I have narrowed my C3 choices down to 2 specific cars, both original paint low mileage 4 speed convertibles. One, an original owner '70 454, the other a 2 owner '71 350. I know the lower compression '71 will be a bit more user friendly, so my question really is this- What is it like to live with a '70 LS5 in 2024? For those of you that have one, what are doing for fuel, what might I be not taking into account between these 2 choices?

Thanks for the insight!

 

The '70 LS-5 reportedly had 10.25:1 compression ratio. My '67 427 has the same compression. It's well tuned (not factory specs) and I have no problems driving it on premium unleaded at sea level.

I'd always choose the big block, but then, I'm a snob in that way. The torque of the 454 is amazing compared to the small block, but rear gearing will play a big role in comparing the performance of the two cars.

 

I had a ‘70 LS5, M20, 3.36 gear. It was a fabulous driving car. Endless locomotive torque from idle to redline. I highly recommend it. 😀

 

To answer your question, it was fuel sensitive but ran fine on 93. I can still hear that induction roar through the Rochester.

 

The best I can get around my area is 91 octane, my big block does fine.....small block or big block,always big block!!!!!!

 

 

I agree with previous posters. Get the big block for the constant amusement factor.

The engine will run fine on most pump gas that's available, and putting an "aftermarket" timing curve in the distributor will help (noticeably) with both summertime engine cooling and everyday fuel consumption.

 

If you don’t go for the LS5, please put me in touch with the seller.

 

It's not the compression thing (other than having to run higher octane fuel), but the cam in the motor that will cause it to have low rpm surging problems in stop of go traffic or not.

My take, but by the mid 70's after the oil embargo, the later C3's all came with the 350, and would try to find one of the early C3s that came with the factory big blocks isntead. Ones with the 427, or god forbid, the L88, going to cost an arm and leg, and so if you found one with OEM LS5 or LS6 454 that is not over priced, would go with it.

Hence the later C2's was the years that the vet went from a light weight racer, to pretty much a muscle car drag strip king with the big block motors. During the C3 years, car started as more of a muscle car than the later C2, then when the price of fuel went up around 73 after the fuel embargo, gas guessers were not long selling and everyone wanted a car with high MPG, and why the later C3 all got the 350's pretty much instead.
Note, was not until the C5 Z06 that the corvette returned to a balance handing machine with higher power output again.

Myself, would be looking for a C2 with 327 motor,since corner flicker like you would not believe since lighter, the 327 loves to rev fast with more then enough power, and if you get caught in the snow, the shaker rear end works very well for that as well.

 

40 years ago, I had a friend with a beautiful '65 C2 convertible. He loved going to the strip clubs, but wouldn't take his car there. Since I always had a clunker around, we would swap cars- He would take whatever I had, and give me the Corvette. Needless to say, I spent a lot of good times behind the wheel of that car.

I appreciate the comments on the big block, pretty much what I wanted to hear. I'll be going for the '70 LS5. Will post photos when I bring her home.

 

10.25 to 1 is not really high compression and does not require special premium fuel. Just keep the timing below maybe 34 degrees total. I would be more concerned about ethanol sitting in a carb bowl while sitting for weeks or months. If you have non-ethanol Rec90 available...use it. I choose to add 20% of 108 race fuel because I have rebuilt my 427 and like to run 36 to 38 degrees and listen to that bad boy smoking the tires...

 

1970 LS5 here and absolutely no issues with fuel from my local pumps.

I use 94 octane and have also used 91 octane on a couple of occasions with no ill-effect.

It's a beast of an engine. Good luck with the purchase.

 

C2's are kind of strange ducks, since early ones had the smaller motors to keep them light for road racing, then later 60's the craze hit for NHRA racing at the strips/streets, and the later C2's where getting the big block motors for those roles instead. When the C3 hit, really the big blocks the ticket for street cars that where going to the strips (dealers steering every one off the L88, since it was the road racers that want that motor/car), and by 73 after oil embargo, the most of the C3 where the 350 motors, since they got better gas mileage.

So for me, C2 with small block 327, and if going for a C3, then go big block all the way, with 427 the first choice (any of them), then 454 the second.
The 454 was more of a sup'd up truck motor that pulled harder off the bottom, while the 427 love to rev hard and fast all the way to red line instead .
Same for the 350, verse the 327 too.
Hence in a sports car for higher rev'g use, bigger is not always better, with the 327/427 the better motors over the 350/454.

 

If you do have fuel ping problems when timing and everything checks good , VP Racing sells a product called Madditive Octanium that can add up to 10 points in octane if needed , take it right up to 101 from 91 (if needed) and/or you can mix only the amount you actually need like if you needed 96 octane you don't have to mix it full strength , they sell it with lead and unleaded if you have catalytic converters