max compression ratio???
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,308
Likes: 1
From: Portsmouth VA
max compression ratio???
any input as to the max compression ratio i can run in a bad butt 409 LT4 and still run pump gas??
i'm considering using Evans Coolant... it's the non-aqueous propylene glycol, any input about that?? it supposedly allows you to run higher compression without detonation... here's the link if anybody cares to look...
http://evanscooling.com/html/home1.htm
thanks!
sonny
i'm considering using Evans Coolant... it's the non-aqueous propylene glycol, any input about that?? it supposedly allows you to run higher compression without detonation... here's the link if anybody cares to look...
http://evanscooling.com/html/home1.htm
thanks!
sonny
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Re: max compression ratio??? (SonnyinVA)
A friend of mine ran about 12.5:1 in his 396 LT1 for a little while. There was no apparent knock but the computer could have been retarding his timing a little bit, we never got the chance to data log it.
12:1 is probably about as high as you would really want to go for the street. The reverse flow cooling of the LT1/LT4 helps a lot, but I still wouldn't try to take it much further.
12:1 is probably about as high as you would really want to go for the street. The reverse flow cooling of the LT1/LT4 helps a lot, but I still wouldn't try to take it much further.
Burning Brakes
Joined: Oct 2002
Posts: 1,152
Likes: 1
From: Wichita KS
Re: max compression ratio??? (tpi 421 vette)
I'm running 11.54 CR on a 355 CI motor, no knock counts yet while under load W/93 octane. :D
Keeping the deck height/quench to a bare minimum will help eliminate any chance of detonation W/ high comp. ratios. :)
Keeping the deck height/quench to a bare minimum will help eliminate any chance of detonation W/ high comp. ratios. :)
Instructor
Joined: Apr 2002
Posts: 105
Likes: 0
From: Charlotte NC
Re: max compression ratio??? (SonnyinVA)
My buddy Chuck Riddeck had a great writeup on his tests of the Evans system, and if I recall correctly, it worked pretty well.
FWIW, though it depends somewhat on the cam, you've got to take into account diminishing returns. IMO run ~11-11.5
FWIW, though it depends somewhat on the cam, you've got to take into account diminishing returns. IMO run ~11-11.5
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
Re: max compression ratio??? (tpi 421 vette)
Cam timing has alot to do with it, but to play it safe on pump gas, I would stay under 11.25:1 compression
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Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,308
Likes: 1
From: Portsmouth VA
Re: max compression ratio??? (GlockLT4)
why do you say diminishing returns? cuz you have to take out too much timing??
where is that write up about evans cooling systems??
thanks guys
where is that write up about evans cooling systems??
thanks guys
Instructor
Joined: Apr 2002
Posts: 105
Likes: 0
From: Charlotte NC
Re: max compression ratio??? (SonnyinVA)
Not only giving up timing for CR oftentimes, but pumping losses as well when you start to get that high.
I thought I had Chuck's writeup somewhere.. I'm tryin' to dig it up, it was pretty interesting :)
I thought I had Chuck's writeup somewhere.. I'm tryin' to dig it up, it was pretty interesting :)
Pro
Joined: Aug 2002
Posts: 702
Likes: 1
From: the corner of walk and dont walk
Re: max compression ratio??? (SkarodoM)
Camshaft choice will be a big factor in the amount of compression you will be able to run. Make sure you know your cam choice before ordering pistons/cylinder heads, and build your engine to compliment all the componants you want to use. A package designed to work together can be smaller than one that is mis-matched and give you much better results. You shoud be able to run well into the 12?-1 range without any troubles at all. I've done it with carburated street engines so a good management system should be even better! :cheers: