Ok, running USDM R pistons in my B18C1, yielding 10.8:1 compression according to cspeedracing.com. When it was fully rebuilt, it pulled 270 across on the compression tester. Been boosted since August, with various fuel setup problems until about a month ago.

Compression test yesterday came to 210-130-240-240. Now, keep in mind I did a valve adjustment last week, and I can hear ticking now as much as I could before. Can a bad valve adjustment throw it out of wack enough that it won't hold compression? If so, could that be enough to give me 130 in the 2nd cylinder? What are other causes? I'm not thinking it's a ring land problem because generally ring land problems seem to yield very very low compression numbers.. mine isn't quite that bad... correct me if I'm wrong.

Assuming that the walls of the cylinders are not scarred and the ring lands are intact, can I get away with a simple hone and a new set of rings? Hoping to get out of this with a simple valve readjustment (assuming i screwed it up), and/or a hone. Does a hone job require that I go .25 over and get OS pistons?

 

it sounds like you broke some ringlands.

 

what engine management did u have? and who tuned it?

high compression motors have a small window for tuning error...

 

My main concern is what is likely needed to repair this...

PM me or catch me via AIM if you're interested in talking about my fuel management.

 

^

 

How old are the actual sleeves? As long as there isnt any bad scrapes that dig into the cylinder walls a hone should fix it, but if you froze a ring inside your piston chances are it scraped up the wall and will need a .20 over bore. honing doesnt remove enough material that you would need to run OS pistons.it basically juts gives it back its cross hatch pattern and cleans up any minor scuffs.

BTW does it smoke much?

 

i had 200 accross with the #4 reading 80. upon dissasembly 3 of the 4 pistons had craked to **** ringlands. just goes to show you that the nubers can be high but you still have a problem. stock pistons are weaksauce and like MASE said there is a very small window for error. i never detonated, never ran lean and still they couldnt hack it....

Landon

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">what engine management did u have? and who tuned it?

high compression motors have a small window for tuning error...</TD></TR></TABLE>

Hm, just noticed I'm at 98%... I'm guessing this is why? Bump.

How much you want to tune my car if I drive up to Gainesville?

 

Ring lands broken doesnt always yield low numbers...Unles my motor is the exception..When i took my block apart to build it for boost(going from High CR NA to FI) we encountered 3 broken pistons..the ringlands where completelly cracked/destroyed due to pinging and my car still pulled 200+PSI on compression tests..

My CR numbers where
250
235
230
160 (blown HG around this cylinder)

If u want to see a pic of how bad the pistons where just let me know.