Powertrain Loses

[Lucille]

New to this forum. Think I may have the last 6.0 Avalanche to leave the line. But this post is about my 2003 4x4 Avalanche recently converted from the 5.3 to a GMPP LS376/480 and I'm wondering if this would be normal powertrain loss? Bad Dyno? or a tuning problem? I went from 480 peak at 5950rpm at the crank to 321 rwhp peak at 5350rpm and also lost about 100 lbs of torque.

[molitor]

wow! thats alot of horses lost, had your trans serviced lately? and did you put a new converter in while you were at it?

[Lucille]

I put in a new converter, Transgo shift kit, Vette servos, and Kevlar Band.

[WARLOCK]

Whos your tuner?

[Lucille]

I used Hesco in Birmingham. Guys seemed to know what they were doing.

[WARLOCK]

Never heard of them. BUt seems like something is wrong somewhere.

[sprayedenali]

welcome, im from birmingham as well...
and ive actually had HESCO tune my old truck and my dads yukon. im now tunning my yukon myself with the help of some friends...

Jon did the tunning id assume? with my dads yukon the tune was good from what i can tell, but very very conservative FWIW.

hopefully theres something more to it than the tune, cause itll be tough to get another 100hp out of it. whos dyno did you use?

[farmtruc]

Something is obviously wrong, look into transmission slipping or if get a second dyno reading to be sure.
That power is close to what a hot 5.3L puts out.
As long as the a/f ratio is good, timing is good with no KR, the tune is probably good enough, cause like it was said, there isn't that much power left in the tune if it's close.

Did anything else change besides the engine?

[Lucille]

Jon did do the tune and seemed to really know his stuff. It was actually a dyno tune so they also did the dyno. If I can figure out how to get the graph below 19.5 kb I'll post it and see if some of you guys can make sense of the outcome. It shows some strange things, like torque rated above HP and a 50+ HP and FtLb dip at 2500 rpm. At this point I'm thinking that something I've done on the install is the limiting factor but I can't figure out what. Either that or GMPP seriously overrated this engine. It does sound great and throttle response is awesome.

By the way, how do your tuners dyno trucks without reaching speeds beyond the tires rating?

[Lucille]

A/F stays consistent at 12.4 up to about 5500 rpm and then drops slightly above that. Tranny is a GM Certa with about 5k on it. Convertor(2300 because its still a towing 4x4), servos and shift kit were done at the time of the engine swap. Kevlar band was added after the first dyno attempt smoked the stock band. Swap required Lingenfelter 58/24x module to work with the Gen III computer. Also, added American Racing LT 1 7/8 primaries and Efans for the swap.