8ba rod bearing problem

[3739ford]

Without removing the crank and taking back to the machine shop is there a way to remedy two rod bearings when tightened down you cannot turn it over. The motor does not have the heads on it yet just slowly rebuilding the motor.

[cadillac512]

Originally Posted by 3739ford

Without removing the crank and taking back to the machine shop is there a way to remedy two rod bearings when tightened down you cannot turn it over. The motor does not have the heads on it yet just slowly rebuilding the motor.

The problem may be the rods rather than the crank. Make sure the caps are on the matching rods and that they are on the correct way 'round. Then install one at a time to see which is the problem. Finally, you may have to remove the rods and measure them for out-of-round and size. Also the crank throw can be measured in-place with a 2-3" micrometer to make sure the size is correct. Bearing thickness can be measured with a dial caliper or ball-end mic to make sure you don't have an incorrectly marked/packaged bearing.

Terry

[3739ford]

Caps were installed on correct rods. I went ahead and pulled all the caps off and picture 2 and 3 the bearing has a spot that hangs your fingernail. These were new bearings and wiped clean and moly lubed before installing. The motor has only made two complete revolutions with pry bar on the fly wheel.

[JWL]

What are the details? Is this a fresh regrind crank with a larger fillet?

[3739ford]

It is a Mercury crank with 4" stroke that came with the 1CM block. The machine shop just polished it as it was in good condition. Had to bore the engine 3 5/16 to get a good clean bore. Reusing the original rods had the machine shop check for being round all were good. I had the machine shop install the new Egge pistons to the rods. When I picked the block and crank up I had the machine shop recheck the size bearings I needed. According to him I needed .20 under for the rods which I ordered. I cannot remember now where I ordered the rod bearings from.

[Kohnke Rebabbitting]

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Originally Posted by 3739ford

Caps were installed on correct rods. I went ahead and pulled all the caps off and picture 2 and 3 the bearing has a spot that hangs your fingernail. These were new bearings and wiped clean and moly lubed before installing. The motor has only made two complete revolutions with pry bar on the fly wheel.

Make sure you check, rod alignment!

Herm.

[Kohnke Rebabbitting]

Originally Posted by 3739ford

It is a Mercury crank with 4" stroke that came with the 1CM block. The machine shop just polished it as it was in good condition. Had to bore the engine 3 5/16 to get a good clean bore. Reusing the original rods had the machine shop check for being round all were good. I had the machine shop install the new Egge pistons to the rods. When I picked the block and crank up I had the machine shop recheck the size bearings I needed. According to him I needed .20 under for the rods which I ordered. I cannot remember now where I ordered the rod bearings from.

Using a so called good enough crank, could mean it can very in a few tenths in size. Mic closely the pins that turn good, compared to the one that doesn't. As previously stated, check Radius, a .001 to tight is enough to lock a motor.

The black marks in your bearings, are the spots that are touching.

Herm.

[3739ford]

Well, sometimes my memory is not what it use to be. I went back to the barn and the old bearings were .20 under. I found the paper the machine shop guy wrote the bearing sizes down on I needed and it was .30 under. Here are a couple pictures of measurements from my cheap HF tool. The current bearings are .30 under.

[Bob C]

If the old bearings were .020 and they just polished the crank why would
he say you needed .030 bearings.

[3739ford]

He whipped out his little measuring tool and dialed it up on the journal and without hesitation said .30 under.


I found this site interesting: http://pbwdist.com/catalogs/Mahle_Clevite_Bearing.pdf

[Ronnie]

Turn the bearings over chances the size is on them


R

[cadillac512]

Originally Posted by 3739ford

Well, sometimes my memory is not what it use to be. I went back to the barn and the old bearings were .20 under. I found the paper the machine shop guy wrote the bearing sizes down on I needed and it was .30 under. Here are a couple pictures of measurements from my cheap HF tool. The current bearings are .30 under.

