Alright, now we know! Thanks Allan!

 

Well that's why we have rational discussions on here from everyone's opinion. I don't know how these GENIII motors react in terms of VE, flow, etc. vs other motors I've played with. It's very possible that they do react better with a larger 2" intake valve.

I'd like to see the same ported/polished heads witha 5 angle job on stock valves put up against heads w/ larger valves w/ 5 angle job. Dyno, track, etc. They'd have to be the same setup though.

If they were my heads 5.3 heads on the 5.3, I'd be keeping stock valves and would get them fully polished and some very mild porting to keep the small port, high velocity aspect from them. The higher your powerband you want, the more port work I'd put to them.

 

Yeah, there aren't many people on here that have gone the head route with the 5.3. A member on here by the name of 12sec.5.3 on here has run damn good for the mods he has listed. I think he is running the stock valve size with his port work though. I would have thought more people would have gone the H/C route by now. I am still open to the opinions, so please post on.

 

The $$$ for full head work alone (not counting cam matched, rods, retainers, etc) you can get a 6.0 low output motor. That's why almost no one does it...the '01+ 6.0s also have big chamber LS6 heads if I remember correctly and they are better than the LS1 and 5.3 heads too.

I'd just disassemble a set of 5.3 heads... get them fully polished (chambers, runners, valve throats, etc), very lightly ported if at all, peep at the valves to make sure they are okay, etc. Just a very mild maybe $400-600 job. The costs to put fully worked 5.3 heads on a 4.8/5.3 just don't make sense to me due to that limiting bore factor.

I'd rather have an LS1 or 6.0 block than a 4.8/5.3 anyday even if the LS1 and 6.0 had a shorter stroke. Their increase in bore is well worth it.