LT4 Torsional Damper vs. ASP LT1 Bal/Pulley?

[Eric 97LT4SS]

The LT4 came from the factory with a GM Performance Parts damper which is used on all LT4 engines like mine. This LT4 only balancer must have been used for a reason, right?

My question is if I installed an ASP LT1 Balance/Pulley 23% Crank, 15% Alt to take advantage of the Underdrive pulley systems could I damage my engine by tossing the LT4 Torsional Damper?

The ASP #ASP945103 replaces the factory balancer/pulley. On the other hand most underdriven pulley's are just sandwiched in front of the factory balancer which would probably just put additional weight on the Crank, right?

Bottom line is the Part worth 10 hp or am I just waisting time? Hopefully this mod would get me close to my goal of 375 rwhp. Thanks

Eric 1997 LT4 SS #093

[Eric 97LT4SS]

Link to the Balancer/Pulley in question.

http://www.lmperformance.com/3668/2.htm

[fastTa]

LT1/LT4 crankshaft dampers are zero balanced, meaning they have no weight bias. The LT1 uses a single mass damper while the LT4 uses a dual mass damper. Since the LT4 comes from the assembly line with a higher redline of 6300 RPM, it was important to design a better damper. The dual mass damper has the ability to be 'tuned' to dampen harmonic frequencies at multiple RPM ranges. There is a different external balance on a LT4, due to it's pistons having a 3 cc less valve relief on the piston than the LT1, but this is accomplished with the flexplate(auto) or flywheel(manual).

Also, the damper on these LT4/LT1's is unlike other pre-biased (external/external) balanced traditional Gen 1 SBC motors, the LT1 in our cars uses a crank pulley and dampner integrated into one piece with a zero balance, rather than having a separate crankshaft pulley bolted onto the harmonic balancer.

This ASP underdrive setup will likely not harm your LT4 motor. Many people have used them with no mechanical problems. Can it dampen crank harmonics as well as your LT4 stocker damper? Honestly, I don't know. Maybe not.

Also don't expect a 10 HP gain with this. Don't even expect a 5 HP gain.

[Injuneer]

I doubt you'll see 10HP. That might have been a reasonable guess if the water pump was driven by the belt, but it isn't. Here's a dyno test of a sandwich type U/D pulley, to put you in the ballpark on power gains.

http://www.ws6.com/mod-2.htm

I had the ASP 25% U/D crank damper/pulley and the 15% U/D alternator pulley, and was not able to measure any performance improvement, using an accelerometer. I found the volt meter approaching the red on a hot day, stopped in heavy traffic (800rpm M6 idle speed).

To me it isn't worth it.

[Eric 97LT4SS]

Thanks guys, think I'll stick with my LT4 balancer. A 5 HP gain is not worth $160.

Eric 1997 LT4 SS #093