I currently have 3 options 862s/706 or 317 i can have my experience cousin port them but im not sure which will be better on my build i have a colorado 5.3 swap ls6 intake 216/220 560 lift cam 3.73s not cats and stock manifolds (couldnt find any headers that fit). So which mild ported heads will be better on my truck thanks!!



​​​​​ps 243s are out of the budget

 

I understand what ya mean about "out of budget", but you can sell 862s for like $150 and pick up a set of 243 on eBay for $400 shipped or less. They will flow better than the ported 862s...

 

significantly better...

 

Ive actually heard of some ported 5.3 heads outflowing the zo6s, and with the higher compression and good flow i think they should be the best option for the budget build does anyone else agree??

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Ported 706/862 heads will out flow stock 243 heads.

The limiting factor on a stock 706/862 head is the intake valve size.

If I recall the ported stage 2 706/862 heads were used as a budget alternative to increase compression on the 5.7L back in the day when there were very few alternatives out there. When you add forged pistons with valve reliefs you have to do something to get the compression back. It's costly to have the chambers welded up on a set of heads and re-shaped.

Once ported and the valve size increased on the 5.3L castings, the flow was similar to the ported 241 and other heads on the market at the time.

 

Short answer, the 862/706 will be best ported with the larger 2" intake valve. The larger combustion chamber on the 317s will not be beneficial to your goals. If you're getting machine work done anyway, you can get an inexpensive set of stainless 2.02/1.6 valves on eBay.