nomorews6

iTrader: (7)

I heard through the grapevine that 98 ls1 heads didn't flow as well as the 99+ ls1 heads. Is this true?

GTA91

iTrader: (14)

That's what I was told so we ported mine. I also changed my valves to the newer style "tulip" shaped ones... side by side you can see the difference in the back cut area of the valves. Hope someone else replies...

ss427ci

iTrader: (3)

I have a 98 and am curious myself.

transAm-98

iTrader: (1)

i'm in the same boat, and i'm curious as to what gains i would see by swapping my stock 98' heads for some stock LS6 heads

gkrocket

iTrader: (6)

Me too.

transam1998

iTrader: (5)

I bought the Vortek truck heads. I had also read this. Just don't forget that 99+ heads have a different valve cover bolt pattern. After buying 99+ valve covers and coil brackets from a dealer and shims from Thunder Racing to clear my roller rockers, I had $600.00 invested in valve covers.

WKMCD

iTrader: (2)

I've got a set of center bolt -99+ - valve covers sitting right next to me that I just got from another forum vendor. Cost me less than $160 shipped complete with coil brackets. Switching to 5.3 heads for a H/C. Those must ne some expensive shims!