Engine 351w Swap Question

Discussion in 'Fox 5.0 Mustang Tech' started by joetrainer31, Aug 12, 2013.

  1. Brainiacs,

    For a future build I am considering a 351w swap into my 95 SVO GT-40 Mustang convertible. Since I have just restored the vehicle to factory I'd like to stay with the factory theme. Thus, I'd like to build the GT Ford should have built in the first place during the pony car wars of that era.

    I'm aware that the SVO GT-40 package was supposed to cover that pony car competition base, but I'm wondering why Ford didn't simply put a 351w in the car to match the Camaro/Firebird of the times. Since I want to stay with the factory theme and pass smog I'll be using my 373s, GT40 heads w/1.72 rockers, 65mmTB, and upper SVO intake manifold.

    I'll be acquiring some 24lb injectors, 95 Cobra ECM, and 155lph pump to feed the motor. Since Its going to be a DD, and I'm not looking to race everyone, and since I'm only looking for a similar power band as I have now, but with the added torque of more cubes, can I use the stock GT cam?

    I'm hoping that this combo will have improved street-able torque to move my convertible, pass smog, and be very reliable since it is not built to the limits. Again, considering the theme of factory, can I use the stock GT cam?

    Thanks for any help, suggestions, etc.
  2. Sure you can use the factory GT cam, but going a little bigger wouldn't hurt anything, including gas mileage, but sure would make it run better. Those GT40 heads are really going to limit those 351 cubic inches. If you want to stay Ford, how about the Ford Racing X heads?
  3. The Stock HO cam in the 351 is not going to be very good for power. You will be leaving a TON on the table. The heads work OK on a 302 and will make the 351 feel like a heavy 302 (weighs more).

    Your best bet is a simple 302 rebuild and save money on the swap parts. It will likely perform just the same. The 351 has the advantage if you build it and plan on racing. Otherwise your wasting money on swap parts, cowl hood etc.
  4. I wouldn't run the 95 cobra computer.... those things are touchy with mods. I'd run a fox a9l and matching calibration Pro-M 80mm meter.

    I'd also go custom can...give you best of best worlds and you can make it pass smog

    Sent from my XT907 using Tapatalk 2
  5. I hear you, believe me I do. However, I live in CA for the next couple/few years and must be able to pass the sniffer. I wonder if a B or E cam would be okay for passing considering the extra cubes eat up 302 cams so to speak. Also any clearance issues if using one of those letter cams or something equivalent & the 1.72s I already own?
  6. Good points. The car already has a 96 Cobra hood on it, but yes, all the other swap parts.

    So maybe instead I could just, in this scenario, get a new 302, transplant my heads, intake, etc, add maybe a lighter billet steel flywheel, maybe an older B or E cam, and a cobra ECM w/24lb injectors? From everything I know this is a nice mild build that will last a long time, but will it pass CA smog with one of those cams? Should I just forget about a cam, go stock, and get some Y303 heads?

    Help me think this through and narrow things down. I don't want a stroker. Its either a 302 of 351 for me.
    #6 joetrainer31, Aug 12, 2013
    Last edited: Aug 12, 2013
  7. Certainly something to think about. Thank you for your input.
  8. If you're running a stock cam why worry about the heads? Go custom cam either way if you do a 302 or 351! It'll run better,make more power and pass smog. Do that with a rebuilt 302 and the extras you have already. IMO be the best bang for your buck and satisfy what I think you want to accomplish.
  9. Thanks for the input! Are you saying that if i get a custom cam that I could have it built to give more power AND pass CA nazi smog tests?
  10. UPDATE: Thanks for all your help guys. If I were to tell you that I could obtain newly rebuilt 302 ($625) or 351w ($775) short blocks, both rollers, both with a 90 warranty, and only $150 difference between the two, would that change any of your advice?
  11. Yes. It'll be better than a ford letter cam for sure! Talk to one of the custom cam guys. They can grind you a near "factory" cam with more performance. Don't get me wrong smog=:cry:but that's what id do. Keep the heads,accessories,exhaust,etc and pass smog
    joetrainer31 likes this.
  12. 351 still need motor mounts,dizzy,oil pan,lower intake,computer change and I'd still do custom cam. IMO
  13. Okay, I'm soaking up the advice man. Correct me if I'm wrong, but you would stay with a 302 SB, my aforementioned toppings, and a custom cam?

