jboice06

if so whats the advantage of them???? ive got a ls1 and have a good set of 5.3 stock heads laying around what would they do for me if i bolted them up the 99 346 ls1 lowerend ????? will i pick up any power??? stockers for stockers replacement?

Hamrdown

iTrader: (25)

they will fit an LS1. They are the same heads but with smaller combustion Chambers wich will raise the compression over your stockers. They will bump up the compression and give you somewhere around 15rwhp. But a valve job is mandatory since the 5.3 heads have such smaller valves than the 5.7. Its a nice bump in power but I do not feel it is cost effective unless they are ported. You have to figure in new head gaskets, valve job, head bolts, probably valve cover gaskets, while your in there you might as well change the spark plugs, and the time it would take to do the swap. Just my two cents.

jboice06

3 angle valve job or just bigger valves in general?

Hamrdown

iTrader: (25)

Both. Larger valves at least LS1 sized and the proper valve angles. If you go LS1 sized you can use your stock LS1 valves and springs and save a little money. If you have it milled you can even bump it up close to 11:1 compression. But look into spending at minimum $500 for machining and gaskets. Check with a reputable machine shop for pricing and ask if they have done any LS1 heads. If they say "Ls what" or "what did they come off of" then run and go somewhere else.

96autoformula

LS What?