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Need your help fellow Stovebolters. I have a 1949 Chevrolet 3100 with a 235 engine out of a Chevrolet Belaire. I recently tuned the engine up giving it new points, new rotor button and distributor cap, new condenser, new plugs, and new plug wires. I set the new points to .022, which is what the manual calls for new points. I set the timing according to the manual. I never have gotten it to run good. It idles good, but it misses when going down the road and I can hear popping back through the exhaust. Tonight, I started over. I checked the compression on all cylinders and it had the following compression:

Cylinder 1 - 150
Cylinder 2 - 150
Cylinder 3 - 150
Cylinder 4 - 160
Cylinder 5 - 135
Cylinder 6 - 150

I checked the points again and set them to .018, which is what the manual calls for once the points are used and have worn a little. I set the timing again. Truck idles good. Going down the road, it started missing again. Came back and checked dwell. Dwell was 29. I think that's a little low. I believe I've read it should be around 39 for a six cylinder. I reset the points and got the dwell to 39. Reset the timing after setting the dwell to 39. Truck idled good again. Went down the road and same story. Bad missing and popping through the exhaust.

I'm at a loss. I don't know what else to check. Could the coil be bad? Is there a way to check it to see if it's going bad? Any advice or suggestions will be greatly appreciated.

Hy Darrell Day, how did the engine run before the tune-up? Do you have a vacuum gauge, if so hook it up and tell us how it behaves as you rev the engine up. Does the vacuum advance on the distributor cause the distributor to move when you rev the engine?

It ran rough before the tune up. The points were burned badly. I'll have to buy a vacuum gauge. Don't have one. The vacuum advance on the distributor does work when you accelerate the engine.

What did the old spark plugs look like? Your #5 cylinder is significantly lower than the others. I would suspect that the old #5 plug would have looked different.
You need to find out why the #5 cylinder is lower in compression. If you squirt a tablespoon of engine oil and do a new compression test, and the number comes up, it would indicate a problem with piston rings. If the number stays the same, you likely have a valve problem. Either a burnt exhaust valve, sticky valve guide, or the rocker arm is adjusted too tight. Do you have hydraulic lifters? You might have a dirty/bad one.
Carl

Carl is probably on the right track. But for a potential easy win, recheck your firing order. 1-5-3-6-2-4 It’s pretty easy to get to fiddling with things and not realize you’ve swapped a couple wires. (Don’t ask me how I know)

Do a power balance test and a cylinder leakdown test. You need to pinpoint the cause of the compression loss on cylinder #5. No amount of tuning or tinkering is going to compensate for a leaky or tight valve. Always do a valve adjustment BEFORE doing a compression test!
Jerry

Check the points are they the same as the old ones that came out. I had a simmular problem were the new points from napa came in two pieces and a spring piece had to be clipped in with the points. If not clipped in correctly had the same popping and missing on acceleration.

[quote=JW51]Carl is probably on the right track. But for a potential easy win, recheck your firing order. 1-5-3-6-2-4 It’s pretty easy to get to fiddling with things and not realize you’ve swapped a couple wires. (Don’t ask me how I know)[/quote] I double checked the firing order and it is correct. Thanks.

It may have to go to a mechanic. It sounds like this is getting above my head and certainly beyond the time I have to tinker with it. [quote=Hotrod Lincoln]Do a power balance test and a cylinder leakdown test. You need to pinpoint the cause of the compression loss on cylinder #5. No amount of tuning or tinkering is going to compensate for a leaky or tight valve. Always do a valve adjustment BEFORE doing a compression test! Jerry [/quote]

Those are basic diagnostic procedures that every stovebolter needs to master. These old rigs were not intended to be maintenance-free for tens of thousands of miles like today's computerized "smart" vehicles that are made to be driven by dumbed-down owners. Estill Springs isn't that far from Dellrose- - - - -drop by some weekend and I'll be glad to walk you through a basic tuneup including a valve adjustment, carburetor adjustment, and a proper timing check with a delay-flash light. That tests ALL the advance functions, initial, centrifugal, and vacuum advance.
Jerry

You need to describe the trouble to us a little better if you can. Going down the road for a while then starts missing and some backfire is what I read.
I would suggest that timing does not run good then miss. A intermittent spark problem or a CARB problem OR BOTH are my thoughts. Can't tell which by the symptoms yet.

