Ok, i just started up by B18 and it sounds healthy. I know the rings havent seated yet. The pistons are low compression for future boost. Oil pressure and fuel pressure are in check. So, i descided to run a compression test.

How i did it:

- disabled the dizzy and fuel system
- opened the throttle all the way
- cranked it over 5 times

results: i first tried on cylinder 1 and got a number of 120 and got discouraged and stopped. I thought it was too low for what it shud be. should be around 180psi correct?

Question is, is it so low because the rings havent seated properly? Bad gauge? When i installed the rings i gapped them and clocked them like CP Pistons says.

 

after a build/rebuild its best to do a lot of deceleration to get the compression back up and let the rings seat.

to be sure, do a leakdown to make sure its not something else if you think its rings.

 

Yeah, you really shouldn't bother with a compression test until the engine has broken in or if you think there is a serious problem. Have you driven it?

 

no sir, i havent driven it yet, but it idles smooth and revs up smooth also.

another quick question, is it normal for alittle bit of smoke from the tail pipe, im guessing oil is burning off from the rings not being totally seated yet. When it gets to optimum temp, the smoke goes away. I guessing the rings then have expanded. I pulled the plugs and there is a slight bit of oil on them and on top pistons.

Heads been rebuilt and block was rebored, rings gapped and clocked to CP standards

 

I wouldn't worry about a little smoke at startup with a fresh build but that should go away once the engine has been broken in. Go and drive it after you make sure its not going to overheat, etc. Drive mellow until you reach operating temp and then get into it moderately. Is it a manual transmission?

 

is this built for boost or n/a? whats the piston to wall clearance? if its gapped pretty loose then itll smoke a little on start up untill the pistons expand at operating temp. your checking the compression warm right?

 

yeah, it was built for boost. I gapped top ring .020, second .022, oil .015. i checked compression cold. But i will wait till 500 miles or so to recheck the compression.

 

im talking about the piston to wall clearance. not the piston ring gap.

 

oh thats one thing i forgot to check.

 

one of the most curcial things to check on a build and what may determine your problem.