OK … where to start? So my uncle bought a 31 phaeton a few years ago to go with his collection of 31’s. Problem is we have never been able to get it to run correctly since we got it. The problem has been popping out of the carb. At first it was at all conditions, starting the car rolling and running down the road. Over time we have changed the carb to one form one of the other 31’s. Then found out we had problems with the head when we found water in the oil and started working on the head last fall. We found out that the head was cracked which might have been one of our problems to start with.

Fast forward to current time, we still have a popping coming out of the carb at steady speed over 30. Driving 30 or less you don’t have the problem. Otherwise it runs great at idle. We’ve gone through the head completely, new guides, new valves, new springs, new seats. Checked for vacuum leaks, new spark plug wires, new plugs, new points, and new condenser.

So the one thing which I have noticed today is the problem gets worst after driving for a few minutes. Come home and let is sit it will run great and start getting worst again. This is telling me something is getting hot and opening up causing the problem.

The only things which I have left to try is taking the electrolock out of the loop and changing the coil.

Can anyone think of anything else to look at or try?

Thank you,
Bruce

I would definately try changing the spark coil. I have had bad coils do things like that when they got hot.

Hey Brucie! Ya, try changing the coil. I know you talked about doing that several months ago.

OK, tried the coil tonight, not difference. Tried changing the distributor with no difference. Took the electrolock out of the loop, no difference.

Now what? Please come up with the solution.

Possible solutions:
1) Don't drive over 30 mph.
2) Turn up the radio.
3) or... analyze the problem.

After it gets hot, there is either a) too much gas, or b) too little gas, or c) early spark, or d) late spark (or no spark).

Something new that you can try. Hook up the dwell meter and tape it to the windshield with electrical tape. Drive at 30 mph and watch the dwell. See if it is STEADY.

Then, switch the dial to Tach and do the same thing again, but observe the RPM to see if it remains constant.

You're looking to see if the electrical conditions change as the car heats up. If you don't see anything with either of these, then shift your focus to fuel.

Now what is the definition, or sympton of "popping". Help me out guys. Is it excessive gas, or lack of gas? I'd guess it could be either. But the RPM gauge should tell you whether it's lack of gas because the R's should decrease or flutter if it is being starved..

Who's next? Continue with a detailed analysis for poor 'ol Brucie. :-)

Don't drive over 30?

I suspect a leak or crack in the intake system or restriction that is causing the mixture in cylinder(s) to lean at higher flow rates. Lean mixture is by far the most common cause of popping through the carb. Ignition timing (which is coordination of initiation of burn by spark of the plug to the position of the piston and valves) is another.

A second suspicion is the valve timing. Have you checked that? Is it possible that the cam/crank are not properly timed? Is the cam lift up to spec? If the cylinders can't properly take in gas/air mixture the burn mixture will be lean. Cam lift and duration and timing all have a effect on the amount of fresh gas/air mixture to each cylinder.

If you can't find the problem take it to an emissions testing facility and have them test at various engine speeds. The ratio of unburned hydrocarbons, NOx, CO2 and CO can indicate the mixture ratio which should be 14-14.7:1. Lean mixtures cause sharp rises in the amount of nitrogen oxides (NOx). If the mixture becomes too lean, the engine may fail to ignite the mixture, causing misfire and a large increase in unburned hydrocarbon (HC) emissions. Lean mixtures burn hotter and may cause poor performance, rough idle, hard starting and stalling.

There are a few other things that come to mind but are not as likely. Pre-ignition due to rough combustion chamber (which causes a hot spot) is possible cause. Restriction in exhaust is another but it typically shows as loss of power at higher speeds. Loose baffle in muffler can also result in irregular performance.

OK, Thanks Bill and Chip.

Chip your going down the same road that I was going. The manifold is the only thing left which I have not changed. So the reason why I'm thinking the manifold is that I still can't get more then 15 inches of vacuum. With the compress that I'm getting and all the new parts in the head I can't see why I'm getting a vacuum so low. Also the manifold is not a Chevrolet manifold.

As to the valve timing I don't know and really don't want to take the front of the car off to check. But I'm just about there.

Bruce,
I added a few other comments to the post likely when you were writing your response. So you might re-read it.

