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Crankshaft and connecting rod end play

Hello,

I am stroking my 91 cherokee 4.0 with a 258 crank and 258 rods. My crankshaft end play is at 0.0055 inches. The range is 0.0015-0.0065 inches . The ideal range is ~ 0.002-0.0025 inches. My machinist tells me that the end play is perfect and less could cause friction problems, i.e burn out. To me, if it is engineered for .002-.0025 that should be the optimal range. I'm at the high end for wear according to the manual, and I see this giving me less engine life.

Also, my side cleance is 0.022 in. and .019 in. for two of the connecting rods. The range is 0.01-0.019 inches. My machinsts told me the .022 will not be a problem.

I'm concerned with my machine shops responce. Yes it will run fine, but how about 50K mi from now? Is my machinist BS'ing me becaused they screwed up or are thses tolerances acceptable for a rebuild?

Thanks

Reply to
Brent
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Crankshaft endplay is not something that is usually controlled by the machinist. The main thrust bearing and the thrust face on the crank will determine that for the most part. There really is not a way to tighten the endplay up. The crankshaft thrust surfaces wear and a new bearing is manufactured to match up with a new crank. Personally I wouldn't worry about it. A little more clearance there will allow a bit more oil to pass over the thrust surface. In all honesty, most engines have a larger endplay dimension than that. About the only way to tighten the clearances are a different crankshaft. Again, the rod side clearances are pretty much determined by the width of the rods and the width of the rod journals. The only way to change it is to replace the rods or crank. One other thing to consider is that since this is a 258 crank, what are the end play and side clearance dimensions for a 258? You might find that they are right in spec. When you mix and match parts these things need to be considered. It is good that you are concerned about these clearances of course. In all honesty most non-stock engines that are going to see more severe duty than normal usually have these clearances opened up a bit.

Chris

Reply to
c

I wouldn't like those numbers and I would have the journals plastigauged before installing it. If the machine shop is that sloppy on end play, how good are they with bearing clearances?

When I hear crap like that coming from a so called professional shop, I tend to find a new shop sooner than later.

I am going to refresh a 258 I have in my garage maybe with my 4.0 block and I certainly would 'not' go to all that work and expense to put in parts that are already out of or at the limit of their tolerances.

Not a hope.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Brent wrote:

Reply to
Mike Romain

Reply to
L.W.(ßill) Hughes III

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