Block Thrust Reapair

[SS/GN]

I have found a 109 block all std/std however the crank thrust in the block is damaged. Can this be repaired and if so what options are recommended.
Thanks in advance for any ideas.

 

[Turbo6inKY]

You can have it welded and re-cut. Probably not worth the effort and expense.

 

[BEATAV8]

Crank thrust? Or Cam thrust??

 

[Anthony P]

I figure it's cam thrust / block question. If so...

Yes, it's a straight forward repair.

- Damaged block thrust surface area is machined for a spacer washer (bronze) to work with the Torrington cam bearing. Sizing depends on repair and shim stock.

- cam might be shaved a bit in lathe to finalize timing set alignment.

the following videos and threads provide the details...

S

Thread 'How to repair cam thrust surface on your block.'

Jan 11, 2017

My comp 212/212 roller non billet cam was eating into my block. The way Richard Clark showed me how to repair it was to machine the block on a mill, then install a bronze washer cut out of bronze shim stock.

This is the before pic, notice the thrust surface near the oil galley plugs.

This is the washer. It's .040 thick. Not pictured we drilled a hole for oiling.

Here's the brass shim stock

This is what my cam looks like.

Setting the block up on the mill

Here we are indexing the bit to a surface on the block that's...

• Steve V
• Replies: 19
• Forum: Engine Tech

Cam/block thrust surface repair

www.turbobuicks.com

my block cam thrust surface fix...

So, a few years back I picked up basically a shortblock that had been machined from a shop that was closing. I noticed it had some wear(up to about...

www.v8buick.com

New development

the weber setup, do they cut the cam and the back side of the timing gear?

www.v8buick.com

There is another video I can't find at the moment showing blocks lined up waiting to go through a CNC mill for this same cam thrust surface repair. Don't recall the shop or the builder but recall some of the known Buick engine builders commenting on the video that it's quite a few bucks for that CNC station.

 

[LANDAU LIMITED]

According to other posts it's the crank thrust surface in the block. How that happens I would like to know.

 

[Chuck Leeper]

According to other posts it's the crank thrust surface in the block. How that happens I would like to know.

When the converter pressure forces the converter forward.

 

[Anthony P]

Ahh, crank thrust...ok. Yes, as Chuck noted, if the converter ballooned due to too high line pressure or too high line pressure from a misadjusted TV cable or maybe installer error of a shift kit.

crank thrust bearing failure and in-turn damage to the block can also come from a poor manual polishing of the crank and thrust surface itself and/or errors during setup assembly of the rotating assembly.

As such, like Andrew noted, repairing crank thrust bearing surface in block is welding and machining.

For more in-depth reading, I pulled up this writeup....

Crankshaft Thrust Bearing Failure - Causes And Remedies

For years, both transmission and engine rebuilders, have struggled at times, to determine the cause, of crankshaft thrust bearing failure. Diagnosing a

dannysengineportal.com

 

[LANDAU LIMITED]

When the converter pressure forces the converter forward.

That will eat away the bearing but how does it hurt the block? That's what doesn't make sense. The bearing totally disintegrated and continued to chew up the block? I can't see it getting that bad.

 

[Anthony P]

I asked a couple of my senior steering committee members about this. here's what I got...

In the '70s, each of them were racing in C super-modified class. Index then was 10.90, most were going 10.70s. A new Rehr-Morrison engine was sourced for one car. Crank thrust bearing kept getting eaten up on the thrust face in that new engine. On teardown, crank was fine. Block checked out fine. Everything checked out fine. But the thrust bearing kept getting eaten up time and time again.

Another block was sourced. The internals from the problematic engine were transferred to this block. Car ran 10.60s with this replacement block reusing the rotating assembly from the problematic engine. the only thing that changed was the block. No crank thrust problems were to be had with this block change as they pursued the class national record.

So, this buick block could have spun that thrust bearing and caused damage to the block. Main caps walked? or cap chatter to egg shape the caps, destroy bearings and crankshaft because someone isn't paying attention? with only the block, tough to conclude what caused the initial damage.

But the problem could be the block itself. Something in the casting metallurgy whereas when it heats up, things move and problems result. But cooled down, like during assembly, everything checked out fine.

 

[Turbo6inKY]

That will eat away the bearing but how does it hurt the block? That's what doesn't make sense. The bearing totally disintegrated and continued to chew up the block? I can't see it getting that bad.

If the thrust bearing spins, it can chew up the main boss.

Now, getting the thrust bearing to spin? Dunno how you do that, but I've broken enough stuff to know anything is possible so I'm not gonna judge.

 

[Chuck Leeper]

The law of unintended consequences in play?
** A cheap casting w/ mass production machining processes.
** An engine initially designed for < 200FWHP is put into service w/ virtually zero upgrades and the FWHP doubled.
In our case, maybe tripled.
My machine guy has stories of lifter bores all over the place, deck hgts way off, crank bores nowhere close to parallel to the deck, cam tunnels off.
Bottom line, a mom and pop engine for 87 octane horse piss.