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Shim on a rod bearing?

S

Speed_racer

NAXJA Forum User
Location
Ft Myers, Florida
Got a rod bearing going out on my jeep, although she's still strong. perfect oil pressure, acceleration (even tho' im babying it) and so on...

Im saving up for a stroker from titan engines, and was talking to my friend about the rod knock, he said that in his old SFA yota that his mechanic put a shim "under?" the rod bearing and kept it from rattling? said it went another 50k!! anyone ever heard of this?
 
Speed_racer said:
Got a rod bearing going out on my jeep, although she's still strong. perfect oil pressure, acceleration (even tho' im babying it) and so on...

Im saving up for a stroker from titan engines, and was talking to my friend about the rod knock, he said that in his old SFA yota that his mechanic put a shim "under?" the rod bearing and kept it from rattling? said it went another 50k!! anyone ever heard of this?
Click to expand...

A Toyota with a berring shim? :laugh2: Thats a new one. I highly doubt he did this. And for another 50K miles? Im speechless. I have never heard of this. If you think your rod berring is going out, why shim the old one, which is worn, just buy a new one and see what happens. :dunno:

:D
 
as it happens, I've heard of this. ;) I used to work for an old automotive machinist (he was in his 70's when i was a teen). I wouldnt try it on a modern car, but he had a box of very thin feeler gauges cut down he kept for use at the race track - he raced old flatfender fords.. I had the impression it was only good for a few miles, but that's enough on race day I guess.

-C
 
Yeah, I love how everyone on here thinks that if you're not as smart as they are, that youre a jackass....

Upon further research, they DID used to use shims on rod bearings in the older style cars, much as the guy above me said. Racecars used to have them in, and if you had a problem youd remove them, same of the old MGs.

As stated before, I AM BUYING A STROKER AND ONLY NEED TO NURSE SOME TIME OUT OF MY JEEP!
 
I still think it would kill your engine, I certainly wouldnt try it on my 4.0 ;)
 
Shimming rod bearings? Yeah, it's possible - I've also heard of being "between undersizes" and "shaving" a bearing to get the clearance you need (frankly, I'd sooner grind the crank.)

I've also hear of "mixing" rod bearings - mainly -.000" and -.001" under - to get a slightly undersize crank journal to work out - but even that sound shonky to me.

All else being equal, I'd sooner regrind the crank. If you're planning on replacing the engine anyhow, change a couple quarts out for a straight 40 or straight 50 at your next oil change - I'd sooner use that idea for a "band-aid" than anything else...

5-90
 
Speed_racer said:
Got a rod bearing going out on my jeep, although she's still strong. perfect oil pressure, acceleration (even tho' im babying it) and so on...

Im saving up for a stroker from titan engines, and was talking to my friend about the rod knock, he said that in his old SFA yota that his mechanic put a shim "under?" the rod bearing and kept it from rattling? said it went another 50k!! anyone ever heard of this?
Click to expand...

Since the oil pressure is still normal, I somehow doubt that you have a bad rod bearing at all. The knocking sound could also be from a collapsed lifter or a worn piston pin.
 
As Dr. Dyno suggests, it would be surprising for a bad rod bearing to coexist with good oil pressure. Perhaps the best thing to do is to ignore it until the oil pressure starts to drop.

I can see the possibility of shimming a bad bearing by putting a shim behind the insert, but I suspect it would be a very short-lived repair, and very hard to get the surfaces to make good contact. It would also be very hard to get good heat transfer through the shim, and I think the repaired bearing would run hot.

Back in the days of poured babbitt bearings, connecting rods were shimmed, but it's my understanding that the shims were between the two halves, and were removed as the bearing wore. Compression ratios and rpms were a lot lower in those days, too.
 
Being old as sin, I too remember shimming bearings. We did it on the farm equipment, but that is old stuff.

I didn't see what year your 4.0L is. Some of the later 4.0L's have a pronounced piston slap noise that scares a lot of people. If that is not it, and it really is rod bearing, just get a new set of bearings. They are not that expensive and they are relatively easy to replace. If the engine has never had the bearings replace, in other words, it did not have oversized bearings, I would simply get a set of .001 bearings and replace them, as long as the journals are not gauled.
 
what you think is a bad rod bearing could be flexplate bolts or the cracked plate. Mine sounded just like a rod bearing.
An old trick used to quiet some engines was to....GET THIS.... take a leather belt and cut sections to fit the bearings and tighten the hell out of the bolts. Would last a while depending on the amount of mileage, much like the old sawdust in the rear end trick to quiet them down.
 
dizzymac said:
what you think is a bad rod bearing could be flexplate bolts or the cracked plate. Mine sounded just like a rod bearing.
An old trick used to quiet some engines was to....GET THIS.... take a leather belt and cut sections to fit the bearings and tighten the hell out of the bolts. Would last a while depending on the amount of mileage, much like the old sawdust in the rear end trick to quiet them down.
Click to expand...

I once read a story from the Model T era about a guy who had a bearing go bad, and stopped at a farm. The farmer went out and got a piece of really lean bacon and made the bearing out of that. He said it worked for years.
 
LMAO!!!!! Did driving make him hungry? I lost track of a screwdriver under the hood with a slant six, it wound up arcing it's way through a brake line. Smelled like doughnuts frying.

I know of one guy who does a lot of horse-trading, replaces his bottom end bearings just because the engine has 60K or more. Makes him happy, it's cheap, why argue?
 
I've seen simular things done with leather cut from a leather belt on flathead fords.
 
Been there done that

Dad was B17 mecahnic in WWII / Cadillac in late 40's learned it there

We re-built several Opels in 70's - only had Std beaings available - did it on mains and conns

If you think about just moving the bearings close together with shims you get an oblong shape.

trick is to overshim to get better contact all around when it breaks in. No plastigauge needed - did it by feel -- tight is right - but not so tight as to smear the bearing material when you start-up

Did a full set on one motor - had to tow the damn thing aound the block to get it going - starter not strong enough to pull it through

That one is still running - I know cuz it's in my garage!
 
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