Those two measurements are of two different crank journals? The 2.106" is .032" undersize and the 2.115" is .023" undersize! It may be that you have a crank that's been previously ground to different sizes on different journals...was done sometimes back when. Obviously a dial caliper isn't accurate as a mic would be but close enough for what you're diagnosing. You may need to measure with a mic, and maybe either get different bearings for different journals (not the best but will work) or have the crank ground to .030" on all the journals (if the existing ones check out.)



Terry

[3739ford]

My rough calculations was telling me something was not right. I think having it checked again would be best route. If not try to mix and match. The motor was previously a hot rod with very hot cam. Am I correct with a stock crank rod size of 2.1390

[cadillac512]

Yes, stock rod journals are 2.139". My Clevite bearing book shows 2.1380"-2.1390" as limits for stock.

Terry

[Lawrie]

Dont use a vernier caliper ,USE a micrometer,
Measure the crank pin diameter,(using a Mic)
Measure the bore of the rod,
Then measure the thickness of the bearing shell, using a 1 inch mic and a 5/16 dowel ,then subtract the dowel diameter from the reading and that will give you the bearing thickness.
Start with the rod diameter subtract twice the bearing thickness and you should have the crankpin size plus the clearance.
Lawrie

[JWL]

If those measurements are reasonably close to being accurate they represent one at .020 under and the other at .030 under.

[GOSFAST]

Originally Posted by cadillac512

It may be that you have a crank that's been previously ground to different sizes on different journals...was done sometimes back when.

Terry

Very accurate statement here, not only on an individual rod journal but sometimes an occasional cylinder bore also! (See photo below, it's just one brand of a "portable" boring bar used at the time for very this purpose)

Many of these type repairs were done with the engine still in the ride, it's how it was done back then!

Thanks, Gary in N.Y.

P.S. At one time I had the "portable" crank grinder along with the boring bar pictured here, I still own this bar, the crank grinder went a long time ago. In retrospect it wouldn't have hurt to hang on to both?? Nice conversation pieces today anyway! I have customers today have absolutely no idea what the bar was used for when I show it to them?

[3739ford]

JWL, the front and rear measure the same 2.106 and the two middle ones measure 2.115. I got to ask since I don't know what is the downside of running .030 on front and back and .020 on the middle ones.

[Gene1949]

find another machine shop. No REPUTABLE shop would grind a set of rod [journals] like that. God know what else they missed.

[JWL]

There is most likely no problem with having different size journals, with proper coordinating bearings. I would say no problem except for my inability to actually examine the conditions.

[3739ford]

I still have the old bearings separated and marked where they went. If using plastigage what is the desired clearance on rod bearings. Just wanted to check and see how it would turn out. Perfect world would be getting them all the same and that is still option I'm considering. I want to change out front seal to one piece anyway since I'm back inside the engine.

[Bored&Stroked]

Originally Posted by 3739ford

JWL, the front and rear measure the same 2.106 and the two middle ones measure 2.115. I got to ask since I don't know what is the downside of running .030 on front and back and .020 on the middle ones.

Did you have the crank reground at the same machine shop? Even if they just polished it, should have measured/checked ALL the journals . . . so I'm still not letting them off the hook.

[40 Deluxe]

Originally Posted by Gene1949

find another machine shop. No REPUTABLE shop would grind a set of rod [journals] like that. God know what else they missed.

Wait a minute Gene. Apparently this crank was ground in the distant past when it was common to do this. Either by customer request or the crank guy wanted to save a little wear on his grinding wheels. The engine apparently ran a long time set up this way, so it was not a problem; nothing overlooked.

[philipswanson]

Check it with Plastigage.

[rotorwrench]

Ford allowed more clearance on the connecting rod big end bearings than they did the mains. My old Mercury manual lists .0005" to .003" for rod big end bearing clearance and .001" to .0026" for main bearing clearances. Side play on the rods is .006" to .020" for two rods on one crank pin.

