HELP, engine rebuild thrust clearance issue

[tyhoppy]

Ok. rebuilding 7-bolt. Installed a crank and new crank bearings, after torqued, the middle main bearing, thrust bearing is suposed to have .002 - .007 inches of play, and with the new crank and bearings it has .011 on one side if pushing the crank towards the flywheel, and .018 towards the other side if pushing the crank towards the timing belt side. I do not know what to do, I have contemplated running it this way, because the crank surface and bearing surface are both smooth, so It shouldn't really hurt that much, I don't think... Any help is appreciated because I just don't know what to do, I have the head ready to torque down and the oil pan already in, but I decided to ask before I slap it together.... Any and all suggestions are appreciated, Thanks... -Tyler

 

[92awddsm]

Ok. rebuilding 7-bolt. Installed a crank and new crank bearings, after torqued, the middle main bearing, thrust bearing is suposed to have .002 - .007 inches of play, and with the new crank and bearings it has .011 on one side if pushing the crank towards the flywheel, and .018 towards the other side if pushing the crank towards the timing belt side. I do not know what to do, I have contemplated running it this way, because the crank surface and bearing surface are both smooth, so It shouldn't really hurt that much, I don't think... Any help is appreciated because I just don't know what to do, I have the head ready to torque down and the oil pan already in, but I decided to ask before I slap it together.... Any and all suggestions are appreciated, Thanks... -Tyler

Was the thrust ground .010+" oversized and then you got standard thrust bearings? If you put it together with those clearences, you will experience crankwalk really quick. I prefer to keep mine .003-.005" when assembling an engine

 

[tyhoppy]

I am not sure if it were ground or not.. do you know what the specs are suposed to be to measure the crank to see if the thrust surface were ground, I don't even know what sized rod or mains they gave me, they are ACL bearings. I have a micrometer.

 

[baocoyyie]

DO NOT finish assembling your engine. Find out if its been ground, worse case, take the crank and/or block out and have the machine shop examine it for you. Guaranteed crankwalk if you assemble it as is. If you are lucky, the crank has been ground and you just have to buy oversized bearings to bring it into specs. Also, if you're nice to the auto parts guy, he might let you come back and swap out those oversized bearings until you get it to where you want it, about .003"-.005" just like 92awddsm said(bearings are manufactured with a tolerance too, sometimes you get the right size by chance, I build my engines with all clearances as identical as possible, thats just my way of quality control).

 

[tyhoppy]

all of my oil clearances are good. same on all bearings.. the box my bearings came in just say .5 on them or .050 on them... something like that. I know that there is .018" of endplay. Now, can I get a bearing .050 with a .010 bigger thrust part???

 

[Defiant]

2G cranks are not serviceable, and are never to be ground. Per Mitsubishi.

 

[tyhoppy]

what's the difference between a 2G crank and any other crank that someone makes that is serviceable, doesn't mitsubishi grind the crank when they manufacture it?

 

[Defiant]

what's the difference between a 2G crank and any other crank that someone makes that is serviceable, doesn't mitsubishi grind the crank when they manufacture it?

Yes, and then they surface treat it.
Motor reconditioning is a practice that began fading out in the eighties, with more and more designs having non-serviceable crankshafts, bores that weren't meant to ever be rebored, and a general lack of factory parts support. There are a couple of reasons for this- for one, labor costs make it impractical to pay a machinist and a mechanic to spend twenty hours doing a proper job of engine rebuilding when a new engine costs less than the aggregate of parts and labor. And, engines started lasting for absurd mileage- how often do you hear of a 2G, let alone a 1G with less than 100K on it? And that's under turbocharging, without even having the valves refaced.
Manufacturers make cars for new car buyers. They really don't care what goes on with them after three years, and they want you to come in and buy a new one by then. It's all just business. Some of the advertising wonks might occasionally refer to the "heritage" of a Z or an RX-7, but the builders don't give a shit. They're only in it for the profits.