need help with cam selection

[RobMcQuarie]

We build quite a few small blocks for the local Shelby club guys that run open track and vintage racing. We have a number of different custom grind solids that we use and could probably give you a good recommendation for a cam. But....no matter who you talk to on the cam, there are a number of areas that have to be addressed first.

The stock cast rockers cannot handle much lift. If they are the "long slot" cast replacement rockers, they will handle some more lift, but clearance must be checked. If upgrading to a roller rocker, you will typically have to use longer rocker studs. The studs Ford used on the HIPO's utilized a flat thread pitch which will have to be re-tapped with std 7/16-14. Don't really want to do that with heads on the block. This upgrade may have already been done on your heads though with the work you describe as already having been done.

Valve springs: do you have enough spring pressure for an agressive mech cam? The old mech HIPO cam was a softy and didn't need a lot of spring. Not so with today's grinds. If they are true HIPO heads, they will have cast in spring pockets which greatly limit the spring choices, unless the pockets are opened up very slightly. You cannot tell the heads were modified once done, but it allows use of a much better spring. Heads have to be off and disassembled for this procedure though-we do it as part of the rebuild.

Next, a hiperf cam should be degree'd in. Are you comfortable with degreeing a cam in, or can you call on a friend for guidance? Note: push rods should be upgraded as the spring pressure goes up. Push rods are one of the most often overlooked sources of power in the engine. Very few engine builders understand thier importance. But, don't buy pushrods until you have the rockers you are going to use and have checked push rod geometry/length. If this is new, get experienced help here also. Just trying to help you avoid some of the pitfalls we see in many of the home built motors.

Intake choices: I'd start with the Blue Thunder version of the "Cobra" high rise-best all around intake on the engines we build, plus it looks "right". Makes about 20hp more than the old style small runner "Cobra" or SVO intakes. Right behind it in order of preference would be the RPM Air Gap, the std RPM, the old F4B and Cobra intakes.

Lastly, I'd have the distributor curve checked to see if it is compatable and have a professional carb tuner go through the Holley. The out of the box Holley's (List 3310 and others) leave a LOT to be desired, depending on which model. The 750 is a bit big for the 289, so a good Stage II or III set up would work wonders.

Good Luck,
Rob