Help… engine skips after driving 30 minutes.

[jcsmith23]

I’m new to this site. My father just gave me his 40 Ford Coupe. He has had it over 40 years and never put it on the road. I have finished it and trying to work the kinks out of this fresh rebuilt flathead. After driving around for 20-30 minutes it wants to skip or something. Runs fine up to that point. Not running hot. It is 59AB block with offenhauser intake and heads. Bored 30 over with an Isky cam. Electric fuel pump and electronic ignition. Running 2 stromberg 97s rebuilt by uncle max. I have fuel pressure set on 2. Any ideas?

[Ggmac]

Nice car . Its a lot to go over . Possible wrong fuel cap , blocked exhaust , crap in the gas tank , loosing fuel volume or pressure, coil , etc . Lets start , your fuel filter doesn’t catch enough , the fuel pressure regulator has been known to not be precise. Have you actually checked the fuel pressure with a gauge ?
When you say miss , are there any circumstances where it doesnt miss ? Does it ever stall and not restart until cool ?
What temp does it run at ? Are the spark plugs wires on tightly, a good check is to open the hood and run the car at night with no flashlight and look at the motor , look for spark .
Are there any noises , hiss from the exhaust? If you remove and reinstall the gas cap doe it make any noise or difference in its running ?
Any white smoke out ofthe exhaust ? Have you retorqued the cyl heads ? Should do 3 hot - cold cycles retorquing after normal running temp , let cool then retorque . Do this 3 times .
Check plugs for water . Any loss of radiator coolant ?
Is it still 6 volt pos earth ? I see the unilite and coil but I dont know if the coil is 6 volt ? Could be any .

[petehoovie]

Originally Posted by jcsmith23

I’m new to this site. My father just gave me his 40 Ford Coupe. He has had it over 40 years and never put it on the road. I have finished it and trying to work the kinks out of this fresh rebuilt flathead. After driving around for 20-30 minutes it wants to skip or something. Runs fine up to that point. Not running hot. It is 59AB block with offenhauser intake and heads. Bored 30 over with an Isky cam. Electric fuel pump and electronic ignition. Running 2 stromberg 97s rebuilt by uncle max. I have fuel pressure set on 2. Any ideas?

[Ggmac]

Thanks Petehoovie , now I see the 12 volt battery !

[Ken/Alabama]

Could be ignition coil.

[jcsmith23]

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Thanks for replying. I know it’s like looking for a needle in a haystack. To answer what I know, it’s not losing anti-freeze. Not smoking. Runs about 170 degrees. I have not checked the fuel cap or fuel pressure with a gauge. Wires are tight. I haven’t noticed any hissing or noises from exhaust. It runs fine for about 20 to 30 minutes and then starts to act up. I don’t know if it’s skipping or not getting gas. Just frustrating trying to figure it out. I’ll check your other suggestions tomorrow. Thanks again!

[jcsmith23]

Ken, I wondered the same thing.

[petehoovie]

Tank venting - gas cap???

[JayChicago]

“Skipping” could be intermittent spark. Both coil and condenser will often work fine when cold, then fail when warm from operating. I would start by replacing the condenser. Don’t see it in your pics. Under the coil?

[tubman]

Originally Posted by JayChicago

“Skipping” could be intermittent spark. Both coil and condenser will often work fine when cold, then fail when warm from operating. I would start by replacing the condenser. Don’t see it in your pics. Under the coil?

He has electronic ignition. (Which can be flakier than points in many cases.)

It stll could be the coil, though.

[Zax40]

The style fuel pressure regulator you have installed are known to not keep a consistent pressure. That could be contributing to your issues.

What is the condition of your fuel tank? Has it been refurbished or replaced? It could be clogging the pickup with trash and killing the fuel supply after running a while if it is not clean inside.

[deuce lover]

Replace the Coil

[aussie merc]

from past experience i would change the coil and move it from the engine to the inner guard dont know where you are higher or lower states but im guessing it could be cooking the coil had very similar problems moved the coil and all good coil was that hot you couldn't touch it

[AnthonyG]

JC, welcome to the Ford Barn, very nice car! Not only old or in ur case rebuilt Ford Flatty’s but all carss issues! Some times things r obvious others you chase the gremlins & get overwhelmed. As said there are a few more several issues that could be ur problem. My suggestion when chasing gremlins is the same on all cars! To reduce stress & becoming overwhelmed make a check list of the potential issues provided & any u might have. Starting w the easiest ( in this case change the coil). If no make note & check off & move on. Having said that does the engine do the same if sitting in neutral idling after 30 min’s, increase the rpm & hold to see as well, if it happens while not under load If no probably means only happens under load. make note check off move on to the next easiest on the list probably fuel cap if no check off & move on. Continue w this process, it works 95% of the time & u know where u r in the process! Keep track, don’t randomly try things & you’ll get there without throwing wrenches around, lol!
BOL!!!

[FlatheadTed]

Add a ballast resistor to the coil .Ted

[jcsmith23]

Originally Posted by FlatheadTed

Add a ballast resistor to the coil .Ted

I have one installed.

[FlatheadTed]

try a Flame thrower coil ,with a BR ,

[TJ]

Those type of pressure regulators have been known to have problems. Take it off and see how it runs. I used one of those regulators once and I emphasize once. I switched to a Holley one and had no more problems.

[jcsmith23]

Thanks for all the input. I’ll try some of these suggestions this week starting with the coil. I’m pretty sure the gas cap is not vented. Not sure about the tank. I’ll have to ask dad about that. Been raining all weekend so I haven’t got it out. I’ll post when I get to the bottom of it.

[deuce lover]

Regarding the vented gas cap.Here is an original '40 gas cap,back side.You see the hole for the vent.There also might be a vent tube in the filler neck.