Hey all, I have my 86 5.0 EFI 4 speed (no overdrive) ready for added performance. Since I bought it May for $800, I've changed every fluid, rebuilt the entire braking system, replaced the battery, all filters, all sensors, both fuel pumps, and water pump, cleaned everything, and put on a 6" lift and 35's. This thing has amazed me. I was getting 22 mpg before my lift and tires, and 18 mpg after. Also, it'll cruise at 105 mph like a Cadillac. It has a good amount of power, but i want more.
What's the best way to achieve this? Intake work? Exhaust work? Possibly forced induction?

On another note, she burns oil on start-up. Once it's run for a few seconds, it burns clean. Because of this, I assume it's a blown valve seal. Should I worry about this, or just ignore it like I've been doing? It burns about 1/4 quart of oil a month/1 quart per 5000 miles.

Thanks in advance
Quinn

 

Bull *****

 

If you want easy power then bolt ons are the way to go. There are many proven builds around that show increased power output if you look around.

 

18mpg from a 5.0 truck with 35" tires? I suppose it's possible if you have everything setup just right and you drive at a constant 50mph most of the time, but you gave no indication that you have recalibrated the speedo and installed 4.56 gears in the axles which incidentally should be the first performance mods you do. After that put a cam in the motor and put a full exhaust system on it with headers, that's all you can really do to an '86 without a MAF conversion which is more complicated than usual because of first year differences in the wiring pinout at the PCM.

 

You caught me, I never did recalibrate my speedo. It's 5mph slow at 70 mph. So no, my gas mileage isn't 18, I suppose. But it's still impressive. Anyhow, that's not what this post is about.

Why do I need 4.56s? It runs great with the stock gearing, and I still never use 1st to take off, even up step hills. Is there another reason to change it?
What cams would you suggest?
Thanks again for your input

 

It's off more than that, those tires are 21% larger than stock so your speedo is low by 13mph.. when it's indicating 62mph you're actually going 75mph!

What is the axle ratio right now? Does the truck have a tach? What rpm does it turn at Hwy cruising speed?
As it stands your motor makes about 180hp peak at 3500rpm and everything you can do to it to get more power will push that peak to higher rpms. Gearing is needed to match the powerband with the rest of the powertrain, otherwise you just have to live with having to downshift to accelerate. But we need to know exactly what the truck has now for gearing.. maybe it's already optimized given the fact you don't have an overdrive trans.

Options would include the Comp 31-255-5, 35-255-5, and Crane 444232... the last two having the 351HO firing order which will work fine as long as you route the plug wires to match.

 

Maybe my bronco was off before, or maybe it came with 31s from the factory. I have a GPS speedometer, and that's what I'm basing my actual speed on.
I think I have the 8.8 in the diffs, but I'm not positive. Is there a way to check without ripping it open and counting gears?

 

There should be a calibration decal on the drivers door pillar with an axle code, once decoded that will tell you what ratio the truck came with you should also see what the factory tire size was on there.

 

Alright, I have code 16. So I think that's a 9", being 3.73s. But I don't think I want to gear lower. I already never use 1st, and the rpms in the freeway are high as it is

 

Alright, I have code 16. So I think that's a 9", being 3.73s. But I don't think I want to gear lower. I already never use 1st, and the rpms in the freeway are high as it is