Octane level for 1970
Drifting
Joined: Sep 1999
Posts: 1,970
Likes: 91
my 70 350hp would run best on aviation fuel after the first rebuild about 10 years ago. Rebuilt again last year and now it runs fine on premium.(sunoco ultra). Don't know what engine you have but I would put premium in it.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Originally Posted by TSAGG
Guys, If I have a 1970 that has NOT been re-built ever, am i OK on regular gas? Do i need a Re-build to run it on regular. If not, what Octane level is ideal?
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Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
100+ octane was available in 70.
on the high c/r engines. (MY=Model Year)
Actual C/R was lower than spec.
Originally Posted by jackson
Corvettes began dropping compression ratios with MY1971 ....
Actual C/R was lower than spec.
Thread Starter
Racer
Joined: Dec 2005
Posts: 492
Likes: 31
From: NJ
Originally Posted by Ganey
100+ octane was available in 70.
on the high c/r engines. (MY=Model Year)
Actual C/R was lower than spec.
on the high c/r engines. (MY=Model Year)
Actual C/R was lower than spec.
Thanks guys. i'll run it on the highest quality premium I can find. Its a base 350/300 SB 1970.
Safety Car
Joined: May 2003
Posts: 3,814
Likes: 105
From: Dearborn Heights Michigan
My 70 owners manual shows premium for all engine options , but, no octane rating. Says if engine knocks , use a higher octane (Duh!) I'm not sure, but, didn't 70's use leaded gas? I have been putting lead substitute in mine. Previous owner mixed leaded Av gas & unleaded regular. Have only had the car a short time, so would appreciate any info on leaded requirements?
Fred
Fred
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Don't bother with hardened valve seats. That was a myth perpetrated by the anti-unleaded contingent in the 70's. As the prior owner/operator of my own automotive machine shop, I never saw a single valve seat messed by unleaded fuel. Damaged valve seats were more commonly the result of Bubba getting his hands on valve grinding equipment.
Although I sold my machine shop, I still do valve jobs.... I have professional (SIOUX) equipment, and after nearly 40 years, I still have not seen any seats damaged by unleaded fuel.
Nothing wrong with having hardened seats if that tickles your fancy, but don't waste your money thinking it's required.
Although I sold my machine shop, I still do valve jobs.... I have professional (SIOUX) equipment, and after nearly 40 years, I still have not seen any seats damaged by unleaded fuel.
Nothing wrong with having hardened seats if that tickles your fancy, but don't waste your money thinking it's required.
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
Originally Posted by Fubba
When comparing the regular to premium, you're talking .20 cents a gallon difference. If you buy 15 gallons of gas, you're only paying $3 more a fill-up. It's worth the $3 to just not worry about it.
penny wise pound fuelish.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
This subject has been beating to death so may times the archive are probably choking on it.
1) No Corvette ever built NEEDS lead to avoid valve recession. The engine does not run hot enough. Period.
2) SOME Corvettes need high octane gas to avoid preignition/knock/pinging call it what you want. If your car needs it because of the foregoing reason, lead is one solution. There are others, choose your favourite
Here's the thing that seems too difficult for some to grasp:
3) If your car does not suffer from 2) above, putting high octane gas in your tank is just wasting money.
Go do some research if you don't believe it.
1) No Corvette ever built NEEDS lead to avoid valve recession. The engine does not run hot enough. Period.
2) SOME Corvettes need high octane gas to avoid preignition/knock/pinging call it what you want. If your car needs it because of the foregoing reason, lead is one solution. There are others, choose your favourite
Here's the thing that seems too difficult for some to grasp:
3) If your car does not suffer from 2) above, putting high octane gas in your tank is just wasting money.
Go do some research if you don't believe it.
Drifting
Joined: Sep 1999
Posts: 1,970
Likes: 91
Originally Posted by FKING1
My 70 owners manual shows premium for all engine options , but, no octane rating. Says if engine knocks , use a higher octane (Duh!) I'm not sure, but, didn't 70's use leaded gas? I have been putting lead substitute in mine. Previous owner mixed leaded Av gas & unleaded regular. Have only had the car a short time, so would appreciate any info on leaded requirements?
Fred
Fred
my 70 L-46 ran great av100(100 octane low lead). Use to pull right on the runway of the local airport and"fuel up".
The only other combo that worked as well was a fill up of sunoco ultra 93, plus a qt of real lead 2000. (lead supreme same) Car loved that as well.
Drifting
Joined: Dec 2004
Posts: 1,345
Likes: 3
If you have the 350-300, the 427-390, or 427-400 you will likely be OK with the current octane system ((R+M)/2) of 93. If you have a 350-350 or 427-435 and your engine is in new condition you will need to have at least a new rating of 96 to avoid knock. If your valves and or rings are a little tired you could get by with a 93 rating. You can also retard your ignition timing to reduce or eliminate knocking, but will loose power.
When octane ratings started falling I utilized Edelbrock Varijection water injection to run without heavy knock. I "burned" up to 10% water when operating in the city and as low as 2% if cruising on the highway. I ran that systm for over 100,000 miles.
Av Gas (100 LL (low lead)) also worked VERY well but was expensive.
The other way around knock, if your engine still has high compression, is to install a wilder cam with more overlap. This reduces the effective compression ratio. This is because VERY little compression starts to build until both valves are closed. The OE cams had relatively little overlap and had very effective high compression ratios.
When octane ratings started falling I utilized Edelbrock Varijection water injection to run without heavy knock. I "burned" up to 10% water when operating in the city and as low as 2% if cruising on the highway. I ran that systm for over 100,000 miles.
Av Gas (100 LL (low lead)) also worked VERY well but was expensive.
The other way around knock, if your engine still has high compression, is to install a wilder cam with more overlap. This reduces the effective compression ratio. This is because VERY little compression starts to build until both valves are closed. The OE cams had relatively little overlap and had very effective high compression ratios.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Originally Posted by grybdn
i believe the owners manual for my 71 350/270 says use super 93.
A 93 octane rating in 1971 is not the same as 93 octane rating from 2006. 93 rating today (I think) is barely 87-89 today.