I have a 91 F150 with 302. I have read numerous threads talking about using heads from an Explorer. Can I do this without changing anything else on the motor? I need to get my heads done and would prefer to get a set reworked and just swap out so the truck isn't down for more than the weekend. Also what are some of the other changes/bolt-ons I can do with speed density and e4od tranny (intake change, air filter system mods, exhaust, headers)? Any help is appreciated. Thanks.

 

You can use the gt-40 heads pre 97 explorer/ mountaineer.

You can use the gt-40p heads post 97-2001 explorer/mountaineer.

The p heads need attention to the header design, as the spark plug sticks for the most part straight out from the head. There are companies that offer such headers to take the guess work out of trying different header designs.

Longtube headers would be a good idea but the other stuff you mention just isn't necassary. You will end up aggravated at what you spend and received power wise in return.

You might consider lower axle gears, they'll give you more of idle punch and would compliment any serious modifications you make to the engine.

Personally I wouldn't spend a dime on bolt ons, other than headers and gears, save that money for internal mods, like more compression, better cam, and a 351w shortblock with a 5.8 upper and lower.

Now to answer your question, if your truck requires egr or some other aspect of the emission system to be connected to the back of the head(s) and you need to keep the emissons working, then you need to pay attention to the gt-40p heads you receive, some have smog holes some don't, other than that its a bolt on deal...other than the header issue. Good luck

 

Thanks for the reply. In response, if I chose to go with the gt-40 heads, will I need to worry about the egr or any other emissions parts? Also, if I have 3.55 gears now and have 31" tires, which way do I need to go with the numbers to get a little better acceleration? 3.73 or 3.20s? Thanks again to any replies.

 

Pretty sure all the gt-40 heads used emissions so you should be okay there, the p versions are another story.


From my experience trying to get my hands a set of the gt-40's, everyone wants $300 for high mile bone stock heads. Even when you figure up the P versions which you can get for $200 bone stock, brand new, yet bare. ONce you figure in everything required to set them up, you've spend a combined total of $450-500, then you need headers, you would probably end up spending the same freshening up a set of gt-40 heads.

Here comes the kicker, for a few more dollars you could get roush 200 world heads for $850 +/- they flow a little better than oem heads.

For a few more dollars than that you can get afr or edelborcks for $1250+/-, and many consider the afr heads to be the best to happen, the edelborck performers would be good for your 4X4 as well.

If you have emissoins testing you will need the smog versions of any of these heads.

Plus side, you could open up the head bolts and resue any of these heads on a 351w engine.

You wanna go with 3.73 if your looking for off idle grunt.

Good luck

 

Thanks again for the knowledge. Time to start searching. What would be a good set of headers like you described above for a set of gt-40 heads. I would also like to convert to a dual exhaust. Thanks again.

 

What casting numbers should I look for for the gt-40 heads? Also, what kind of improvement would underdrive pulleys do for me? Thanks.

 

gt-40 # F3ZE
gt-40p # F7ZE

An easy way to identify them on the vehicle or off for that matter:

facing the cylinder head freeze plug, look to the left, you will see three vertical lines if its gt-40's and four vertical lines if its gt-40p's.

Another easy way, facing the side of the cylinder heads, look to the lower right corner, you will see GT or GTP stamped there.


I will put it this way, you might notice some difference in the engine if you add bolt ons to your truck but the difference would probably be equivalent to driving your truck on a cool day vs a hot day...you know, how sometimes the truck seems to perform better than others? I say save your money, the first bolt on you try will have the most impact no matter what it is and it won't be much at that, like previously mentioned, then any bolt on after that will leave you wondering if you installed it right because there won't be any seat of the pants improvement.

My advice save your money and go big, changing the engine combo (internally-stroker/cam/head/intake) or altogether (351w+) will have the biggest impact on actual hp and tq.

Long tube headers will build slightly more torque, more so the more performance oriented the engine is, nothing wrong with shorties, they bolt right in and will make a noticable difference, but give up a slight amount of potential torque production.

This is my opinion, good luck with whatever you decide.

 

Thanks JW you da man.

 

Geokel1014,

I have to echo what JWTAYLOR says about saving your money and not trying all the boltons. Short of superchargers and nitrous, I've tried just about everything you can buy to bolt onto my 91 F-150 with the 302. In my experience, I don't think they've made much of a difference on the old engine (142k miles on it) or the brand new engine (now with 20k on it). The truck sure SOUNDS faster and more powerful with K&N, shorty headers, dual exhaust, MSD, etc, etc. But really faster, more mileage, etc. Nope.

Just my $.02.

Spudco

 

Thanks spudco.

 

It has always been my understanding that short-tube headers are able to give you better low-end torque and tend to somewhat stifle (in comparison) high-end horsepower production. Long tubes, in my understanding, allow for more high-end horsepower by design, while sacrificing some low-end torque in the process. Please could you clarify this?

 

Actually long tubes are designed to make more low end and overall torque vs shorties, as a matter of fact they can make more over all power in some cases. It really depends, it might not be as drastic with a stock engine as it would a highly modified one but they do make more torque. who knows?

 

How hard would it be to swap a 351 into my 91 f150 2 wheel drive with e4od tranny?

 

You would need the 351w short block or longblock, if you go shortblock and plan to reuse your heads then you need to have the bolt holes enlarged on the 302 heads. You will need a 351w upper and lower intake and a 351w distributor, swap your injectors and electronics over, throw everything from the timing cover forward off the 302 onto the 351w, install a 351w flywheel if it didn't come with one and your set. There may be a couple odds and ends but thats the bulk of it. Good luck

 

By electronics you mean the cumputer module and the likes? That's where I get dicouraged. I am mechanically inclined and have no doubt I can swap the engines and accessories, but when it comes to electronics I get scared.