A little more Horsepower

[patrickt]

Go here: http://www.keithcraft.com/ourheads.html and you can see that the cost of good heads goes up with the more work that is done. Shop around though and actually talk with the guys before you plunk down your money.

[blykins]

A set of AFR 185cc heads and a new camshaft will make a world of difference.

If you're running a hydraulic roller, I can recommend some cams that will give you a hp/tq boost without really changing the operating rpms/street manners.

If you're running a flat tappet cam, you will gain a great amount of power by switching to a roller cam.

I don't sell the AFR heads, but I can spec/sell you a custom Comp or Jones camshaft.

[patrickt]

Brent, do you know whether you can pull the cam out of a SBF on most of our Cobras without having to pull the engine?

[blykins]

Yes, if the radiator came out, I think it would be easy.

[blykins]

I can sell the AFR heads now.

[patrickt]

On ERAs the radiator and fan pops right out. fastd, I really think you should change the cam and heads as a "matched set" so to speak. If your mechanic is changing out the heads, changing out the cam is not that much more work. You can get an astounding increase in performance and still be very, very streetable.

[patrickt]

Brent, with the right heads and hydro-roller cam, think you'd have any trouble bumping him over the magic 450HP number?

[blykins]

If he wants to keep the same powerband and manners, my gut says that we wouldn't hit 450.

That's 1.28 hp/ci, but doing it without a single plane intake, considerably larger cam, 10-10.5:1, etc., may prove to be a challenge.

I don't like to peak a hydraulic roller motor any higher than 5500. That will let you shift at 6000 and will hopefully keep you out of valve float.

[fastd]

blykins and patrickt,

Thanks for all of your comments; I am going to take this one step at a time; going to get dynoed as soon as the weather clears; try to figure out whether I want to take the next step with the cam and heads. I really like the way the car drives now; really like the way I got boosted by adding racing fuel; am looking for ways to boost 10-20 hp at a pop by being smart. Trying to decide if I want to take it head on to get 100 hp increase.

Patrickt, you seemed to come out pretty strongly against changing the rear gears - any particular reason?

[Cobra #42]

Fast, What are you really looking for? Faster at the drag strip or faster at the track day events? Or is about bragging rights, you know, you can say that you have "X" hp. Decide the answer and we can come up with a great plan. Thx, db 2723

[RodKnock]

Originally Posted by fastd

Patrickt, you seemed to come out pretty strongly against changing the rear gears - any particular reason?

It's not easy and it's expensive to change the rear end gears. Also, finding someone who can do it right is difficult as well.

I think you'll find that most Cobra owners run between 3.31's to 3.54's and there's a reason for that.

If I could offer my .02, then I would say to build a 2nd engine on the side, where you have time to plan and match all the parts so that they all work together and then make the switch sometime down the road.

[patrickt]

Originally Posted by fastd

Patrickt, you seemed to come out pretty strongly against changing the rear gears - any particular reason?

RodKnock answered absolutely correctly. So correctly, in fact, that I'm not even going to attach a wise-a$$ retort to my post.

[patrickt]

... Nantucket427 sums it up nicely in this threaad:

Originally Posted by Nantucket427

I have 3.73 gears in my SPF and that coupled with a big block makes first and second gear useless. I want to change it to 3.50 or 3.25. I understand I may not be able to do it myself. Who would do something like that? Anybody in Mass or New Hamshire?

Change the rear end Ratio

[blykins]

Any 2500 lb car with over 500 hp is going to have traction problems no matter what ratio they have. You just have to match the rearend to the rest of the drivetrain.

I had a 3.70 gear in my Cobra, behind a 530hp 428 FE and a TKO. The 428 was cammy, with the horsepower peaking at 6500. The deeper gear worked well in this situation, but you still had to have some sense and know that you couldn't go to WOT in 1st/2nd gear.

With a regular 5 speed, you can even use a deeper gear to your advantage with a larger cam. An engine with a fussy powerband coupled with a high rear gear a .64 OD is going to keep you bucking along at cruising speeds.

A radical gear change is the cheapest way of increasing the seat of the pants excitement. I do my own work, so $150 for a set of gears and $50 worth of bearings is great fun when you're going from a 3.08 to a 4.10. LOL

[fastd]

Thanks for all of your comments guys; all very helpful.

I thought I would add one more bit of information as I figured out a little more info regarding current heads;

Turns out that the heads are World Products Windsor Sr Heads; 200 intake, 58 cc chamber, 1.25' single spring; weight of 55
at 600 lift, intakes flow at 272 cfm, exhausts flow at 191 cfm.

I called AFR to see what they would recommend for an update; they suggested 185 cc with a 58 cc chamber; and they flow nearly identically to the World Products heads...The sales person thought that the 205 cc would be too much for my application...? Sales person said I should pick up about 50 hp switching to these heads with current cam.

[patrickt]

Remember he's a salesman. Don't buy anything until you've had your engine dyno-tuned and you have a benchmark graph of your TQ/HP numbers to work from. Then you might want to ask your mechanic for a quote on the labor to put on the new heads, assuming you bring him the new heads and the new gaskets, etc. Then you might ask him how much additional labor he would charge you if you also brought him a cam to put in as well. I know you're reluctant to do change out the cam, but just seeing the labor cost numbers wouldn't hurt.

[RodKnock]

Just keep in mind, before you embark on upgrading your existing 351W engine that you can buy a complete crate engine like a 408/410 from KC for about $8,000. Maybe less, if you delete some things you don't want or need.

Yes, I know it's considerably more money, but when you buy an engine like this or one from any of the good engine builders around the country, you get a complete engineered and dyno'ed package.

[blykins]

He is indeed a salesman, but there is more to it than the flow numbers. For a high performance street application, you can't beat AFR head performance.

When you can compare two heads and the flow numbers are the same, but one head has a smaller port volume, you know something is right. This also helps on flow velocity, which in turn gives good street performance.

[bobcowan]

Originally Posted by fastd

Turns out that the heads are World Products Windsor Sr Heads; 200 intake, 58 cc chamber, 1.25' single spring; weight of 55
at 600 lift, intakes flow at 272 cfm, exhausts flow at 191 cfm.

Those are excellent heads. 50hp with AFR's? Maybe, but I wouldn't bet on it. With a small amount of bowl and port work, those heads are ready for everything but the most extreme cams. If they'er aluminum, I'd keep them and use the money elsewhere.

[patrickt]

Originally Posted by bobcowan

If they'er aluminum, I'd keep them and use the money elsewhere.

Nope, they is FE....