[cadillac512]

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I'd have no problem running dissimilar sized bearings if their crank journals are round,smooth,and correctly sized to their respective undersizes. And yes...it's time to get a micrometer and check-OR-if not possible, careful use of plastigauge on every journal of this crank after determining undersizes with the caliper. The machine shop personnel really should have checked and noted every journal-shame on them.


Terry

[rotorwrench]

When journal sizes are odd, I'd be wanting to make sure there was no runnout anywhere. That would make sure things are still concentric with the center line of the crank. There can be a problem if journals are polished too far. Some folks used to lap the bearings too so you never know what your going to find on these old cranks.

[3739ford]

I removed the pistons/rods with bearings and have everything ready to go back to the machine shop tomorrow. I'm going to see what he figures out and tells me what the problem is. With my cheap measuring tool it seems to me the rod journal is not round, but more egg shaped. Will let you know what the outcome is.

[Gene1949]

Originally Posted by 40 Deluxe

Wait a minute Gene. Apparently this crank was ground in the distant past when it was common to do this. Either by customer request or the crank guy wanted to save a little wear on his grinding wheels. The engine apparently ran a long time set up this way, so it was not a problem; nothing overlooked.

Precisely my point (distant past), customer request or "saving some wear on his grinding wheels" is a patch job.

Eyeballing a "polish" on a crank without measuring it is not something a reputable shop would do.
I doubt if the crank even had a bath after the polish.
The owner himself picked up on the original patch job (grind) AND egg shaping the journal, who knows.

[Bored&Stroked]

I think you answered your own question when you measured the journals - two are at .020 and two are at .030 . . . a miss-matched affair. Now, if the journals are in good shape, concentric, no taper, etc -- then I can see no real issue with running .020 bearings on two journals and .030 on the others. Would I do it this way . . . well 'No' - but I'm a perfectionist and I wouldn't want the "next guy" to see an engine I built done in this fashion.

BUT - with all that said, if it is about spending less money - then you can probably put it together with the two different rod-bearing sizes - as long as the resulting clearances are correct.

On my Soapbox: What is still of concern is that the machine shop obviously didn't measure the crank . . . so what else didn't they measure? Quality machine work and correct clearances are everything in an engine build . . . .

[Pete]

Originally Posted by GOSFAST

Very accurate statement here, not only on an individual rod journal but sometimes an occasional cylinder bore also! (See photo below, it's just one brand of a "portable" boring bar used at the time for very this purpose)

Many of these type repairs were done with the engine still in the ride, it's how it was done back then!

Thanks, Gary in N.Y.

P.S. At one time I had the "portable" crank grinder along with the boring bar pictured here, I still own this bar, the crank grinder went a long time ago. In retrospect it wouldn't have hurt to hang on to both?? Nice conversation pieces today anyway! I have customers today have absolutely no idea what the bar was used for when I show it to them?

As a side note Gary, Rottler is having their annual open house to the industry this weekend. Everybody will be there. I first met the old man in 1955.

[JWL]

As another side note, I own both a "in-car" crankshaft grinding machine and boring equipment.

I saw the crank grind done once and the operator was very skilled and efficient. The job was a new Rambler 6 cyl. that was under warranty. As far as I know it survived the warranty period and is still going. Grin.

[Bored&Stroked]

Originally Posted by JWL

As another side note, I own both a "in-car" crankshaft grinding machine and boring equipment.

I saw the crank grind done once and the operator was very skilled and efficient. The job was a new Rambler 6 cyl. that was under warranty. As far as I know it survived the warranty period and is still going. Grin.

Hey John: Was sitting here scratching my head - trying to imagine how the rod journals could possibly be ground in the car (given the stroke/throws of the crank). Did this magic gismo somehow handle the rods as well? I'd love to see that machine in action! And I imagine it would take a hell of a skilled operator to use it!

