Was wondering if I should do ported polished 706 heads or go with milled 243's (otherwise stock 243's) with a 212/218 cam. I've seen a couple of magazines lately doing some build ups on 5.3's and they used trick flow "205" heads which I think are based on 706 castings. I know milled, ported and polished 243's would probably be best, but not in the budget.

 

id find some 243s... probably best bang for buck..... flow 13 percent better on the intake and the valves are larger....

 

I tossed this idea around alot myself and spoke with alot who did the swap and this is my opinion.... If you have no heads: go with milled 243's and see the small/decent gain. If you already have the 706's keep them because the cost of new gaskets, bolts, labor, and even the 243's would be alot to pay for the small 10-15 hp gain. Hope that helps.

 

How much and what thickness for head gaskets if milling 243's for 5.3?
I was thinking .030-.035 for milling of the heads to have a slight bump in compression over stock 9.5 to 1. Looking for direction to go

 

stay away from a head with big intake runners..it will hurt bottomend on a 5.3

 

seeing as how 706s came stock on 5.3s, go for the 243s with some work done.

 

I have a set of 799 same as the243 just different valves if you are interested shotme a pm

 

Definately go the 243 route, will be worth it in the end and will leave you a better haead for future use, but if consider going more cubes in future, consider haw much to have them milled as ptv clearances may arise, just my input.

 

by the time you buy a set of 243s have a valve job and mill done your about the same cost as a used set of PRC ported 5.3 heads
OR
find you a $50 set of 706s,get some 2.0 intake valves from a set of 317s for dirt cheap
Have them milled and a performance valve job done for about $500 total!!!
By doing this it will out flow the stock 243s and have more compression with no change in intake runner size

 

So how much would I mill the 706's since there already stock 5.3 heads. I wouldn't mine upping the compression a little, I'm already running 93 with the tune. So it sounds like for heavier trucks the 706's might be better for low end torque and the 243's are more for upper end hp. What if any is there between the 862's and 706's????