Silver_Whistler

I bought a motor over ebay about nine months ago to build up. Its done and in the truck. I was told that it was a 5.3, but after my recent trip to the dyno, i am beginning to believe elsewise. Heres a list of my mods.

Ported and polished heads(stockk valve size)
MTI Hammer cam 222/222 .566/.566 112lsa
Asp pulleys
Long tube headers no cats
ported throttle body and MAF sensor
Built 4l60e 3200 stall convertor

A/F ratio ranges from 13:1-13:4 throughout the pull.
I pulled it up to 6700 rpms and my maximum numbers i could pull out of the thing was 312hp and 315tq! What the hell is going on?!?
How can i tell if this motor is indeed a 5.3 or a 4.8?

NOSjohn

iTrader: (9)

That sounds about right for a 5.3 w/ cam & headers. Chevy Perf. Magazine did one recently with about the same mods /same numbers as yours.

You can check the numbers on the heads and the block. They should be:
heads - 12556743...99......325..........Gen.III, 5.3L, aluminum, truck, van
12559895...00-up...325..........Gen.III, Vortec 5.3L

block - 12561358...325...99-up...Gen.III, used with 5.3L motors
12577396.........02-up...Gen.III, 4.8L or 5.3L, cast iron, truck

Silver_Whistler

One quick question, How much power do you think im losing or not reading on the dyno when the convertor is unlocked?
All of my pulls were made with the convertor unlocked. I just now remembered that.

NOSjohn

iTrader: (9)

15-25 rwhp at that level