1. Does it start right up?
2. Does it take off and drive some?
3. Then it begins "missing" ?
4. When does it backfire? Acceleration or deceleration or ?
5. If you live anywhere near Jerry. Go there ASAP.
6. Any vacuum leaks?
7. Ignition switch OK, all ignition wires tight?
8. You don't have a compression problem. There are inaccuracies in that test if not done carefully and cylinders are within 10% of each other anyway.
9. LOTS OF BAD new points and condensers being sold. Try NAPA next time.
10. You "set the timing again". Please explain carefully to us how you are doing that. What is your total procedure?

This past summer my friends (ah) 1963 Ford Unibody truck with a 223 6 cylinder was doing exactly what you describe. I checked timing, carb, points, compression, spark, coil, distributor cap. The condenser was causing the problem. It was popping out the exhaust and the carburetor. Rick

As bartamos mentioned in part #9 of his post above, lots of junk on the market. Try to find NOS for ignition parts when you can. This message approved by Hotrod Lincoln, bartamos and others. Paid for by................well, no one! :eeeek:

Take advantage of Hotrod Lincoln's invite to his empire. You will not regret it. Corny jokes and racy double entendres are at no extra charge. :D
You will, without a doubt, thank me later if you do. He is a peach and a wealth of knowledge. He is a great teacher of things mechanical.
Carl

The truck does start right up and idles good. When the truck is warmed up, you can shut it off and turn the key back on and hit the starter button and she fires up immediately. It will take off, but as soon as the truck is under a load (pulling itself), it begins to miss. I don't know if you would call it backfiring, but it does pop out the exhaust some on acceleration, not deceleration. I have not checked for vacuum. It could be bad points or condenser. How would I know without buying another set?

One other note...the spark plugs are sooty black, but are not wet. I also noticed that when I accelerate the truck in the shop, it blows an oily substance out of both exhaust. I have a place on the floor right below and behind each exhausts that looks like someone sprayed oil. Not thick, but enough to notice.


[quote=bartamos]You need to describe the trouble to us a little better if you can. Going down the road for a while then starts missing and some backfire is what I read.
I would suggest that timing does not run good then miss. A intermittent spark problem or a CARB problem OR BOTH are my thoughts. Can't tell which by the symptoms yet.

1. Does it start right up?
2. Does it take off and drive some?
3. Then it begins "missing" ?
4. When does it backfire? Acceleration or deceleration or ?
5. If you live anywhere near Jerry. Go there ASAP.
6. Any vacuum leaks?
7. Ignition switch OK, all ignition wires tight?
8. You don't have a compression problem. There are inaccuracies in that test if not done carefully and cylinders are within 10% of each other anyway.
9. LOTS OF BAD new points and condensers being sold. Try NAPA next time.
10. You "set the timing again". Please explain carefully to us how you are doing that. What is your total procedure?
[/quote]

Would love to drop by. Maybe I can venture out that way some Saturday. You're also welcome to stop in at my place if you're ever in my neck of the woods.



