SpoolnByYou

whats up guys,
i recently bought a car from a guy and it came with a fully built lsvtec. the bottom end is built with arias forged pistons and scar rods. when i bought the car he said the motor had 1200 miles on it and still needed be be broken in and tuned,he also said he put in 12:1 or 12.5:1 pistons,he couldnt remember. I went home and did a compression test and the numbers came out to be 210 across the board. this didnt seem right to me seeing he said it had 12:1 pistons in it. So i dropped the oil pan to see if it had what he said and it does have forged internals in it. but why the low compression when i tested it? could it be the rings werent seated all the way....but even after 1200 miles? could he have blown the rings by not breaking in the motor or cracking on it,or would that only hurt the bearings? im going to try to put some more miles on the motor and do another compression test.....but why is it so low...210? shouldnt it be at like 270.

DonF

Do a leak down. Or go to the tech forum to learn how to do a compression test.

SpoolnByYou

i know how to do a compression test,if you would of read the post,i already did one

threeplugs

It could be your valves. Check the clearince and then do a leak down on it.

Fat Chick Magnet

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SpoolnByYou &raquo;</TD></TR><TR><TD CLASS="quote">i know how to do a compression test,if you would of read the post,i already did one</TD></TR></TABLE>


lmao.

DonF

When you read in the tech forum on how to do a compression test did it tell you to hold the throttle open? Did it tell you the % of differance between cylinders that made a differance? If all the clys. are the same you are good to go, or that all your cyls. are fucked up. Pick one. My guess throttle not open, it is in the tech section.

RedEj8

My b18c1 with usdm ITR pistons and b16 head only made 180 across the board.. But the numbers were consistant in each cyl. And yea the Throttle was open..Maybe its the Oreilly's compression tester im using

Fat Chick Magnet

so if your doing a compression test your supose to do it with throttle open all the way?

RedEj8

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dc2rtek &raquo;</TD></TR><TR><TD CLASS="quote">so if your doing a compression test your supose to do it with throttle open all the way?</TD></TR></TABLE>
Yes...and you should remove the fuse so the injectors dont squirt fuel

NJIN BUILDR

Big cams will have a big effect on a compression test,as well as how they are installed.The bigger the cams (duration) the lower the compression number in a compression test.

slowsleeper

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR &raquo;</TD></TR><TR><TD CLASS="quote">Big cams will have a big effect on a compression test,as well as how they are installed.The bigger the cams (duration) the lower the compression number in a compression test.</TD></TR></TABLE>

this may be why, if you are running cams with big primaries then the compression numbers are gonna be less compared to using cams with smaller primaries. If the numbers are consistant and it runs good then you shouldn't have anything to worry about.

SpoolnByYou

that might be it. i know for a fact it has aftermarket cams in. i was told they were skunk 2 stage 2's. thanks for all the input guys.

Fat Chick Magnet

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RedEj8 &raquo;</TD></TR><TR><TD CLASS="quote">
Yes...and you should remove the fuse so the injectors dont squirt fuel</TD></TR></TABLE>


which fuse?

SpoolnByYou

usually i just pull the connector on the injectors. but beware of doing this,afterwards you might need to re-set the ecu (ie: disconnect the battery) becasue it may throw a injector code