I recently purchased a 1965 Corvette 327. It runs great, but when I shut it off, it runs on, sputters and then eventually will shut down. What causes this and what can I do to correct it?

Asked by Sep 07, 2015 at 01:11 PM about the 1965 Chevrolet Corvette Convertible Roadster

Question type: Maintenance & Repair

3 Answers

71,895

There's a couple of things that can cause the "dieseling" that you're experiencing. First, too low an octane fuel. These cars were designed to run on premium gasoline with an octane rating of 100 or higher. I'd suggest using a premium gasoline and a bottle of STP octane booster at every fill up. My '70 Pontiac Catalina used to do the same thing. That's how I cured it. Since your Corvette was made before 1971, unless the heads have been rebuilt, you'll need to run a lead substitute at every fill up as well. For around town, low speed driving, it's not as critical. But if you plan on doing any expressway driving, you'll need the lead substitute. Again, I always used STP Lead Substitute in my Catalina. An idle speed that's too high can cause dieseling, as well as an engine that's running to hot. But given the poor quality of today's gasoline and the lower octane available I bet a bottle of octane booster at every fill up will solve the problem. HTH. -Jim

23,815

Wow! What a car- yeah, what he said- but understand, you will have fuel problems trying to use pump grade modern gas, most of which has ethanol- and it could be that you might need to adjust or rebuild the carb- to cure the dieseling- sometimes an old carb will continue to drip even when the ignition is switched off- in short, everything must be perfect-

1 of 1 people found this helpful.
16,465

Not all gas stations in the U.S. of A. put in ethanal. Yes the older engines need work to run on todays available fuel. Correct on the old heads. The old leaded fuel protected the valves and valve seats from pitting. Unless you get new valves and valve seats, you run a chance of burning valves. Have the timing checked also and get the carb rebuilt and perhaps new jets. Better or hotter plugs may be called for along with a hotter coil. My 69 does this also, but I have high compression and am running dual quads. If you have a stick, leave it in gear and start to engage the clutch when you turn it off. That will stop the engine. If your cars has a slush box, leave it in gear, give it a little gas and turn it off. That will keep the engine from dieseling or running backwards. That should help for now. My first Corvette was a 1965 327. Really loved it but without A/C in So. Ca., we traded it in on the 69. Still have it.

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