[quote=Hotrod Lincoln]Those are basic diagnostic procedures that every stovebolter needs to master. These old rigs were not intended to be maintenance-free for tens of thousands of miles like today's computerized "smart" vehicles that are made to be driven by dumbed-down owners. Estill Springs isn't that far from Dellrose- - - - -drop by some weekend and I'll be glad to walk you through a basic tuneup including a valve adjustment, carburetor adjustment, and a proper timing check with a delay-flash light. That tests ALL the advance functions, initial, centrifugal, and vacuum advance.
Jerry

[/quote]

"Both exhausts"???????? What other non-stock equipment does your truck have? Sometimes it helps to let us know what kind of "improvements" have been made to what was a pretty well-engineered vehicle when it rolled off the assembly line. We've got one long-term member here who still hasn't figured out that two carburetors is one too many! LOL! Jerry

Dual exhaust on a 6 banger? Awesome'ish.......

The oil spritz may or may not be related. Could be a plugged breather system maybe. Anyway it's kind of good news that it starts and runs good for a while. You can check points and condenser but easier and cheap to replace. So try new points and condenser. Next time it starts to miss, take off gas cap and see if it helps. Change all gas filters. Be sure gas hoses are new. What do you know about the fuel pump? Visually check all vacuum hoses, connections, plugs, gaskets. Move the hoses back and forth to discover any breaks you can't see. (it's kind of nice to do one thing, advised by members, at a time, so that you know what fixed it)

Any gas smell? or leaks? Any smoke? Blue? White? Gray? The exhaust can spit out condensation and carry some oil in that mix.
Tighten all exhaust manifold bolts and pipe flange bolts to specs.

I'm leaning towards a fuel delivery problem if motor does the exact same thing after new points and condenser.
What does temp gauge say after driving 15-20 minutes?

Yes, someone put dual exhausts on the six banger. Why, I don't know. I don't smell any gas or see any fuel leaks. One thing I think I might have done wrong when setting the timing was not unplugging the vacuum advance from the distributor. I'm going to go back tonight and reset the timing with the vacuum advance disconnected and plugged. I'm also going to check for any vacuum leaks. If that doesn't make any improvement, I'll try adjusting the valves. I'll keep you all posted. The temp gauge reads right around 185 after driving it a while.

I think you have a couple of things going on at the same time. You state that your plugs are sooty. So your motor will fire up and idle, but the soot on those plugs can really interfere with the plugs ability to provide an acceptable spark under load. The rub is that something is causing those plugs to be covered in soot. I would fire it up and check for vacuum leaks. Also, confirm that the diaphragm in the vacuum advance is not ruptured. Get a little piece of brake line and some rubber hose, install it into the vacuum advance (with the motor not running), and blow through the hose. If you can blow through the hose, the advance is shot and will need to be replaced. if you cant blow through the hose, try turning the distributor first and see if it springs back. If it does, apply some vacuum and see if the advance will move the distributor. If you cant get the vacuum advance to move the distributor, its either jammed or frozen and will need some tlc. Might be the source of the problem. If the vacuum advance is ok, I would check the point gap and then check the timing. the other thing that may be an issue, but will require a little bit of tearing apart, is whether the mechanical advance in the distributor is free and working. I just recently rebuilt a 2403 distributor where the spring for one of the advance weights broke off and jammed under the advance. That and rust froze the weights and so the advance was inoperative. You have to take the point plate off the distributor to check as the mechanical advance is under the plate. Next, I would remove the plugs and do a compression test. Spark plug wires would be next on my list to check. Clean the plugs on a plug cleaner, regap. All low hanging fruit but easy to check off the list. If still sooting up the plugs and running poorly, I would think your next move would be the carb. Give it an adjustment and see if that makes a difference. Just keep in mind that these original carbs are pretty old now, rebuilt by who knows how many different people, who knows how many times, with who knows what skill, on a carb with who knows how many miles. It may just be that your carb has reached the end of its serviceable life and needs something more then a basement rebuild (throttle shaft bushings, warped body, frozen power piston, bad ball checks and seats).

Btw, any chance the stuff out of the tail pipes is just sooty condensation?

He has done the points and he has done a compression test. Read his first post. All good info but he has already done some of the tests. Suggesting the same things over and over again may lead to frustration on his part and cause him to give up. Hang in there Darrell.

