Valvetrain

[SappySE107]

Gen 3 stamped steel rocker arms are 1.6:1, just like the roller rockers used in later gen 3 motors. The roller rockers are better however due to having less friction at the fulcrum. For valve springs, you can use LS1 or LS6 springs, using the proper hardware.

Requirements for using LS1 or LS6 springs

LS1 Springs
LS1 Spring Seats (bronze shim)
3.1L vin"T" mpfi Valve seals 6 Exhaust, 6intake (they are different)
For the LS6 Springs, the GM part# is: 12586484

You can reuse the gen 3 locks and cap if you want, or the LS1.

The newer GEN 3 heads starting in late 99 have a bigger valve guide. the LS1 spring seat will NOT fit unless you grind it out with a die grinder stone bit and drill to 9/16 I beleive. Use 92 GM 2.2 Valve seals on these guides as a perfect fit. All GEN3 early design valve guides will accept LS1 spring seats and gen2 valve seal with no alteration nesessary.

Aftermarket Valves

SIvalves.com

Part number: #SEV-01811 Exhaust Valve 1.42"
Part Number: #SEV-01929 Intake Valve 1.76"

[SappySE107]

You can also get larger valves, from a 3800. You will need to have the seats removed and install larger OD/ID seats. The Sunnen book on rebuilding cylinder heads and engines only talks about OD in relation to what we are trying to achieve. Take the OD of the head and add .060. The ID is supposed to be as close as possible to stock, but that defeats the purpose of getting larger valves, and it hurts the flow.