[oldman]

Originally Posted by Tim M

I've asked about better valve springs when going from NA to blower and was told, not necessary. I used to change valve springs out seasonally on my 7200 rpm LT4 (Gen II) motor as they were consumable. I'll probably address in the future as boost on the backside of the valve reduces the resulting spring pressure - I do like to hear those 6500 rpm shifts!

what you wrote is gospel truth. I too consider valve springs consumable. In general over the past 32 years race 4 valve engines. So boost over the valve head did NOT require stronger springs (heads really small). I'm of the opinion now with these huge valves that boost does require stronger springs or you subject the intake valve to bounce as the related lifter overshoots the lobe and deceleration ramp and impacts on the cam. Think of it as a motocross overshooting the landing. This fails either the lifter or the valve (probably the hollow intake), in my case the lifter. I think this problem is further complicated by dual valve spring harmonics (should have gone conical), fast lobe lifts (add HP and brings customers in), and extended RPM, and most importantly large valve lifts (customers like that too). Try 7000 RPM sifts... OMG sounds great. Especially with a near stock exhaust that you can actually hear the metallic engine sounds.... not just loud exhaust. I posted an idle rev video on the NA section of large cam and stock exhaust.

BTW always luved the LT4 as the final evolution of the SBC.

Originally Posted by Tim M

I'm interested in the discussion only because I will be putting the stock LT4 blower on my LT1...may not be the best idea for my application, but can't deny the need for 650 HP!

Price seems good, performance better than stock LT4, looks bad action. It was my first choice.