The Stovebolt Site Forums The Parking Lot Early 'Bolts (1916-1936 1st Half) Engine question -- 171 Main Bearing Caps

To do as Dean suggested, I am putting the engine (171 4-cylinder) on a stand to inspect the bottom end. I received my shop manual in the mail yesterday and I eagerly thumbed through the pages to get to the part where it addresses reinstalling the crankshaft and the main bearings and caps. Breathlessly I read, looking for clearances, torques, etc ...

What I got was ...

"By putting pressure on the connecting rod or crankshaft, any looseness can be detected...."

"... each bearing should be tightened seperately and when the proper adjustment has been secured, loosen the cap screws sufficiently to take the pressure of the bearings from the crankshaft. Then proceed to the next bearing in the same manner."

And the gem (about the main bearings):

"Squirt oil on crankshaft, replace caps and draw down snugly." Snugly???

So I get the part about mistaking tight cam and timing gears for tight bearings, but how do I check the tightness of the rod and main bearings? On the 261 rebuild, Jerry had me run down all the rod and main caps with the torque wrench to double check everything. On this engine, all I get from the manual is "snugly" and "tighten down good and snug, using an "L" wrench for this purpose."

So, is this like setting the wheel bearings or adjusting Huck brakes? You tighten down until you feel drag when you turn the crank and then back off just enough that you don't feel the drag?? Jerry has taught me enough to think that "Good and snug" is a touch vague ...

???????

Here's a good discussion of this topic: Torque for rod and main bearings on a Chevy 4 banger

Cheers, Dean

Thanks Dean -- Gives me something to work with. I hope to get the engine on the stand this afternoon ...

John, a pretty good rule of thumb on bolts or studs without a torque spec is "snug plus 1/6 turn". Tighten the bolt or nut until all the clearance is taken up, then continue turning one flat on the bolt head or the nut. That stretches the fastener slightly and the internal tension keeps it tight. If there's a castle nut and one or more holes drilled in the stud, "snug plus the next pin hole" works well. Most studs have two holes drilled at a 90 degree angle to each other, and the castle nut has six slots. That gives the assembler a choice of how far to tighten the nut before inserting the cotter pin.

Give me a call on my land line at your convenience and I'll walk you through the procedure for checking the clearance on those Babbit bearings- - - -it involves some shim stock and a calibrated elbow on the flywheel. That's definitely NOT a keyboard exercise!
Jerry

Are these bearings made of wood? Leather?

John, did a hand crank come with the truck? That tool is VERY handy when turning the crankshaft to 'feel' your way through checking the bearing clearances and it is also handy with setting the engine to TDC when timing the distributor.

And, don't forget how much fun it is to start it with the hand crank at a car or truck show! ;-)

If you don't have one, I will measure Lurch's hand crank so you can fabricate one.

Dean

Thanks Dean -- Yes, a hand crank was in the stash.

I hope to have the engine on the stand this weekend.

John , it was great to see you appear over on the VCCA. There used to be a tread there called "School is in session". It had multiple lengthy entries and most of the material was on rebuilding the engine. I think it will be a really fun truck!!

Fred

The "School is in Session" information is still on the VCCA site, but it is not a thread anymore. The entire thread is now contained in a PDF that resides in the list of Technical Articles in the Members Only area off the main site page at vcca.org. That thread is a wonderful, 250 page 'classroom discussion' of rebuilding a 1928 engine by Ray Holland, a Master Mechanic and Chevy four cylinder expert.

BTW, to get to the Members area of the above site, you need to log be a club member and log on to that site. The forums and the main VCCA site do not share security info, so you have to log onto them separately. You can use the same user name and password, but being logged on to the forums does not translate to being logged on to the main club site.

Dean

Thanks Fred/Dean!

Got the flywheel off today. Found out a few more things! And I am studying up on the lower end. I have something cool in the works for that project. Not at liberty to say more just yet, but this should be a pretty cool exercise.

Also ... stopped by a friend's barn to check out a true barn find ... That is in a separate post ..