I know porting heads increase air flow, but where are the advantages in the powerband? Mostly upper rpms (greater than 4500)?

How about combustion chamber sizes and milling? Are there advantages across the board or lower rpm range?

Basically, I am tossing around the ideas on swapping heads on my lq9 (317). I have a TSP224r cam on a 112. I want to try to maximize naturally aspirated power between 2500 and 6200 to 6500 rpms.

 

Most guys see from 20-40rwhp and a torque increase of 30+ft/lbs across the rpm range. Generally the larger the cam the more more the cylinder head work helps. In the case of the truck intake manifolds, the upper rpm power is pinched off. Still the cylinder head work makes a felt seat of the pants difference.


Richard

 

The difference in performance is comparing stock 6.0 heads to worked 6.0 heads without milling for reduced compression?

 

Yes. Same chamber sizes.

Richard

 

Not to hijack this thread, or anything... but how do ported 317 heads, from WCCH, compare with STOCK L92 heads. I saw the article in the November 2007 Hot Rod, and wondered if I could get close to the same results with ported 317 heads? The L92 look interesting, but using stock parts would be way less of explain to the SMOG police.

 

For a tow package what kind of gains would you see for a H/C package?

 

Head and cam tow packages will see a greater gain in rwtq rather than rwhp. It's not uncommon to see close to 25ft/lbs from 1800rpms on up to 5000 with just head porting alone on a 6.0l engine. Add in a towing cam and rwtq will gain another 25ft/lbs. Since towing cams don't hold high rpm torque, rwhp numbers are less than a larger cam grind, however the rwhp numbers will still jump up some. The truck intakes flatten the power curve above 5000 so small cams in the 208º-212º range will make for nice towing type cams.
There's no glory in the small cams, but IMO towing cams are more pleasurable to drive daily due to the rapid torque response from the accelerator pedal. Small throttle inputs are met with crisp acceleration.

Richard

 

personally i wouldnt worry about ported headswith a stock truck intake. its kinda like kicking yourself in the nutts. you cna only take in so much air and if your intake is restrictive then everything else is just blah. i would find an intake that allows enough air in to take advantage of the ported heads

 

does that mean larger TB opening or different length runners? both?
Is the car intake that much different?
what else could we use that would not cost $$$

 

Good explanation Richard..