You can check the cam lift and timing with a dial indicator on a rocker arm. Determine TDC and then rotate the engine slowly noting when the particular valve (No. 1 cylinder is by far the best) begins to open and close. Note the max. lift distance. All you need to do for timing is one valve. Actually you don't even need the dial indicator if you really pay close attention to the push rod (rocker) position. If you do that then I will need to look up the cam timing and lift. Don't remember where I put it for a '31 engine. Maybe someone else will have it handy.

Thanks Chip,

As to the idle, it idles great and will come done to about 100 to 200 RPM with out a problem.

Now on the cam lift and timing. I tried that with a dial indicator but never could get a good reading. I never could find a good place to put the magnetic base. Any thoughts on that?

I'm will to try anything right now, could you look up the lift info? Now when you say lift your talking how far down the rocker pushes the valve?

Hi Bruce,
The valve lift is how far the valve is lifted off its seat in the cylinder head.
( so from the top rocker side, it is how far the valve is pushed Down)

Valve lift for a 1931 head with all 1931 rocker arms is .277"
(for the 1932 model it is increased to .309")

Hi Jack,

Thanks! This is great! Only one problem, its 11:30pm and I need to go to work in the morning.

Any idea how to mount the dial indicator so I can get a good reading? Maybe I need to make a bracket to mount to the rocker arm bolts.

Thanks,
Bruce

Bruce, I havent done the task, but the dial gauge normally has some sort of a clamp, maybe bend a small L shape bracket off the manifold bolts. or water outlet.
Cheers Jack

Bruce ,
My thoughts on the popping through the carby as the engine gets hotter is that maybe the valve guide clearance to stems is closing up as the engine gets hot,and maybe that is why it is linked also to the higher speeds over 30, ..more engine work and more heat. And in particular a sticking intake valve, staying open and allowing burning fuel back to the carb.

Maybe the new guides which you mentioned were installed are just a touch too tight.

I saw a 1927 chev 4 cyl at the Last anniversary rally which had sticking bronze valve guides after about 20,000 miles of use.

If you purchased your new valve guides from Egge Machine that might be the problem since guys have had problems with those in the past.

If it is valve guides wouldn't they also stick at lower engine speeds once the engine is hot?

You could pour some MMO into the intake when this occurs and see if it helps. The MMO would lubricate the guides (for a short time) and relieve the problem.
If popping back through the carb. it would be an intake that is hanging up.

hey bruce no one mentioned a rust through in the exhaust manifold a place where you can loose vacuum . if so it can be repaired just bore it out and put a sleeve in .hope this helps . i have done a couple of them and it works

Maybe it is a combination, of sticky valve guides and possible weak springs, and the heat is affecting both the guides and the springs with increase heat and RPM,s???
Maybe check all the springs on a tension machine.

Hi Guys,

This is great information, thank you all. We have been trying to fix this for about 2 years now with out finding the problem.

Jack and Skip, as to the valve guides, I changed the guides hoping to fix the problem. So just over 2 weeks ago I had original guides in the head and changed them to new ones because the old ones were moving around. So I’m very positive that the guides are not the problem. Also on the Valve springs since I changed them to new ones before I redid the head again and the problem didn’t go away. I don’t think it springs. Also tried shimming the valve springs with no change. Forgot, also measured all the new springs before installing.

Gene, as to the MMO, how would you do this with an updraft carb? :) I did put some in the gas hoping to do the same thing. Thank you for the help.

Hi pushrod, can you give me a little more details on where to look? As you might have seen Chip and I were talking last night about the manifold being the problem since I can’t get higher then 15 inches of vacuum. Also that is the last part on the car with I have not changed.

Can you pull 1 plug wire at a time and see which one if any causes the popping to stop? This would narrow it down to 1 cylinder, then I would look for a vacuum leak on or around that runner. You can also carefully spray carb cleaner around the intake gasket and see If the motor speeds up . This indicates a vacuum leak as well. Popping thru the carb is usually an indication of a lean condition.

With all of the other things you have tried then I would suggest changing out the manifolds since that is about the only thing you haven't done yet.

o k here goes on the exhaust manifold where the carb bolts on the intake passage which is the gas preheat section . exhaust goes around this section heating the gas rust out i have seen holes in this section or crack you will have to remove the manifold or remove the carb and use a mirror . i have found several to be leaking . if you cant find a replacement you can bore it out and put a sleeve in . i dont remember exactly what the hole size is some where around an inch and three eights . hope this helps

Pushrod fixed one for me by putting in a sleeve. It is still working.

