PDA

View Full Version : 307 questions



68chevyboy
03-17-2001, 12:14 PM
im building a 307, and i installed crank after having it ground, and having the block hot tanked,and had freeze plugs,and cam bearings installed. i bought fresh bearings and installed the crank correctly. i checked it twice, so im sure i have it installed properly correct torque and everything. my problem is, the crank will spin, but its pretty snug, and its hard to turn it. is this right? i thought it was supposed to spin somewhat loose. help me please. thanks! van on.

Vanner68
03-17-2001, 05:11 PM
What you need is some Plastigage- the shop that turned your crank should be able to tell you where to get some in your area. It's a putty like substance that you put in between the bearing and crank and torque it down. The putty changes color and this indicates your clearance. Refer to a shop manual for clearance specs. The crank may be stiff turning if you didn't have the block line-honed. This trues all the bearing surfaces and corrects any coreshifting. It's not absolutely necessary, but it does free up some power and decrease bearing wear.

Yeggster
03-17-2001, 10:46 PM
A brand new crank will turn tight......just hard to tell what you mean by tight http://www.vcvc.org/ubb/frown.gif

There is a torque methode you can use with a scale and a string wrapped around the crank........but it's not reliable.

Another way is to take off one cap at a time......test it by turning......retorque take off the next cap........ .etc............if one journal or cap is bad that will show it up.

By far the best way though is like 68 says........it's the GM recomended methode........the plasic gage goes between the bearing and the ground journal......torque it and remove the cap.....measuer the plastic guage with the chart that comes with it.......it will give you the clearance acutate to .001" easy.........compare that to specs!

I would not ressemble an engine without plastic gaugeing the main journals

Yeggster

TurboVan
03-17-2001, 11:49 PM
The problem could be lack of end play in the rear main bearing. Loosen the bolts a little, protect the crank with a piece of wood, smack the front of the crank with a heavy hammer, then the rear, to set the bearing. Then re-tighten the bolts. Hope this helps. --- TV

Ross
03-18-2001, 12:47 AM
You did use an assembly lube between the bearings and the crankshaft bearing surfaces, didn't you? Just checking.

68chevyboy
03-19-2001, 02:14 PM
its notreal tight but its kinda snug. im gonna try some of that stuff and see what happens.