Cam Clearance

[TTipe]

I bought a cam from a friend (212/206,111-austentemper roller) and the lobes are perfect. However when the cam was originally run (maybe 3k miles) the oiling to the shoulder of the cam was insufficient (my engine has an oil jet behind the cam cog).The cam shoulder and the front of the block wore on themselves. Both the block and the cam shoulder were machined flat.I'm trying to achieve a cam button to (new) front cover clearance of 0.003 to 0.011 ". Is this clearance range correct?.I think the cam shoulder was thinned about 0.040. Since the cam shoulder was trimmed approx 0.040 on the block face , the cam will now allow 0.040 motion going to the cup plug. I'm concerned about this possible allowable motion going to the rear inspite of almost zero forces (because its a roller) along the cam axis. I'm considerring purchasing another cam but would like to see what others might think.

Thanks for Reading

 

[jhanson1750]

.040 would put the rollers either on or over the edge of the running surface of the cam. The only way to run that cam would be to make a spacer to ensure rear motion was 0 and the button controls foward. The gear driving the cam sensor/oil pump keeps a fairly constant rearward(I think, gotta check) pressure but that is a LOT of avalible movement. That may even be enough to allow a cam button to partially unseat and jam the cam rearward and grind a hole with the edge of the button. Just my opinion but unless you can get a spacer I wouldn't risk it.

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[Nick Micale]

On a stock-type hydraulic cam like your, we used a spring loaded metal roller button rather than the one with a shim.

If the lifter rollers are in a proper position on the cam lobe, that would work fine as the cam would held in place without it moving back and forth. The movement using a shim could add wear to the cam/sensor gears?

We have done method this over 100 times since these cams have been available, and never have seen an issue.

 

[earlbrown]

I'm concerned about this possible allowable motion going to the rear inspite of almost zero forces (because its a roller) along the cam axis.

That's actually not true. The load from the oil pump on the bevel gear makes the cam want to push against the block.

 

[TTipe]

On a stock-type hydraulic cam like your, we used a spring loaded metal roller button rather than the one with a shim.

If the lifter rollers are in a proper position on the cam lobe, that would work fine as the cam would held in place without it moving back and forth. The movement using a shim could add wear to the cam/sensor gears?

We have done method this over 100 times since these cams have been available, and never have seen an issue.

Nick I think what you are saying is that with roller lifters positioned "perfectly" perpendicular to the cam centerline the spring force on the lobe keeps the cam from moving. From an engineering standpoint the sum of forces on the cam in the cam centerline axis are equal to zero. Therefore no front to back motion "almost" (because I see some wear on three cam buttons from rollers in my posession). Nick you are still the "Godfather" of the V6 turbo. Oh one more thing. When material was removed from the cam (0.040 deep) the hardening is probably gone. Its austentemper rubbing on Grey Iron (with oil in between). Any thoughts ??

 

[TTipe]

That's actually not true. The load from the oil pump on the bevel gear makes the cam want to push against the block.

Great observation Earl. I completely forgot the resistance to motion of the oil pump/cam sensor. There is likely to be abnormal wear on the cam sensor gear and side loading to the oil pump drive. Time for a camshaft.

 

[TTipe]

Great observation Earl. I completely forgot the resistance to motion of the oil pump/cam sensor. There is likely to be abnormal wear on the cam sensor gear and side loading to the oil pump drive. Time for a camshaft.

Also premature chain wear/stretching perpendicular to the length of the chain which is not good

 

[turbodave231]

Wayne,

I measured that cam face area on that camshaft before you bought it from Tom. Very little material was removed to clean up the damage. It was .001-.002" less than a brand new cam. If you shim it you WILL have problems. Use the cam as is and set the end play to .006".

I believe the initial damage to the block and cam was caused by too little end play.

Dave

 

[jhanson1750]

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[bison]

Wayne,

I measured that cam face area on that camshaft before you bought it from Tom. Very little material was removed to clean up the damage. It was .001-.002" less than a brand new cam. If you shim it you WILL have problems. Use the cam as is and set the end play to .006".

I believe the initial damage to the block and cam was caused by too little end play.

Dave

Ive seen this before myself Dave. Usually the block wears more than the cam

 

[jhanson1750]

1-2 thou is a nothing issue compaired to .040, that was listed by th OP. Sounds like Dave checked and verified a good part. Good luck with the build.

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[TTipe]

Wayne,

I measured that cam face area on that camshaft before you bought it from Tom. Very little material was removed to clean up the damage. It was .001-.002" less than a brand new cam. If you shim it you WILL have problems. Use the cam as is and set the end play to .006".

I believe the initial damage to the block and cam was caused by too little end play.

Dave

Dave I could physically see (with my tired eyes) the amount of material removed from the cam shoulder and it was significantly more than 0.002 especially when I have a new cam in my hand. It looked to me to be about 0.020. I tried to measure the shoulder thickness (across the cheeks) which made no sense. It looked like material was removed from the front of the cam shoulder as well as the back (this was comparing it to the fresh cam in my hand from Brian). This is a great mystery to me.I worked with different shims and cam buttons and I indicated the cam forward motion to 0.006 with the front cover gasket squished and the front cover torqued down. The cam button had about 0.025 of shims behind the button to get 0.006 clearance not to mention doubling up on the torrington bearing caps which go under the "C"clip. Different button thicknesses were also available which I tried. This was a bad arrangement. The cam motion rearward put my new "silent/tensioned " TA chain at about 1 deg out of alignment (89 deg) with a gentle push. The normal force created from pumping oil is going to put rearward force on the cam. I got a new cam based on these observations. I have not set the end play yet. It looks very promising. Hey thanks for all the help.
Wayne

 

[turbodave231]

Wayne,

Sounds like the new cam is the answer to your problems....good luck with the build.

 

[TTipe]

Wayne,

Sounds like the new cam is the answer to your problems....good luck with the build.

Thanks Dave