Compression - Is 11:1 too much?
Burning Brakes
Joined: Jul 2015
Posts: 823
Likes: 57
From: Austin TX
Is that due to the ability of aluminum to carry heat away from the combustion chamber faster? Or is it a mechanical design difference relative to older cast iron heads (quench area or something)?
Burning Brakes
Joined: Feb 2014
Posts: 1,045
Likes: 226
From: Cape Neddick Maine
2020 C3 of the Year Finalist - Modified
Its because of the aluminium's ability to dissipate the heat better. So in order to get an aluminium head to run efficiently you actually need to raise the compression ratio to build the heat. All this though is moot if you cant flow enough air through the runners which is important to sustain the VE of the engine. also most aluminium heads have more core shifting in them over iron heads. Which is again important to buy a quality casting.
So much more to this than just buying a bunch of brand name performance parts and putting something together expecting to make over 350 .fwhp.
I've seen many people buy the latest and greatest parts expecting to have a street slayer only to have a slug.
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
Modern engines with reverse flow cooling systems can tolerate higher cylinder pressures because the heads get cooled first. But for our aging C3's I feel its best to limit the compression ratios to around 10 to 10.5 to 1 to avoid detonation. I'm running a 9.95 to 1 compression ratio in my 454" powered '71 and I can barely get by with 91 octane and 31 degrees of advance.
I can remember compression ratios as high as 13.5 to 1 in the late 60's muscle cars but that was when 102 octane gasoline was available but even then an octane booster was added for racing. Many folks used 115 octane aviation gasoline which was about 5 times the cost.
I can remember compression ratios as high as 13.5 to 1 in the late 60's muscle cars but that was when 102 octane gasoline was available but even then an octane booster was added for racing. Many folks used 115 octane aviation gasoline which was about 5 times the cost.
Burning Brakes
Joined: Jul 2015
Posts: 823
Likes: 57
From: Austin TX
So only people who agree with the majority can post? His experience in this case matches up with mine. Now maybe it's not 100% applicable being as this discussion seems to center on small blocks and aluminum heads. However, he was pretty careful to define the conditions. Does he really need to be reprimanded for that?
Drifting
Joined: Jan 2012
Posts: 1,908
Likes: 129
From: Fredericksburg Virginia
Another high-compression engine here.
350 with aluminum heads. High duration cam.
10.5:1 compression.
I run 93 octane and have been happy as a clam.
Occasionally, I'll be forced to put a 'lesser' 92 octane fuel in...Citgo/Wawa/Sheetz...I prefer to purchase from BP/Sunoco/Exxon/Shell and the like. I keep a bottle of Octane Booster handy and put in a half bottle just to make sure I'm good. I feel comfortable that I would be OK, but it's cheap insurance. I'd prefer keep this engine around for a while.
11.0:1 would be closer to the edge, but probably not over the limit with the right things done to the engine.
350 with aluminum heads. High duration cam.
10.5:1 compression.
I run 93 octane and have been happy as a clam.
Occasionally, I'll be forced to put a 'lesser' 92 octane fuel in...Citgo/Wawa/Sheetz...I prefer to purchase from BP/Sunoco/Exxon/Shell and the like. I keep a bottle of Octane Booster handy and put in a half bottle just to make sure I'm good. I feel comfortable that I would be OK, but it's cheap insurance. I'd prefer keep this engine around for a while.
11.0:1 would be closer to the edge, but probably not over the limit with the right things done to the engine.
Last edited by keithinspace; Dec 6, 2015 at 08:49 PM.
Burning Brakes
Joined: Feb 2014
Posts: 1,045
Likes: 226
From: Cape Neddick Maine
2020 C3 of the Year Finalist - Modified
So only people who agree with the majority can post? His experience in this case matches up with mine. Now maybe it's not 100% applicable being as this discussion seems to center on small blocks and aluminum heads. However, he was pretty careful to define the conditions. Does he really need to be reprimanded for that?
I am doing it with both BBC and SBC. Big deal for me right? The only point I'm trying to say is IT can be done I'm doing it and I'm not really smarter than everyone else. Its just careful consideration of parts and using todays better head designs that are superior in flow and design than earlier heads.
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Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
So only people who agree with the majority can post? His experience in this case matches up with mine. Now maybe it's not 100% applicable being as this discussion seems to center on small blocks and aluminum heads. However, he was pretty careful to define the conditions. Does he really need to be reprimanded for that?
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
Seems that toobroke's post was relevant to the question being asked. I also happen to agree with it his opinion. The OP was asking for opinions. He got them. Not all opinions are going to be exactly the same as our individual experiences are going to vary. I also notice you seem to be trolling everywhere he posts. I'm personally tired of seeing you troll toobroke for no apparent reason other than you just don't have anything else better to do.
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
The original question was is 11:1 compression too much. Many people here are running 11:1 or close in both big and small blocks with good results on pump fuel.
