Hey guys, I really need your help.I'm 20 years old and my dad just helped me picked up a
1997 F250HD 4x4
351w with an E4OD
Speed Density
3.55 Rear end
33" tires (big no no with my rear end)

I've done a little bit of homework into putting some power into my engine mostly from Conaski (Sorry if i mispelled your name) and browsing other forums. We have already ripped off the cat and muffler, threw on 2.5" true dual exhaust and I'm really not quite sure on where to go from here.

I know that while I'm on SD my options are really limited to upgrade wise what I can do. I already plan on doing 6litre tune up and throwing some shorty headers on though many of you advocate long tube instead, explain? Come to find out my dad has GT40 (not the P's) heads wrapped up in his garage that we would like to put on my truck. I know that the upper and lower intake manifolds are really constricting on air flow and i would like to swap those out however i don't really know what to look for.

Really my questions are this:

1. Short vs longtube headers

2. Will I need to do anything to my GT40's in order to make them engine ready (springs, valves, pistons, etc.)

3. What intake manifold can I throw on this thing? Please include a part number if you mean a specific one as well! Thanks!

4. Camshaft and roller rockers maybe? Not really sure what i need to be looking for in these.

5 Anything else i can do, or need to maybe do?

 

Shortys will bolt right up to everything you have. Longtube require custom fab work either way you go be it true dual or 2 to 1. I wanted longtubes but wanted single exhaust. Have to custom fab a crossover and a y-pipe and some how get my o2 sensor in there. To much of a hassle for me. Each to their own though. If you do go longtube and get it done post some pics!

 

1: any headers will help but long tubes will produce more HP/torque but can have fitment issues.

2: If these gt40 heads are off of a explorer the valve springs are known to be a little soft. So you will need better springs. Also if these are off a explorer they won't have a egr hole drilled into the back. (if needed) On a 351w the bolt holes will have to be enlarged to bolt it down. I think your current heads have around 64cc chamber. It's going to be around 66cc on the GT40 heads if they came from a explorer. Unless you mill the heads it will drop your compression ratio some.

3: the stock 351w efi intake has long small ports made for producing torque but can choke down performance. The 351 lighting intake would swap but are now expensive. The cheapest EFI route is to get a lower adapter intake and use a upper off of a explorer. But this would mean swapping out a lot of parts to get everything working correctly on your SD set up. Maybe you will need a MAF conversion to be planned in the future. Just something to think about.

4: The truck should have the F4TE roller camshaft. I have seen 302's on dyno put out right at or a tad over 300hp at the flywheel with this camshaft (all had long tube headers, carb's and were tuned on the dyno). This cam is more about lower end torque then top end. If you wanted more lift with this drop on a set of 1.7 RR.

5: any other mods will depend on how you plan on using this truck. If it's your daily driver and your only ride some mods may need to just be passed on for now.

 

I did a GT40 head swap on the roller 351 in my 96 E150 van three years ago. Of course it's got a Mass-Air system not SD. I went with a used set of three bar GT40's, a set of Cobra roller rockers (1.7 ratio) and a set of Pace Setter shorty headers with a new 3" single exhaust with a Dynomax super turbo truck muffler. Only other change was a K&N filter in the stock box. Difference was noticeable, fuel mileage improved by 1-2 mpg. You don't need to change the upper/lower intake here, the one's you have now are fine.