Octane level for 1970
Drifting
Joined: Dec 2004
Posts: 1,345
Likes: 3
Originally Posted by grybdn
i believe the owners manual for my 71 350/270 says use super 93.
Pro
Joined: Mar 2004
Posts: 640
Likes: 1
From: Mertztown Pa
My 350/300 always would ping on 93. It was the worst I ever heard. I tried taking it to two different shops and they could not fix it. I ended up mixing a few gallons of 100 octane leaded racing fuel to a tank. Took away all my pinging.
Race Director
Joined: Sep 2005
Posts: 18,640
Likes: 121
From: Farragut,TN
Your 71 had a lower static compresion ratio than the 70 did. my 69 has a static compression ratio of 10.25:1. I wouldn't run anything less than the highest octain that i could find. GM lowered the compression ratio in 71 on the engines to run on unleaded gas. but unleaded gas has been around since '68 when amoco came out with it.
Thread Starter
Racer
Joined: Dec 2005
Posts: 492
Likes: 31
From: NJ
Originally Posted by Carl Granquist
My '71 350/270 does okay on pump 87 regular. Of course, I've no clue what seat-of-the-pants high performance is 
Seems to be a couple schools of thought here on the subject. I'll try 94 for a tank or two and see how she likes it!
Pro
Joined: Apr 2005
Posts: 618
Likes: 0
Originally Posted by Mike Ward
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.
A little condescending, aren't we?
Despite a thread search being useful, I appreciate this thread. I've got a '70 350/350 and am getting ready to pull the motor and rebuild it. I'm all ears on this topic. The car pings now under hard accleration. I've got the carb and distributor out for rebuilds right now. That should eliminate them as contributors to the ping, once the timing is set, etc. After that, it will be finding the right gas and/or additive if necessary.
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Thread Starter
Racer
Joined: Dec 2005
Posts: 492
Likes: 31
From: NJ
Originally Posted by AirTrafficController
A little condescending, aren't we?
Despite a thread search being useful, I appreciate this thread. I've got a '70 350/350 and am getting ready to pull the motor and rebuild it. I'm all ears on this topic. The car pings now under hard accleration. I've got the carb and distributor out for rebuilds right now. That should eliminate them as contributors to the ping, once the timing is set, etc. After that, it will be finding the right gas and/or additive if necessary.
Despite a thread search being useful, I appreciate this thread. I've got a '70 350/350 and am getting ready to pull the motor and rebuild it. I'm all ears on this topic. The car pings now under hard accleration. I've got the carb and distributor out for rebuilds right now. That should eliminate them as contributors to the ping, once the timing is set, etc. After that, it will be finding the right gas and/or additive if necessary.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
[QUOTE=AirTrafficController]A little condescending, aren't we?
[QUOTE]
Possibly a little bit, but more just tired of seeing people responding to these threads and continuing to spread incorrect technical information.
Next time, I'll just add an
and mind my own business. 
[QUOTE]
Possibly a little bit, but more just tired of seeing people responding to these threads and continuing to spread incorrect technical information.
Next time, I'll just add an
and mind my own business.
Thread Starter
Racer
Joined: Dec 2005
Posts: 492
Likes: 31
From: NJ
[QUOTE=Mike Ward][QUOTE=AirTrafficController]A little condescending, aren't we?
Possibly a little bit, but more just tired of seeing people responding to these threads and continuing to spread incorrect technical information.
Next time, I'll just add an and mind my own business.
Like i said, if you're tired of the subject matter in a thread, move on. no need for wise remarks and "i'm with stupid" comments. I like the part where you said you would mind your own business.
Once again, thanks to all who have taken the time to comment on this thread.
Possibly a little bit, but more just tired of seeing people responding to these threads and continuing to spread incorrect technical information.
Next time, I'll just add an
and mind my own business.
Like i said, if you're tired of the subject matter in a thread, move on. no need for wise remarks and "i'm with stupid" comments. I like the part where you said you would mind your own business.
