hey yall i've got a 91 f150 with a 351w that i'm looking to hop up a little. I've see alot of old explorers in the boneyard lately so i thought it would be a good time to grab some gt40 heads. What i want is something that will give me tons of torque for super cheap and be super reliable. i do rev the engine up alot so a little top end kick would cool to but i really want the low end torque.

should i go with gt40s or something else? if i get the gts would they make more torque as is or if i ported them out? i plan on long tube headers. and if i port them, should i focus on intake or exhaust? also what intake manifold should i look for? the 91 stock one seems ok but is there anything else i can dig up at the boneyard that would work better? i'm planning on using a comp 4x4 cam that makes lots of low end.

And while i'm at the boneyard, anything else i should look for? what all can i swap onto my 91 351w?

do i need to do anythign with the computer or will it run fine with the new heads?

i have the e4od trans and 3.55 gears and the trans and 3.55 gears are staying put so you know.

btw, i'm super hard on my truck and engine so whateveer i put on it has to be able to handle alot.

thanks

 

oh and what about pistons? can i pick up some cheapies that would raise my compression a little? how hard a job would that be? how would they affect me power band?

i know its alot of questions but i thought i'd get it all in one thread instead of in a bunch of different ones. thanks

 

The heads are a good upgrade but you can't just throw any cam in there the computer will not play nice with it, I suggest you bolt on a set of 1.7 rockers instead. If you're going to do some porting then port match the lower intake runners to the heads, that is the area where they are the smallest, and clean up the exhaust ports in the heads. There are no other junkyard 5.8 intakes so you're stuck with this one, and besides that the EFI system in that truck will only handle so much and an intake could very well put you beyond it's adjustment range. I'd also suggest you leave the bottom of the motor alone if it doens't burn amy oil and has good compression.

 

The GT-40's are an upgrade that is worth doing. They will flow better ported if done right. The exhaust has always been the weak point in SBF heads, particularly the thermactor hump. Some info on porting the GT40's can be found at diyporting.com.

You might be able to get some flattop pistons, but I don't know what CR you are starting with or what the GT-40's with a little surfacing will have, too many variables. You would have to know all the variables and plug them into a CR calculator.

Really hard to tear up a 351W without making a TON of HP. or getting really stupid or neglecting maintenance. The trans will go first.

 

thanks guys

if i put bigger injectors on it could i run a low end edelbrock intake? if not, how do i mess with the computer to get it to work?

the cam wont work even if its specifically for my 351? how can i make it work? i really want to run this particular cam.

also, what about putting bigger valves in the head? is this hard/expensive? would it hurt my low end?

thanks

 

Sorry this post is a little late but I can answer some of your questions... In 91 EFI still only a couple years old and so your truck has SD or speed density intake on it... unfortunatly so do both of mine being 88's. The SD really limits what you can do to upgrade your engine because it just can't take 100hp worth of improvements and be able to feed the motor the right amount of air. The newer 1994 and later i believe have MAF or Mass Air Flow. These trucks have a senser by the air box that allows the engine to be fed more air when you do all the big upgrades.

Search MAF and SD on the forums to learn more I probably didn't explain it vary well...

As for your truck... I would stay on the top end and get the GT-40s and a pair of headers. that will free up the flow of your engine and give you the power boost you want (but not more than your engine can handle). If you have low compression and your truck is burning oil then you should pull it and do a rebuild with a new cam. But I like the other guys would suggest staying away from the lower end if you don't need to do work there already! Also you can convert your engine to MAF instead of SD but you'll have to do your research and get all the right parts. there are kits out there on the internet but you can do a junk yard swap as well. If I were you I would go for the top end and if you really want to spend the time and money I would switch it to MAF... Then and only then should you consider doing a cam and lower end power upgrades... Hope this helps!

 

No you can't put bigger injectors on it, that is one of the limitations of the SD system. You can't "mess" with the computer to make it work either, you first have to swap in a mass air computer and harnes and then you have options.

Again you can't "make" it work, the cam must conform to some strict specs to be SD compatable.

It will cost more than the heads are worth, and the GT40 heads already have bigger valves than the E7 heads you're taking off, so it's a waste of time and money.

 

what size tires are you running? is this a daily driver or something you take out on the weekends and wheel?

Ford Fuel Injection has all your efi related questions answered. and listen to conanski