Not Ranked
I also have a 302 with the GT40X heads and importantly the "B" cam from FMS. This is the basis for the 345HP motor. I have had the car on a chassis dyno and I will tell you that with a 750 DPer, open headers, and a RPM performer I got right at 280hp at the wheels. That is pretty close to 345 at the flywheel give or take.
Now... here's the deal. This setup made 280Hp at 5200 revs and 315 ft/lbs at 3800 ish. It also completely ran out of steam at 5500 making 270hp and 250hp at 6000. Its really a combination of the very soft valve springs that come stock on these heads, the 194 intakes, a sloppy valve pocket casting, and the cam. Both, cam and heads, just don't work above about 5500.
I think you can get maybe 365hp out of these heads if you change the cam and springs but that's with a 302. Asking to feed another 50 inches is asking too much from the GT40X head as cast. I think there is another 30HP with a good pocket port job and a 3 angle valve job but not much more. Going to a 202 intake would be worth maybe another 15Hp but unless you are doing the work yourself for free they just aren't worth spending money on.
The bottom line is I would do a couple of things.
1. Rebalance the rotating assembly and reuse the 351 crank rods and pistons if still in good shape. Do not reuse the stepped Ford rings. Perfect circle makes a good ring set for these metric pistons in these motors. Leave the engine size at 351.I would use APR rod bolts however and a good crank dampener. The FMS ballance job is well known to be a stock ford ballance job and not intended for revs much above 5K or so. A good ballance job is the best money you will ever spend.
2. Pick out a better cam with about .550 -.575 of lift and 285-290 degrees of duration.
3. Replace the heads with the AFR 185's, 2.02/1.60 valves, 58cc chamber volume, and run the comp cam magnum roller rockers. This should be right in the neightborhood of 9.5 to 1 CR. You will need to check valve clearance but you would want to do this anyway. The AFR springs are good for about 6300 and work well with the hyd roller lifters in these motors. Running theses HYD roller lifters beyond 6200-6400 is a just dramma and a waste of time anyway. Limmit revs to 6200 and all will work well together.
This should get you about 1.25HP per inch with a good flowing exhaust and a 750 DP on a rpm performer intake. Be careful here, those side pipes can really eat up a lot of power if they aren't made to flow properly. This should put you right at 435HP on 91 octane gas and thats just about right for 10 inch wide street tires on a roadcourse through a limmited slip diff.
Last thing... If you don't have a limmited slip diff.. do that first.
|