Heads 306 To A351

Discussion in 'Fox 5.0 Mustang Tech' started by werner, Oct 10, 2012.

  1. I got a 88 f150 5.0 would 351 heads fit 302??
  2. Stock heads on the 351 are e7's as well on the later 351. They make bolt inserts to make up the space between 7/16" (302 size) to 1/2" (351 size)
  3. Would putting on 351 heads on a 302 be worth it then or would I lose H.p.
  4. Ever since the mid to late 70's, the 302 and 351 had the same head castings.
    SOME say that the intake and exhaust runners on the 351 heads are larger. Which yes that would grant you more power. But, I do not believe in this.
    I don't think you will gain any power by switching. Buy a set of GT40 or GT40P heads off of mid to late 90's Explorers/Mountaineers if you want some good factory performance parts.
    ratio411 likes this.
  5. I can get my hands on a 90 5.0 mustang would the heads fit ?????
  6. Yes they would fit. They're the same head as your truck, though. So no point in it at all.
  7. What a cam work
  8. well first question is how much money do you want to spend to hop up your engine? i have around 3500 in my engine and make around 300 hp at the wheels..

    stock for the truck is around 150 at the wheels if your lucky..
    werner likes this.
  9. Question is the truck 4wd or 2wd? What are your wants and needs. Budget friendly setup would be gt40 or gt40 ps , explorer intake and decent cam for it, with that the valve springs will need too be upgraded. Again the application and what your doing would help in pointing you in the right direction.
  10. Fact: The only factory 351w heads that are any good are the 69-73 heads.
    If you don't have those, don't bother, you won't gain anything, and probably loose compression, which = power loss.
    Even those heads need exhaust porting, and your valvetrain will need to be changed from pedestal to adjustable.

    I believe the old Lighting 351w used GT40 heads, and you can access those from an Explorer.
    That's probably your best bet, unless you want to spend a bunch of money.
  11. As for cam, unless you have gone through a bunch of trouble to convert the EFI to MAF and sequential, instead of batch-fire SD, you don't want to mess with the cam. You probably have a roller block with a flat tappet cam, and you could get away with installing a stock roller from a 289 firing order 5.0 (non-HO). That is what I did... gives you the benefit of far less parasitic power loss, while saving you from having to convert to MAF, which in the case of my truck, is crazy expensive because I have an E4OD tranny. It's still expensive, but easier if you have an AOD equipped pickup.

    SD will let you change all sorts of things to gain performance, but generally speaking, the cam isn't one.
    Anything that causes variation or loss of vacuum signal will confuse the SD system.
  12. I thought of that for mine, but if you look at some older (1990s) dyno shoot-outs, the truck intake is a really good piece.
    Holley used the lower for their Systemax intake if that says anything. (As did some other aftermarket companies)

    If you go with a GT40 from an Explorer, you not only will likely gain nothing, but you have all sorts of changes to make for it to fit a truck.
    The truck TB, air intake plumbing, throttle/TV/cruise control linkage, EGR, heater tubes, valve covers, etc... are all TOTALLY different than the parts used on car intakes. There is a long list of mods to add a GT40 to a truck.

    Same with the cam. The trucks are 289 firing order, instead of 351 like the car HO engines. The EFI is batch fire, instead of sequential, but would still require modding the injector harness to change firing order. The system is SD, not MAF, which is totally dependent on smooth, strong vacuum, which is lost with a performance cam. SD will take just about any mod in stride, except for a cam.
  13. all my junk is running on speed density... and the sd ecu is having a lil trouble controlling idle once in a while cause im pulling around 15" of vacuum.. instead of 18" like stock..
    5.0 .030 overbore
    Flat Top Pistons, Trick Flow 170cc Track Heats w/58cc combustion chamber
    Comp Cam XE-264 HR, Pacesetter Headers, Scorpion 1.72 RR's, Ported Truck Intake, EGR & Smog Delete

  14. i guess i didnt see this when i originally replied.. the trucks when they got the Roller Cam blocks they went to the 351W firing order..

    and on SD the batch firing is the same for the old non HO firing order or the 351 firing.. batch firing is the same.. doesnt matter..

    only thing he'd have to do if he put a 351W firing order cam in, is reorder the plug wires... thats it.. nothing else..
    ratio411 likes this.
  15. I am glad we had this discussion!
    I have put off using an HO style cam in my 90 F150 because of being told about the rewiring of the injector harness.
    This thread forced me to look further into it, and get a straight answer on it.
    I stand corrected, and am glad to find out that no injector firing changes are needed on a batch fire SD!
    That is great news IMO.
  16. no problem!!!!