rollovercomancheguy Posted July 23, 2012 Share Posted July 23, 2012 So i have a 1988 jeep comanche pioneer 4.0 aw4 4x4, but the engine doesnt crank. I checked the main bearings they were fine an am wondering what size rod bearings i would need , due to the po installed them an I'm leaning towards thats the issue. I used plastigauge for the main bearings an moly lube.All the main bearings were torqued to 80 ft lbs. . Any help would be greatly appreciated thanks tony. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 23, 2012 Share Posted July 23, 2012 Whaddya mean "won't crank"? Link to comment Share on other sites More sharing options...
rollovercomancheguy Posted July 24, 2012 Author Share Posted July 24, 2012 well cruiser the crankshaft won't rotate when i try to spin by harmonic balancer with even the rod bearings unhooked. I had to break torque free on the main bearings to get it to rotate. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 24, 2012 Share Posted July 24, 2012 That doesn't sound good at all. Perhaps wrong bearings or the thrust bearings installed on the wrong journal? Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 24, 2012 Share Posted July 24, 2012 Is this the 4.7L stroker in your signature w. a 4.2 crank? Has it ever run at all? How 'bout some history on this. Link to comment Share on other sites More sharing options...
rollovercomancheguy Posted July 24, 2012 Author Share Posted July 24, 2012 this is not the 4.7. This is a 4.0 renix 1988 an it needed new bearings an i installed them they needed standard i used new standard bearings.Oh by the way the stroker runs great ps i work at a jeep dealership as a mechanic. I just checked the thrust bearing again in the wright journal. Thanks. Link to comment Share on other sites More sharing options...
Eagle Posted July 25, 2012 Share Posted July 25, 2012 It sure sounds like the new bearings are just too small. How did you determine that you needed standard? Although there were no oversized cranks from the factory, only .010 undersized. Is it possible your new bearings aren't standard? The bearing caps didn't get mixed up for position, did they? Or reversed in orientation? Wait -- you said you used Plastigage. What kind of clearance did the Plastigage indicate? It's not the rod bearings, right? With the main bearing caps loosened slightly but the rod caps torqued you can turn it over? Link to comment Share on other sites More sharing options...
rollovercomancheguy Posted July 25, 2012 Author Share Posted July 25, 2012 Well eagle the new bearings arre stamped STD on back sides of bearings.As for the orientation of them #1 at #1 cylinder then 2 through 6.When I'm looking at the engine from underneath passengers side all numbers face me correct me if I'm wrong but thats wright.Correct also if the connecting rod bearings are torqued an the main caps are loose it will spin.Also for torqueing them down start from center #4 cap then 3,5,2,6,1,7, an all torqued to 80 ft lbs. I'm wondering if maybe i should oil up the cylinder walls an try it. Link to comment Share on other sites More sharing options...
Eagle Posted July 25, 2012 Share Posted July 25, 2012 Yeah, the cylinder walls are dry? I guess you're not doing rings, right? This is just a replacement of the bearings with the engine in the vehicle? I would go after the cylinder walls. Fill up a squirt can with some 20W50 and maybe a bit of STP in it for good measure, spin it with the mains loose so you can soak the walls with the pistons all the way up, then tighten the main bearing caps and try again. As you start to draw the main bearing caps up, before they're really tight-tight, tap each cap with a plastic or brass hammer gently to be sure it's properly seated and square to the block. Link to comment Share on other sites More sharing options...
rollovercomancheguy Posted July 25, 2012 Author Share Posted July 25, 2012 Well eagle its fixed.The problem was the mains that i got were stamped std. but really were twenty over i learned this by using a micrometer. Thanks again guys for all the help. Link to comment Share on other sites More sharing options...
Eagle Posted July 26, 2012 Share Posted July 26, 2012 Well eagle its fixed.The problem was the mains that i got were stamped std. but really were twenty over i learned this by using a micrometer. Thanks again guys for all the help. Makes sense. I was going to suggest that, but I figured it "couldn't possibly happen." So much for THAT theory. Link to comment Share on other sites More sharing options...
rollovercomancheguy Posted July 26, 2012 Author Share Posted July 26, 2012 Yup thought same thing since theyre quality federal moguls. How long will it take for the oil to burn of which i used in the cylinder walls so my truck will quit smoking whit lol. Link to comment Share on other sites More sharing options...
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