03 truck swap, 5.3 to 6.0

[Z28LS2]

I built an 6.0 for a '03 Z71 wich had an 5.3. I am having serious probs, the motor is built as a stock lq4 with a Isky truck cam and ls1 camaro heads. The motor is really not that hot, just looking for a little more torque. The truck doesn't idle correctly and has a serious lack of power, I was aware of having to tune the truck, but the people tuning it is now saying that the engine is to tight. When I let them know that the machine shop miked everything then was sent to Faereman Racing to be checked and then I built it I checked it, they then said the valve springs are bad! I think these people are a bunch of IDIOTS!!! Can anyone help me????

Z28LS2

[RedHeartbeat]

what lift cam and what springs do you have on the heads?

[Z28LS2]

the lift is around 500 and duration is around 208/220. I dont have the specs on me but i think I'm close, the heads came off a 98 ls1 firebird

[RedHeartbeat]

Yuck, perimeter bolt heads

valves should be okay but I'd upgrade them to the LS6 springs just to have the better springs for the increase ramp rates. They're only $60 from SDPARTS.com.

Maybe they say it's too tight because you have high compression for a 6L engine.

[Z28LS2]

intake: .510
exhaust: .530

intake @ .50 is 212
exhaust @ .50 is 220

compretion ratio is 9.5
valve springs are stock puke springs LOL!
I have the matching Isky springs for that cam, but the retainers were defective so we compared spring pressures and seat pressure was 20lbs different so we just went with stock springs to get the job done last fri. at 4:00 p.m.

[RedHeartbeat]

You need the LS6 springs in the worst way!

[Z28LS2]

I'm going to hang it up 4 the day, I appreciate your help! Could you explain why the springs would be affecting power from 1,000 - 4,500 rpm due to "valve spring problems" the power takes a nose dive on the dyno at 4,500 rpm BIG TIME! It is a dog for power. Also what else would you reccomend, does this tune shop my customer is using possibly not know what they are doing? I will check my post in the morn. I REALLY APPRECIATE YOUR INPUT ON MY PROB.

[RedHeartbeat]

coil spring bind causing the pushrods to deflect or bow or collapse the lifters. It also could just be valve train harmonics. Did you put hardened pushrods in the valvetrain?

[GasGuzzler]

4500 is right where inadequate springs show their ASSES.

[Z28LS2]

this is just an everyday driver truck, so I didn't put hardened push rods in, but you do have a valid point I will be checking for coil bind. Also I am going to go ahead and install the recomended spring from Isky.(should've just took the time and waited to get the defective retainers replaced from Isky) I should know better I work on a fleet of 300 G.M. trucks all day long!
Also thanks for the info GASGUZZLER