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Glen's

1996 Chevrolet Impala

SS Big Block Chevy Swap

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Build Points

23

  • Color: Black
  • Horsepower: 575
  • Drivetrain: RWD

Vehicle Overview

An L21 has replaced the original LT1, and a 4L80E has replaced the original 4L60E. The original 8.5" 10 bolt is still there, but with 3.73 gears. The L21 is somewhat unique in that it has a 24x ignition system but is based off the Gen VI L29 454. They only came in Kodiak/Topkick's, RV's and school buses. I got mine out of the 2000 school bus with 60K miles on it. It got punched out .060 over with forged rods and pistons. I read that they all came with forged cranks, but unfortunately that was not true. I installed a mild Straub HR cam and topped it off with a pair of AFR 265 oval port heads and a bunch of Holley intake components. I then tuned it to an 0411 PCM using an 02 Camaro calibration. It has run well, but I've been unable to tune out the lean spike at tip in. I suspect the problem has to do with plenum volume of the stock LS1 intake compared to the single plane and elbow setup. Next step is to replace the GM PCM with a Holley Dominator ECU.

Completed Modifications

Drivetrain/Transmission/Differential (2)
Engine Management (ECU) (1)
Engine Parts (6)
Exhaust (2)
Fuel System (1)

Future Plans

Install Holley Dominator ECU.

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