Reply to "Bullet Cobra Jet Cam"

Monty, what are YOUR priorities?

In regards to street cams, my specs fall into two categories:

(1) Lowest overlap ... the priority is drivability and vacuum. Nowadays the cams I spec with this priority are all 114° LSA. A little bit of power is given-up to achieve these goals. The guy interested in this type of cam will never miss the nuance in power that is lost, but he WILL miss the drivability if he chose a cam with more overlap.

(2) 60° overlap +/- 2°. The priority is a bit lopier idle and a bit better power, but still usable vacuum and drivability. Boss 351 kinda power characteristic.

I stopped specifying 115° LSA because of the resistance such cam specs received, now 114° LSA is getting resistance? The spec of mine you quote is 114° LSA and +2° indexing. This is a cam for the guy who wants the drivability and vacuum. 115° LSA would be better, but I already explained why I no longer spec cams with that much LSA.

The Bullet spec is 113° LSA and +3° indexing. That amounts to 2° more overlap, and the intake valve closing 2° earlier. Small changes in cam timing don't amount to a hill of beans. I'm surprised Bullet would make a big deal about it. I get the feeling when guys sweat small changes that the changes are based upon a computer program ... not experience. Some guys at Bullet seem to do this, others do not. Having written that, I'll make these comments.

As long as the intake valve opens and the exhaust valve closes within the dwell period at TDC, all is well. That's 30° BTDC and 30° ATDC. Both cams fit that criteria. I consider any cam that has 55° or less overlap to be a "drivability" cam. My cam is 2° better in that regard, but both are within that criteria as well. Finally, the Bullet cam closes the intake valve 2° earlier, which will increase dynamic compression a small amount.

The Bullet cam opens the intake valve 2° earlier, which "should" make more power, but we're not talking about a big difference. Blocking the manifold heat passage would make a bigger difference ... as would lower back pressure mufflers.

If "power" is the priority, we could pen the same lobes with 111° LSA, +4° cam indexing, an intake centerline of 107° and 59° overlap. This cam would perform a bit better than the cam suggested by Bullet. So, getting back to my first comment, what are YOUR priorities?