1990 460 Speed Density
 

Bill,

first post from a newbie. I have a 1990 F250 4x4,7.5l, 5 speed zf,4:10 gears on 44TSL's, a mud truck. Engine mods consist of Hedman Headers,Underdrive pulleys, K and N air filter, BBK adjustable fuel pressure regulator (set at 41 lbs), a custom 3 inch plenum spacer, a 1 inch throttle body spacer, and timing set at 14 degrees. I have done an EGR and Smog pump delete as well. My question is would any of my mods conflict with the programing in the Pegasis Chip? I don't have the ECU part number in front of me, but I can get it no prob. The truck runs good, but I notice a miss under highway driving conditions (EGR delete?) and I tend to bounce of the rev limiter while racing in the mud. I would love to eliminate those two problems, and i would love an all out race setting for more power while mud racing. Is any of this stuff possible?

Richard Scott
staff of www.monsterphotos.com

I'm not Bill, but I might be able to help.

The modifications will only be helped by some custom tuning. The EEC-4 PCMs are pretty brain dead and don't know much...especially the older speed density ones.

I'll say that the only real problems caused by any of your modifications come from the increased fuel pressure and the headers. The plenum spacer and throttle body spacer aren't doing anything in the way of engine breathing so those don't hurt your drivability.

The EGR delete isn't going to cause a miss. It can cause detonation. Again, your PCM is pretty clueless so it doesn't even have a knock sensor.

As far as the rev limiter goes, it can be taken care of pretty easily but don't expect to gain much as the 460 in stock trim is pretty well out of steam by 3500 RPM anyway (I have dyno charts to prove it).

Richard,

First, let me welcome you to our humble forums. :2thumbs: I used to spend a lot of time as a kid in Port Salerno and Stuart, with many a morning spent with dad and granddad snook fishing under the Palm City Bridge and at Roosevelt Bridge. Good times for sure. :D

The mods that you have shouldn't be too big a deal to handle. As Cody mentioned, the increased fuel pressure probably isn't accomplishing much. Also, we need to closely scrutinize the timing curve to avoid any detonation. When you have a moment, if you could locate the PCM code it would be helpful. This way I can see what we're able to handle for tuning and can give you a better idea of what you could expect.

Take care.

Bill and Cody,

thanks for the reply(s). I will get the PCM code gs soon as I can and post or send them to you. As far as the timing goes, I am open to settinr the timing back to factory specs.
Small world Bill. I cross the Rosevelt on a regular basis. I can't say I have fished the area much, but have been boating down the St Lucie river and the Indian River lagoon. This is definately the place to be if you like fishing. Take care.

Richard