Heya.

Rebuilt an FD engine today with all new seals/springs/o rings.

Turned the short-block engine over by hand (no plugs installed) and got three strong WHOOSHES out of the rear rotor. Very nice.

Front rotor is giving 1 whoosh and two fizzles with almost nothing.

I poked my finger into the exhaust port on the rear (good) rotor and felt the apex seals. All three were springy on the left and right sides.

Poked my finger into the exhaust port on the front (bad) rotor and two apex seals felt springy left and right like on the back. BUT - one apex seal is springy on the left and feels "hard" on the right side. Like it is stuck or wedged or something is not right.

THere are no abnormal noises. No grinding, no scraping, nothing bad except the compression is **** on the two chambers. I've rebuilt about 5 other engines and none had any problems.


Here's the question - Is this something that self-corrects when you run the engine, or is this a sign that I should tear it back apart and check everything out? The engine block is sitting in the garage, so it's only a few hours work to take it apart, clean it / check it and rebuild again but I'd rather not do it if this is a known issue that will self-resolve.

Thanks,
B

 

Took it back apart and found that one apex seal groove was just barely messed up right at the very tip which was pinching the apex seal just a little so it wouldn't move smoothly. It was a brand new rotor too!

Just goes to show, check your parts carefully even if they are new.

 

I apologize for bringing this back from the dead, but...

Did you replace the rotor or fix it?

 

The damage to the rotor was extremely minor. Basically not even VISIBLE. I just used an old apex seal to "work" the groove just a little and it was fine. I made sure there was nothing sticking up/out and put it back together. We're talking about a few thousandths of an inch at most on just the very corner of the rotor. It was more of a machining flaw than real damage. The corner seal never had any trouble moving and the side seal was fine too. I think just a burr or something. On a scale of 1 to 10, this damage was like a 0.1

I've got about 250 miles on the engine and aside from some leaking oil (see my other thread from today!), it runs very well. Better than my last engine actually. Pulls about 17 inches Hg at 1000 RPM idle (street ported engine), and feels very good all through the rev range.

 

Strange that they wouldn't a better screening for things like that on a new rotor... I guess they leave that up to the installers.

 

Rotors are very easily damaged in shipping, especially if they're not packed very (very) well.

 

I'm glad you got it figured out and the damage was extremely minor. My used Cosmo engine's front rotor was damaged in the same area, keeping one side of the apex seal down. I think it sucked in something; either my fault or it happend before I got it, and that's why I got it cheap.

I'll need to work the slot like you did to bring it back to .002" clearance. The corner seal and side seals appear to be fine.