I am doing it with both BBC and SBC. Big deal for me right? The only point I'm trying to say is IT can be done I'm doing it and I'm not really smarter than everyone else. Its just careful consideration of parts and using todays better head designs that are superior in flow and design than earlier heads.
I am doing it with both BBC and SBC. Big deal for me right? The only point I'm trying to say is IT can be done I'm doing it and I'm not really smarter than everyone else. Its just careful consideration of parts and using todays better head designs that are superior in flow and design than earlier heads.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
Seems that toobroke's post was relevant to the question being asked. I also happen to agree with it his opinion. The OP was asking for opinions. He got them. Not all opinions are going to be exactly the same as our individual experiences are going to vary. I also notice you seem to be trolling everywhere he posts. I'm personally tired of seeing you troll toobroke for no apparent reason other than you just don't have anything else better to do.
Cute , you call what you just did what ?
And this in not about individual experiences it is a specific question being asked , no one needs to tell a story about there cast headed BB LMAO or there engine builders dumb statements
OP 11.1 on street gas is not only doable but done easily and often.
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
Cute , you call what you just did what ?
And this in not about individual experiences it is a specific question being asked , no one needs to tell a story about there cast headed BB LMAO or there engine builders dumb statements
OP 11.1 on street gas is not only doable but done easily and often.
And this in not about individual experiences it is a specific question being asked , no one needs to tell a story about there cast headed BB LMAO or there engine builders dumb statements
OP 11.1 on street gas is not only doable but done easily and often.
Last edited by SH-60B; Dec 7, 2015 at 09:22 AM.
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
Cute , you call what you just did what ?
And this in not about individual experiences it is a specific question being asked , no one needs to tell a story about there cast headed BB LMAO or there engine builders dumb statements
OP 11.1 on street gas is not only doable but done easily and often.
And this in not about individual experiences it is a specific question being asked , no one needs to tell a story about there cast headed BB LMAO or there engine builders dumb statements
OP 11.1 on street gas is not only doable but done easily and often.
:total:And a junior member, whom is void of the trolls doings,,, well,,, you know:-)
peace brother
don't feed the troll... 
Burning Brakes
Joined: Jul 2015
Posts: 823
Likes: 57
From: Austin TX
OP's first post: "Is anyone doing this?" You read that, right? Seems to me, individual experiences are exactly what he's asking for. I get that you think the responses aren't sufficiently relevant, but that's a judgement call. No reason to tell someone to shut up. Damn, I was hoping Vette forums wouldn't have so much of this egocentric crap.
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
Trolling is when you constantly follow someone and post everywhere they post. I just did it once. Did I call anyone names? Did I make any untrue accusations or untrue statements? NOPE. Therefore, not trolling...
Where in the rules of this forum does it say we can't talk about our own individual experiences? I do it all the time. Is this **** Germany? Do we need to relocate to exercise our First Amendment Rights?
Yeah I know, I have 11.3:1 in my 10 sec Firebird (street car), and I run on 93 octane and have well over 100 passes on the motor.
Yeah I know, I have 11.3:1 in my 10 sec Firebird (street car), and I run on 93 octane and have well over 100 passes on the motor.
Last edited by htown81vette; Dec 7, 2015 at 01:38 PM.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
If any relevant member of this forum thinks I follow any member around please post up.
And you other 2 are still crying because I pointed out your useless posts in a different thread that completely changed a topic on the OP .. LMAO get over it .
OP 11.1 is fine ,, No need to ask "My engine builder" and then post I have a 10 second firebird .. LMFAO ..
And you other 2 are still crying because I pointed out your useless posts in a different thread that completely changed a topic on the OP .. LMAO get over it .
OP 11.1 is fine ,, No need to ask "My engine builder" and then post I have a 10 second firebird .. LMFAO ..
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
If any relevant member of this forum thinks I follow any member around please post up.
And you other 2 are still crying because I pointed out your useless posts in a different thread that completely changed a topic on the OP .. LMAO get over it .
OP 11.1 is fine ,, No need to ask "My engine builder" and then post I have a 10 second firebird .. LMFAO ..
And you other 2 are still crying because I pointed out your useless posts in a different thread that completely changed a topic on the OP .. LMAO get over it .
OP 11.1 is fine ,, No need to ask "My engine builder" and then post I have a 10 second firebird .. LMFAO ..
If I had that 427 SBC it would be running 9's thats a fact.
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
And further, if you say 11:1 is fine without knowing the angle ABDC in which the intake valve closes (from the cam card), you are making a very dangerous blanket statement that could result is someone destroying their engine. OR you want everyone to be as slow as you? Ahhhhh....I get it now....
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
Speaking of irrelevant....anyone who has an SHP 427 and only runs 11's....or dreams to one day...that is truly sad. You do know that, at this day and age there are LS engines with mere bolt ons running those times don't you? I thought my car was slow...
If I had that 427 SBC it would be running 9's thats a fact.
If I had that 427 SBC it would be running 9's thats a fact.