So i just did a compression test with motor warm/hot
220-240-230-240

now i have 9:1 cp pistons, zex stage 3 cams, rev hard valves, isky valve springs/retainers, 3 angle valve job, PnP head

i believe i have a blown headgasket as sometimes when i start up a puff of smoke comes out. I am losing little coolant somewhere. I smell it on start up.

anyways i was wondering if those numbers are remotely right. when ih ad a 10:1 compression i only had about 210-220 compression. How am i getting such a higher compression numbers with a lower compression set up? with 240 i would think i have a high 10 ratio.

what do you guys have?

 

i get 180-185 with my 8.8:1 motor

there will be a small variance across different compression testers

 

185 across the board cp 9:1 and supertech flat valves and milled head and decked block with the sleaves install so im figureing around 9.2:1? who knows.

 

8.5:1 CR..cold engine.. 165PSI on all 4

 

so wtf is up with my motor! why am i pulling 240 psi on some cylinders for a 9:1 compression motor.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by The Lobster &raquo;</TD></TR><TR><TD CLASS="quote">so wtf is up with my motor! why am i pulling 240 psi on some cylinders for a 9:1 compression motor.</TD></TR></TABLE>

it also depends on how many times you turn in over. Also if you have any oil or maybe even coolant in the cylinder when you do the test it will up you compression. do a wet compression test pour a cap of oil in each cylinder when you do it should jump up 20-40 psi unless there was oil in there already

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SFlCrx &raquo;</TD></TR><TR><TD CLASS="quote">

it also depends on how many times you turn in over. Also if you have any oil or maybe even coolant in the cylinder when you do the test it will up you compression. do a wet compression test pour a cap of oil in each cylinder when you do it should jump up 20-40 psi unless there was oil in there already </TD></TR></TABLE>

i turned each one over 10 times

what does it prove if i do wet compression test? and ill hit 260 psi.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by The Lobster &raquo;</TD></TR><TR><TD CLASS="quote">

i turned each one over 10 times

what does it prove if i do wet compression test? and ill hit 260 psi. </TD></TR></TABLE>
If you do a wet compression test and the numbers go up that much it points to a ring problem, but with that high of numbers in the first place i wouldnt worry about it at all. Dont people usually only crank the car over like 5-6 times?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by The Lobster &raquo;</TD></TR><TR><TD CLASS="quote">

i turned each one over 10 times

what does it prove if i do wet compression test? and ill hit 260 psi. </TD></TR></TABLE>

maybe you have massive amounts of carbon build up?

 

doesn't matter exactly how many times you crank it over. Just crank it over until the compression on the guage doesn't get any higher. On my 8.2:1 motor i get roughly 165 across the board

 

on my 9:1 i get 165 across... something wrong? motor has 280 miles currently. did a fast break in

 

?

 

well it is also going to depend on other things not just the compression of your pistons.

milled head?
headgasket thickness?
flat valves?

etc.

 

9:1 .... 180psi accross the board after about 50 miles on the motor. I have yet to check again recently with 500-600 miles now. Probably about the same.

 

Compression testers are not calibrated so you really can't compare what one will read to the other. I have two and there is a 30 psi difference between the two of them and they are both the same brand.

The difference between the cylinders is where you need to look and your's are pretty close so I wouldn't stress.

 

ill redo it with another tester.

motor was built 900 miles ago.

im sorta stressed cause i dont want to blow my motor when i go get it turboed and tuned.

240 is just way to high for a low comp motor. but as i said agian im do another test with another tester just to make sure.

 

my head was milled but i compensated with a cometic .49 gasket, skunk2 non-flat valves, ported head, ctr cams... i believe the pistons are actually 9.2. maybe its my compression tester? hmmmmm

 

~8:1 dohc zc and 160psi in all cylinders.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jay_Sensing &raquo;</TD></TR><TR><TD CLASS="quote">Compression testers are not calibrated so you really can't compare what one will read to the other. I have two and there is a 30 psi difference between the two of them and they are both the same brand.

The difference between the cylinders is where you need to look and your's are pretty close so I wouldn't stress.</TD></TR></TABLE>

I always stress that. Mine has read low from day 1, no problem the numbers are always consistant

 

7.5:1 D15.

150 across cold.