I putting my project car back together, getting close to starting it up, and decided to a quick compression check for giggles.

I don't know much about the motor, I picked up though various deals, about a year ago, its has been sitting at least a year, the motor was ported, before I though the motor in the car I checked out the chambers though the exhaust ports, and everything looked OK, all apex seals where in place, no "noticable" damage to the housings by inspecting the motor though the exhaust ports.


I didn't even bother removing the valve to check bumps, the motor total compression is way to look, Front rotor is able to get about 30 PSI (I checked this with two different gauges), oiled the chamber down and got the compression up 50 PSI. Rear rotor 5-10 PSI, didn't bother oiling it down, little to pissed at the time.

So what does everyone think? worn seals? springs? or rotor housings?

 

how can you inspect the engine's chambers through the exhaust ports???

you won't see anything related to the health of your engine beside of seeing if all apex seals are there and non stuck and if rotor tips look messed up!

you cannot really tell about housing damage by the exhaust port...

since the engine is sitting there for around a year... I'd say either your apexes or side seals are stuck or engine is simply worn out...

you're supposed to hit good compression numbers even with a very worn engine just by putting oil in each housing...

I'd rather look for a rebuild if I was you... but since I'm not very experienced with engine building, you need other advices...

 

Well, stuck seals was one thought, you can see a good portion of the rotor housing through the exhaust ports I would say at least 25% of it, enough to see if something came loose in there and scratched the hell out of it.

 

IF you put oil in it and still only got 50 then I'd look to do something about it while it was out. I mean, even an old motor will push 55-75 with no oil, and oil should add 25-40psi on top of that. You sure you were cranking it at speed? 250rpm or higher? You need a strong battery and trans/starter/flywheel to check compression accurately, you know. And, keep in mind that, a cold test yeilds numbers higher than a warm test, you lose 5-10psi when warm. A cold test is usually best case scenario.

 

Thanks Kevin, I was using a battary charger set at 60 amps putting out just over 15 volts out, for the power source. So it had plenty of power, I am sure it was going over 250 RPMS, but before I pull the motor back out of the car (it was just put in) I will trying again with the charger set at 250 amps (jump start mode)

 

Pushing it up to 200A start mode usually makes your cranking rpms around 275-300...and you should make some really good numbers there. But the numbers at 25prpm are 85 or better...without oil. With oil, I'd expect to see 100+.

 

Kevin thats what I will do Monday, I was little too pissed off this afternoon, I was hoping to start the car up this week.

Thanks again.