Mycarispurty Posted November 23, 2009 Share Posted November 23, 2009 So I got a F54 motor with a P79 head for free yesterday, assuming I pulled it. So I trek up there with an engine lift, tools, and pull this motor out. I get it home today and finally get a right size socket that'll fit the crankshaft bolt. The engine is out of the car and of course not at operating temperature, so it's not going to be the best, accurate number for compression, but have read it should only be 5-10 or so psi off of what the number would be should it be warmed up. Anyways, with nothing on the motor (no intake so no throttle plate to hold open) and all plugs out of the head, here are the numbers before, and after a few squirts of oil in each spark plug hole for round #2 (the number after the / is the 2nd round with oil) 1-65/95 2-65/70 3-80/90 4-105/105 5-90/100 6-88/100 I haven't taken the head off to see if they're dished pistons or the flat tops, but even so, the numbers are so far across the board, and raised with oil, the rings may as well just not even be in the motor. I guess I won't be using this motor and will probably just part it out. Quote Link to comment Share on other sites More sharing options...
FlatBlack Posted November 24, 2009 Share Posted November 24, 2009 I'll get in line for those flat tops if you part it out. Quote Link to comment Share on other sites More sharing options...
Mack Posted November 24, 2009 Share Posted November 24, 2009 How did you spin motor to get the readings? Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted November 24, 2009 Share Posted November 24, 2009 why not just drop a new set of rings in, assuming no broken lands or groove? it's not hard to put on a new set of rings. Quote Link to comment Share on other sites More sharing options...
Mycarispurty Posted November 24, 2009 Author Share Posted November 24, 2009 Well the block has redeemed itself. I got the head off finally, in the dark mind you lol The bores have no scratches, no gouges, and still show plenty of crosshatching. So a new set of rings and bearings it is. Still going to get messy taking the block apart and having it dipped to clean it out, and still some $ to be spent having a machine shop check the crank to see if it's been cut before or if it's stock, and the bores so I can get the right rings. Then eventually I'll get it put back together and have essentially a fresh motor for me to play with on weekends. Quote Link to comment Share on other sites More sharing options...
Mycarispurty Posted November 24, 2009 Author Share Posted November 24, 2009 Mack, I just took all the plugs out like I normally would for a compression test, then put a big ass 27mm socket on the crank bolt and spun it over with a breaker bar to get my readings. Muuuuuuch slower than if it was in the car and a starter hooked up, but gave me an idea of my inner condition, so it worked out. Quote Link to comment Share on other sites More sharing options...
Mack Posted November 24, 2009 Share Posted November 24, 2009 thats no way to get proper readings. you should basically take those readings and throw them out. a starter spins at around 225 to 250rpm, you were maybe doing 10. If you were to go by those readings, Id just look at #2, as all of the other ones are fairly close. I bet #2 just has some gunk in the ring lands. These motors are tough. I wouldnt even bother with new rings or bearings unless they dont spec out as per a shop manual. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted November 24, 2009 Share Posted November 24, 2009 thats no way to get proper readings. you should basically take those readings and throw them out. a starter spins at around 225 to 250rpm, you were maybe doing 10. If you were to go by those readings, Id just look at #2, as all of the other ones are fairly close. I bet #2 just has some gunk in the ring lands. These motors are tough. I wouldnt even bother with new rings or bearings unless they dont spec out as per a shop manual. I'll second that! Absolutely! My guess is you've pulled apart the engine for nothing other than to replace parts that probably didn't need it. Sorry, but the truth man Still, it'll be fresh after you're done, like you said. Quote Link to comment Share on other sites More sharing options...
Mycarispurty Posted November 24, 2009 Author Share Posted November 24, 2009 I'd rather spend a few bucks on some rings and bearings just to be safe, plus the head was coming off anyways to make way for my E31. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted November 24, 2009 Share Posted November 24, 2009 Don't you need to hone the cylinders to break the glaze? I've always been told that just throwing new rings on without doing that results in rings that never seal properly. Or is that just an old wives tale? Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted November 24, 2009 Share Posted November 24, 2009 You are very correct Zmanco. i prefer to use a ball hone so it doesnt take to much off. Quote Link to comment Share on other sites More sharing options...
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