one of my friends has a question for you guys.
-matt


i've got a 92 ford f-250 5.8L 351 tbi. i've heard that some early 90's fords needs 2-3psi back pressure from the cat to run right. i was wondering if i could get away with strait pipes. also any suggestions on exaust systems for this motor would be helpfull.

I'd like a nice, throaty rumble, but legal.
jim

That is a myth. No engine runs better with back pressure.

Ill amend that on back pressure, being that 2 strokes require it, but they arent germane to the topic.

It depends upon the type of EGR system used. If the engine calibration is built with the Internal Pressure Transducer EGR Valve, it requires exhaust back pressure to operate correctly. If a free flow exhaust is introduced without system modification, driveability issues will appear.

SSheesh. talk about going backward with technology.

What about just a cat back system. Wouldn't affect anything because its after the cats and any sensors. Would save him money while still giving the sound and being emissions legal.

Some back pressure is good and some computer controlled cars have a back pressure egr valve, although I,m not sure on yours. I would definitely go with a cat back system. You have a computer controlled engine with all the parts designed to harmonize with one another. Just changing one thing can upset the whole applecart. There is a lot of good high tech hotrodding stuff out there but you need to get the whole system, then you can set in the front seat with your laptop and map fuel and spark curves ect. If that is beyond you, then buy something older that you can work on, unless you are paying someone experienced to do the mods.

I'll let Jim know your replies; does anyone know which type of EGR system is used on the engine '92 FoMoCo 351.

Any suggestions for exhaust? I feel that Jim is looking for "a classic musclecar" type sound... low, growly, and a bit gurgly. Also, this is on a budget.

Jim's girlfriend got a 87 DOdge Dakota with the 3.9v6. It has a carb, and an air pump. Would she get better gas mileage and a little extra power if that air pump belt was removed (the v-belt that drives the air pump runs off the crank and waterpump pullies, nothing else. there is a seperate v-belt that does the alternator, power steering, etc.)

thanks again,
matt

On the 87 Dodge" You won't even notice a difference with the belt on or off but the system will go bad after a while with it off. The pump will freeze up and concensation will rot out the check valves.