straight edge accross the ports to check for flatness, the manifold may need to be planed. Sometimes the manifolds will sag at the rear and cause misalignment of the ports and also cause misalignment at the exhaust pipe flange that will cause leaks. If the manifold is found to be sagged, about the best bet would be to replace the manifold. I would also look very close for cracks in the manifold. I use the exhaust sleeve, part number A-5234 on page A-112 and exhaust sealant part number A-5252 same page.

I'm running a Zenith side bowl on my tudor. Tillotson carbs usually run leaner than the Zenith. If your Tilly isn't backfiring apon acceleration, stalling when the brakes are applied or dripping gas, I wouldn't mess with it. I'm not allways right, there is usually several things that will cause the same symptoms with model A miseries. I just noticed your post and wanted to offer help.