i started building a 5.3 that was given to me its out of a 05 silverado. i also have a extra set of ls1 heads laying around. my question is right from the start the ls1 heads flow better and i know to make 5.3 compression with a ls1 head they need to be milled around 30 to 35. ive been told both that im wasting my time milling the ls1 heads thats its well more worth it to put the ls1 valves in the 5.3's.

BTW its going in a very light car, around 2700 lbs with me and the 5.3 in it. im planning on the 224 cam ls6 intake and a 150 shot.

 

Those ls1 heads arent 241s. They are the 98 853 cast. You might want to check on the 853 flow numbers. You might be better off just doing a valve job on the 5.3 heads. But what the hell do i know, you built my car after all.

 

I dont know for sure if my old heads are 853s or the 806 head cast. You might want to look into that b4 you just cram them on that motor.
Im pretty sure they have similar flow numbers, but dont hold me to that.

 

lol ite frank when u can build ur motor ur self instead of me doing it for u u lemme know

 

my 98 heads are 806 casting. perimeter bolts instead of center bolts on the 853s. ohhh do i hate perimeter bolts lol