[rotorwrench]

In car work was usually done on warranty situations where the car was still in near new condition and there was less chance of heavy wear or bending on any of the rotating components. Older components with a lot of wear and tear should get more scrutiny to insure serviceability. A dedicated crank grinding machine is the best way in that situation. Checks are simpler that way and repairs would follow as necessary.

[Kohnke Rebabbitting]

Originally Posted by Bored&Stroked

Hey John: Was sitting here scratching my head - trying to imagine how the rod journals could possibly be ground in the car (given the stroke/throws of the crank). Did this magic gismo somehow handle the rods as well? I'd love to see that machine in action! And I imagine it would take a hell of a skilled operator to use it!

It was for Rods, NOT mains.

Herm

[Bored&Stroked]

Originally Posted by Kohnke Rebabbitting

It was for Rods, NOT mains.

Herm

Hey Herm - just checking . . . RODS, not mains??? I can see a fixture for the mains working, but the rods - that has to be complex! It would have to somehow rotate/articulate with the crankshaft rotation - that seems to be a hard situation to ponder - unless it indexed off the mains in some fashion.

Just curious!

[Kurt in NJ]

The grinder has a hook opposite the grinding wheel, there was a motor to turn the rear wheel, or fit in the place of the starter to rotate the crankshaft , the grinder moves with the rod journal. It can only make the journal round, but the center of the journal will move if the wear was only on one side

[Ol' Ron]

I had a crank ground in the car on a Chrysler 383. The wheel on the grinder was quite skall and the starter turned the crank with the lugd removed

[Kohnke Rebabbitting]

Originally Posted by Bored&Stroked

Hey Herm - just checking . . . RODS, not mains??? I can see a fixture for the mains working, but the rods - that has to be complex! It would have to somehow rotate/articulate with the crankshaft rotation - that seems to be a hard situation to ponder - unless it indexed off the mains in some fashion.

Just curious!

The best one was built by Sunnen, Model KN, look on E-Bay. It was made to be used just for Rods mostly when just one pin went bad. You jacked the car up, pulled the pan, put an electric motor and V-belt to turn the crank, the machine was clamped to the pinand the metal was ground the main part of the pin, and centered of, I Think ????????? off the Radius to keep the same stroke.

Herm.

[Kohnke Rebabbitting]

Originally Posted by rotorwrench

Ford allowed more clearance on the connecting rod big end bearings than they did the mains. My old Mercury manual lists .0005" to .003" for rod big end bearing clearance and .001" to .0026" for main bearing clearances. Side play on the rods is .006" to .020" for two rods on one crank pin.

Most bearing books have a maximum, and minimum for any given crank. On say a 2" crank, the actual minimum size should be .002 thousandths, and plus, one more .000-50 for a maximum.

If you set a 2" crank clearance to .000-50, or even a .001, the crank when hot will expand about .002 thousandths. So what happens is the crank pushes bearing material out of the way until it has the clearance it wants to get enough oil to the bearing to cool the bearing, and stop its expansion, so why waste bearing material, and taking a chance on smearing a bearing.

Depending on how fast the car is driven, most of the time will determine what the bearing clearance will be when, Cold, or Hot.

Herm.

[outlaw]

Back in the mid 70's I worked for a large at the time automotive parts store/warehouse here. They sold remanufactured motors by a company named Lomac. It was very common to have new remanufactured motors by them that had 1 main journal or rod journal turned under sized or single hole bored over size & some time multiples in a single motor. We are talking on the order of 1 hole .30 or .40 over size & the rest std or maybe .10 over. The same with the journals. You could find any combinations. This was in all types & brands of motors. We sold a lot of them back then. Just sayn.