Thanks Dragsix. I'll try and answer your questions as best I can. I do still need to check for vacuum leaks. I have not done that yet. The vacuum advance is working fine on the distributor. Give the truck gas and the distributor advances. Let off and it goes back, so I don't think there's a problem there. I did a compression check already and most of the cylinders checked at 150. Cylinder 4 maxed out at 160 and cylinder 5 was a little weak at 135. The truck has new spark plug wires. I replaced them back in the spring when I put in new spark plugs, points, condenser, rotor button, and distributor cap.

Two things I have yet to do before checking the valves for needing adjustment. I think I need to reset the timing with the vacuum advance disconnected from the distributor and plugged and I need to check for vacuum leaks. I'm hopeful that one of these two actions will solve my problem. If not, then I will remove the valve cover and go through the process of adjusting the valves.





[quote=Dragsix]I think you have a couple of things going on at the same time. You state that your plugs are sooty. So your motor will fire up and idle, but the soot on those plugs can really interfere with the plugs ability to provide an acceptable spark under load. The rub is that something is causing those plugs to be covered in soot. I would fire it up and check for vacuum leaks. Also, confirm that the diaphragm in the vacuum advance is not ruptured. Get a little piece of brake line and some rubber hose, install it into the vacuum advance (with the motor not running), and blow through the hose. If you can blow through the hose, the advance is shot and will need to be replaced. if you cant blow through the hose, try turning the distributor first and see if it springs back. If it does, apply some vacuum and see if the advance will move the distributor. If you cant get the vacuum advance to move the distributor, its either jammed or frozen and will need some tlc. Might be the source of the problem. If the vacuum advance is ok, I would check the point gap and then check the timing. the other thing that may be an issue, but will require a little bit of tearing apart, is whether the mechanical advance in the distributor is free and working. I just recently rebuilt a 2403 distributor where the spring for one of the advance weights broke off and jammed under the advance. That and rust froze the weights and so the advance was inoperative. You have to take the point plate off the distributor to check as the mechanical advance is under the plate. Next, I would remove the plugs and do a compression test. Spark plug wires would be next on my list to check. Clean the plugs on a plug cleaner, regap. All low hanging fruit but easy to check off the list. If still sooting up the plugs and running poorly, I would think your next move would be the carb. Give it an adjustment and see if that makes a difference. Just keep in mind that these original carbs are pretty old now, rebuilt by who knows how many different people, who knows how many times, with who knows what skill, on a carb with who knows how many miles. It may just be that your carb has reached the end of its serviceable life and needs something more then a basement rebuild (throttle shaft bushings, warped body, frozen power piston, bad ball checks and seats).

Btw, any chance the stuff out of the tail pipes is just sooty condensation?[/quote]

I'm just thinking out loud and I still plan on doing the things mentioned above. Could my problem be a coil going bad? Would I be better off to put a new one on? They're not that expensive. Everything else electrical has been replaced with the exception of the distributor itself.

I just re-read this thread. You have new points. New points these days very often have some kind of substance on them which needs to be removed. You can do it with a clean piece of stiff paper or smooth cardboard (not corrugated box material). Just run a small piece back and forth between the points. The points spring will do all of the work for you, just move the paper back and forth. I have had to do this on so many new point sets that I do this every time I change points regardless. Carl

Thanks Carl. I'll give that a try. That would be an easy fix. Will probably be tomorrow night before I'm able to get to it.

Quick question for the group. I was reading in the engine section of the shop manual for the 1954 engine, which is what is in my truck, and it says that after you time it, you should adjust the octane selector on the distributor for the octane of gasoline that you are using. The manual says it should be set just so you get a slight ping from acceleration to wide open throttle. Anyone know what this should be set at for 87 octane non-ethanol fuel? I currently have it set at 0.

