Ok. so I had a new exhaust system installed, and added an eclectic fuel pump, existing fuel pump still inline and functioning. Went on a test run it was wonderful, Quiet, great power, could hear all the inside rattles ( another project ). Got back, big ass smile on my face. Shut the ignition off, and all hell broke loose. Engine loping along and backfiring like crazy. Turned the ignition on and off several times and it finally shut off. P30, 454, carbureted.

Where should I start the trouble shooting process? Thanks

Run on requires hot engine, plenty of air/fuel mix to keep on running.

#1 thing to try: adjust idle speed as low as possible. Less likely to run on. Also, try shutting off in drive to load it down a bit. (Keep foot on brakes, don't forget to put it in park when done)

The problem you have is also referred to ad "Dieseling" in a spark combustion or gasoline engine. Your octane rating is to low. Octane rating is the capacity for the fuel NOT to burn under high compression. The higher the octane rating the better the fuel will withstand compression ignition. Old fuel will also have little of no octane.

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I suggest trying premium fuel with a higher octane rating. Look also for a fuel without alcohol in it.

Run-on is rare; it used to be caused by combustion chamber deposits from leaded fuel retaining enough heat to ignite the fuel, so your prob;em is odd.

Changing gaso grade may help, but if the issue persists, shutting the engine of in gear usually cures the problem.

I may have caused this problem, I noticed the engine ran a bit smoother at a bit higher idle, so I set it up just a smidge!!!

So I took Steve VWs' advice, reset the idle as low as possible, actually no adjustment screw touching at all.

Took the same trip as yesterday, came back home, still smooth and quiet, no big ass smile though. Backed it in the driveway as before, put it in drive and shut it off, big ass smile returned!!

Thanks you all again!!!

With an eclectic fuel pump, shouldn't the fuel grade be irrelevant? I'd imagine the pump, being fond of diverse fuels, would be able to temper any of the cylinders' closed-mindedness.

Quinn, I hope you are right, in Iowa the state loves ethanol so a lower tax rate and normal regular is like $0.20 higher per gallon.

The P30 Chevy engineers once again need some age and experience. The rear fuel tank, installed by GM is centered in the vehicle right behind the differential, next to each side not more than 4 inches away run the exhaust pipes for about 3 or 4 foot. It is like a heater on each side. I put my hand on the tank after an hour or so run and it was actually kind of warm. I read some of todays gas can boil at around 140F, so any external fuel pump be it electric or manual pulls it to negative pressure...hello Vapor Lock!!

MY electric pump is in the rear so it does not have to evacuate as hard to get fuel as the engine pump did. I hope enough to stop my vapor lock problems. The electric pump also puts positive pressure on other hot spots in the fuel
line.

I am obviously not as funny as I think I am.

Don't worry Quinn.

It's so hard to get into a fuel pump's head to understand!

My electric fuel pump came with a humor detector, but I failed to install it....Oh well its Iowa!!

I'm still googling eclectic fuel pumps. and get only synonyms and non-fool related pimps.

Google "eclectic fool pimps"

Daaannnng! ggooogle gggggggooooooooooottiitt