I have a 1991 F150 with a 5 speed and the 5.0. I have already done exhaust modifications (single straight pipe, going to delete the 2nd cat) as well as a K&N drop in filter. For the time being I am in grad school which soaks up time and money, but I have managed to save up about $250 for one (or a few) good engine modification. The question is, which one would be the best bang for my small collection of dollars?

I've read through many of the posts on this forum and it seems that outside of exhaust and airbox/intake modifications, some of the most popular suggestions have been:

GT40 Heads
GT40 Intake
1.7 Rocker Arms
48K Ignition Coil with .55 gapped spark plugs
Performance Cam
...and a few others.

My thought is that, with my small budget, the best thing would be the rocker arms. From what I've read, everything else seems to be contingent on other mods: GT40 heads by themselves are good but to really get the effect I should also do intake and cam (which I can't afford). Are rocker arms the best choice for my budget or is there something that will be more effective?

 

If you can pick up a set of 3-line GT-40 heads for $250, DO IT. They will give you quite a bit more performance all by themselves and will provide a solid basis for getting the most out of future modifications.

The stock intake and T/B will be more than adequate for the power level to which you aspire. Don't waste your money on upgrading them. Make a set of ceramic-coated shorty headers your second mod and the 1.7:1 roller rockers should be your third

 

all that stuff might be gettin the cart before the horse on a 91 302, so i would suggest a mass air conversion, if you have looked into this before you know it aint real easy but it aint too expensive either, i know for a fact i have less than 250 in partsin mine, but i hope you have a good bicycle cuz if you get it done in one weekend you deserve a round of somethin light, domestic and cold, but i guess a layover harness from ford racin would be easy or easier than the way i did it. but its yur truck do what YOU want.

 

No need for mass air if you dont plan on ever doing the mods to warrant it.

As stated above, you would gain nothing from upgrading intakes. The stockers flow just fine.

I would spend however much it would cost to do the ignition upgrade and timing bump, make sure all fluids are topped off and filters are fresh, and save whatever you have left over.

Why are you deleting the cats?

 

I'm deleting the 2nd cat only and putting my Flowmaster 44 in it's place. I may replace the first cat with a Magnaflow, depending on how much I spend on the other mods.

 

Do you understand that the two cats perform different functions? The first cat reduces NOX into N2 and O2. The second cat oxidizes CO into CO2. If you remove either cat you will be increasing emissions without increasing performance. If you replace them both with a single high-flow cat, you need to use a "3-way" cat (i.e. one which has an air injection tube) which performs both functions.

 

You dont replace a cat with a muffler. You replace cats with cats and mufflers with mufflers.

 

I get that. What I meant is that the Flowmaster will go in the giant hole where the cat used to be. The first cat will eventually be replaced by a 3 way Magnaflow off of a Y pipe, which was the point of the "Magnaflow Cat" thread I posted a while back. The $250 I was talking about is to be used outside of the exhaust system.

There have been a couple of listings on Craigslist for GT40 and GT40p heads that I might go check out. What should I look for to be sure they're in good condition?

 

Avoid the "P" heads. They work slightly better but the hassles inherent in dealing with the spark plug / header clearance just isn't worth it.

 

Not to mention headers will not work with P heads without rediculous modification.