Build My Motor

what year is the motor? if it as f4te casting then you have a roller block 351 which is awesome, i would almost trade my built 351 for it. anyway if it is a roller block you're in luck, any 5.0 mustang roller cam will bolt right in. to get 350 RWHP i would look at a b303 or bigger motorsport cam maybe even an x303 shouldn't be too lopey in a 351, other than that a good intake like a weiand stealth and a set of headers with a 750 carb and electronic ignition and that should be good to go. i'm going to assume this is a roller motor for now, since you did not say what year truck it came out of but you did say it was a truck and low mileage so i'm going to assume 94 or newer which would make it a roler block. if not let us know and we can post mor combo's but we need more specifics

DIY port and polish might help.
--Brown

Ah well hell I'm not missing out on this one.
Who wants to stop by my house and pull my heads and do a valve job. I will supply Tools, warm enviroment, Beer (to a point) maybe even some lunch and dinner; you supply parts and labor.
If I have any takers email me asap before someone else beats you to it!

I would sell the GT40p heads and get a set of good aluminum ones. AFR 185’s are the way to go. If they are too pricey look for a used set of the top brands like Twisted Wedge or Edelbrocks, even an old set of the iron Windsor Sr’s. The GT-40ps will not support the airflow needed for the power levels you are looking for. Since you are on a budget you can forget about the roller cams because they are expensive when you start adding in the roller lifters ($250+). A good alternative would be a solid flat tappet cam with duration numbers in the mid to upper 230’s, lift around .580 on a 110 LSA. Make sure to get your compression around 10.5:1 to make power. A good ignition (electronic) and an MSD6AL would help, too.

yes I think that you can reach your goal in hp but you will be limited from the heads bnickle has the best combo I think central coast mustang I think offers that combo for a 302 and I think that it makes or so they claim 350hp so you should make more easily with a 351

if the casting number is a D9 then yes it is a 79 model, but i think the A denotes it as a passenger car block, but i could be wrong on that one. at any rate a cam with about .525 up to about .550 lift or so should with about 230*-240* duration @ .050 should get you where you want to be. the p heads should be ok for the power level you're looking at, but probably no more than that, but that's ok, any more and you would need a much more aggressive short block assembly antway. i would recommend at least port matching the intake side of the heads, and a little bowl blending for better airflow, but those are pretty easy to do, even with just a dremel tool, although a die grinder would be much quicker.

RXTbone said:

I'm going to sound like the noob I am...

I've heard very good things about GT40P's, including a number of articles that claim they have better flow than the Cobra heads. I understand the higher priced aftermarket performance heads will ultimately flow better, but will the GT40P's flow enough to get the numbers I want? With the addition of a cam, intake and exhaust, I figured I could easily reach 350-375HP. Am I wrong?

Which brings me back to the stock parts - can I use the stock crank, etc.?

Thanks for the input!

Click to expand...

The GT-40 or GT-40p heads are very good heads, even under-rated heads for a 302. But they simply don’t have the port volume to support an engine in the 347+ CID range that is looking to make good power up to around 6000-6200 RPM’s. These heads will choke off a 351-357 CID Windsor and cause them to be very torquey and responsive up to a peak in the 5200-5400 RPM range where they will run out of breathe. If you want a very responsive low to mid RPM 351 Windsor the GT-40p heads would be fine, but they are not a performance head by any stretch of the imagination for an engine that size. Remember, the GT-40/p’s are actually a copy of the original 351 Windsor heads. That’s right they are actually 351 Windsor heads, which was the hot swap for a 302 in the 1970’s. We know that the stock 351 Windsor heads were not world beaters for the 351 Windsors. Therefore, sell the GT-40p’s to someone that has a 302 and get a set of heads that have at least 185cc runners, all the way up to 205cc’s if you are daring – like the AFR 205’s, Victor Jr.s, or Windsor Sr.’s. Hell, my 351 Cleveland has reduced/stuffed intake ports that still measure approximately 225cc’s (stock is ~240cc’s).

Again, the AFR 185’s are probably a great compromise for a 351W street motor. But there are other very good alternatives that might be cheaper. Define your goals from a cost and performance stand point and then your options become clearer. Good luck.