Tight Thrust Bearing, Why ?

[Scott 440 TNT]

Hello
Obviously I’m not a motor guru.
My 72 440 is new to me so I don’t know it’s history, just trying to get it running.
It’s been very stiff to turn by hand and has not been started yet.
I started pulling main caps looking for a spun bearings. The center bearing is tight where the thrust surfaces meet the crank and the bearing is worn down to the copper on both sides as you can see in the pics. The bearing surface is still good.
Why would that be an issue, I would think that’s a standard width. Is the crank the problem or the bearing?
Thanks

 

[Lefty71]

Did you check end play??? As-in you had none before starting to teardown?? You should be able to fit a feeler gauge in between each bearing shell and the crank.

Both top and bottom shells have the same issue??

Also, if you put the crank back in without that #3 bearing, torque the other 4 caps in place, does it now spin quite easily??

It is possible that you have a '74 and later bearing in an early block/cap, but recess in your pic looks correct....maybe a pic of the shell in the block may help??

 

[Big_John]

My 2 cents.... Judging by what you've said and the pics, whoever rebuilt that motor skipped a crucial step and that's checking for endplay when putting the crank in the engine. I would be going through everything on this if it were me.

The cause could be an oversize bearing, but I'm betting that it was a replacement crankshaft that wasn't right.

The thing to do is measure the width of the thrust bearing and the width of the journal of the crankshaft. A cheap pair of digital calipers from Harbor Fright will do just fine for that measurement.

I don't know what that dimension is supposed to be and a quick google search along with a couple minute in the FSM didn't tell me, so I'll leave that to you to dig that up. You may want to pull the crank out and take it to a competent shop, preferably one that specializes in crankshafts and get it checked.

 

[Davea Lux]

Thrust wear can be an indicator of a balance issue. A couple of things that could cause this. Firstly, how many miles are on the engine and is it the correct year for the car? If someone dropped in a junk yard engine the components might be mismatched. There is a machined pad on the top of the block directly across from the distributor on the driver's side. In '72 the code on the pad should read H 440, there will usually be an assembly date on the pad as well. If the letters HP appear, it is a forged crank engine. Second, check the numbers on the crank to determine if it is a forged unit or a cast unit. If a rebuilder substituted a forged crank into an engine that came with a cast unit, the engine will be way out of balance. Check your torque convertor to see if it has weights welded to it. If it has weights, the engine came with a cast crank. Forged cranks did not use the weights. Check the harmonic balancer. if it has a round center, it came off of a forged crank engine. If the balancer has an egg shaped center, it came off of a cast crank engine. A mismatch of the crank, the converter or the balancer will cause a vibration that will toast the thrust surface on the main bearing. A worn thrust will not usually cause the engine to be hard to turn over, you might try putting some light oil into each cylinder to see of the engine will then turn over easily.

Dave

 

[413]

I doubt a 74 and newer sized thrust bearing would go into an older block. You would have to pound it in caveman style.

 

[Scott 440 TNT]

Did you check end play??? As-in you had none before starting to teardown?? You should be able to fit a feeler gauge in between each bearing shell and the crank.

Both top and bottom shells have the same issue??

Also, if you put the crank back in without that #3 bearing, torque the other 4 caps in place, does it now spin quite easily??

It is possible that you have a '74 and later bearing in an early block/cap, but recess in your pic looks correct....maybe a pic of the shell in the block may help??

View attachment 644686

There was no end play before removing , the cap with bearing was a pain to get out it is so tight. Engine still turns stiff with top bearing still installed. Engine is in the car. The recess is a bigger diameter than the bearing so that’s not the issue I’m thinking. I would like to remove the top #3 bearing but I would need to pull the front timing chain and pull the trans also.
But that seems like my next move.
Thanks for your feedback, keep the ideas coming.

 

[Scott 440 TNT]

Thrust wear can be an indicator of a balance issue. A couple of things that could cause this. Firstly, how many miles are on the engine and is it the correct year for the car? If someone dropped in a junk yard engine the components might be mismatched. There is a machined pad on the top of the block directly across from the distributor on the driver's side. In '72 the code on the pad should read H 440, there will usually be an assembly date on the pad as well. If the letters HP appear, it is a forged crank engine. Second, check the numbers on the crank to determine if it is a forged unit or a cast unit. If a rebuilder substituted a forged crank into an engine that came with a cast unit, the engine will be way out of balance. Check your torque convertor to see if it has weights welded to it. If it has weights, the engine came with a cast crank. Forged cranks did not use the weights. Check the harmonic balancer. if it has a round center, it came off of a forged crank engine. If the balancer has an egg shaped center, it came off of a cast crank engine. A mismatch of the crank, the converter or the balancer will cause a vibration that will toast the thrust surface on the main bearing. A worn thrust will not usually cause the engine to be hard to turn over, you might try putting some light oil into each cylinder to see of the engine will then turn over easily.

