Hello Everyone, I am a recent owner of a 1927 Dr. Coupe. My first model T and oldest car I have ever owned. It has been sitting up a long time but sometimes in the past it has been painted, new top with a repo seat cover and new whitewall tires. Other than that it is original as they come. I have been trying to learn how to maintain and get the car roadworthy. I am an aircraft mechanic by trade and understand instructions and procedures and consider myself a fairly good mechanic. I have looked at the rear end dope and it seems to be fresh without and signs of babbitt. Do not know if thrust washers have been replaced. Topped it off with 600 weight. Adjusted the bands, stops and goes like it should, I think. It seems to be a little shaky when you take off in first and reverse but shifts out smooth. One of my issues is the #3 sparkplug looks like its running lean, clean as new, the others are gray but the car does not smoke or seem to burn oil. Is this normal? I have tightened up the manifolds. It idles well but seems to be popping/missing at any other setting. I did get it out on the highway and I think something is wrong with the engine. I have put in new fuel without alcohol and pulled the bowl off and is getting good fuel flow, cleaned the coil box. They are plastic and I noticed where they are put together they have gaps at the bottom. The plugs are Champion X’s but the electrode is an angled piece instead of a wire. I have looked but cannot find anything like it on the internet. I probably have many more questions but if I can get her running correctly than I can move on from there. Thanks and if anyone knows someone in the Central to North Alabama region I sure would like to talk with them.
Try hour #3 coil in another position. If the misfire moves with the coil, your coil is at fault. Do a compression test. All cylinders should have nearly the same compression. If #3 is low that could be your problem. Maybe a sticking valve which closes at idle, but sticks open at high speed. Very unlikely to have poor fuel flow to only one cylinder because both #3 and #4 use the same manifold port. You could also have a problem with the timer. Clean up the timer and be sure that no wires are grounded at the timer or between the timer and the coil box.
Hope you find the problem soon
My quick test, is to lay a screw driver across the top of a good cylinder and bring it down to the head to get a good spark. Then do the some process on the weak cylinder.
You should see a big difference.
Then start working my way back to the timer.
You will find the problem.
If water is leaking into the #3 cylinder it would clean the top of the piston and the spark plug. That may be something you need to check. With the plug out look in and see if the top of the piston is clean.
I just pulled the plugs out after about 15 minute run. The #3 plug was like the others but I looked in the cylinder and looks like the intake valve was clean looking. What do yall think? Maybe a head gasket, the others were all black looking. Thanks
I'd do a compression test on all four cylinders, even if it wasn't misfiring.
I always do that on an antique, when I first buy them.
This will help ID a valve issue.
Do not forget to consider a vacuum leak. Tightening the manifold won't help if the manifold to block rings are bad; when I bought my '27, they were and so was the exhaust manifold. It ran quite similar to the way that you describe.
Steven: Dan Hatch here. I am in Trussville Al, near B'ham. I have parts and work on cars. Pm me if you want to. Dan
Thanks to everyone for help, Real Work is getting in the way of my fun work. I will try to be back on it next week and report back with progress.
Here's a page about your plugs: http://dauntlessgeezer.com/DG95.html