i've spent quite a few hours installing an '86 engine into my '84 and hooking up all the EFI goodies. as i was turning the engine to put it at tdc for the dizzy install, i noticed one chamber has a lot more compresion than the other. the one that's low felt like it was building up a little and releasing it little by little, kind of a slip-stick action as i turned the e-shaft.. and you can hear air escaping through the seal when you turn it.

the guy i bought it from told me it had 130k mi and it ran great when it was pulled (in favor of a turbo motor).

the engine has been sitting approximately one year and i suspect the chamber with lower compression may be dry and/or sticking apex seals.

should i be worrying?

 

It could just be that the one thats "low" sounds different because of the apex location in relation to the ports. Like on a piston engine, one cylinder can sound "low" because of the alignment of the valve over the cylinder at that particular time. Then again, as you say it could be stuck/sticking. I would say the only "true" way to know would be to put a little MMO in each rotor housing, and spin it over with the starter and listen. If that doesnt float your boat, do the same thing but slap a compression tester on there instead of just listening.

~T.J.

 

hopefully i can turn it with the starter tonight.

 

yeah turning it by hand is not a real great way to judge compression... its definately by no means steady

 

i have read if you pull the plugs and put in some ATF and let the seals soak in that for a while it can loosen them up... itll smoke when you starter up tho hehe..

see how you go with the starter first, I have noticed with mine ~20k miles that after first starting up it sounds like its not getting the best compression, but as it warms up and the apex seals loosen up more it seals much better! so maybe once u get it started and the OMP starts pumping in oil and it all heats up, shell be right

 

ATF is a no-no. Glove, I wouldn't worry about compression until it's something to worry about. Just crank it and listen. Then go from there.

 

i was gonna squirt a bit of 20w50 into the plug holes before i crank her over.

 

well i hooked the starter up and cranked her over.

puff-ssh puff-shh puff-ssh puff-shh puff-ssh puff-shh

so it sounds good. encouraging.

 

someone needs to take out the atf trick and delete all the atf crap from the forums. All it will do is swell the soft seals and then they will leak.

 

does this atf hatorade extend to mmo as well?

 

never had a problem w/MMO it even helps me Breath better!!!
Glad to hear you have good compression

 

I haven't had a problem yet with MMO. I poured some in my 20B after I got it because it had carboned-up apex seals and low compression. The MMO sat in it for months while I worked on other projects until I finally got back to the 20B. It fired up last year and ran with only a light bit of smoke at the beginning. In other words, it didn't destroy the oil o-rings like ATF could have. It remains to be seen whether the o-rings have since deteriorated or not. I estimate the MS EFI setup will be done quite soon so I'll have my long-term-use answer soon enough.

As for what Glove is doing, I'd just add a little oil too. Infact, I'm going to dribble a little into the carb primaries of my rebuilt R5 13B 4 port when I'm finally ready to fire it up for the first time. Hopefully it'll be some time this week or as soon as I can finish the exhaust.