VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Clearances for bearings

I have a '28 chevy and would like to check the clearance on my rod and main bearings. Does anyone have the proper clearance handy?

Thanks for your help

Thanks Qman, I was hoping we would see some comments on this as all my 4 cylinder repair manuals seem to keep the clearance number confidential. My early 6 cylinder book shows .002 inch and I have used .002 to .0025 and plastigage since the 50's. Plastigage is still available at my local parts store. No instructions come with it anymore so let me know if you need more details.
Herb

Like Herb, I was just waiting in the background to see what the opinions were. I agree that .002 is in the ballpark. Measuring the rods is straight forward, however if the engine is in the car you have to take extras steps to do the mains as you have the weight of the crank to deal with. Qman, you didn't ask about how to adjust, but if you have questions, either post the question or contact one of us direct. Good luck on the project.

Thanks for the replies.

I have been searching for this answer for the last few months and I guess I will just have to run with your suggestions and what I found in a Dyke's Automobile Encyclopedia (this is like a modern Chilton's but for that vintage) Matter of fact they have a great section on the RAXKO carburetor and that is the correct carb for my truck so I feel good about the information.

So what do they recommend?

Main bearings using splash or gravity lubrication should be approximately .0005” minimum and the maximum being .0025” It lists .001 to .0015 as being desirable. They also recommend increasing the clearance by as much as 50% if the bearing is greater than 2 ¾”

As for seating the clearance without the weight of the crank on the bearing, they accomplish this by turning the motor over so that the bearings are facing up. Since my motor is still in the truck, rolling the truck over is not an option for me….

For the connecting rods, they are listing .0005” as a minimum with a maximum of .002 with .001” being the desirable clearance.

I was able to purchase Plastigage ($.65 per package) from my local auto part store.

So this is my project for this weekend. Got to get the truck ready for the upcoming tours.

Looks like you are on the right track. My personal opinion is that .00l is a bit tight, however on a re-adjustment it would be okay.

To do the mains in the truck you must get the weight off the bearings in order to get an accurate measurment. You can do this by jacking the crank up with one or two jacks. Just enough to keep the crank against the top (now bottom) bearing. Measure each crank bearing one at a time and retorque after the measurment/adjustment.
Then go to the next bearing.

When you have completed all adjustments, turn the engine over with the hand crank before you attempt to run it. This is to insure you don't have something egg-shaped and too tight after the adjustments.

Wish you luck on the project.