need help with cam selection

[flgearhead]

i have a Cobra FIA currently running the following....289 bored
.20 over,...flat top pistons..10-1 compression...289 cast iron heads that have 2.02 and 1.90 valves...heads have been ported and polished....performer intake with new Holley 750.....electronic distributor with MSD box...headers...hydralic cam with factory
rockers..electric fuel pump...i would like to install a solid cam and a new intake that would give me very crisp throttle response....any ideas as to what combination of parts i should use..thanks for the help:

[Frank Gleason]

Do you have flow numbers for your heads?

[HighPlainsDrifter]

Valves ?

Your 289 hasn't got a big enough bore to run 2.02 / 1.90 heads !
A 1.60 exhaust valve maybe,probably a 1.50 valve. It's not only the size of the valve, but how much velocity .

As for the cam , I would call comp cams cam help line they are experts.
Perry.

[Mr.Fixit]

What is the expected redline of your longblock?

Where do you want to make power, mid-range, top-end?

Why do you want a solid, are you planning on spinning over 6000 rpm?

What is your car's gearing, it matters.

[flgearhead]

thanks for the questions....i spoke to the machine shop that did the work.....the block was bored .30 over then line honed, a polished steel crank was installed, the pistons are cast 10-1, the heads are hi-po, and have had a real nice porting and polishing job, the heads were milled, the old valves were removed a 3 angle valve job was done and a set of chevy 2.02/1.90 valves were installed along with new springs and push rods, i can not say what the cc volume of the heads are....the rear is a 3.31 posi, the tranny is a Ford Top Loader wide ratio, i am old school, i like the noisy valves and the crisp throttle response...i would like the motor to rev quicly to 6k...probably would not run much over that....i would like power to come on strong at about 3k rpm all the way up to 6-6.5k rpm... i don not know what the red line on the block is...maybe i need a whole new motor...what are the thoughts....thanks for the help

[Mr.Fixit]

3.31 gears with wide ratio toploader
6000 rpm redline

I'd just say smaller will be better for you, avoid the temptation to put a monster cam in there, you need good midrange torque to move that car.

something in the neighborhood of 225 degrees @ .050" lift on the intake is about what I would be looking for. Your engine builder probubly has a pretty good recommendation as to what cam you ought to run with your combo, you trust him to do everything else so perhaps you should trust his advice on cam choice. I can admit I have gone back to my machinist and bought a second camshaft after picking "just the right one" and I got the cam he tried to sell me in the first place.

[flgearhead]

thanks to everyone for your help and suggestions

[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

[Keithc8]

I feel if you want to go with a solid flat tappet that a 236 intake and a 244 exhaust on a 106 lobe seperation would work real well in this application. Install the camshaft 2 to 4 degrees advanced. The Ford Racing double roller indexable timing set makes this easy. I would also try to get something in the mid .500 lift as well. You have to remember that when you lash a solid camshaft you loose some of your duration and lift where with a hydraulic you don't, this is one reason you run the solid with a little larger duration. A 650 double pumper like the DaVinci's we use on the Elinore Mustang 306's would work great. Good luck, Keith Craft