Hey, so I'm new to this forum. I have a 92 F-150 with a 5.8L efi engine, automatic transmission. I have on it headers, true dual, no cats, a k&n air filter, and a mild cam. I've been told its a speed density. I was wondering what else I can do to get more performance while keeping her NA. Maybe a set of heads? The performance I'm looking for is speed! I don't haul stuff nor tow and its not 4x4. Also, should I lower the suspension? I have boss 22" rims as well.

 

Lower suspension will help in the corners and look nicer on a 2wd.

Look at the "6-liter" tune up and head work. With a cam and the heads a larger throttle body MAY help and possibly an aftermarket upper and lower intake manifold. Throttle body spacers and chips on these trucks won't do anything so don't throw money away on those. The only other thing I can think of is a lower gear set in the rear end for better acceleration. Most of my HP knowledge is for stock engines so I don't know how much good the TB and intake will really help.

 

Define "mild" cam? What are your horsepower/torque goals? The factory E7 heads will get you to the 300 FWHP range with some work and a better intake. As soon as you start down that path you will find the factory 5.8L intake is useless.

The Gen 1 Lightnings were factory rated at ~245 FWHP. They had GT40 intakes and heads as well as factory shorty headers. With a little work, mainly a better cam and a tune, the Gen 1 guys are running 300+ FWHP.

A Lightning upper and lower intake, AFR/Trickflow heads and a decent Speed Density friendly cam will take you far in your quest. The biggest limiting factor is finding someone who can tune a Speed Density truck. A factory tune, even if it is MAF, will not allow you to realize a full value return on your investment of "go-fast" parts IMHO.

 

I didn't pu in the cam. The person I bought it off of purchased it new in 92 and he put it in there. I trust his work, he was a head mechanic at a ford dealership for years. So I'm not sure on the brand but you can hear it and feel it when you get to higher rpm's. My goals are around 350-400 hp and lb./ft torque. I don't want to go overboard. I have thought of getting a positive drive supercharger from a ford lightning though. She's already pretty quick, but I love power.

 

I don't know if this helps, but the truck has 150k on it but the engine was rebuilt at 99k.

 

You are not going to hit those goals with E7 heads and factory 5.8L intake. You will need a 5.8L Lightning intake or aftermarket and better heads. For the price of used GT40 heads and clean up work I would go with aftermarket heads. Then you have to overcome the Speed Density engine control. A blower from a Gen 2 Lightning is going to be a custom fit. Two completely different engines.

 

Didn't the gen 1 lightnings have a charger?

 

Not from the factory. Companies used to make supercharges for the 5.8, but stopped years ago... Your best bet for 400hp is going to be a 393 or 408 stroker...

 

Oh ok. I wasn't aware of that. The heads sounds like a great idea. What about upgrading the cam. What would be a good fit? Any gains without changing the engine is what I'm after.

 

Is there a centrifugal supercharger that is still made for that engine?

 

Unless you find a used supercharger kit (last used one I bought was almost $2000) it will run you quite a bit.
Forced induction will almost require aftermarket tuning. The older kits had an MSD 6-btm and an fmu for timing and fuel, but were limited on adjustability.

I really think what you're looking for is fast and fun.
I'd suggest
392/393 "economy" stroker kit. This kit uses stock rods and 302 pistons, and a crank that was designed for those two parts. You can usually get it balanced on eBay for 900-1200 bucks I think. It's good for 500hp or so.
Aluminum heads. Your goal of 400+ is very tricky with iron heads unless you boost it. Most any alum head will work. Procomp is cheap, but beware that people have had a bit of trouble with the older ones. Edelbrock, afr, or any other brand name is preferred, but you can get a cheap set for 500 complete on eBay.
Roller rockers (usually nessisary with aftermarket heads)
Roller cam. I have just been talking with conanski about good roller cams for efi and there are a couple that are pretty healthy.
Intake is restrictive on a 351. The small oval ports were dumb on fords part. Any mustang style intake and tb will be a great upgrade and an easy swap.

Lots of info on this forum. Just start reading.

 

Thank you very much for everyones input. I appreciate it! I got a lot of good knowledge.

 

Without making any changes to the motor forced induction is the only option that will get you close to your goals. If the cam in the motor now is anything half decent the heads and intake are already restricting the engine, but the next step up is gonna be expensive because it will require larger injectors and tuning so even at $2000-$3000 a blower kit is gonna be cheaper to do.

 

Well, I think my next step will definitely be the heads and intake. Thanks again!

 

But dont forget bigger injectors, a larger capacity fuel pump, and a tuner.