Gt40 Upper/lower On Stock 302 Ho

Discussion in 'Fox 5.0 Mustang Tech' started by DM87GT, Jul 20, 2014.

  1. I have a GT40 upper and lower intake (non EGR) I plan to put on my 3o2 HO. I'm wondering how the engine will perform and what HP gains can I expect? I plan to install a new 70mm throttle body, and plan to keep the stock EGR, although I will have CEL code on my dash which I can live with til' I get a tune done. Any help is much appreciated. Thanks everyone!
  2. anything else done to your car?
  3. Yes, I have other mods done which include A/C and smog pump delete pulleys, BBK equal length shorty headers, new pacesetter 2.50 H-pipe, flowmaster exhaust with turn downs before the rear axle, 3.55 gears, sub-frame connectors (welded), new street/strip TCI C4 trans with 3000 stall, aluminum drive shaft, stay-cool aluminum radiator, electric cooling fan, flex fan on water pump, new o2 sensors for the new H-pipe, trans cooler with cooling fan. That is all thats been done so far.
  4. You should gain about 15-20 hp over the stock 5.0's worth the work.
  5. that will wake it up for sure then,i had the same bolt ons like you once,i ran a 65 throttle body though,and it made a noticeable difference over stock.
  6. I recently sold some GT40P heads (rebuilt) but kept the GT40 upper and lower intake since I plan to swap out the motor for a 331 stroker crate engine in the Spring. The 5.0 HO is all stock except the above mentioned. The stroker should make the car completely different since the TCI C4 back to the rear axle is all done. I don't plan on racing it at the track, just want a nice potent street car that sounds "pissed off" if you catch my meaning. The crate motor will have aluminum heads and 375 hp at the crank, and a .512 lift roller cam by Comps Cams. I am hoping for a Ford 9 inch and mini-tubbed within the next 2 years. I was always into building Camaros and Chevelles from the 60s and 70s that I have owned in the past, but this is my first Ford Foxbody..........and I am more than pleased with the performance and all the aftermarket go-fast parts for these cars! I simply love it!
  7. Years ago, I put an untouched Cobra intake (very similar performance to the GT40), 65mm TB, and 75mm MAF on my engine which was a bones stock shortblock, stock cam, stock heads. It already had 1-5/8 EQ-length shorties, off-road H, and 2.5-inch cat-back. With just the addition of the intake, TB and MAF, I picked up a consistent 3.5 tenths and almost 4 mph in the 1/4. When I later added GT40 heads and a mild cam, I got nowhere near the same kind of improvement.
  8. It's really ironic not touching the bottom end of a stock 5.0 HO and add a few things up top that really wakes up a HO 5.0 The E7TE heads are somewhat restrictive, but with bigger valves and some porting, they can perform just as good as the rest in my opinion. That is what I am running now, and the E7 heads aren't as bad as some people may think. I am planning to swap out the the stock upper and lower intake for the GT40 intake and install my 70mm TB when I do the changeover. That way, I can enjoy driving the car this summer and let it breath a little better with the GT40 upper and lower, then in the Spring is when I plan to drop a 331 stroker EFI in the car. That would make a vast improvement over stock.
  9. You state the lower intake on the GT40 is NON EGR. Therefore you cannot keep your existing EGR valve as that intake used an external EGR. You will either need to find an intake that has provisions for the EGR , or install that intake and then you can block off the EGR, buy a EGR simulator and cap off the vacuum hose.

    IMO, adding an intake to an other wise stock engine is not worth the effort, time, and expense. You are talking maybe 10-15 hp. The E7 heads are still a choke point. Save the money and parts for when you do a H/C/I swap and do it once. E7 heads are not worth to do any work on unless you are in a specific class or trying to keep it all original. Most aftermarket heads out of the box will run circles around even ported E7's.

