WOW my 93Z have 300 psi
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Registered User
Joined: Mar 2002
Posts: 54
WOW my 93Z have 300 psi
I just check all the cyl and all were from 290 to 302 psi. I was no sure how much psi the stock engine have and read in some post here the stock compression in 220 psi I think the last owner up the compression ratio to 12.5 to 1 or more I only use 95 oct.gas the car only have the h&n Cai.
I make this chek because the car overheat a lot and I need to used the fan on allways to be under 200 deg.
how can l know what CR have my car now.
I make this chek because the car overheat a lot and I need to used the fan on allways to be under 200 deg.
how can l know what CR have my car now.
Registered User
Joined: May 2003
Posts: 2,275
The stock compression ratio is 10.4:1. That gives you about 150 PSI. I think you're reading the wrong scale on your gage.
Never heard of a compression problem causing overheating. What have you looked at in the cooling system? What are your symptoms of your overheating problem?
Never heard of a compression problem causing overheating. What have you looked at in the cooling system? What are your symptoms of your overheating problem?
Registered User
Joined: Oct 2000
Posts: 2,915
From: Sacramento
Originally posted by robvas
Compression ratio shouldn't matter when you're compression testing, right? You're just checking the seal of the cylinders I think.
Compression ratio shouldn't matter when you're compression testing, right? You're just checking the seal of the cylinders I think.
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Joined: Dec 2003
Posts: 45
From: San Diego, CA
cam, airfilter, battery, and such can affect PSI
(high lift cam, small overlap, long dur. == higher PSI)
(low lift cam, large overlap (ones that idle cool), short dur = lower psi)
my 11.5:1 LT4 is 265-270psi
my 10:1 1968 350 is 190-193psi
my neighbors Z06 is 210-214psi
my firends 454ci is 210-250 (big difference between cylinders - needs a rebuild)
battery level can affect it also, along with only removing one plug at a time, or all of them
my tests were done w/ all plugs removed, and a battery charger hooked up
(high lift cam, small overlap, long dur. == higher PSI)
(low lift cam, large overlap (ones that idle cool), short dur = lower psi)
my 11.5:1 LT4 is 265-270psi
my 10:1 1968 350 is 190-193psi
my neighbors Z06 is 210-214psi
my firends 454ci is 210-250 (big difference between cylinders - needs a rebuild)
battery level can affect it also, along with only removing one plug at a time, or all of them
my tests were done w/ all plugs removed, and a battery charger hooked up
Thread Starter
Registered User
Joined: Mar 2002
Posts: 54
my tests were done w/ all plugs removed and the battery have 13.8 Volt. I made the same test in my 3000 VR4 and the stock comp is 180 psi and have 8 to 1 CR. when l do the test all the cly were close to 179 to 183 psi in all cyl. Bot cars have close to 30.000 miles.
I dont belive 150 psi is the stock pressure for the Z28 V8 350 CI.
I have search the forum and find somes stock lt1 in 200 220 psi. and there are a lot in the 150 psi too.
Like chad_g69 say something can affect to lower the resut.
and the plate have to be open 100% too.and warm but this is pain in the a**. to do.
I dont belive 150 psi is the stock pressure for the Z28 V8 350 CI.
I have search the forum and find somes stock lt1 in 200 220 psi. and there are a lot in the 150 psi too.
Like chad_g69 say something can affect to lower the resut.
and the plate have to be open 100% too.and warm but this is pain in the a**. to do.
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