Roller cam questions

Old March 1st, 2014, 05:54 AM
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Roller cam questions

I am planning a fairly stout big block build for this spring (if it ever arrives, -20 F yesterday morning) and have some questions for the roller cam experts. I have built a few engines in the past, Pontiacs and Ch*vy all flat tappet cams.
I am aware that I need some form of cam walk control / thrust button. I found the image below on the net a while ago, and
I believe it is from a factory Olds 307 roller cam set up. My questions are:

  • Is anyone using this thrust plate on a performance engine? It looks to me like it would be better than just a thrust button.
  • Why does it use a thrust button as well as the thrust plate? I am guessing to stop wear on the thrust plate.
  • If a thrust button alone is good enough why would the engineers have designed this plate for a relatively low HP engine?
    It must be worth something or it wouldn’t be there.
  • Will this set up work on a big block / aftermarket roller cam? If I can find one of these, I would like to use it along with a torrington bearing fitted to the block.
  • Does the block require any additional machining to use the thrust plate?
  • Is the thrust plate in the picture maybe facing the opposite direction of how it is actually installed and it acts as the thrust surface for the cam, thus eliminating the need for a torrington bearing?

I see comp cams makes a similar set up (#249-225) but I can’t find much info about it.
Just trying to get my ducks in a row before the fun begins.

Thanks, Matt
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Old March 1st, 2014, 06:52 AM
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A new roller cam from Comp, Lunati and others will have the flange as part of the cam core itself.
I use the cam button setup with no issues. You can also use the stock cam bolt along with shims to achieve similar results.
And you can use a Torrington bearing if you like but the block will need to be machined for it. One thing to remember, lots of guys have gotten away from those because when they scatter they cause more problems. Fwiw I use the bronze washer on the cam and steel washer on the crank. No issues and no extra machining.
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Old March 1st, 2014, 08:34 AM
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On blocks with no damage to the can thrust area of the block I only use a button on the cam bolt.

If a block has damage there I'll use a bronze thrust washer between cam and block. To go with it a spacer is put between crank and lower cam gear. They are not always the same thickness. Just depends on how bad the damage to the block may be.

Personally I've not run into any block with severe damage behind the cam thrust. There have been a few that were scored from debris but that's about it.
I have installed one camshaft that was machined to accept the Torrington bearing because it was already in the engine when it was brought here for repair after another shop built it and there was bearing failure.
I would not waste the money on the Torrington setup. To me its just some peoples way to milk money out of their customers.
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Old March 1st, 2014, 11:34 AM
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Thanks for the replies guys. I have zero experience with roller cams, I guess I am over thinking it.
The block I plan to use shows very little if any wear on the cam thrust surface.

cutlassefi: I have read a lot of your posts on cams and will most likely be seeking your advice when the time comes.
I need to get the rest of my stuff together.

Smitty: I have been following the Lower End Support thread and am very interested in your 4 bolt main conversion.
Is this something my local machine shop could install? Look forward to seeing the installation photos on that thread.
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Old March 2nd, 2014, 06:27 AM
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I can understand your over thinking on using a roller cam. But in all reality they are not really different than flat tappet cams as far as installation goes. You just need to have the right valve springs and a bronze distributor gear.
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Old March 2nd, 2014, 07:34 AM
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Originally Posted by Smitty275 View Post
...You just need to have the right valve springs and a bronze distributor gear.
Smitty:
Why is the bronze gear required for a roller cam but not for a flat tappet?
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Old March 2nd, 2014, 07:40 AM
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Solid roller cams are made from a different material and are not recommended to be ran with an iron or steel gear. Plus the bronze becomes the sacrificial gear of the two this way. Bronze gear is a lot cheaper than a new cam. Though I will add that a friend of mine had a bronze gear on his roller for a few seasons. He then bought a new MSD distributor with a coated steel gear on it. He decided to take a chance and run it as is. The motor is now down for a freshening after several years and both gears look fine.
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Old March 2nd, 2014, 08:33 AM
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You really only need a bronze gear for true billet cores.
If you use a cam ground on a SADI core (selected austempered ductile iron) you don't need a bronze gear. Then to really extend the life you can add an even more compatible distributor gear (made by Mallory) and basically never worry about it.

A SADI core is more similar to the types of cores used for flat tappets.
Above that ask yourself one question, are all the factory 80's and 90's GM and Ford roller motors using bronze distributor gears? No, just think of the warranty costs would they have!!!! Those V-8's are using the same type of core I described, a SADI.

Hope this clears things up a bit.

Footnote;
Crane and Crower both use an 8620 billet steel core. But the Crane one has a pressed on iron gear so a special distributor gear is not needed. These cores are getting scarce though because Crane used to own the foundry but sold it to Callies a few years ago. However Callies hasn't resumed production yet on those Olds cores.
The Crower core is all steel and requires a bronze or treated distributor gear.

I offer roller cams ground on either SADI or steel cores if you're interested.

Last edited by cutlassefi; March 3rd, 2014 at 05:19 AM.
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