Topic: Premium gasoline
in Forum: C3 Engines
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I have a 1970 Vette LT-1 with 15:1 compression. The previous owner used premium gas with no lead additives and it seems to run fine. Someone just told me this could damage the engine. Is this true? Thanks Rich
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Bladenboro, NC - USA
Joined: 1/22/2006
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Vette(s): 1972 conv., sunfire yellow, blk interior, blk vinyl and convertible top. Off frame restoration with American Speed 383 stroker engine producing 500hp plus a 200hp NOS system. MSD ignition. Hooker super competition headers with chambered exhaust.
Rich, are you sure your compression ratio is 15:1? If I remember correctly the 70 LT1 had a compression ration of 11.0:1.
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
I can guarantee it won't run on premium fuel with 15:1 comp ratio...unless you happen to have 100 octane premium in your neighborhood!
Our '72 drag/street car had 13.5:1...it would barely even start on premium back then, and sounded like a diesel when it did!
I'm sure the above has to be a typo...
The '70 cars should be fine without the lead additives, tho it wouldn't hurt to run some in it every other tank or so. It will definitely need the premium fuel, unless you take some of the timing out, to keep it from "pinging"...
Our '72 drag/street car had 13.5:1...it would barely even start on premium back then, and sounded like a diesel when it did!
I'm sure the above has to be a typo...
The '70 cars should be fine without the lead additives, tho it wouldn't hurt to run some in it every other tank or so. It will definitely need the premium fuel, unless you take some of the timing out, to keep it from "pinging"...
Joel Adams
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Lifetime MemberManteca, CA - USA
Joined: 11/20/2005
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Vette(s): 1978,two tone,Metalic Rootbeer & gold
1975 L48 4 speed
Yeah ! Compression RULES .
I'd like alot more than what I've got 
.
I'd like alot more than what I've got .Jimmy B.
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Leavenworth, KS - USA
Joined: 1/24/2007
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Vette(s): MM Red 1971 T-top,LS5,4-speed, black leather C5 seats, Hooker sidepipes.
Previous: 64 Coupe, 65 Roadster L76 / N14
Richard, You sure it ain't a ROCKET??? 
15:1 sounds out of this world. If it were possible, and true, I'd sure do somethin' about that, 'cause you could never drive the beast.
15:1 sounds out of this world. If it were possible, and true, I'd sure do somethin' about that, 'cause you could never drive the beast.
I agree -- must be a typo. I run mine on premium (specs for an LS5 says it is 8.5:1), but I feel confident I could run on regular, or a mix. But, hey, it's only money! 
Sorry, brain burp. Yes, it's 11:1 Thanks
I have a 1969 427 .060 over and I use regular gas. Refuse to spend any more $$ than I Have to. It hasn't blown up yet. I think my compression is 9.25.
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Lifetime MemberIrving, TX - USA
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Vette(s): #1 -1969 Corvette Coupe Riverside Gold, black interior,MN,A/C,350/350,PS,PB,window cranks.
#2 -2000 C5, black/black, 6 sp, Bose system & lots of buttons.
I've got the old 350/350 in my '69 and I use the Premium and a lead additive, but I don't know what the comp ratio for that is, hhhuuuummmmm............!
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Yours should be 11.0:1 also...
Joel Adams
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in Forum: C3 Engines
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