well im checking all the clearances in my motor and crank endplay specs out as only .005. from what ive read or seen, it should be at least .007-.010
is this too tight? im using h series bearings, and i think thay are tight on the thrust, but i'm still a little concerned. my block has been fully machined (line honed) and the crank is new.

 

I would not run it that tight if it was my motor... Mic up the bearing and see if there are high low spots

 

Loosen the rear main cap to where there's no more than 5 ft-lbs or so on the bolts; take a BFH and a block of wood, and give each end of the crank a good whap, to align the thrust surfaces of the 2 halves of the bearing; re-torque the cap; and check it again.

 

i did hit it with a rubber hammer, guess now im gonna try a bigger one with a block of wood, thanks.

 

That 0.005" will allow 0.0025" oil clearance on either thrust face. That should be more than enough to start and run the engine.

Manually oil up the bearings, slide your crank socket on the snout, and spin the engine over several revolutions to allow all the rods, wrist pins, and crank to find their "home" and square up the pistons. That will assure that none of the rods are holding back the crank as you move it from end to end.

Did you install an undersize main bearing shell set?

 

I think the crank endplay spec is .004-.0016 or something, mine came in at .005" too.

 

the bearings are all standard size, all of my journals spec out within .0001 of each other, and crank runout is less than .001. i checked the thrust with no rods or pistons installed, just crank and bearings. i have been too busy at work lately to do any further checking, but tomorrow i should be able to get back at it. thanks

 

Sounds like you did it right. You want to check/set the thrust before the rods/pistons go in. Did you have any oil on the thrust face when you measured it? The oil will take up a couple .0001". You want to measure it dry. If you've still got .005" then align the faces the way SofaKingdom said.

 

Not to sound stupid but could someone explain this a little more? I am currently building an engine and I was confused on how to measure this.

Thanks,
Josh

 

put your crank in the block, bolt on all the bearing caps. Then use a flat blade screwdriver and pry it forward on the engine, and stick a feeler gauge into the spot at the very back, it's hard to explain where, but at the thrust surface....
.005-.020 or so is the range you'll be seeing. Apparently this isn't something that usually wears, or is something that is often out of spec, but good to check none the less.

 

Best way is to check it with a dial indicator on the snout. Pry it back and forth and note the reading on the gauge.

 

The dial indicator is the most "accurate" way to measure it; but the feeler gauge method works fine in most cases too.

Franky I hardly ever "measure" it, myself; I just eyeball it, and if it looks in the right range, which is roughly the thickness of a thick sheet of paper, then it's OK.

Remember, this isn't a real tight-tolerance kind of thing, like it has to be within a thousandth or something; anything from about .008" to .020", and maybe even more depending on what the motor is being used for, is OK. Ideally it should be around .012" - .015" in a typical rebuilt motor. But it's not something to get all spun up about, like the actual bearing clearance would be, or ring gap, or stuff like that, that really matters. All that's important, is that there's SOME end-play, but not TOO MUCH.

 

I'm dropping in my crank now and when I tried to move it back and forth (with only the front and rear bearings in and NO main caps) I couldn't get the crank to move back or forth at all!

First COMPLETE rebuild so I may be doing something wrong. Any ideas?