Dave

Hello
It’s not the original engine for my car and I have no history for it. The pad is unreadable, it has 440 on the side and a late 71 date. I’m sending a pic of the crank, maybe that will allow someone to identify if it forged or not. The engine has been pre oiled and the cylinders also.
It has a 833 trans attached.
Thanks for your feedback, keep the ideas coming.

 

[Lefty71]

Any pix or clues given from post #4 may help you (and us). That is a forged crank engine, or at least it has one in it now. Maybe pull the bearing shell you already have in hand off the cap and give us the info you find on the back of the shell?? Also, there may be a forging number stamped into one of the counterweights vertically. Does each pair of rods have some side play if you wiggle them??

 

[Davea Lux]

If the engine has a late '71 production date, it is probably a '71 engine, but some did find their way into '72 cars. "71 was a forged crank engine. On the passenger side pan rail about 1/3 of the way back from the front of the engine there is a pad that will be stamped with the VIN number, that would tell you what car the engine was native too. With the 833 4 speed, somebody riding the clutch or a throw out adjusted too tight will wear out the thrust. Is this in a B-Body car?

Dave

 

[Scott 440 TNT]

Any pix or clues given from post #4 may help you (and us). That is a forged crank engine, or at least it has one in it now. Maybe pull the bearing shell you already have in hand off the cap and give us the info you find on the back of the shell?? Also, there may be a forging number stamped into one of the counterweights vertically. Does each pair of rods have some side play if you wiggle them??

Hello
Yes the rods all have similar side play and I pulled one rod bearing and it looks good.
I can’t read the number on the crank but maybe you’ll know what it is.

 

[Scott 440 TNT]

If the engine has a late '71 production date, it is probably a '71 engine, but some did find their way into '72 cars. "71 was a forged crank engine. On the passenger side pan rail about 1/3 of the way back from the front of the engine there is a pad that will be stamped with the VIN number, that would tell you what car the engine was native too. With the 833 4 speed, somebody riding the clutch or a throw out adjusted too tight will wear out the thrust. Is this in a B-Body car?

Dave

Hello
9-14-71 date
Pad looks blank

 

[Davea Lux]

Since the pad is blank, this could be a replacement crate engine, fairly common of 4 speed cars as a lot of the factory engines were over reved and blown up. Looks to have been a 375 hp engine as the 350 horse engines were blue. If you pull a valve cover and the engine has buffered valve springs it is probably a 375 hp engine. The main you pulled is .010 under, so the engine has probably been rebuilt at some point.

Dave

 

[Scott 440 TNT]

Since the pad is blank, this could be a replacement crate engine, fairly common of 4 speed cars as a lot of the factory engines were over reved and blown up. Looks to have been a 375 hp engine as the 350 horse engines were blue. If you pull a valve cover and the engine has buffered valve springs it is probably a 375 hp engine. The main you pulled is .010 under, so the engine has probably been rebuilt at some point.

Dave

Thanks for your feedback.
I’m not sure what buffered valve springs look like but I’ll send you a pic when I go back to my shop, and I’ll learn something new.

 

[Davea Lux]

Thanks for your feedback.
I’m not sure what buffered valve springs look like but I’ll send you a pic when I go back to my shop, and I’ll learn something new.

Buffered valve springs have a second spring inside the coil of the outer valve spring.

Dave

 

[Scott 440 TNT]

Hello
Obviously I’m not a motor guru.
My 72 440 is new to me so I don’t know it’s history, just trying to get it running.
It’s been very stiff to turn by hand and has not been started yet.
I started pulling main caps looking for a spun bearings. The center bearing is tight where the thrust surfaces meet the crank and the bearing is worn down to the copper on both sides as you can see in the pics. The bearing surface is still good.
Why would that be an issue, I would think that’s a standard width. Is the crank the problem or the bearing?
Thanks

View attachment 644683

View attachment 644684

Question
When a crank is undercut for new bearings is the width of the thrust surfaces cut wider.

 

[Davea Lux]

Question
When a crank is undercut for new bearings is the width of the thrust surfaces cut wider.

No, thrust should stay the same. The thrust limits end to end movement of the crank and should be unaffected if the crank is cut undersized. The only exception I can think of is if the thrust surface on the crank was damaged and welded up and re-cut to stock specs. As a practical matter, welding the thrust is usually a last resort because a replacement crank is unavailable, not recommended for performance or racing applications.

Dave

 

[Scott 440 TNT]

No, thrust should stay the same. The thrust limits end to end movement of the crank and should be unaffected if the crank is cut undersized. The only exception I can think of is if the thrust surface on the crank was damaged and welded up and re-cut to stock specs. As a practical matter, welding the thrust is usually a last resort because a replacement crank is unavailable, not recommended for performance or racing applications.

Dave

Hello
Thanks for the info, I will take some dimensions of the bearing and crank thrust width and report my results.