I HAVE PURCHASED AN AUCTIONED 1991 F250 5.8 4W DRIVE <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com[img] /><st1:time Hour=[/img]3:55</st1:time> REAR WITH AUTO. 3 SPEED TRANS…

I HAVE INQUIRED WITH JASPER ABOUT PUTTING IN THEIR CLASS II FORD 351W REPLACEMENT ENG. (365 HORSES OUT THE BOX) DUE TO THE FACT CURRENT ENG. IS BLEEDING OUT EVERY HOLE IMAGINE WITH OVER 200K MILES TO HELP IT DIE SLOWLY ( 200K GO FORD!!!).

JASPER TELLS ME DUE TO E.F.I. SYSTEM THEY CANNOT SUPPLY COMPATIBLE MILL (ENGINE) DUE TO COMPUTER& CAM COMPLICATIONS UNLESS I GO 4 BARREL CARB. WITH A 305Hp TURNKEY CLASS 2 LESS HORSEPOWER MOTOR (WRONG!!!).

THEY ALSO TELL ME THAT DUE TO THE COMPUTER IF I GO-AHEAD WITH THE 351W I STAND A CHANCE OF EITHER RUNNING LEAN AND DETONATE A PISTON/S OR RUN RICH AND FLOOD THE CYLINDER/S ALL BECAUSE OF CAMSHAFT.

QUESTION/S: CAN I CHANGE COMPUTER CHIP/S I REALLY DON’T WANT TO GO TO EXTREMES AND CHANGE COMPUTER TOTALLY (DUE TO MY INEXPERIENCE & IGNORANCE) OR IS THERE SOMETHING SIMPLE LIKE AFTERMARKET OPTION I COULD USE TO MAKE CAM AND COMPUTER AS ONE?

OR IS THERE MORE I SHOULD KNOW TO DO THIS JOB RIGHT THE FIRST TIME (NO COSTLY CONSEQUENCES)?

CAMSHAFT SPECS.: HYDRAULIC, .050 DURATION: 224* INTAKE 234* EXHAUST; <ST1lace>CAM</ST1lace> LIFT .310 INTAKE; .325 EXHAUST; VALVE LIFT .496 INTAKE .520 EXHAUST; <ST1lace><st1:PlaceName>LOBE</st1:PlaceName> <st1:PlaceType>CENTER</st1:PlaceType></ST1 106* INTAKE 114* EXHAUST.

THANK YOU FOR ANY AND ALL HELP IN THIS DREAM.

 

If it were mine I would investigate the option of simply replacing your worn out engine with a rebuilt crate engine the same size, if you don't want the headache of matching the ECM/PCM (computer) to another engine. If you replace the stock engine with something different, you should also replace the computer as they are generally a matched set coming from the factory. That said, you could drop in any rebuilt Ford engine that matches the mounts/set up under the hood as long as you replace the computer with one that is matched to the engine you choose.

 

FYI, CAPS LOCK is usually interpreted online as someone yelling at you.

Mike

 

Welcome to FTE!

This simply comes down to a speed density/mass air situation.

Your stock EFI is speed density - a system that does not generally allow for changes in vacuum caused by the camshaft. When doing a project such as what you're looking to do (more hp engine) most will switch from speed density to what's called mass air.

Mass air is a slightly different setup in that rather than relying on manifold vacuum for the computer to see the engine's load - it uses a sensor in the air intake ducting that directly measures the amount of air flowing through the engine. It's much more adaptable for modifications as well - as it's almost like a standalone EFI where you can change parameters and basically run almost any combo. They can be tuned to your engine's specs by either a SCT dyno shop or you can do it yourself with some of the aftermarket programmers out there (like TwEECer and PMS).

I suggest you do a search in this forum for "mass air" "mass air conversion" "speed density" and other keywords like that. You'll pull up a lot of information.


What they are telling you is that your stock EFI is not going to work with this engine. You can't take that engine and install it and expect your stock EFI to be able to run it. It will still think it has a stock engine under the hood. You need to change the engine management system (the EFI) to accomodate such a change.

I put in a 393w instead of a 351. My truck is running a 302 mustang massair EFI - which was modified to accomodate my 393. It's been on a dyno checking air/fuel ratios and chipped to modify the computer's programming to work with my engine.

Hope that sheds a little light on the subject.