Have you checked or eliminated the vacuum line for the wipers?How about connecting the vacuum gauge to the intake manifold at the wiper fitting and watching the gauge as you drive at 30 mph or whatever speed you are having the problem at.Also unless I missed it I didn't see any mention of a compression test.I had a similar problem with my 32 Sedan and found a pinhole in the wiper tubing in the windshield pillar post.

Hi Bruce,
What kind of manifold do you have on this '31 since you say
it is not a OEM Chevrolet, A heater manifold ?

Good morning 32confederate,

I guess it cannot have anything to do with the wiper, because switching on the wiper is "a kind of leak" too because vacuum gets lost otherwise the wiper would not work.

If it would create popping sounds my old chevy should pop too during rain and does not.

I guess the idea of a sometimes sticking intake valve sounds good. This could create backfires with popping sounds. The compression of the going upside piston might be enough too to "pop" too

It should be possible to take away the valve cover and to heat the engine really hot by covering the radiator than run the engine and see if everything works as it should work. Should be possible to see the difference between a working and a sticking valve.

All the best
Stefan germany
mostly working with the systematic method: Make experiments, try to find out what happens, analyse it, find a way...done...

Hi All,

After month of kicking the tires and not wanting to work on the 31 I have found out what was, I think, wrong.

So last Wednesday I got a call from a friend telling me about a book he has with a procedure of checking the valve timing. It read something like this, set number one intake valve to 0.010 and crank the engine over and the number one intake valve should just start closing at 1.5 teeth after U/C. Well it turns out that my valve was starting at about 18 degrees before U/C. See pictures below.

Also many of you may know or have heard about 4 cylinder gears being marked wrong, well here is a 6 cylinder gear which was never marked at all.

In the below two photo's notice where the white marks are. If you read your shop manual you will see that by taking a straight edge and lining it up with the left side of the key way you will find the number one tooth on the gear (marked in white). Then count 11 teeth over on the cam gear and the forth crank tooth drops into the valley after the 11th tooth. You will see on the third picture the correct way it should look.







Please let me know if you have any questions.

Thanks to Ray, Chip and Jack for all the support and information.

Bruce

Hi,

I made a mistake on the last post, should be right side of the key way, not left side.

Bruce

Great explanation and illustration. I have my feet crossed to see if this solves the problem. Nothing like having a problem and each time you think you have the answer and the solution may be no change or it runs worse.

Complete this project and you may get to work on your 32 for a change.

Good luck,

Next weekend the plan is to take apart the 32 engine to see what I have to work with.

I think I will know how to install the cam gear when it comes time.

Bruce

What a saga, Bruce! By now I would have had the plastic explosive and detonators out. I admire your persistence.

All the Best,

Chip.

Well Chip, I'm just hoping this will fix the problem. By the way, I was thinking alone the same lines as you. Just had not gotten there yet.

Good work 32confederate !!
We are all waiting to here the report when you put it all
back together. BB will have to make a huge smiling posting icon to celebrate.

PS. the part number on the camshaft gear 835730 is correct in the 1931 parts manual.

Hi All,

Got the car running tonight after a few tries. Adjusted the valves and could right away see a difference. Where before I was getting only 15 inches of vacuum I'm now getting 17 to 18 inches.

After adjusting the valves to the best I could (could not get the car hot enough with the cold weather) I took the car for a joy ride. It runs great! Had a couple of pop's on my normal test track, in the past I would have about 40 or so on the round trip. So getting down to about 2 is doing good.

One other thing, before I could run the engine at a high RPM in the shop and get the popping to happen. That no longer will work, so things have really changed.

My big problem right now is getting it to idle right. It keep's losing a cylinder or two, using the vacuum gauge. I'm thinking it might be the plug wires, I changed back to the original wires which were on the car when I first started this project. I had made the other wires I was using for my uncles roadster he is working on.

Any thoughts on the idle problem? Which I think is causing the few pop’s I have now.

Over all the car is running 98% better then it was.

Thank all for the help.

Bruce

You don't know how glad some of us are that the problem seems to be 98% fixed. It is always frustrating when the solution is so elusive but persistence will eventually pay off.