Once again, thanks to all who have taken the time to comment on this thread.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Originally Posted by TSAGG
Like i said, if you're tired of the subject matter in a thread, move on. no need for wise remarks and "i'm with stupid" comments. I like the part where you said you would mind your own business.
Once again, thanks to all who have taken the time to comment on this thread.
Once again, thanks to all who have taken the time to comment on this thread.
Have a great day!
Parrothead
Joined: May 2002
Posts: 48,231
Likes: 289
From: Margaritaville Embassy
St. Jude Donor '08-'09,'13, '14
the thing to do is run her at WOT. if she pings you need more octane. for 1970 the compression ratios were 10.25:1 for the 300hp 350 and the LS5 454. for the L48 and LT1 350s it was 11:1 it was 12.25:1 for the ls7 454. if you dont have the LS7 LT1 or L48, I think you will be fine with 89 octane. just keep an ear out for pinging.
Racer
Joined: Jan 2004
Posts: 292
Likes: 0
From: Thomasville Ga
My 71 is original 350/270 auto (200R4 now) I use regular always. Runs fine. No other probs. I agree there seems to be a lot of mis-information about this. There have been some very good threads with answers from seemingly very knowledgeable people (chemists? engineers?) that give a good rationale for using regular..in cars like mine, anyway..
Race Director
Joined: Sep 2005
Posts: 18,640
Likes: 121
From: Farragut,TN
Yes your 71 has a lower compression than the 70 it was desinged to run on regular. the earilly ones were designed to run on higher octaine gas. 9/1 will run fine on regular anything above won't.
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
Decompression
I purchased my '70 350/300 in 1998. At the time it showed 46.000 miles on the clock (!)- I bought it from a little ol' lady, and though it was a little tired, it didn't show signs of abuse. With 10 1/4:1 compression I was a little concerned about pinging so I put 92 octane swill (the best you can get here in the People's Republic of California) in it with octane booster. Without the booster it would ping, and that was regardless of where I put the timing. Eventually I pulled the motor just to see if it had 46,000 or 246,000 miles on it and it was very clean. I threw a 9:1 compression Summit kit at it, bored it +.030, put a slightly-bigger-than-stock Summit cam in it, had hard seats put in the heads......it worked great. The car now runs forever on 87 octane swill, gets 16 mpg on the freeway if I balloonfoot it, still gives a decent rush when I mash the pedal, and doesn't overheat even on 100 degree days. Yeah, I know, I butchered a numbers-matching motor, but I have yet to see any base-model '70s fetching 100+k on Barrett-Jackson. I bought it to drive it, I've put nearly 40,000 miles on it since the rebuild, and it still turns heads like no C5 or C6 I've seen.'Nuff said
Pro
Joined: Apr 2005
Posts: 618
Likes: 0
Originally Posted by birdsmith
I purchased my '70 350/300 in 1998. At the time it showed 46.000 miles on the clock (!)- I bought it from a little ol' lady, and though it was a little tired, it didn't show signs of abuse. With 10 1/4:1 compression I was a little concerned about pinging so I put 92 octane swill (the best you can get here in the People's Republic of California) in it with octane booster. Without the booster it would ping, and that was regardless of where I put the timing. Eventually I pulled the motor just to see if it had 46,000 or 246,000 miles on it and it was very clean. I threw a 9:1 compression Summit kit at it, bored it +.030, put a slightly-bigger-than-stock Summit cam in it, had hard seats put in the heads......it worked great. The car now runs forever on 87 octane swill, gets 16 mpg on the freeway if I balloonfoot it, still gives a decent rush when I mash the pedal, and doesn't overheat even on 100 degree days. Yeah, I know, I butchered a numbers-matching motor, but I have yet to see any base-model '70s fetching 100+k on Barrett-Jackson. I bought it to drive it, I've put nearly 40,000 miles on it since the rebuild, and it still turns heads like no C5 or C6 I've seen.'Nuff said
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