Bent P'rods and compression test.
 

About a year ago I did the dreaded 3-2 misshift at about 80mph. Bent 4 p'rods. Well my mechanic replaced the p'rods and everything seemed fine. Well it doesn't feel like it's pulling like it used to (before the 3-2 miss) so I look through some of my crap and find the results of his compression test. They are as follows

#1 135
#2 130
#3 135
#4 135
#5 130
#6 140
#7 135
#8 130

Did some searching and it looks like this is way to low for a stock internal LS1 (99). Do I have slightly bent valves? Mods are in my sig if they would have any bearing on this. As always, thanks.

From a balance perspective that's not bad. A leak down test will better tell if you have bent valves but chances are you do not. Have you had the tune checked?

All those values are on par with each other, I doubt anything is broken. Try a leak down test and see how much air is actually leaking. I doubt there is much leakage at all there and if there is it will likely be from worn rings since all the cylinders are putting out the same compression numbers. Rings tend to wear together compared to other parts that bend and such.

The car was just tuned in September, that is where I got the numbers in my sig. I don't think the rings are worn out the car only has 39,000 miles.

When I did the search I was seeing others post up with PSI ratings around 180, should the PSI not be higher or is the consistency what matters? Can someone explain that a little for me?

Your consistency between cylinders is what really matters. At 39k miles you should be just fine, i wouldnt even bother with the leak down test in that case.

Thanks for you help Brad.

Aren't I losing some air somewhere here or am I just being paranoid? I coudn't have slightly bent all the valves that close lol and the rings aren't the problem considering the low milage. Am I just worrying for no reason?

One other thing I was reading, if he did the test when the motor was cold it could show lower numbers right? The metal hadn't expanded yet?

Oh yeah if it was a cold test then the numbers will be lower. You are supposed to do the test warm.

You are worrying for no reason IMO.

Wow those numbers are low... I did a compression test on my 99, also with 39K miles (the day before the pedestal fiasco that trashed my engine) and the engine was cold, it sat overnight, and I did not crack the throttle blade, and I got 175-180 across the board. Could your altitude affect things like that? I remember when I lived in Denver for a few months I couldn't breath and my car ran like balls.

Battery strength, ect. a lot of factors affect it. Get it dynoed. See if she still puts down 325ish.

The car was dyno'ed after the p'rods were replaced and the compression test was done. So it is making the 325 rwhp N/A. I wish I could find the damn dyno graph, I think I lost it.

As far as the altitude causing the lower numbers anyone else have thoughts on this? I know when I bought the car in Iowa and drove it home it would blow the tires off the car, no where near the power once I got it home.

Ummm....think altitude plays any part there? :judge:

I'm sure it does! lol But how much. I think I'm probably making something out of nothing.

The altitude makes a HUUUUUUGE difference, my car was an absolute MONSTER at sea level, in Denver, not so much.

I know what you mean man. So most likely the compression numbers are lower because of the altitude it sounds like.

Feels like I have to make 500 rwhp to get where it feels stock at sea level! lol

That is a LARGE reason why I chose not to transfer to Denver :lol: