By the compression calculator I should have around 13.9:1 CR. I just did a compression test after putting 38 miles on the engine. I did it while the engine was cold with the intake on the and the Throttle open. Here are my results

#1-260
#2-260
#3-255
#4-255

I was expecting about 280 to 290.

 

How big are your cams?

I just comp tested my 14.0:1 comp motor and it pegged the compresion tester against the 300 mark in all cylinders.

 

compression test are done properly at operating engine temp. a cold engine will yield lower numbers.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by junbb1 &raquo;</TD></TR><TR><TD CLASS="quote">compression test are done properly at operating engine temp. a cold engine will yield lower numbers.</TD></TR></TABLE>

I was thinking maybe heat expansion would make a difference.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by asubennett &raquo;</TD></TR><TR><TD CLASS="quote">How big are your cams?

I just comp tested my 14.0:1 comp motor and it pegged the compresion tester against the 300 mark in all cylinders. </TD></TR></TABLE>

Yea I was expecting around the same......I am running Crower 404's.
-Intake: duration: 308 Lift: 445
-Exhaust: duration: 305 Lift: 434

 

Yeah, warm it up and try again. They all look even, so I'd say it's pretty good.

 

Do you have a LS head milled

 

I heard that cams can lower your compression numbers when testing.

 

Yea my cams are compression bleeders I think........I redid it warm and the results were the same.

 

that is correct about the comp bleeders. remember that the longer the duration, the longer the valve will be open to allow air to escape. that is why when you run a bigger cam you need to up the comp to fully take advantage of the extra air. my friend had 14.1 comp 2.0l and the thing would baely run with stock b16 cams w/ pump gas. he threw in some custom 310 duration cams and the thing ran fine on pump gas. about your motor though. the numbers seem to be even all the way across the board so i would say you are looking pretty good. also because you have a non-vtec motor, the cam is big all the way through. you don't the small cam/big cam **** so the cam is going to open the same at idle is it is at redline. good luck with you **** though, high comp non-vtec sound inticing.

 

Any one out there got an LS with over 12:1 comp. I would like too see the Comp test results. Just curious.

 

i was just wondering how ya'll figure out what the compression is after you run a compression test??

 

you also have to wait for rings to completely seal as well. Not sure but your number maybe right. Check this link so you can determine what your dynamic compression and cranking pressure should be. It will also calculate for your elevation as well! I have the exact same cams as you; our intake valves should be closing at 34 degrees ABDC.


Dynamic compression calculator:
http://www.rbracing-rsr.com/comprAdvHD.htm

All measurements are in inches, so here is the measurements you need:

Bore: 3.189"

Stroke: 3.504"

Rod Length: 5.394"

Your altitude should be between 0-800ft where you are at in NC!

 

Thanks I will give it a look!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dohcter g &raquo;</TD></TR><TR><TD CLASS="quote">Thanks I will give it a look!</TD></TR></TABLE>

 

Looks good to me. Give it another try once you get some more miles on the motor.

 

i had an LS motor back in the day, like in early 2000.. it was all stock with CTR pistons and 40 off the head, and it spiked my Sears compression gauge to 300 then broke it. this was with 1990 B18A cams.

 

engine needs to be full operating temp and dynamic compression will drop from the large cams....

EDIT- crap....my computer showed me as one of the first replies....WTF?