csmc711

iTrader: (4)

Got a 98 camaro with 241 heads on it. That told me something funny was up, so, I wanted to do a compression check to see how worn the engine was, and, if something else was bad in her to warrant having to put heads on, amongst other things.

Now, I know good compression is good compression and I should be within 10% of highest cylinder and all that, but, I am new to the GEN III engines and would just like some feedback.

This is what I got assuming front drivers side is #1 (I forgot on chevy's...heh heh) and all were done dry (no oil squirted into the plug hole).

1) 171
3) 185
5) 154
7) 175

2) 160
4) 172
6) 164
8) 163

Anything look funny there besides #3 being very high and #5 being a wee bit low?

Thanks.

jebcamaro

iTrader: (28)

Don`t quote me, but it seems like I remember the cylinders need to be within 15 psi of each other.

csmc711

iTrader: (4)

Oooooh, well, that would not be good then...

gearheads78

iTrader: (29)

Was you throttle all the way open during the test?

csmc711

iTrader: (4)

Well, there are two things that might be going on.

1) I did not get a good enough seal on the preassure gauage/sparkplug hole. I have the king that has a long hose with a threaded end on it, so, it might have been leajking a litte as the only way to tighten it was to twist it.

2) I put my foot on the throttle and pushed it all the way to the floor. I know some like to stuff a screw driver into the trottle blades to keep it open.

I pulled the fuel pump fuse so no fuel should have gotten in, well, excessive fuel anyways.

I am not too concerned with TOP performance as this thing is going out the door it came in on, but, I am thinking the readings look good enough not to worry about a major failure somewhere???

ArcticZ28

iTrader: (14)

What does that have to do with the compression test?

Dave88z

To be accurate you should have the throttle wide open to ensure the cylinder has enough air. If air can't get past the throttle then the readings can be way off.

99blancoSS

iTrader: (115)

Your numbers look low and very uneven whicxh is not a good sign. I had about 180-185 on my 99 w/80k on it in all except for one wich had 60 psi. I'd re-check and make sure. Was the oil warm when you tested?
I'd be concerned about the one at 154, check and re-check it. Make sure you crank the motor the same amount for each cylinder. At least 4 cycles.

csmc711

iTrader: (4)

What would the low preaasure be indicitive of, if I had enough air coming in and the guage on tight? Would it just be worn rings? As long as it is nothing serious like a hole blown in the piston or sticking valves, I can live with that.

I did the test when it was stone cold, 75 degrees.

PREDATOR-Z

A leakdown test would determine that one (valves or rings)