[bobH]

Originally Posted by outlaw

Back in the mid 70's I worked for a large at the time automotive parts store/warehouse here. They sold remanufactured motors by a company named Lomac. It was very common to have new remanufactured motors by them that had 1 main journal or rod journal turned under sized or single hole bored over size & some time multiples in a single motor. We are talking on the order of 1 hole .30 or .40 over size & the rest std or maybe .10 over. The same with the journals. You could find any combinations. This was in all types & brands of motors. We sold a lot of them back then. Just sayn.

For the young guys... I worked in a small, independent shop in the 50's. At least where I was, it was VERY common to grind a crank in the car (or pickup). We had one customer that ran a small fleet of Chevy trucks for moving bee hives around. And, his drivers really pounded those old Chevy's. So, they had rod failures quite often. The guy that did our 'in-truck' rod journal grinding had a steady customer at our shop. And, some of the under-sizes would be un-heard of today. Like one I remember as .090 ! The guy that did the grinding also provided the bearings, or in the case of Chevy's, the babbited rod. So I never knew how those odd-size bearings came about.
I think the current-day generation that tries to make precision in old engines would likely never understand 'how-it-was'. After all, they're just old Fords, Chevy's, Plymouths, etc, etc. JMHO

[Kohnke Rebabbitting]

Originally Posted by outlaw

Back in the mid 70's I worked for a large at the time automotive parts store/warehouse here. They sold remanufactured motors by a company named Lomac. It was very common to have new remanufactured motors by them that had 1 main journal or rod journal turned under sized or single hole bored over size & some time multiples in a single motor. We are talking on the order of 1 hole .30 or .40 over size & the rest std or maybe .10 over. The same with the journals. You could find any combinations. This was in all types & brands of motors. We sold a lot of them back then. Just sayn.

WOW.

Herm.

[jimTN]

I have a old 977 Cat with the 318 engine that had a couple of throws turned by one of those machines under the engine years ago and still runs well.

[JWL]

It would be a long explanation to describe how it was done. First the grinding is done with the end face of the rock. The electric tool has a long snout to provide clearance for crankshaft counterweights. There are 2 types of drive systems for rotating the crankshaft during the regrind. One is a set of motorized rollers for a rear(drive) wheel and the other is a starter replacement driving system for automatic transmission cars. The operator must find areas of the journal which are "round" usually involving some hand filing and sanding to accomplish. Even a badly galled or spalled journal will have small areas outside of the rod contact area to use. There is a hinged/jointed device, like a claw, attached to the grinder motor which over reaches the journal and provides the support and a guide for keeping it round. There are more details but this might give you some idea.

Obviously small cuts are the norm but it actually worked reasonably well.

[3739ford]

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Just picked up the crankshaft, rods and bearings. The rods are all the same now .030 and he test fitted rods/bearings to crankshaft and all turned smooth. He said one of the rod caps had gotten smashed a little and he run through a rod bore hone.

[cadillac512]

There 'ya go...that's a good deal now. That rod would have given you trouble too,and possibly a LOT of trouble. Well done for questioning things the way you did!


Terry

[Bored&Stroked]

Originally Posted by JWL

It would be a long explanation to describe how it was done. First the grinding is done with the end face of the rock. The electric tool has a long snout to provide clearance for crankshaft counterweights. There are 2 types of drive systems for rotating the crankshaft during the regrind. One is a set of motorized rollers for a rear(drive) wheel and the other is a starter replacement driving system for automatic transmission cars. The operator must find areas of the journal which are "round" usually involving some hand filing and sanding to accomplish. Even a badly galled or spalled journal will have small areas outside of the rod contact area to use. There is a hinged/jointed device, like a claw, attached to the grinder motor which over reaches the journal and provides the support and a guide for keeping it round. There are more details but this might give you some idea.

Obviously small cuts are the norm but it actually worked reasonably well.

Thanks JWL! One really has to appreciate the innovations and ingenuity that our forefathers applied in figuring out how to solve problems such as this. We had some really good entrepreneurs now didn't we! I can't imagine using such a machine, but I'd sure like to see one in action.