So after I put my rebuilt head (port & polish, 3-angle valve job, milled 0.030", supertech valves, omni springs & Ti retainers, CTR cams) back on my block, I tested compression prior to starting my engine and got ~160 psi across the board. I knew it was low, but this was with a cold engine that hadn't been turned over in about a year.

Now my car is up and running, and today was the first time I got it out and drove it around (I'd started it up a couple times, but had to finish suspension & brake work). After I drove it around a bit, I rechecked compression and got:

1: 155 psi
2: 200 psi
3: 205 psi
4: 190 psi

The bottom end is stock with ~130,000 mi on it. Does this seem like the rings are bad on cyl. 1, or could it be my head? I want to do a leakdown test, but don't have a leakdown tester yet. What do you guys think?

 

did u block the throtlle open. if u did then you know compression is leaking. u dont need a leakdown tester to see where compression is going. just use your compression tester hose, take out the shunt valve. hookup air and listen to where its coming from. this wont tell you how much its leaking, just where its leaking from.

 

Yes, I had the throttle all the way open. I'll have to try the compression tester tube method, about how much air pressure should I use? Does it matter?

 

how is ur car running, with those result?

 

Seems to run fine, but it's still un-tuned running off the gsr ecu (I have a skunk2 mani). I have a chipped p28 I'll be throwing in next weekend.

The only problem I have is if I cut throttle quickly, the car almost dies (did die a couple of times) I think this is due to not having the idle set corectly though (I have a 70mm throttle body). The car sure rips! I spin falken azenis bad in second gear, haven't taken it beyond that yet.

Anyone else have any ideas? Sound like bad rings on cyl 1?

 

put a little oil in the #1 piston, then do a compression test if it goes up your ring are bad

 

I'll try that along w/ the leakdown test.

Besides reduced performance, would running the engine with low compression in one cylinder cause any harm to the motor? I do want to rebuild the bottom end, but was going to wait until winter.

BTW, this is not my daily driver, just a weekend warrior that will hopefully see some auto-x time.

Thanks for all the suggestions!

 

Besides reduced performance, would running the engine with low compression in one cylinder cause any harm to the motor?

I don't really want to rebuild the bottom end until winter, don't have the $$$ right now.

 

Anyone? I want to know if it's okay to run w/ low cyl. 1 compression until I can rebuild my bottom end. Thanks.