Thread: crank help

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can anyone out there help me? i wiped out a crankshaft by not checking clearances. i went by what was on the back of the bearings. anyway i got another crank by trade talk the journals are nice and smooth ,when i went to pick it up the guy had it standing up wraped in plastic and it was nice and oiled . so i know i got a good buy for fifty bucks . im using a digital micrometer the main journals are 2.094 in and the rod journals are 2.437 can anyone tell me what size bearings i should purchase? i have the book HOW TO BUILD A SMALL BLOCK CHEVY it says on the regrind chart that 2.094 should be 0.010 bearings and 2.437 should be 0.010 . my cofussion is i have a 83 305 crank that measures the same on the rod journals 2.094 and i had the 305 since it was new the crank never been cut . could it have been cut from the factory? my next question is why would any one cut just the mains and not the rod journals? im refering to the 350 crank i just bought i called the guy i got the crank from he bought it from someone else. so he dont have the bearings from it write back soon let me know any inpute would be greatly appreciated

Probably because only the mains needed to be cut??? I've had a few cranks that way, most of mine were the other way, with the rods cut .010. Can't help you on the crank sizes, not a chebby guy and don't have a book handy. I'm sure someone will be along to help you out. Lots of chebby guys here.

Either something's goofy here or I've lost my mind. Chevy 350 cranks from 1968 on, first gen, have a main journal diameter of 2.450" and a rod journal diameter of 2.100" unless I'm goofy.

Your figure of 2.094" on the rods makes no sense, that would be 0.006" under standard.

It's been several years since I put a motor together and I am getting older, so I don't remember if the clearance is on the journals or in the bearings. If it's ground on the crank, then I would think 2.437" would be 0.003" clearance with a 0.010" under bearing on the mains and 2.0875 would be 0.0025" clearance with a 0.010" under bearing on the rods. If the clearance is in the bearings, they should measure 2.440" and 2.090".

HELP !!

You are correct techinspector according to my book on a standard larg journal crank the minimum size the rod journal should be is 2.095 and the main 2.4479 to use standard bearings