    If I got the custom cam would that warrant y303 heads, or just stay with the iron GT40s?

    What I want is long time reliability, a factory look, and more streetable torque (gears are steep enough already).
  14. Working within your parameters I'd stay 302 with your heads and a custom cam. That's the cheapest most reliable way. The 351 reference I made was just the additional parts you'd need if you went that direction. I personally would sell the ford heads and buy either TFS or AFR alum heads. But that's not what you were asking about. Lol. We all have budgets and a certain direction we want to take our projects. The gt40 heads and custom cam(&tune) will run well. The 351 will cost more and you'd need better heads. IMO. If $$ aren't that big of a concern the 351 would have more torque and HP obviously with good heads. Sorry if I'm confusing the issue. It depends on what you want to do. Keep gt40s and keep cost down=302. No need to buy the y heads if staying 302
  15. Yes, that makes sense. I know this may be a tough question, but I'll ask it anyway, ha! Okay, no need for Y heads. However, on paper, would this custom ground cam we are discussing actually give me more seat of the pants feel than I have now (all parts considered), like a 351 could with the same parts and a stock or B/E cam?
  16. The 351 will make more torque and a little more HP. I'd still go custom cam either with the 351 or 302!! If you want the most performance and pass smog and a little more $ isn't a concern build a 351 with alum heads and a custom cam!! If you want to keep $ down and still have fun build the 302 gt40 headed motor. Not to be an a** but you initially were talking about keeping the gt40s and 1.72rr as a concern to keep costs down. Now I'm confused:scratch:
  17. No, its okay. You're fine. I'm probably not communicating clearly enough. I initially thought of keeping the iron 40s and 1.72 roller rockers if I were going to go with the 351. My idea was to simply remove the 302 & slip a 351 in its place (obviously adaptation parts would be needed). Thus, the mustang would have a larger CID like the Z28/Firebird of the day and have similar performance. It was to be a "What should have come from the factory" theme. Does that make sence?

    The question of a 351 w/aluminum heads is not an option for me, but I was wondering if it would be worth it on a 302 because I can get them assembled for about $500 a pair. I'm trying to compare a 351 with my current bolt ons & a 302 with maybe that custom mild cam & possibly aluminum heads.

    I'd like more torque and I'm trying to figure out which will be most pleasing within the framework of my scenario. Is it that the 351 is more a novelty idea and the 302 is more reality? Does that make sense?
  18. A 351 will make roughly 30-50 hp and 50-70 ft pd torque more than a a302, all other things being equal. It will also weigh an additional 50-100 pounds, and if you're running a T5 transmission, have it that much more over the limit. The 351 will require some adaptations to make it work. I ran a Crane 2031 (Crane Cobra cam) with 1.7 roller rockers in my 302 for many years and passed Ohio smog several times, with TF TW heads among other items. I liked that cam a lot better than the B and E cams, though a custom cam would be a superior choice. Iron Ford Gt heads are still going to be your biggest limiting factor.
  19. Ok, so all things being equal a 351w will make more power & torque than a 302 with the same bolt ons. However, it will also weight 50-100lbs more than a 302. I'm assuming the additional power of the 351 will be more than enough to compensate for the additional weight?

    I had a good friend who ran the Crane 2031 with 1.7 rockers in his 95 GT 347 (Windsor Jr heads) and he loved it. Its good to know that you passed emissions with that cam.

    So, best guesses: If I simply exchanged my 302 for a 351w and used the same bolt ons, or if I used a fresh 302 with a 2031 or custom cam and same bolt ons, which is the best bang (seat of the pants) for the buck?
  20. A cam is not going to make 30-50 hp, at least not the type you're talking with GT40 heads etc. You'll have to add up the cost of everything you need to bolt that 351 in, including headers and intake. Also, that extra weight is going to negatively impact handling, not a lot, but it will. A lot of people go 347 stroker so everything factory bolts right up, while it gives the same cubic inches of a 351, with the bonus of no significant extra weight. Once you go 351, you might as well stroke it...all the same arguments apply, and you can't tell from the outside.