Greetings fellas, I have a question about a mod that I would like to perform on my 88 F-250. It has the 351W motor in it and it is a 4x4 with the ZF-5 speed tranny.

I know its a big truck, but i'm under the impression that the 351W can be putting out a helluva lot more power than what it is. I want to start adding some "shadetree mechanic" modifications to it and I would like to install a set of headers to start off with.

I've done my pricing and have read other forum posts on the results of others doing this, but I want everyones feedback to my situation. My biggest concern right now is this funky stock emissions system the 351W has on it. I'm registered in a county that doesn't require emissions, so thats not a problem. My worry right now is that if I convert to long tube headers that it'll screw up the fuel injection system on the truck cause of the lack of the emissions system. I will, of course, have the O2 sensors plugged into the new exhaust system, but i'm concerned about the EGR system, being that it'll more than likely be disabled. Has anyone out there performed this mod on their fuel-injected truck and what were the results?

Also, this truck has this giant stock fuel injection manifold on it. Are there any tricks of the trade to get more airflow into it?

Last question goes out to those who have the exact same truck as I do: What kind of MPG do you receive with no modifications to the motor? When my truck is full (both front and rear tanks), and I go on a road trip, I average about 200 miles on the trip gauge per tank, giving me about 400 miles of drive time before I have to stop and refuel. In the city...forget it. I'm lucky if I get 170 miles on each tank before they are empty. Is this the norm for a truck like this?

Any info will help! Thanks for reading my post and I look forward to any replies!

Thanks!

Dave
Staff Sergeant, USAF.

 

I put long tubes on my 93 302 4x4. I hooked up the emmissions equipment because in PA we have emmissions. They went on fine with no rubbing and didnt mess up the fuel injection. Since the 351 is wider, you may have clearance problems.

 

No clearance problems!!! Just get 351 headers for the truck, not 302 headers or mustang headers. You can have fittings for the EGR and O2 sensor welded on if you don't buy a set already equipped... that's what I did.
The EFI system will have no problem with the headers as long as the O2 sensor is inserted into the passenger side collector and connected correctly.
The Intake manifold is not the bottle neck on these trucks, it's the exhaust system and the cam... especially the cam on the pre '94 models. If changing that is not withing your job scope, though it's the best bang for your buck power improver you can do, install 1.72 roller roockers instead.
I get about the same milage as you in the city, but my highway milage is better at close to 300m/tank.

 

Its not that your county doesn't require emmissions, they just don't inspect vehicles...yet. Its coming.