How to repair cam thrust surface on your block.

[Steve V]

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 not chewed up. We checked both side and the top of the block. Sides where the same, top was .002 thicker.

First pass.

Half way there. Took off .021

All done. Took off .0415 total. Adjacent cam lobe interference was checked before and after. No issue there. Big thanks to RC as usual .

 

[ek02]

Comp makes a .030 bronze washer for small block Chevy's that works well on the Buick cam. Not enough end play (.004) wore a block out for me. I now use .008 to .010. It did not hurt the cam since it is harder than the block. Looked like yours. Just smoothed it and put it in another block. Thanks for the photos.

 

[TurboWh1]

Luckily I’ve never seen this issue before! Did you only take enough off the block to clean it up or were you shooting to run a .040 for some reason? Id be curious to know how the cam lives after some abuse. In theory it sounds like a great idea to save the block. These 109's are getting more scarce by the day!!

 

[Steve V]

Comp makes a .030 bronze washer for small block Chevy's that works well on the Buick cam. Not enough end play (.004) wore a block out for me. I now use .008 to .010. It did not hurt the cam since it is harder than the block. Looked like yours. Just smoothed it and put it in another block. Thanks for the photos.

Good info, another option.

 

[Steve V]

Luckily I’ve never seen this issue before! Did you only take enough off the block to clean it up or were you shooting to run a .040 for some reason? Id be curious to know how the cam lives after some abuse. In theory it sounds like a great idea to save the block. These 109's are getting more scarce by the day!!

We took .040 because that was the thickness of the washer Clark had. Block was clean after the 1st pass.

 

[TurboBuRick]

Nice fix but tell us why it happened.

 

[bison]

Comp makes a .030 bronze washer for small block Chevy's that works well on the Buick cam. Not enough end play (.004) wore a block out for me. I now use .008 to .010. It did not hurt the cam since it is harder than the block. Looked like yours. Just smoothed it and put it in another block. Thanks for the photos.

.004" is enough and not why you had thrust failure


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[Steve V]

Nice fix but tell us why it happened.

This motor was a complete abortion that I acquired last winter. Block already had some wear 1st go round. RC blessed it and said it would be fine last April when we built it at his shop. Fast forward to now--it's out and apart not due to failure but leaks and changes---the block is worse--hence the repair. My guess..a bur from a cam at some point in time during it's life. It was a flat tappet engine when I tore it down initially.

 

[TURBOELKY]

Had to do this on my block too. Went about it the same way. Really the only way to do it.

 

[earlbrown]

Years ago I built a 'plug' that slides into the front two cam bores and put a hole in the middle for a valve grinding mandrel. Then dressed a stone and ground the leading edge until it was clean.

Guaranteed to be square with the centerline of the cam that way.

 

[mtocrs1]

The last roller Camshaft I installed would cut your finger at the oiling hole, spent some finessing it before the installation. I never would have thought to check but there was an old post from turbofabricator on the issue. Possibly the cause here.


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[Steve V]

Years ago I built a 'plug' that slides into the front two cam bores and put a hole in the middle for a valve grinding mandrel. Then dressed a stone and ground the leading edge until it was clean.

Guaranteed to be square with the centerline of the cam that way.

That's a real smart idea, take some pics.

 

[Steve V]

The last roller Camshaft I installed would cut your finger at the oiling hole, spent some finessing it before the installation. I never would have thought to check but there was an old post from turbofabricator on the issue. Possibly the cause here.


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Could of been with the orginal cam that came out(long gone), the roller I installed was checked and good to go. The surface was never perfect before.

 

[Wahoo]

Anyone figure out if the problem is only when running a solid roller?

I'm going roller with my new engine build but I don't want any of these issues lol

 

[earlbrown]

The problem usually comes from a compromised surface being put into use. You can't lose 80~90% of your thrust area without running into issues. A stiff pump spring/thick oil/high volume pump all adds to the accelerated wear.

 

[turbofabricator]

As stated above, I find most cams have the thrust oil hole to have a burr. Remember, the cam is case hardened and this burr WILL eat a block. First thing I do after visual inspection is take a small stone in a die grinder and chamfer the oil transfer hole.
Same with thrust surface of the crank.........hand polish it if it is turned, as the grinding wheel will make the thrust surface look like a saw blade. I tell the crank grinder, do NOT touch the thrust face. They still do it. So I spend a half hour or so and hand polish it out.

 

[Buick Mark]

What Earl said, Hi volume pump, or too thick oil, slams/presses the cam HARD into the block face.
Buick 350's and 455's have the same issue.
Cant see how a but could take out the entire thrust surface, unless that but was huge.

 

[Steve V]

What Earl said, Hi volume pump, or too thick oil, slams/presses the cam HARD into the block face.
Buick 350's and 455's have the same issue.
Cant see how a but could take out the entire thrust surface, unless that but was huge.

A but huh...

 

[Buick Mark]

A but huh...

LOL, a bur, a bur

 

[turbodave231]

My factory 109 block out of my 60K 87 Turbo Regal had this same problem. Seems the original owner installed a HV oil pump kit.
The teeth on the cam gear were all knife- edged, the cam sensor bearings were wiped out and the cam started eating into the block due to the added load from the stupid pump.

So in my case, the extra load from the HV pump caused the unusual wear. Other causes might include: Poorly machined block, poorly machined cam, and a lack of lubrication.

I have fixed a couple of blocks with this problem. I bought a bronze washer from McMaster Carr and machined it to fit over the cam and onto the block. I recessed the area around the cam on my mill and drilled and tapped the block with #4 or #6 countersunk screws (can't remember which at the moment). I used the same bolt circle pattern as the Danny Bee thrust plate to hold the washer in place. I made a fixture for drilling and tapping this area many years ago so I could install the Danny Bee thrust plates. It comes in handy for this repair.