The Stovebolt Site Forums The Shop Area Engine Shop 235 Connecting rod shims?

A few of my connecting rods are about .005 undersized due to wear, but if I take the shims out the rods fit the crank perfect. So, my question is are the shims necessary? Same goes with a few of the main bearing shims. If it's a stupid question, go easy on me. My 235 is a 1952.

The shims are there to allow adjustment for wear so removing some or all them is correct procedure, however .005 is a lot of slop and likely the shaft journals are pounded flat. Mike the shaft for out of round and if all is good, take the shims out. Watch out for cracked babbit also.

I guess my next question then would be how much play is acceptable? Max .003?

That's not the problem - the journal isn't round anymore.

how can you check for journal roundness?

Let us go back to original description. If the journals were not measured than the .005 came from the fact that removing the shims produced a good fit, right. What this probably means is that the babbitt on the rods has worn near that amount. The journal probably would not be worn .005 without having ridges or being egg shaped. I think you should look at the babbit on the rods to see if some of it is worn through.

The babbits look pretty good to me, but I could be wrong. Should I just play it safe and have the rods re-babbited at .010?

Use michrometer. Check across the vertical orientation at top of travel vs perpindicular. How the heck do you describe this normally??

Dan Bentler

I'll give the micrometer a shot and see what I come up with. I've been using calipers, but it sounds like a need to add a new tool to my collection. There shouldn't be any play at all between the rod babbit and crank?

If you get a 52 shop manual it will tell you how much the specs call for and how to adjust the crank and rod bearings it is a very important part of building an engine and if done right You're engine will last a long time if done wrong it will not.The manual would be the best money you can spend on You're build ,I've read mine before I do alot of stuff and keep it on the work bench during things like engine builds or trans builds it will give you a step by step on the take down and the build .

Pete

I'll grab a shop manual too. Thank for all the info, guys.

Those rods have very thin babbitt and there probably aren't many or any people doing the rebbaitting on them. They are different from the older ones that used a thicker babbitt. The easiest way to recondition them is to have them bored to take inserts. There are inserts made for that application.

If you take a piece of shim stock, say .001" or .002" cut 1/4" wide, you can lay it across the journal and do up the rod. If it locks the rod there is less clearance than the stock. You want to get the clearance down around .001". If the babbitt looks good there probably is more life left in them.

Thanks. I'm gonna try the shim stock trick. I am weighing my options right now. Jim Carter has a rebabbiting service, but it's over 300 bucks...

I think you will find having the rods machined is less money. You end up with a modern bearing material. JC i think sells converted rods with a core charge. In case you are wondering, having the rods converted doesn't alter the dipper setup but you loose the ability to adjust with shims, unless you are a rebel like me!

Converted rods? I'll have to look into that. I'll check the JC website again. Thanks for the tips, truckernix. If you don't adjust with shims, how do you make adjustments?

When they machine the rods to take inserts, the inserts are precision parts, just like modern rods. Thus if your crankshaft is within standard spec, then the insert gives the correct fit. What I did was use .001 inserts and shimmed as necessary.