I am assembling a small block 350. Can't seem to find clearance specs so am asking here.

1. Connecting rod bearing clearance
2. Main bearing clearance
3. Connecting rod side clearance.

Using plastigauge, I got between .001 and .0015 on the mains. My machinist says this is fine for a street motor. Seems just a tad tight.

I haven't measured the rod bearing clearance, but expect it to be around .002

My side clearance is around .024. This seems wide to me. The rods and crank are brand new (Eagle) so they should not have a problem - yet that clearance does seem large. Any opinions?

thanks


gene

 

crank thrust .002 to .007
main .0017 to .003
rod .0012 to .0037
rod side clearance .006 to .017
if you're doing this you ought to buy a manual and not trust waht some dumbass tells you over the net

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ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

 

almost forgot, i wouldn't be trusting
plasti-gage to tell me very much either. i use mikes, snap gages, and a dial bore gage to check bearing clearances with. plasti-gage isn't that accurate to read to the tenthousandths

 

I agree that plastigage isnt the best stuff on the face of the planet but used properly it works. The bearings and crank have to be completely clean or the results are no good.

The mains sound a little tight, but some good tools might be necessary to verify its really that tight. The rod side clearance is too much IMO, thats alot of floating going on there. Are you using a feeler gauge to check that? I hope so.

 

I agree with the dumbass thing ;-).
Just looking for some advice, just the same.

My thrust clearance was fine, something like .003 (off the top of my head, I don't have my notes here). That one is fine.

I am concerned about the mains. Plasti-guage isn't the greatest, but what's the accuracy on it? can't be off that much. I want to use it as a rough guage since I don't have any snap guages, etc. in my tool box.

The machinist felt that .001 to .0015 was ok. He claims anything from .0008 to .0003 is good for the street.

The side clearance has me worried. The rods are full floaters, if that makes any difference. I haven't yet torqued them down, just tightened them enough to keep it in place - that's when I notice the gap. Seems high. I'll recheck it when I torque down the rods. Don't expect it to change that much.

So what do you do if the side clearance is too much? The crank and rods were bought as new, balanced assembly. Sounds like a mess to me!

I've seen varying specs on allowable side clearance. Some as high as .025 or so. I need to see what chevy recommends.

 

your side clearance on the rods sounds too much to me ,i'd be checking everything very carefully and asking the rod and crank makers what they recomend for clearances. to me plasti-gage is to tell you soemthing is way out of whack, not to get a measurement to the 10thousandth

 

Plastiguage is another tool. I use it in conjunction with snap guages, inside/outside mikes etc. It is as an aid to double check my own machine work as well as anyone elses.

The side clearance does seem to be on the loose side. Was the crank and rods bought as an assembly or did you by them seperately? If they were bought as an assembly you could contact the seller with your questions. If you are using non GM aftermarket rods you might try contacting the rod manufacture.

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Dan

 

i have a question, lets say that his side play is to much, so then what does he do?

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Wide Open Till You See God...Then Brake

 

Your rod side clearance measurement is meaningless until you torque down the rod bolts/caps to spec. Your clearance'll tighten up after you do that.

 

Sorry about not getting back to everyone -

The crank and rods are manufactured by Eagle and are a complete assembly. I checked with them on this. The rods are manufactured with manufacturing clearances of .015 to .025. Pretty wide tolerances, if you ask me but that's how they make 'em. They said my setup is on the loose side of the spec, but is within manufacturing tolerance.

So, in my opinion, it'll be ok - just expect some extra oil to squirt out on the sides! The rods are floating style, if that makes any difference.

Oh, as for what to do about it if they are out of spec - send them back. You can't fix it.