Fuel or Electrical Problem

I have a 67 Firebird with a factory 400 engine. I changed out the 4 bbl for a 66 GTO tripower and also an Accel dual point distributor. The car ran great for a year but now I can drive it about 300 miles and it will start missing and eventually just die. It will not restart until the engine cools down. I have replaced the fuel filter, fuel pump (AC/Delco), gas tank, sending unit, coil, distributor cap, condensors and plug wires. I have had it to several different shops and they cannot pinpoint the cause of the problem although they do duplicate the problem. Any suggestions?????????????????
Thanks:frown:

While the engine is hot and won't start, does it "arc" a spark from the wire to ground?

Is your Accell distributor electronic in nature (no mention of the type of trigger)? If so, the module could be bad. We see this a lot in older HEI distributors.

It most certainly does NOT sound like a fuel issue. If it were an electronic injection system, I wouldn't be as sure.

Jim

The distributor is a dual point distributor. As you know, the issue is either fuel or spark related. Some of the mechanics say it is related to the electrical because when it gets hot, something is breaking down. Other mechanics say that we are losing sufficient fuel pressure to the center carb. Changing the fuel pump did not fix the problem so we are just getting frustrated. The car is in the shop as we speak and the techs working on it say it is fuel related!!! I will listen to any suggestion as this point.
Thanks
runaround

do you smell gas right about it die on you???........ something like that was wrong on a 74 grand prix my grandmother passed on to me, it used to be my uncles' (RIP). long story short, it was the floater on the carburator. After running it for a while, the floater would get stuck and evantually die. So me and my uncle overhauled the carb. and VIOLA!!! ran like a top.

Therbs were rebuilt and it did not impact the problem. The car runs great and I can drive it on a trip of 100+ miles and not have a problem. To me it would seem that everything that could be a cause of the problem has been checked unless it is a resistance wire or something that breaks down after about 4 hours of driving. It would seem to me that the engine heat and heat in the compartment would reach the operating temperture on a 100 mile drive as much as a 400 mile drive. But who knows................?
Thank you for your idea.

Dual points rules out a module... Do you have an MSD box (or other like it)? What about the coil? Take a spare coil with you. When it fails, see if the new coil brings it back.

Maybe...

Jim

The engine failed last Saturday and Sunday morning we put on a new coil and distributor cap and it failed again Monday afternoon after driving approximatley 70 miles. This is one really tough problem to pinpoint!! We were told that the distributor checked out good so we are at a loss as to the exact cause of the problem. Thanks for your input.

Just a suggestion here --Are you sure the wires are in the correct positions on the coil itself? Sounds like the coil is heating up and shutting down and then when it cools it will refire and run til it heats up again. See if the wires are reversed from the coil to the dist. and from coil to power. Negative from coil to dist. if I remember correctly -its been awhile since I've seen point and coil ignitions.

Thank you for your suggestion. I know that we changed out the coil but I am sure that we just connected the wires the same way as they were. The shop where the car is feels that the problem is FUEL as they put a gas tank the same height as the one on the Firebird and ran a seperate gas line from there to the fuel pump and they once again found that the fuel pump pressure dropped to less then 2lbs once the engine ran for a long time.
Just to cover all bases, I am having them change out the dual point distributor for a new electronic distributor that looks like the stock distributor. We are heading to Biloxi this Friday to pick up the car and drive it back to GA, hope we make it without any car troubles.

Again, thank you.:)

I'd bet on the ballast resistor. Not many people remember or know that the old points distributors used a ballast resistor in the wiring going to it.
If they put in an electronic distributor make sure they remove the ballast resistor or you'll end up with another no start problem.

you keep hitting on fuel and this has reminded me of a fuel problem alot of old timers had and i found out about myself the hard way....kind of a vapor lock. the fuel lines heat up a bit making the fuel in them vapor, and pressure drops and car dies until it cools down. try clipping some WOOD clothes pins to the fuel line and see if that helps. main reason i am suggesting this is all other electrical items seem to check out or have been replaced, and still having problem after new tank and all going into it.....is a bit of a long shot, but worth looking into.....also, keep this in mind in the winter time and see if it doesn't act up at all during cooler months.