Ok Engine Building Experts/ 350 Chevy

[Itoldyouso]

I need to ask some of our engine experts their opinion on this one.

As you know I am rebuilding the 99 Chevy 350 for my T. I took my standard, never been turned crank to the machine shop for polishing, and ordered a standard rering kit from Summit. Got the parts.

Today the machine shop calls and says the crank is ready, and by the way, it is under .001. He says it is common for Chevy to use these in brand new motors. He says I probably should order both rod and mains in under .001 size, but that I could get by with standards as it is only .001 (do I have enough zeros in there?......never could keep that straight) I mean it is under one thousandths, not ten thousandths.

Or should I just bite the bullet and order the exact sized bearings?

Don

[pat mccarthy]

on a gm small block 350 you can have 001.5 to .003 you want to be at no more than .002.5 this will have alot to do with .the make of the bearings and where the housing bores on the rods the mains are at .i keep makers bearings that i use in stock and tq them up. i set the mic off the crank and set the bore gauge off the mic at O and put the bore gauge off the bearing that tells me the size for oil . were i am at. and i ajust from there. if you are telling me your on the lowside and.001 less on the crank you will need them +.001 for sure housing bore on the rods can be up to .0007 big and the mains to so this will throw your size off to i like them at small to mid point on the rods and main bores when i recon them

[cffisher]

Don as I recall and go by. If the crank is UNDER size you need OVER size brgs..by that much. A 10 under crank needs 10 over brgs.

[pat mccarthy]

yes you can get them X 001 . X stands for more wich is less bearing and +.001 .002 .010 .020 .040

[techinspector1]

Don, my advice is to mock up the assembly and plastigage the bearings. The end-all way is of course mike them in the bore with an inside mike, then mike the crank journals with an outside mike and subtract the difference. Problem is, unless you use the same mikes day in and day out and are used to reading them in ten-thousandths and do it at the same temperature all the time, you'll be better off using plastigage to determine the clearance. Then report your findings on here so we can give our opinions.

[pat mccarthy]

if you just use a mic and set your bore gauge off the mic you used on the crank is works very good and i do it all the time and i read and set them to .0002 any more than that i do some things .and will not get in to all the things i will or have done but oil clearances is a very big deal with me and can tell you if you have a low side crank + polished and big rod housing bores on the rods with STD mich bearings it will be loose been thru this may times

[Itoldyouso]

I appreciate all the advice guys. This is just a strange situation, as I never thought a factory motor would come with anything but absolutely standard sized bearings. But, like I mentioned, he said he sees this all the time on 350's/

I trust his mike and mike reading skills better than mine, so I called Summit, and they have bearings in .001 sizes, so I ordered a complete set of new ones. They told me I can return these for credit. I also fiqure he had to take a little off the crank polishing it, so I didn't want to take the chance.

I will take all of your advice, and plastic gauge the bearings when I assemble the engine (hopefully this weekend).

Thanks again everybody.


Don