Well,
for a small block, I use the torrington. If I had a solid roller big block, I wouldn't hesitate to go the same route. IMO, nothing's wrong with the solid brass thrust washer that comes with the manley timing sets. I just don't buy them because summit don't have em in stock

 

Heres what I am going to use :
Crane 13984-1 - Crane Cams Timing Chain



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Roller Sets with Thrust Washer: Uses a fully rollerized, needle-bearing, Torrington-type thrust bearing to futher eliminate engine block damage and operating friction. These sets install with no block machining and should be used only in conjunction with cam button spacers to eliminate camshaft end-play. Pro-Series Steel Billet, CNC Machined Sets: Offer the precision, strength and accuracy of billet steel, CNC machined camshaft and crankshaft sprockets with the strength, friction reduction and wear resistance of a premium quality, double-row, roller timing chain. The billet steel crankshaft sprocket features nine separate keyway locations, providing up to eight degrees of advance or retard. Thrust washer included.



The one I just took out had a bronze type thrust washer and this worked well.
Guy

 

Saddletramp454
I guess I've always used a Torrington bearing because I've never had a failure with one and in my world, if it ain't broke, don't fix it.
482 ci Mud Dragster, 2.69 in a 200 foot pit with gas and NOS.

 

Sounds like Torrington is the way to go, just curious to get an idea of what is out there and what doesn't work.

 

Because of the lack of response to this poll, I assume that wearing of the big block cam thrust is a very minor issue that rarely occurs or is a relatively unknown problem.

 

I use the bearing. I have the Cloyes billet set for like $90. It gives you 9 positions on the crank gear to degree the cam. But as far as an adjustable one, I don't see the need because I never pull the timing cover off between freshen ups.

 

isn't the big core plug in the back of the block supposed to control the rearward travel of the cam?
over the years, GM built millions of V8 (and V6 and I4 and I6) engines over the years that didn't have any sort of thrust bearing or bushing behind the cam gear.

 

If you run a roller, you should have a thrust washer/bearing in there. I have heard of a big block with a solid flat tappet that used to chew the front of the cam journal. The bearing fixed the problem.

 

i know you need something on the front of the cam to control forward motion with a roller, but why would you need to control rearward motion like that? flat tappet cams push the cam backwards without bearings or washers in there, and they can go for 200,000 miles without any problems.

 

flat tappet cams push the cam backwards without bearings or washers in there, and they can go for 200,000 miles without any problems.

Not all of them. Like I said, I had a friend that had to use a torrington bearing to stop the cam gear from chewing the block. IMO, it's cheap insurance,especially if you use the brass washer(no needles to give out). Oh, a solid button isn't a bad idea either. Had a roller button spit rollers out, luckily none got anywhere.

 

Just back from the engine shop and another couple of 454 cores to look at, both high milleage, one the thrust is badly worn, the other the thrust is perfect. These would have been pass/truck engines with stock hydraulic flat tappet setups.

Can someone explain the mechanism that would cause the thrust to get damaged?

Basically if you have two plain surfaces (one turning) separated by a film of oil it should not wear right!

It would have to be some metallic particles getting between the cam gear and the block thrust to start the wear right?

 

Don't fret a worn thrust surface, easy fix. My 402 needed attention, had it machined .030 for a .030 wear plate. Now can run either a stock timing set or a torrington set. Here's a pic.

 

GRN69CHV,

That sounds good.

What type of machine tool is available to clean up the thrust area?

 

I just drill a 1/16" hole in the thrust face of the block to intersect with the oil gallery to the #1 main. Feeds pressurized oil to the face constantly. Never had a damaged thrust surface yet.



JIM

 

Don't laugh, I rigged up a steel cam gear (ground a cutting edge on the thrust), bolted it to a cam, welded on a drive and powered it with a 1/2" hand drill. The cam gear had already started cutting the thrust face, so I know it would work, the depth took several tries to get it correct. Was a slow process, but it worked. I had talked to a shop and knew I could take it in to have the thrust milled down as a last resort, but I wanted the pocket machined in there, this worked great. Oten thought, this would be a great tool to produce.

