The Stovebolt Site Forums The Shop Area Engine Shop 216 Engine shims

I had a conversation with a fellow while at a local show and shine.
While the 216 in my 1 ton is running ok and not burning oil or smoking it does has what I would describe as a bottom end knock until it's up to temp. I did a rear rope seal this past winter and can confirm the existence of brass shims on at least the rear bearing and yes the dippers and trough were checked for correct height and sprayers were checked as well. This person suggested that if the original shims are still in they could be removed to tighten up the crank and possibly elimenate the knocking. Seems like an easy fix!
Anyone have any thoughts on this?

Doyle

That was standard practice back when these trucks were daily drivers. The individual shims are about .001" thick, or maybe a little less and there's usually several of them stacked up together. Peel off a layer or two and snug the cap up to see if the crankshaft gets hard to turn. The ideal situation will be when the crank can be turned with a firm pull on the bottom of the flywheel, but not locked up. Check and adjust the main bearings one at a time with the others loosened up slightly, so the ones you've already adjusted don't interfere with getting the one you're working with right, then retorque all the bearings. Rookies use plastigauge to check for the ideal .0015" oil clearance- - - -us oldtimers use a narrow piece of .0015" shim stock between the bottom bearing shell and the crankshaft and add or remove shims between the main caps and the block to get the right drag. It's possible to split the difference with one more piece of shim under the main cap than the other side. The front main cap has two 5/16" bolts that go into the bottom of the timing cover from the crankcase side.

Connecting rod clearance is adjusted the same way.
Jerry

Thanks Jerry I very much appreciate the explanation.

I am certainly no expert about shimmed main or rod bearings, but back in 1964 auto mechanics class in high school, Mr. Parker said the first thing to do with an engine with a knock is remove spark plug wires one at a time to try to isolate the noise to a particular cylinder. I think that would still be good advice.

What happens? Does the knock stop or change somehow when the plug wire in the problem cylinder is removed?

A rod knock or piston slap will change sound when the cylinder isn't firing. A main bearing knock stays pretty much the same, regardless of the cylinder firing or not. Main bearing knocks also show up on acceleration- - - - -a heavy BUMP-BUMP-BUMP-BUMP noise as the engine speed is increasing, followed by little or no noise at a steady speed.
Jerry

. A heavy BUMP-BUMP-BUMP-BUMP noise as the engine speed is increasing, followed by little or no noise at a steady speed.

Jerry, this pretty much is exactly what it sounds like!
Running at 50 to 55 mph steady or stopped at a traffic light with a lite foot and steady increase to rpm and it quietens down significantly.
Definitely will try to remove a shim or two and see what happens. I'm running 20w/ 50 Lucas oil I may even try to add a Zinc additive also. Nothing to loose.
I used the old fashioned wooden dowel trick and listened to the general area a couple of days ago and was able to isolate the knock to the bottom end as opposed to top end noise.
I have access to a running 261 and just may go that route and update the engine seeing that I have updated the 4:10 gears last year.

Thanks again

doyle 1950 Would forge right into that shim adjustment on those mains,peel the pan off ,let it drip a day or two,then adjust them all rods and mains. A careful job there will last you a long time. They used to sometimes push them to get running,that is a little too tight though !! Doyle 1950 Another test for main noise not mentioned yet is if you let up on it at road speed vacuum will pull the crank up into the block and stop the knocking,like on a steep hill. Downhill that is

I used to have a fine running 216 which I reluctantly retired due to the combination of a severely cracked water jacket, an eventual need of new rings and pistons, and some babbit missing from a couple of connecting rods.
Upon retiring it, I felt cheated out of the opportunity to perform the normal shim peeling procedure to maintain oil clearance.

FWIW Another source of knocks that often go away on warm-up is piston slap, though it's a sharper sound than a main bearing but increases with load like a main bearing. That sound will definitely go away if you short out that plug. I don't have any experience with cast iron pistons to predict whether collapsed skirts are common but that's usually the cause of slap. Chevrolet went to aluminum pistons about 1950 or so.

Slap can also occur if pistons are installed backwards, that is, with the offset to the wrong side. If someone wasn't careful when they replaced a piston and put it on the rod wrong, they might not have noticed it on final assembly. There's typically a mark on the piston crown indicating "Front," an arrow or a notch.

The fix for sloppy cast iron pistons was a spring steel expander device that was installed in the wrist pin area with a special set of pliers. They're still available from some of the vintage parts suppliers on Ebay. They're specific for different engines, depending on the bore size.

www.ebay.com/itm/174391484763?

Jerry

52 Carl That is a good feeling to get one adjusted up like that,biggest trouble there is having round journals to work with !