Real low compression??
 

Well im bored and since my car is still down and probbaly will be down for awhile i thought id ask about a problem i have had for awhile while it was running. As some of you know i turboed my car and blew it up in less then 15 minutes because the vaccum liine from the wastegate melted and came off. So i rebuilt it myself in my driveway. Well i have a jdm b20a from the 85-89 accords in japan and the closest match piston wise i could fine was the usdm preludes b20a5 pistons. So i used those. Well my car has never had more then 140psi of compression in any cylinder since i rebuilt it. I think right now they are all around 130-135psi per cylinder? It runs fine as far as i can tell. I was pushing about 9psi threw it last time i had it running and it was fine? So what could cause the compression to be so low? The only thing i could think of was the new pistons i used were from a different motor and they looked alittle more dished then my old ones were. I have a couple pics of them so maybe you guys could tell.

O and btw: maybe its just my imagination but i check the compression on it alot and it just seems like its slowly going dowm maybe? Its kinda weird? Maybe im just imagining it and just being over cautious or something.

https://img.photobucket.com/albums/v...i/100_0615.jpg

https://img.photobucket.com/albums/v...i/100_0616.jpg

Re: Real low compression??
 

looks like a bigger dish to me.

CC them and calculate it out.

Re: Real low compression??
 

did you hone the block any before you put new rings and ---- in it?

Re: Real low compression??
 

yep the blocked was miked and honed before i put anything back in it.

Re: Real low compression??
 

i bet the wrist pin heights are different. Thats why you cant run a b series piston in an A20 accord engine, its not the bore or the dish, its the pin height

Re: Real low compression??
 

i hope thats the problem. The only thing that worries me if im pretty sure its the same because both the pistons had pk2 stamped into the top of them. Even though they look slightly different they are probbaly basically the same.

Re: Real low compression??
 

1 says pk2us and the other pk2
and u can even tell from the pic the pk2 has more comp

Re: Real low compression??
 

do a leakdown test. dont do a compression test. a leakdown test will tell you how much air you're loosing

Re: Real low compression??
 

what is a easiest way to do a leak down test? I think i know how to do it but ive never done one before.

Re: Real low compression??
 

bump? Anyone know how to do the leak down test???