Any intermittent in the ignition system can cause a misfire. Some will be a popping and others just a loss of power. Could also be a sticking or mis-adjusted valve particularly if you are seeing a noticeable loss in vacuum. Carburetor problems are more typically a consistent miss.

What is your timing and spark plug gap set at?

Hi Guys,

So the timing is set to 18 degrees and 40 thousands on the gap. I'm getting a good hot spark, but it is questionable if it is an equal and constituent spark on all plugs. That is why I’m thinking that the wires are a problem. A few years ago I had about the same problem with the 32 roadster and when you turned out the lights you could see a light show under the hood. Changed the wires are problem solved.

Chip, it is a noticeable loss in vacuum, when running even (only a few seconds) I’m seeing about 18 to 17 inches of vacuum. Then it drops off to about 15 and works its way back to 18 to 17. Now if I run the idle up it will even out and hold 18 to 17. If I remember right the Idle should be about 400 RPM, I need to check this since I have not since all the rework.

As to the valves I need to get the engine hot, when I was working on them last night they were not even worm. After talking with Ray last night I’m thinking about making a thermostat holder and installing one. I have a nice 140 degree stat which will work nice. Also was thinking about putting cardboard in front of the radiator to get it warmer.

Bruce

Bruce,
There is no need to make any adapter for a thermostat. There is a groove between the outlet and head for a modern thermostat to fit right into. The old originals with the large bellows on the head side would not fit so the adapter was needed but he modern fits just fine.

Are you sure you have the idle adjustment screw set correctly? If too rich or lean it will miss.

Poor wires, humidity on the wires, plugs and in and around the distributor cap, carbon tracking are all potential causes of misfire. Add to that weak point spring, wobble in distributor shaft, corrosion on rotor and/or cap contacts.

I think that a perfect idle speed is about 100 rpm. If everything is top notch it is possible to nearly count the revolutions of the fan. I have never measured the speed of most of my early engines but think they are mostly in the 200-400 rpm range.

You'll get it to run better than a Swiss watch. Can't move anywhere powered by the watch only tell how long you have been somewhere.

Hi Bruce,

One more thought, when you took the cam followers out, were
they nice and clean, as varnish which builds up in the bores and on the cam followers can cause the valves to be stuck and hang open.

Hi all,

So tonight I went out to check the plug wires in the dark. Noticed some really cool things when it was dark. So the wires are arcing over to the wire holders and to them selves. Also noticed that you can see the plugs lighting up at the same time. Also notice that some of the plugs would get really bright and then come back to a normal color. This makes me think that other wires are charging a different plug causing the miss.

Jack, check the lifter out and they look great. This engine has only about 1000 miles on it. It was NOS when put in the car from what the owner told me.

Talk to you guys later.
Bruce

I think he is almost there. I listened to it run tonight and it was doing great. However, it sounded like we were loosing a cylinder or so when we ran the speed up.

He called me later after I left and said he had Christmas lights under the hood. (Explanation: You could see the spark jump from the plug wire guides to the plug wire.) I think when he is finished with the new plug wires he can call it JOB FINISHED and put the hood back on.

At 5 cents an hour that he has worked on this car will provide him enough money to by a major part for his own car.

Ah, cloth covered spark plugs leads , thank goodness for pvc and silicon leads for our modern cars.

Looking to the very good pictures above I want to ask:
Should there not be a drilled hole to allow the engine oil to lube the camshaft gears?
Where is it?

Regards
Stefangermany

Stephan,
Oil comes out of what looks like a large flathead screw, it is a nozzle which directs an oil stream directly at the centre of the gears.
Page 39 of the 1931 repair manual shows the alignment of this timing gear oil nozzle.
Regards Jack

Hey Guys,

So I finish my new plug wires today and installed them and they work great!

You would not believe the difference they made in how the engine runs.

Once I had the engine running I put a piece of card board in front of the radiator to get it warm and that did the trick. Got the engine good and warm and set the valves to the correct settings. I now have about 17 inches of vacuum. I have a miss once in a while now, I think it is one of the new valves sticking, I put some oil on the stems and that problem went away for a while.

Now I’m waiting for the rain to stop so I can go drive the car and really test it out. I just would like to thank everyone again for all there help and support.

Brucie,
Just make sure that unc puts a glug of ATF with each fillup. Some folks think MMO smells better when it burns in the cylinders but ATF is much less expensive. It will help keep the intake valves from sticking. And the intakes are the ones that stick after the initial break in.