    It's your money though.
  10. Mike, I understand your point and come to think of it, truly it isn't worth the time, effort and expense to do the intake swap as I figured I would be running into problems since the GT40 is a non EGR (external EGR) intake. One has to look at the long run when trying to do a swap like this, sure it can easily be done, but the extra 10-15 hp for all this work and changes is not worth it. I sat and thought about it and mapped out all the changes that I would have to make with the EGR change, so I cancelled that plan! I'll just leave my top half the way it is on the engine, as I plan to pull the stock engine and replace it with a 331 stroker crate engine come next Spring. I may get a Trick Flow upper and lower intake for the stroker or could I use the GT40 upper/lower and just cancel out the EGR all at once when I drop the stroker in? I can take everything I need off the stock motor to put on the Stroker when that time comes. E7 heads? Aluminum heads are the choice but are a bit pricey unless you come across some good used ones that haven't been abused at a decent price!
  11. Different question same answer. Don't bother building a motor and putting stock heads on it. If you are planning on a 331 I would sell the intake and start from scratch with a well thought out plan. Otherwise you will end up with a bunch of mismtched parts and wonder why your performance is subpar.
    jrichker, 85rkyboby and smkshw like this.
  12. All I'm saying is that I'm getting a 331 crate engine for the car early next year. I'm not taking mismatched parts and building a motor, I'm buying a hi-performance long block and asked if it would be good to use the GT40 upper and lower intake on the 331, after all, they flow about the same as a Cobra or aftermarket intake, and eliminating the EGR. My plans were to use the GT40 intake on my 302 HO, but decided not to for many good reasons.
  13. Sorry, but you are wrong. A GT40 flows no where near what a systemax or Performer II does. Also, building a 302 and 331 motor are different animals. You wouldn't use the same cam, heads, etc. I run a ported Explorer intake on my 302 which I just swapped out the top end, and I know that I probably gave up some hp by not going with an afermarket intake but I got it cheap and I can live with it.

    I also saw you are looking at 375hp on a 331 motor. What are the specs?
    #13 mikestang63, Jul 21, 2014
    Last edited: Jul 21, 2014
  14. 375 hp at the crank, not at the rear wheels. 331 stroker, Hypereutectic pistons, 10.1 compression, 512 lift roller cam, AFR 185 aluminum heads, forged scat crank and connecting rods, 302 seasoned block
  15. Were you running the stock E7 heads and HO cam with the Cobra intake and got these improvements in the quarter? That is very impressive with just the intake and TB change! People on here tell me I'm wasting my time putting my GT40 intake on my stock HO 302! Basically, I am doing what you did by installing the Gt40 upper and lower and a new 70mm TB from Summit Racing. All the other mods to the engine from delete pulleys to the BBK shorties and the new TCI Street/Street C4 with 3000 stall with the intake and TB change should wake up my Mustang. I just want the motor to breathe since the stock intake is choking the performance!
  16. Well i told you before it's worth the work since you already have the intake..15-20 hp increase. Just install it and later if you want to add more performance stuff like heads or whatever you can.
  17. If i had a 331 stroker built and it made 375 crank hp i'd be pissed (really, pssed gets edited?)
    That's roughly 320rwhp, something easily obtainable on a stock short block.

    With such modest goals, why in the world would you be doing a mini tub and 9 inch rear?

    I'll do my best to not be offense with this next comment, but honestly i think you need to re-evaluate literally all your plans. None of them make any sense, sounds like you are building a slow race car.
    85rkyboby likes this.
  18. Many many stock block 302's make 350 hp at the crank with a simple H/C/I swap, including mine. Many people are making 375hp at the crank with that same combo nd a Vortech, including me 15 years ago.

    375 hp at the crank from a 331 would be a turd. I'm not trying to pee in your corn flakes but as others have said, you should realy step back and look at some of the builds here and on other sites. You should easily make 400hp on a 331 with the right parts.
  19. A friend of mine suggested I get the car mini-tubbed and a 9 in. rear end with a 4.30 gear, after I got the 331 installed. It was only his crazy suggestion, not mine. One has to consider what has been done with the car as far as to go that route. Me personally, the 8.8 rear with 3.55 is just fine and serves the purpose very well on the street! The 331 was just a thought later down the road, but a H, C, I swap on the stock block is what most would do before jumping the gun! So, no offense takin' as I know that most in the mustang community mean well!
  20. Let's cross that friend off the "advice" list.

    Concentrate on what you have now and getting the most for your money.
    If your engine doesn't burn oil, just do a good h/c/i swap. Planning for the future is nice, but if that engine isn't currently being built or you have ALL the parts for it, treat it like it doesn't exist or else you sacrifice fun now for a setup that may never come to fruition.

    FYI, a good 8.8 rear will support well over 1000hp and you can run 9 second timeslips in the quarter without mini tubs.
    These two items may have very well costed more than the entire car is worth.
    #20 2000xp8, Jul 27, 2014
    Last edited: Jul 27, 2014
    FoxMustangLvr and 85rkyboby like this.