New Heads

Greg Curtis · #1 (**permalink**) 08-19-2008, 06:49 AM

I have a SPF Cobra with a 460ci 485hp Ford Crate engine that was installed back in 02" with aluminum cobra jet heads. I've been thinking of changing out the heads to the newer Jon Kaase super cobra jet heads. I'm not a mechanic and was wondering if the newer heads were a straight bolt on or if other mods are necessary for the install. How much increased HP am I looking at with these heads. I'm running a Holley 750cfm carb and a Performer RPM manifold.

Tim Brewer · #2 (**permalink**) 08-19-2008, 08:03 AM

I believe those are the P-51 heads. I would just give Jon a call and talk to him about them. I think they are supposed to be good for a 50 hp increase. The P-51 heads are configured differently, but the big question is... what would be the difference in having your heads profesionally ported vs the P-51? It would be much cheaper to port your existing heads than purchasing new ones. I have been thinking of this very same thing. I know Keith Craft has a CNC port program for the Cobra jet head, I'd give him a call as well.
Good luck and keep me posted,
Tim

Silverback51 · #3 (**permalink**) 08-19-2008, 04:55 PM

If you have studs, instead of head bolts, you may have to remove the engine, or raise it up to swap the heads.

The P-51's are worth the money in my opinion.

Tom Wells · #4 (**permalink**) 08-19-2008, 06:13 PM

Greg,

P-51 heads may require new pistons too since the valve angles are different from stock. Also valves and pushrods. Und so weiter...

Question: can you floor the throttle in any gear with street tires without ending up in the trees? If so, and you are looking for more HP I'd suggest getting the thing tuned by a pro.

It's unusual to hear of a 460 that doesn't have more torque than street tires can stand up to - even the relatively tame one you have.

Or are there other reasons that don't appear in your original message?

Let us know,

Tom

Keithc8 · #5 (**permalink**) 08-19-2008, 07:58 PM

You will have to have new pistons with those heads and more than likely longer pushrods. I have not seen that much power over the heads that you have after porting is done. I would look at doing the heads that you ahve and doing a good tune on the car. You do not say anything about the camshaft or compression you have. These may be all areas of improvement for the engine. Thanks, Keith Craft

wizard man · #6 (**permalink**) 08-19-2008, 09:25 PM

Hey Keith Its Rich Ferrara You Just Sent Me My 547ci Monster Back And For All You Who Are Reading I Have The P-51 Heads With A Matched Cam And Keith Dynoed It At 904 At 6800 Pretty Impressive Even Keith And Tony Were Surprised It Should Lift My 67 Fairlane Pretty High

Greg Curtis · #7 (**permalink**) 08-20-2008, 04:43 AM

Its a Ford Racing Hydraulic Cam M-6250- A443 with .562 intake and .588 exhaust, duration at .050" is 234 intake and 244 exhaust. Compression ratio is 10.5. It doesn't feel like it has enough torque, I have a hard time spinning the tires at will. So more HP and torque is a must.

Tom Wells · #8 (**permalink**) 08-20-2008, 06:09 AM

Greg,

If it won't spin the tires gratuitously you have a definite tune/defective engine parts problem.

Find someone local to diagnose and tune before you do anything else.

With that engine in that car you should be able to scare eighteen years off your life any time you get past half throttle in any gear

Tom

D-CEL · #9 (**permalink**) 08-20-2008, 12:32 PM

wizard man,

Can you give me some details on you 547? Im building a aluminum 565 right now and im looking to make that kind of power on pump gas.
How big is your cam? whats your comp ratio?

Thanks

Jason

McD00 · #10 (**permalink**) 09-01-2008, 07:14 PM

Quote:

Originally Posted by Greg Curtis

Its a Ford Racing Hydraulic Cam M-6250- A443 with .562 intake and .588 exhaust, duration at .050" is 234 intake and 244 exhaust. Compression ratio is 10.5. It doesn't feel like it has enough torque, I have a hard time spinning the tires at will. So more HP and torque is a must.

Before doing anything up top, redo your factory side pipes. You can have all the power up top you can afford, but exhaling through a straw will only limit your returns. The easiest thing would be to just replace your factory muffler(the straw) with a Howe racing muffler. You can even get more fancy with your side pipe layout.

After that, SCJ heads will flow almost as well as P51's with a good port job. Then swap out your rotating assembly and cam to your liking.

McRoof