i have a bad exhaust leak on my 89 f150 w/ a 351 W. this year had the speed density set up instead of the mass air flow system. i know effecting the intake makes the engine run oddly. does effecting the exhaust have the same effect? do i have to stick with certain headers? thanks

keith

 

An exhaust leak before to O2 sensor will give a false lean reading and cause it to run rich--this can also fry the Cats.

The motor will compensate if you improve the intake or exhaust flow to a certain degree. Adding headers will not be a problem. The motor will adjust for the fuel ratio using the O2 sensor along with the MAP, temp reading (coolant and air) and TPS. Major flow improvements will require increased fuel pressure (adjustable FPR) or bigger injectors.

If your are going all out with improving flow (intake, cam, porting, heads,exhaust), then a MAF system will be better but, it is possible with speed density management.

 

all i plan on doing is replacing the headers, cats, and a cat back. so i shouldn't have any negative effects? what are som egood headers for the 351W? money isn't much of an issue. i want something good. doesn't have to be top of the line. i'm replacing the engine so i figured i might as well put on new headers and all the exhaust behind them.

thanks

keith

 

Not sure on what brand of headers but, check out Jegs or Summit. I would spend the extra money on ceramic coating. Mine are 2 years old and look brand new. Also retorque multiple times when first installed, then every oil changed or so after that.

I only see positive effects when you change out your exhaust. Make sure the headers are smog legal for your state. I would not remove your Cats. I removed mine for a while and didn't have any gains. The truck polluted and stunk up everywhere I went. When you remove your Cats, the computer still switches from rich to lean to give fuel to the cats. The motor will not run any richer, but the exhaust will.

 

i won't be removing the cats. i'll be replacing the headers and getting new cats and a new piping and new mufflers. so jegs and summit have decent headers. thanks

keith

keep the info coming.

 

waht are good brand headerS?

 

My stroked 351 (392) in my 94 supercab 4x4 is running speed density with no problems (even the Ford Racing guys said it shouldn't work). I'm using Edelbrock shorty headers into true dual with no cats and Flowmaster mufflers, make sure and get 'em coated. I sent my old rusty ones off to Jet Hot (less than $200) and they came back better than new! Highly recommended.
Make sure and use good gaskets, I've heard that a blown out gasket can be common and troublesome with the cheapies.

 

Jet Hot? more info?


NM i found the webs site. i'll deff. look into that!