You're going to get s bunch of canned answers from people who have no idea about your particular situation, and they'll be worth the paper they're written on, so be sure to print them out. Have fun. Whenever you're ready to make that engine run right, get in touch. Bye for now! Jerry

The octane selector is from a time when you never knew what kind of gas you were really getting. So if you got a load of bad low octane gas, you could adjust the octane selector to retard the timing to compensate for the bad gas, or advance it if you got a load of higher octane gas. The selector plate itself limited the amount of adjustment you could make so you could never get too far astray. You also used it to compensate for altitude changes, more or less air. Even though its on your 54 distributor, and is on early 6 cylinder distributors up through 62/63, it is really engineering from an earlier time and not really used much these days.


If you look at the plate you will see "A" and "R" at either end of the plate with graduations on either side of a center hash mark. If you look closely at the distributor pad on the block (you may have to wipe off a little crud), you will see a hash mark on the pad. Line up the center hash mark on the selector plate with the hash mark on the block distributor pad and tighten down the bolt. Pull the spark plugs and bring the motor up to No. 1 compression stroke (thumb over the spark plug hole works just fine). When you feel the compression starting to come up you want to either turn the flywheel by hand or use the fan belt to turn the motor creeping up until the timing mark on the flywheel and the pointer on the bell housing line up. Put your plugs back in. Trace the no. 1 wire to the distributor cap and put a vertical chalk mark on the body of the distributor directly under the No. 1 spark plug wire tower. Remove the cap. If the rotor is not pointing at your chalk mark, loosen the screw on the clamp (not the bolt on the octane selector plate) and turn the distributer until the rotor is pointing at your chalk mark. Put the cap back on. You are pretty close if not exactly on TDC. Now start the motor and check the timing with a timing light and make whatever adjustments, if any, you need.


Yes, burnish the points as noted above and double check the point clearance. I don't always remember to burnish them myself all the time but I should.

I made some significant headway on the truck tonight. I went through the procedure of setting the timing again according to Dragsix's instructions. (Thanks Dragsix for the detailed instructions). I also burnished the points with a thick piece of clean paper. I also took each spark plug out and cleaned them with a wire brush. The black soot just brushed right away and the spark plugs looked brand new again. I rechecked the gap on each one to make sure they were correct. I put the dwell meter back on the truck and the dwell was set right to 39, which I've read is where it should be. The last thing I did was set the idling to 500 and adjusted the fuel/air mixture screw on the carb to where the truck idled the best. I took it out for a spin and it was better, but it was still missing and coughing quite a bit. I brought it back in and loosened the distributor and turned it just a hair and tightened her back down. Took her back out and she ran much better. I still have a slight miss at high rpm, but the coughing and heavy missing is gone. The popping through the exhaust is also gone. I think if I could find that sweet spot on the distributor with the timing, it would make her sing like a sewing machine. I'm almost afraid to tamper with it anymore, but I probably will try to adjust it just a little more to try and get that miss out at high rpm. Thanks everyone for the help.

Setting the timing by "ear" is a tried and true method many use. Without going back and reading the entire thread I'll offer this. With your timing set as it is now, take the truck out and find a hill or incline. In high gear at the speed limit listen carefully as you climb the incline. What your listening for is the valves tapping. If they aren't tapping you need to slightly adjust the dist a little more advanced then try again. You want to adjust the timing to where the valves "barely" tap under the load of climbing the incline. Once set shut down and try to restart, if it's hard to turn over, i.e. drags etc, you may have it alittle too advanced. It should turn over smoothly. IF it corrects the problems, take your timing light and see how far advanced it is at idle and record it for future use.... Good luck Dave

Excellent. Remember, loosen the screw on the distributor to make your timing adjustments. Leave the octane selector plate set with the center hash marks aligned. Next I would think a valve adjustment. If the motor is still not right under load, Then you will have to think about a refresh on the carb.

Do

The

Valve

Adjustment

First!

Do people build the roof of a house and then jack it up to build the walls under it?



Jerry