Best type of Gas for C2 327/350

Asked by Oct 01, 2014 at 08:08 PM about the 1966 Chevrolet Corvette Coupe

Question type: General

Could you tell me what's the best type of gasoline to use in my C2? It has the original 327/350hp motor, about 70k miles, and I'm assuming valves and valve seats have not been altered. I'm guessing no ethanol and high octane. Anything else I should know?


16 Answers


If you can find ethanol free fuel add a can of 103 octane booster then you will have to add some lead substitute on every tank full. HTH

1 of 1 people found this helpful.

Thanks! Just curious - is the lead booster because I have the original valves and seats?



1 of 1 people found this helpful.

Again, thank you! One final question - I'm assuming that the motor has the original valves and seats because the previous owner said he hadn't changed either. It's possible that an even earlier owner did change out the valves and seats. Any way to easily find out if this was done? Any harm to the motor if I add octane and lead to my motor if by some strange chance the valves and seats were replaced?


No, there won't be any problem if used correctly. Lead additive can no longer be found in the States that is why it is called a substitute, it does not contain lead so you won't be adding lead, it is basically a top end lube made just for engines that still don't have the hardened valves and seats that are needed for unleaded gasoline. The only way to really find out if the valves have been done is to pull a head off and take it to a machine shop so they can check.

1 of 1 people found this helpful.

Perfect - thank you again!


Another way to check is to closely look at where the heads attach to the engine and see if there is paint on the gaskets. If it appears the heads have not been removed, chances are they have not. If the car has not been driven hardly at all in the past 30 years, you may be fine on the valves. It would not be a bad idea to have the heads gone over and new valve seats and valves put in. Longevity will cause normal deterioration and valve spring tension loss. Back when these engines were built, around 60 to 75 thousand miles was the limit before a tear down and rebuild. The engines of today can go over 150,000 to 200,000 if cared for right before tear down is required. The old valves will burn, and the seats will get scratches and holes in the seats and leak. If this has started, no additive will fix it.. You break a spring, It happens in the older engines, and you have a piston slapping a valve and all kinds of bad stuff happens. The old timers will remember those days. The cars in the late 40s and 50s, had a max of 50,000 miles on the engines. Normal tear down to rebuild was at 20 to 30,000 miles then. This took 5 years or more also.

1 of 1 people found this helpful.

Thanks! I'll check the head gaskets for signs paint. I have a little less than 70k on it. I've owned it for about 25 years, and have probably put 5k miles on it during all that time. The motor has seemed to run strong for all that time, so I haven't done any rebuild. Yet. ;-) Again, thank you!


If you can do a compression check. If the valves are good, you should have good compression. New oil and filters, high octane, and a can of octane booster either every fill up or every other one to coat the valves and valve seats. Enjoy, and drive it until it has to be towed. Enjoy your Corvette.

1 of 1 people found this helpful.

Sounds like a perfect plan to me - thank you!


Another bit of sage advice. The newer springs are stronger and the old engines may not hold them. If you consider a valve job, look at storing the old heads and getting new modern ones. A lot are available for your engine. New valves, guides, seats and springs. Even one that has been rebuilt and the bolts will hold the new springs will not be that expensive. Some people in my Corvette club just pulled the entire engine and dropped in a crate engine, keeping the old one. Like I said, enjoy. BTW, our first Corvette was a 1965 Nassau Blue Coupe with the 327/350 with 4 speed manual trans. Great engine. We traded it for the 69 Corvette because it had 50,000 miles on it. Yes I still kick my behind but living in So. Cal w/o A/C was a no-no. Now they make after market A/C units better that factory. Oh Well.

2 of 2 people found this helpful.

Gotta love sages and their advice - thanks! ;-) I think the plan now is to do a compression test and see where we are. Financially, don't think I could afford to drop a crate motor in and save the original motor. But these days, I'm guessing I'm only putting 200-400 miles a year on the car. My '66 White/Black 327/350 has A/C, leather, side pipes, knock offs. With a 3.36 rear it's not insanely quick but it's a lot of fun to take drives out in the country maybe 5-10 times a year.... I do have freon for the a/c, but even in its best days the ac never was stellar. But if the a/c is on and you stick your nose in the a/c vents, you can feel real cool air! ;-)


We had our 65 before I joined teh Marines. I got assigned to NAS Jacksonville FLa for school. In late August I was transferred to MCAS El Toro in So. Cal. My wife and I packed everything we had, and headed across the southern states w/o air conditioning. Talk about a hot ride. It was 110 in Needles Ca. at 2 AM when we arrived there. At 10 AM we took off across the Ca. dessert. That's why we wanted one with A/C.

1 of 1 people found this helpful.

Wow - makes perfect sense to me! Hope you made it across the dessert ok... ;-)


No, we both died. :-) Still married after 48 years. Still have the 69 Vette. If I can find it, I'll post what it looked like new. This is me and my wife leaving a motel in Lake Elsinore in 1972. Our Corvette Club took over teh entire large motel for the weekend. We did have fun in the sun.

Really sorry to hear about your deaths... ;-) Hope you're feeling better now. 48 years? Very cool. I guess at 38 years, my wife and I are still newlyweds.. And love the color of your 69. By far my favorite color.

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