350 chevy rebuild question

[jeff81]

I could use some help, I am rebuilding a 97 chevy 350 - have the cam and bearings in, crank and bearings in - pistons in - all turns well until I tighten down to 20 ft lbs on the connecting rod nuts. Then I can not turn the crank over even with a large torque bar on the crank. Bearings are all standard size and were pre lubed with assembly lube

[Dave Severson]

First off, welcome to CHR! Was there any machine work done on the crank, and were the rods resized???? Could be the wrong size bearings, did you measure the crank or rods to see what sizes things are? Are these new parts or the original pieces from the '97 engine?

[techinspector1]

Is it possible that you got the rod caps mixed up upon disassembly?
A small block Chevy short block with the pan on but without heads should require about 35 ft/lbs break-away torque and less than that to keep it turning.

.

[34_40]

X2, my first thought is a cap (rod or main) got put on backward.. did you (or were they) mark them as they were being taken apart?

[jerry clayton]

So-------I take it that you tightened all the rods with the crank in one place without turning it at all???????????????


You need to torque one pair at a time, with some feeler guage strips between the rods(to hold side clearance straight---also this verifys that the rods do have proper side clearance)and then turn the crank to the next pair and repeat---------


We have seen issues where engines have been assembled with assy lube on the mains and rods and the crank was hard to turn, so customers have brought back the engines and we have reverified to them that the clearance s were correct (mike and dial bore gauges), and then have put 3 w 30 on mains and just the weight of a 1/2 inch ratchet would rotate the crank------------


A further issur that you could be having is reversed location of bearing halves which can cause a binding on the crank radius or another side clearance problem----------


If this is a rebuid with same crank/rods and no machine work on the main bearing or rods-----it is either a parts misuse or operator malfunction????????????


Any way welcome to the site and check all of them----------

[jeff81]

First off, welcome to CHR! Was there any machine work done on the crank, and were the rods resized???? Could be the wrong size bearings, did you measure the crank or rods to see what sizes things are? Are these new parts or the original pieces from the '97 engine?

Thanks - no machine work done or any resizing. They are new parts for stock block
I did do some tolerance checks, but probably should go back through them

[jeff81]

So-------I take it that you tightened all the rods with the crank in one place without turning it at all???????????????


You need to torque one pair at a time, with some feeler guage strips between the rods(to hold side clearance straight---also this verifys that the rods do have proper side clearance)and then turn the crank to the next pair and repeat---------


We have seen issues where engines have been assembled with assy lube on the mains and rods and the crank was hard to turn, so customers have brought back the engines and we have reverified to them that the clearance s were correct (mike and dial bore gauges), and then have put 3 w 30 on mains and just the weight of a 1/2 inch ratchet would rotate the crank------------


A further issur that you could be having is reversed location of bearing halves which can cause a binding on the crank radius or another side clearance problem----------


If this is a rebuid with same crank/rods and no machine work on the main bearing or rods-----it is either a parts misuse or operator malfunction????????????


Any way welcome to the site and check all of them----------

Good points, I was able to move the crank basically in two different positions to get all the nuts. I did not use a feeler guage but I did have the halves all laid out in the positions I took them off. It is possible that I could have mixed 1 or 2 but pretty sure i kept them the same - i will go through again and use a feeler guage

[firebird77clone]

You may have a nick on the crank. Happened to me on my first build.

Tighten the caps one-by-one, giving the crank a full turn after each adjustment.

You'll be able to isolate the trouble.

[pat mccarthy]

on chevy SBC and BBC other engine to the rod bearing tags on rods go to the outside of oil pan rails. make sure there that way .as the rods has a off set .if pistons or rods hanged the wrong way it will work in a bind