Compression Question
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 29
Likes: 40
From: Vineland, NJ
Compression Question
Looking to possibly buy a 1970 Corvette L-46 which runs 11:1 compression. If the engine is stock can i run on regular or premium gas at the pumps? Again stock engine specs. Anyone feedback from owners who use this car for a driver would love to hear from you. Thank you!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
You can probably run it on premium pump gas, but you might have to retard the timing a bit to keep it from 'pinging'. 10.5:1 is about as high as you can go on today's premium, if you still have iron heads. But the L-46 engine is worth getting...even if you can use it as intended very often. 
(I'm told that a little AV gas does wonders!)
(I'm told that a little AV gas does wonders!)
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
The 11:1 compression ratio is advertised compression. You can only get to that comp ratio at minimum allowable chamber volume and a truly "blueprinted" engine. The actual production compression ratios were a full point lower than advertised, which means that your actual ratio is about 10:1 (unless someone has actually milled the heads down to minimum chamber volume). You can run 10:1 on premium pump gas with a reasonable timing advance curve (not too aggressive or quick). This "advertised" versus "actual" spec difference is the reason that the guys running in the "stock" drag classes in 1970 had to do a significant amount of machine work and tuning to bring the cars up to their "stock" specs and true performance potential.
Lars
Lars
Last edited by lars; Sep 30, 2018 at 12:35 AM.
Le Mans Master
Joined: Mar 2004
Posts: 7,458
Likes: 1,484
From: Little Rock AR
From my experience with a "close" to factory L-46 configuration you will be good on 93 octane. Only difference for mine is an aftermarket iron head with modern design chambers and built with a tight quench so your results may vary a bit. A true, burette measured 10.4:1 compression ratio with performance ignition curve. The L-46 is not a drag strip beast but it is a solid reliable easy to live with performance street engine. No ping on 93. Never tried but it might even run on lawn mower gas. 
The solid lifter LT-1 would require some ignition timing reduction to do the same on pump gas.
The solid lifter LT-1 would require some ignition timing reduction to do the same on pump gas.
