NEED SOME HELP ! PLEASE

WE TOOK ON A JOB TO HELP A YOUNG MAN, 1994 CHEV 5.0L AUTO, 2WD! BLOWN UP , HE BOUGHT A 1998 5.7L TO REPLACE IT, WE REPLACE THE INTAKE MANIFOLD AND GOT EVERYTHING TOGETHER FOR HIM! STARTS GREAT, RUNS OK , TILL IT GOES INTO CLOSED LOOP , IT WANT MORE FUEL ! THERE IS NO EGR , WE UPGRADED THE ECU 7427, OEM PROM AND REPLACED THE INJECTOR WITH SOME FOR A 5.7 , I DONT KNOW THE PPH, "SORRY", AND A ADJUSTABLE FUEL PRESSURE REGULATOR, HELPED MAYBE ALITTLE! IT WANTS MORE FUEL! LOOKING FOR SOME HELP AND ADVISE! WE HAVE DONE AFEW SWAPS ,5.7 TO 5.7 AND HAD GOOD LUCK, BUT THIS HASNT GONE WELL! THANKS!!

The 1998 would likely have been a Vortec 5.7, with only 8 bolts on the intake. The 1994 would likely have been "High Swirl" design heads with 12 bolts on the intake.

Is the above information correct?

If the above information is correct, a custom PROM chip is needed. The Vortec heads and roller camshaft in a Vortec are very different that the High Swirl heads and flat tappet camshaft.

Please share pictures of the installed 1998 engine.

dave w

I'd say a TPI fuel pump and the adjustable regulator to get the pressure up a fair bit higher than stock might get it running better. Still, Dave is correct that a custom chip is needed to get it right.

YES SIR THAT IS CORRECT! WE USED A INTAKE LIKE THE CRATE MOTORS , THAT WOULD TAKE A CARBURATOR, AND ADDED THE TBI ADAPTER! WHERE WOULD WE FIND A CHIP? THANKS FOR YOUR HELP! I WILL TRY TO GET A PICTURE TODAY FOR YA

Attached is an Excel spreadsheet with the factory timing tables (open throttle / closed throttle) from a 1998 Vortec L31 (5.7 Liter).

dave w

I SAY THAT ALOT DIFFERANT FROM THE 5.0L!WHO CAN BUILD ME A CHIP FOR THIS ?THANKS !