Compression Test

[Ccmano]

Originally Posted by jonszr1

does altitude make a difference in the readings ????

Yes it does! I lived in Denver for 5 years. There is 20% less air to compress at 6000ft where I lived. Power was down by the same amount. Very frustrating. I was getting compression readings in the 170's at the time.
H

[jonszr1]

Originally Posted by Ccmano

Yes it does! I lived in Denver for 5 years. There is 20% less air to compress at 6000ft where I lived. Power was down by the same amount. Very frustrating. I was getting compression readings in the 170's at the time.
H

thak you for the info i feel better now . i was thinking that at 180 at 4000 ft i might be ready for a rebuild . i was going to have my car tested for substance abuse.jk

[rkreigh]

air density definitely affects cyl pressure and power no doubt about it

dyno it up there and you'll be disappointed. come down at see level and let the beast BREATHE!

high altitude = LT5 asthma

[jonszr1]

thanx for the info . i do love going to the strip, but the best air density reading i have gotten is 1950 ft . drag times has an air correction calc. in the tools sec.. when i have used it i have found that the corrected time for my blk car has come down to 11.45 @123.56 mph .i dont know hhow accurate it is .i would love to go to the east coast where the air is -1000 ft alot .

[KILLSHOTS]

I know I'm opening a super old thread here, but it's still relevant. I've been considering the 400 mile '90 at a dealer in Anaheim, which has been previously discussed here in another thread. It tested with all 8 cylinders reading between 180 and 185 psi. Although the numbers are consistent, they seem low in comparison to some of the numbers I'm seeing here, and Anaheim is not exactly at high elevation. Should there be any concern? Could the lower compression readings simply be occurring because the engine isn't broken in? Thanks.

[XfireZ51]

Originally Posted by KILLSHOTS

I know I'm opening a super old thread here, but it's still relevant. I've been considering the 400 mile '90 at a dealer in Anaheim, which has been previously discussed here in another thread. It tested with all 8 cylinders reading between 180 and 185 psi. Although the numbers are consistent, they seem low in comparison to some of the numbers I'm seeing here, and Anaheim is not exactly at high elevation. Should there be any concern? Could the lower compression readings simply be occurring because the engine isn't broken in? Thanks.

I think the spec for the LT5 is in the 180 range and just as importantly how close the individual cylinder numbers are to one another. Some of the compression number is due to cam timing and how good it is and where its set.

[Ccmano]

Originally Posted by KILLSHOTS

I know I'm opening a super old thread here, but it's still relevant. I've been considering the 400 mile '90 at a dealer in Anaheim, which has been previously discussed here in another thread. It tested with all 8 cylinders reading between 180 and 185 psi. Although the numbers are consistent, they seem low in comparison to some of the numbers I'm seeing here, and Anaheim is not exactly at high elevation. Should there be any concern? Could the lower compression readings simply be occurring because the engine isn't broken in? Thanks.

In my opinion an LT5 at basically sea level should at least be at 200psi. I think you hit the nail on the head in that with 400 miles the rings simply haven’t had a chance to seat themselves yet. As long as they are all within 10% of each other I would not be concerned. Seems to me the car had other issues though. Nothing major. The price was pretty good for a 400 mile car. Good luck!
H

[KILLSHOTS]

Originally Posted by Ccmano

In my opinion an LT5 at basically sea level should at least be at 200psi. I think you hit the nail on the head in that with 400 miles the rings simply haven’t had a chance to seat themselves yet. As long as they are all within 10% of each other I would not be concerned. Seems to me the car had other issues though. Nothing major. The price was pretty good for a 400 mile car. Good luck!
H

Thanks! It does have other issues but the big one has been fixed and the others are workable due to the price.

[Vette73]

I think the ZR-1,has to be,one car that many people who have owned in the past,did not drive very much...

Many many examples of low mileage cars out there...

Sent from my LG-TP260 using ZR-1 Net Registry mobile app

[Ccmano]

Funny, I just looked in the FSM. Typical factory speak. They claim 150-200 psi with a 15% Cylinder to Cylinder variation tolerance. I suppose that gave them warranty leeway.
H