 

So how would a well equipped machine shop do the job?

 

I have a Hexadjust right now. Next time I build an engine I'm going to try an SA Gear set.

I found out about them in a post by Mike Lewis in this thread:

http://www.chevelles.com/forums/showthread.php?t=98940&highlight=HexAdjust

Sounds spiffy!

 

For one thing when installing a Roller Cam in a BBC you have to lock the end play of the Cam to be between .003" to .008" - I use .004". After adjusting the forward thrust so the Lifter Rollers track in the Middle of the Cam Lobe you use the Cam Wear Plates to limit the Back Lash to .004". This is typically around .140" which is the thickness of most Torrington Cam Wear Plates. I believe with ISKY Kits you have to Mill approx .140" off the Cam Thrust Boss and install a special front cam bearing. I've seen Torrington Wear Plates fail more then once and believe me the needles are small a can get into the Oil Pump so I stack 3 or 4 Oil impregnated Wear Plates to achieve the desired .004" play and as JIM mentioned drill a hole through the Cam Boss face to intersect #1 main Oil Gallery. I also drill a 1mm hole through the PSGR Tappet Oil Gallery Plup to lubricate the Timing gear or Cam Gear Drive.

If you install a Roller Cam you have to install a Cam Wear Plate to set the End Play.

 

Cloyes makes a wear plate 9-203 which can be used on a block with a worn thrust. The block cam be machined.030 and the cloyes plate measures .031
From memory HV Oil pumps caused the wear over time. Must have been an issue as they made a fix for some reason.

 

How common is this cam gear thrust wear on a BBC? Are we talking 1-in-100 blocks? More? Less? Just curious.

EDIT: Wow... just realized this one is back from the dead! 10+ years. Oh well.. .I'm still curious.

 

I've probably torn down 50 - 60 big blocks and have seen this issue on 3. The worst was the last, one of the oddball Mark IV's that are all 4-bolt mains. This thing was chewed up at least .100. Since it had the casting number that I have been told to avoid like the plague, it found another home. I haven't seen it at all on any Gen 6 blocks.

 

What is that casting number?

 

X2 on casting # I picked up a 2-3 yr old out of "fresh from machine shop" MK IV 4 bolt block that I want to build, maybe?

 

I just picked up a block with some custom machining. Not sure what fits here, any ideas?

 

That "custom machining" was done by the cam gear it ain't supposed to look like that
Can be fixed in a couple of ways
Machine for a bushing to fill the cavity & run any standard gear set preferably with a thrust bearing of your choice
Machine for a Torrington bearing installed backwards & run a standard gear set without any bearing
This is an aluminum World/Chrysler block I fixed with a bronze bushing a while back.. same issue pictures should be self explanatory

 

That "custom machining" on the cam boss looks just like the one I described. It dug in deep enough to scrape a bit off of the front cam bearing.
A machinist should be able to touch that up and add a bronze spacer or some sort of Torrington setup.

 

Nobody seems to have a concrete explanation for why some BBs do that and others don't. I've seen some that were real bad.

The rear core plug doesn't limit rearward motion of the cam at all. There's a gap. the rearward motion is stopped by the back of the cam gear hitting the front of the block. On our hot rod engines forward movement of the cam is usually stopped by a button in the cam gear, rides on the inside of the timing cover. Many but not all BB engines are drilled for a thrust plate, which is the best solution for roller cams. This requires a step nose cam. The depth of the step is a couple thou more than the thickness of the plate. Non roller cams require no thrust button or plate at all, ever.

Obviously, any thrust button must not preload the gear against the block.

BTW, real machine shops use mill to machine the front of the block to repair damage.

I don't run HP/HV oil pumps, not needed, not wanted. increases wear on the front of the block. Not a good thing.

That's my story and I'm stickin' to it.

 

Mike, that last pic it looks like the bronze spacer gizmo is proud of the block. Why is that?

 

Because I haven't faced it yet
It is faced in one of the other pics

 

My favorite semi-local machinist fixes worn block faces by cutting them and then pressing-in a valve seat insert. Hard as hell, you'll never have that problem again.