Former owner of my 59 F100 built the sbc. It runs great for the first 5 minutes then starts to sputter. Doesn't stall, but it does run rough. One thing I'm concerned about is he didn't put a vent in the gas tank. Is it possible it's creating a vacuum and starving for gas? That's the only thing I can think of. It also has a mechanical advance which I've never had before. Any other thoughts or confirmation of my suspicions? Stevie
It'd be real easy to check. Pull the gas cap off, drive it down the road and see what happens. If that makes you nervous, I guess you could just check and see if the gas cap is vented.
Sounds like a fuel delivery problem to me, possible you are creating a vacuum in fuel tank i would do what Larry T said before any thing else. How is the fuel line run close to headers or exhaust, vapor lock? If fuel is all good check into ignition... coil is old and overheating?
That's exactly what I was going to do tomorrow. Bought the truck in January and trailered it home. Just now getting all the changes done and driving it for the first time this spring. Still too damn cold!
Most likely the F-100 is rejecting the transplant, anti rejection drugs may help but who'll write the script? Check for a dirty gas tank or clogged filter maybe water in the fuel. A dirty tank and lines will turn the best carb into shit real quick.
I had a F-100 with a cleveland , started fine then turned to shit in a few minutes turned out to be a capacitor in the dissy.
Good stuff! But it's a 370hp runner with a mild cam. Try to build that cheap with a Y-Block. No apologies here...
Oh good. Maybe he could'a done that yesterday.... Now I'll wait until his report tomorrow before adding any once-removed probabilities.
If it has a brand new shiny gas cap I'd bet on it having a cap that isn't vented even though it may have been bought as a vented cap. I went through three new Stant vented caps on my 51 Merc before I got one that was actually vented. The first time I walked a mile to a gas station for gas and back. Either loosen the cap and try it or run it until it stops and take the cap off and see if you hear a big gush of air running into the filler neck along with the sides of the tank popping back out. Then if that doesn't do it go after the electrical end of it.
Update... it's not the gas cap. It appears that the cap is vented. Drove it with the gas cap off and still the same thing. On to the next thing... carb and electric choke.
Don't know if you said it was heat related or just time, but also check for cracks or pinholes in the pickup tube and fuel line before the pump that might be pulling air.
sounds like a carb problem...runs great when cold choke on rich, then stumbles on the warm side when choke should be open....either you have a sticky choke or you have a vacuum leak...could be a hose-gasket-or on the carb itself(throttle shaft?) is it mix'n the ratio right? adjusted properly.....timing isn't of is it?
Update... After the tuning and driving it a few times, the problems returned. Swapped the holley for an edelbrock that I had sitting on the bench, thing purrs like a kitten. Never had a holley before, don't think I will ever consider having one again.
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