What is the base circle of new roller cams?

[Blazer406]

What is the base circle of those new comp roller cams (non billet) .... ones like Mike Licht is selling.....? I was wondering if they are the same base circle of regular flat tappet cams.....?

 

[Lee Thompson]

I do believe that

If you take a stock cam and lay a straight edge across the bearing journals you will find that the lobe peak is just under the straight edge. Doing the same thing with an after market cam with say .650 lift you will find that again the lobe peak is just under the straight edge. Now do the same thing with the base circle and the after market cam will be much farther away from the straight edge than the stock cam. That is why they can regrind a cam and still have the same spec. Does this make sense?

 

[Blazer406]

If you take a stock cam and lay a straight edge across the bearing journals you will find that the lobe peak is just under the straight edge. Doing the same thing with an after market cam with say .650 lift you will find that again the lobe peak is just under the straight edge. Now do the same thing with the base circle and the after market cam will be much farther away from the straight edge than the stock cam. That is why they can regrind a cam and still have the same spec. Does this make sense?

Yes... it makes perfect sense.....it means the base circle is smaller. This will definately affect the push rod length. I wish I knew what the base circle was for..... say one of those new XR2 HR Comp cams.... 210/215......

 

[Lee Thompson]

pushrods

I have pushrods--depending on what exact length you need. 3/8 and 5/16.
I suppose you could measure off the center line of cam and compare after market to stock. You will have about .050 travel each way on pushrod length once you find the desired length. In other word, once you setup and measure for pushrods that would be perfect length. You can go .050 on length either way assuming you have T&D or Harland Sharp. Best of luck.