Back in the day, we would put 305 heads on our 350 sb's and it would bump up the compression and add good HP. So in that mind set, would there be a good gain from adding a set of stock 5.3 heads to a stock ls1 motor or not? if so, how much est. HP gain?

 

stock 5.3's arent worth swapping since they come with a smaller intake valve 1.89 vs 2.00. ported 5.3's heads outfitted with new vavles are great since they have a smaller CC chamber you get the added compression 10.8 unmilled. the 5.3's flow the sasme as the 5.7's and they have the same port design.

 

Kinda what I thought since no-one does it. I just thought there was a chance for some cheap HP.

 

If I did this combo on a stock ls1, just because thats what i have, would there be any gain?