"Acceptable" bearing clearances

[Dick Steinkamp]

I pulled the pan and started checking bearing clearances today.

The rods don't have any shims left, but the bearing material (at least on the cap) still looks good. I Plastigauged #1 and there is about .0025 clearance.

The Mains still have some shims left. I plastigauged the middle one and got >.003 clearance. Removing a .003 shims from each side gets me to about .003 clearance with one .002 shim left on each side. So it appears I can get the mains back into spec if the other two are similar.

My question is, how bad is .0025 clearance on the rods? Will they knock? Hurt the crank? Be OK for a while?

[DJ S]

.0025 is an acceptable clearance. I start to worry when clearances exceed .003.

[Patrick L.]

I think .0025" is about the limit. I've seen [ well, actually heard] them rattle at .003" .

[Art Newland]

I'll be able to hear you coming!

[Dick Steinkamp]

Originally Posted by Art Newland

I'll be able to hear you coming!

That's the up side!

[Dick Steinkamp]

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Thanks, guys. I'm going to plastigauge the rest of the rods. If they are .0025 or less, I'll move to the mains and hopefully be able to use this engine a little more.

[Jim Brierley]

Your rods are nearing their limit. You can carefully file, or better yet take the caps down a little on a surface plate using sandpaper. Apply more pressure to the side with the most clearance, if there is one.

[tbirdtbird]

...

[Mike V. Florida]

Tony S. tells the story that when he was younger and money was non existent, he would take his A drive it up in the curb, drop the pan and remove the bearing caps and rub them on the sidewalk to get the clearance they needed to quite the engine.

[Dick Steinkamp]

Originally Posted by tbirdtbird

You removed shims from the center main.
Be reminded that you cannot remove more from the center main than you remove from the rear main.
So, let's hope that you need to remove the same amount of shims from the rear main.

We just had a guy on here last week who took more from the center than the rear and ended up needing 40 pounds on a torque wrench to move the crank, when it should move freely. He put the shims back in.

What prompted you to 'pull the pan and check clearances?'

Don't you also have a Stude?

Thanks. I do intend to roll the motor over with the crank (plugs out) after every rod and main adjustment to make sure I haven't done something stupid (Unfortunately, I do have a history for that )

I have not run this car very much. The other day, however, I let it idle for 45 minutes or so and the motor sounded noisier than I thought it should be when it was fully warm. No knocks and no change when the throttle was tipped in but I thought I'd better take a look at the bearings for peace of mind. I wanted to clean the pan out anyhow. I'm glad I did. It looks like I can get away with the rod clearances, but the mains need to be tightened up some.

I've built and owned many Studebakers. The two that were best known were my 54 Starliner hot rod...



...and my 53 Starlight Kustom (the Kart Hauler)...




No Studes in the fleet now, however. Besides the A, I currently have an MGB that I've put a Rover aluminum V8 and Camaro T5 in...



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...and a 69 Mercedes W114 250...





ALL cars are fun and I'm thoroughly enjoying learning about Model As again after a 50 year absence from them, wrenching on it, and hopefully playing with it after I get it safe and dependable.

[Flathead]

Some nice cars you got there.