Looks like it might not rain tomorrow, maybe I can get out there and run the car some and put some of that ATF in the tank.

Bruce

Chipper What would be a good ratio of ATF to GAS and does it make a difference/brand of ATF you use or is it the cheapest.

I use the same ATF used in my Chevy automatic transmissions. It is easier to only buy one type but most should work. A glug is the amount that comes out of a full bottle of oil before the flow stops to ingest more air. That is as scientific as we should need to get. Oh, well, maybe a bit more scientific! An ounce or two for 10 gallons should be okay. 40 to 1 works for 2 cycle engines so should also provide enough lubrication for the intake valve stems on our old Chevys. If someone wants to do a more detailed study to determine the optimum ratio, be my guest but remember to report back with the results.

OK! ONE GLUG I got it.

I intend to use 1.63812 glugs less half a dram.

All the Best,

Chip

Hope you don't get excessiveglugitis. It slips up on you.

Hey Guys,

So it was nice here today so I got to drive the car all day today. It really runs nice now. But I'm still getting a pop now and then. I'm thinking the car is running so cool that the carb is not getting hot enough. Also have not put the hood back on yet, a friend is coming over to help later tonight.

One other thing that I noticed is the fells like you’re pushing it through the higher speeds. It is like I need to advance the timing some more.

Bruce

Glad that you got it all figured out. That's cool!

Hi-Is ATF in the gas harmful to Cat. Converter, in-tank fuel pump,or fuel injectors in any way?
Thanks

I would not add anything to the gas of a car with a cat. or F.I. unless its says on the container it is safe for that use.
I would not even add ATF to the gas in an old car because it has contents that are not designed to be burnt in a combustion chamber....not to say it will harm anything though. I would add 2 cycle engine oil, the type that is mixed with the gas. It has more body so less is required.
ATF is better than nothing but not the best in my mind.

Hey Gene,

What do you think about MMO?

Bruce

At one time I was all for adding MMO to the gas. Then I read what made up MMO. Its highly refined oil and solvents. This led me to believe the solvents would have a very low burn temperature and would provide little or no lubrication to items in or near the combustion chamber. This would make it be of little use when added to the gas.Today I do use MMO to pour through the carburetor to prepare for winter storage, but I wait until the engine cools down before I use it. Its also good when used in that manner to "cure" sticking valves. Being a solvent It can also be addd to motor oil to help disolve
undisreable" things.
You can also add a non-detergent motor oil to the gas for upper cylinder lubrication A quart to 10 gallons was suggested by Chevrolet in a 1929 Service News for the breaking in of a freshly overhauled engine. That sounds like a pretty strong amount. Sure it would produce a lot of exhaust smoke. For winter storage I usually add aboyt 4 Oz of 2 cycle oil to a 1/4 tank of gas. Thats about all the gas I keep in the tank during storage.

The lubricant whether MMO, ATF, 2 cycle oil or other lubricant added to the gas forms a molecular mist that coats everything between the inside of the carburetor to the combustion chamber. Once in the cylinder is burn along with the gas/air. It is this oil coating that protects the moving parts (particularly the valve stems) from oxidized gas deposits. It is the gas deposits the fill the gaps between the valve stems and valve guides and eventually stick the valves.

Yes there are additives to nearly all lubricants that are not the best to be added to combustion chambers as they form ash on combustion. However the amount of these additives that would be carried into the combustion chamber is so small that they would have virtually no negative impact. Yes it is more of the additives than typically bypass the rings in modern engines (with crankcase oil) but below the amount that an engine that "burns" at a quart of oil in 1000 miles.

Just would like opinions as to adding MMO or ATF to the engine oil instead of the gas tank.
Thanks

I would say GAS-Yes
Oil- ? probably NO

And I should have mentioned that my question applies to a fuel injected car(injectors,in tank fuel pump)
Maybe makes no difference?
Thanks

I don't use MMo in the crankcase of either, I do use MMO and also Seafoam in the GAS of either FI or CARB cars or trucks, outboards, lawn mowers. i use Seafoam instead of Stabil in gas engines also with the new gasoline.

31 eng problem check dist for excess movement shaft moving up and down or side to side also gear on bottom of dist tom

Hello.
Had a similar problem until the 6wolt coil was changed.
Simple, mabe too simple.
Bragi