Is compression too high for a S/C?
Thread Starter
Pro
Joined: Oct 2003
Posts: 550
Likes: 0
From: Hesperia California
Is compression too high for a S/C?
I have a recently rebuilt motor in my 89. The builder kicked my compression up to 10:1. He also put a little better cam in. This is a Calif. car and I needed it to pass smog which it sailed through.
My question is, is my compression too high for a Pro Charger or what ever? Would the stock exhaust be sufficent? My car is in great shape as everything that moves is new. I am already way upside down in the car as most of us are. Before I go through another fortune, I will move up to an LS1 or better.
Thanks for any input!
My question is, is my compression too high for a Pro Charger or what ever? Would the stock exhaust be sufficent? My car is in great shape as everything that moves is new. I am already way upside down in the car as most of us are. Before I go through another fortune, I will move up to an LS1 or better.
Thanks for any input!
Melting Slicks
Joined: May 2001
Posts: 3,014
Likes: 18
From: Raleigh, NC
The knee jerk reaction is yes, your compression is too high. However, the 10:1 you are referring to is called the static compression ratio, your dynamic compression ratio might be low enough to allow some boost. Your cam specs will have more effect on dynamic compression than most anything else, so if you can dig up the specs on your cam we might be able to help you further.
The easiest and cheapest thing to do if your compression is too high for a blower is to use nitrous. Nitrous is much more tolerant of compression, and as far as I know is emissions legal. Good luck!
The easiest and cheapest thing to do if your compression is too high for a blower is to use nitrous. Nitrous is much more tolerant of compression, and as far as I know is emissions legal. Good luck!
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Just my .02... I was concerned for the same reason, my '90 already was 10 & I used the thinner headgaskets when I did my valve job a few years back. Then a deal on the SC came alone & I did it anyway. Seems to run just fine. Stock cam here though so as the said above, may effect yours.
Burning Brakes
Joined: Apr 2005
Posts: 1,110
Likes: 0
From: JUPITER FLORIDA
I talked to greg from blower works asking him about supercharging a 10-1 comp engine and he said it would be ok if you only did about 6-7 lbs of boost with an intercooler.
I have that kind of compression and I plan on doing it. Of course im going to research some more to be absolutely safe.
I have that kind of compression and I plan on doing it. Of course im going to research some more to be absolutely safe.
Melting Slicks
Joined: May 2004
Posts: 2,856
Likes: 187
From: Earth
I forget what year, think it was in 2000ish I called Procharger and started getting a bunch of info. on it. Towards the end of the year they sent info on the price and that it was going to go up. I called LPE and unfort. I was put on hold until I could talk to a certain person I wanted. Well after waiting I hung up (big mistake) and went and did it. My compression is 10.5:1 on my build sheet. Clearly I have different internals,etc then you so will make a difference. So I ordered and had it put on by a Procharger installer here in my town. Car ran great, got lots of attention from the whine ( miss that ) 1st and 2nd and into 3rd it just blew the tires off with ease! Never took it to the track cuz the clutch went. Long story shorter I wish I wouldn't have done it. I blew the head gasket between 3 and 5 cyl. and melted the head. Too much compresssion!? Bad tune? Don't know!! After selling it I called LPE again because I was having other problems and when I called LPE told me my compression was probally closer to 10.8:1 Make sure this is what you want to do!!!
I'm going Nitrous next year, Use it when I want it!!
I'm going Nitrous next year, Use it when I want it!!
Burning Brakes
Joined: Apr 2005
Posts: 1,110
Likes: 0
From: JUPITER FLORIDA
Originally Posted by Snakecharmer383
I forget what year, think it was in 2000ish I called Procharger and started getting a bunch of info. on it. Towards the end of the year they sent info on the price and that it was going to go up. I called LPE and unfort. I was put on hold until I could talk to a certain person I wanted. Well after waiting I hung up (big mistake) and went and did it. My compression is 10.5:1 on my build sheet. Clearly I have different internals,etc then you so will make a difference. So I ordered and had it put on by a Procharger installer here in my town. Car ran great, got lots of attention from the whine ( miss that ) 1st and 2nd and into 3rd it just blew the tires off with ease! Never took it to the track cuz the clutch went. Long story shorter I wish I wouldn't have done it. I blew the head gasket between 3 and 5 cyl. and melted the head. Too much compresssion!? Bad tune? Don't know!! After selling it I called LPE again because I was having other problems and when I called LPE told me my compression was probally closer to 10.8:1 Make sure this is what you want to do!!!
I'm going Nitrous next year, Use it when I want it!!
I'm going Nitrous next year, Use it when I want it!!
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Pro
Joined: Oct 2004
Posts: 745
Likes: 0
From: New Hyde Park Long Island New York
with the 10 to 1 compression and no more than 6lbs of boost and a gaseous intercooling from blowerworks and lets not forget about a proper dyno tune i think you should be fine. for a while i had a stock lt-1 with 10.4 to 1 ran in the low 12's with a generic tune and was fine till i wanted more. (you will... everyone does)
http://forums.corvetteforum.com/show....php?t=1546454
http://forums.corvetteforum.com/show....php?t=1546454
Melting Slicks
Joined: May 2004
Posts: 2,856
Likes: 187
From: Earth
Never heard any pinging or any noises. I was very **** about listening to the motor! I was boosting 6 also but was told you lose 2 through the intercooler which I also had. Don't know how true that is?
Car was def. making more power, I could really tell in 4th gear on a pull from lower rpm's.
Car was def. making more power, I could really tell in 4th gear on a pull from lower rpm's.
Safety Car
Joined: Apr 2001
Posts: 3,525
Likes: 2
From: Houston TX
I ran 11.2:1 and 8 psi for several years. If the tune is on it will last. If the tune is off, then the hish s.c.r. will just exacerbate the issues.
Calculate the E.C.R. and keep it down in the 16.5 range, and you should be fine.
Aaron
Calculate the E.C.R. and keep it down in the 16.5 range, and you should be fine.
Aaron