I'm definitely not a show boater type... all about function and efficiency. I could give a rats a$$ if it blew rainbow smoke out of the tailpipe (unless rainbow smoke endangers some sea turtle or something, then I guess its not so good)

 

rainbow would be very pretty......lol. Form and function equate to a light black haze at full WOT. If it looks like a coal plant on full burn, you are over fueled.

 

fixed it fer ya.

 

Do You actually need any kind of muffler on an 86 f250 w/6.9 legally. What kind of performance gain can you expect with out one.

 

These things are ungodly loud without a muffler, and chances are you won't last very long without getting a noise disturbance ticket.

They sound like big block gassers with a loud bark in high RPM's under load.

 

I just picked up an 84 F-250 with the 6.9, and was also thinking of turning up the fuel just enough to get the haze at wot, just not quite sure how the turn it up. Does anyone have a picture of where the screw is on the ip?

I'm also planning up opening the exhaust, and probably using a high flow muffler instead of deleting muffler entirely. I've heard 4"-4.5" exhaust is a good size, gives a nice tone and opens it up enough, w/o being ridiculously large.

 

i'm planning to turbo mine one of these days, but thats to the tune of a few thousand bucks, so not gonna fit the OP. and after that, i intend to get myself a gearvendors overdrive unit to further enhance my economy.
@realtrucksrattle, there is a cover just under the oil fill that you remove, and there is (i'm told) a screw there in the center of the IP's drive gear (IIRC) that you turn in to increase the fuel or out to reduce the fuel.
hope that helps
...and since you're new, IP=injection pump, IIRC=if i remember correctly, just in case you weren't up on the local lingo

 

nope, the fuel screw is under a little plate on the side of the injector pump.

before you turn up the fuel, you should get a pyrometer to watch the exhaust temps. if they go over 1200 degrees you risk engine damage.

 

thanks for the correction, i was going by what i thought i'd read