SR20 head porting gains?
I posted a msg on the force/n2o forum, but there is more activity here. The 180 i just bought makes 355rwhp @ 25psi on pump fuel, but has an un-modified head. What sort of power gains would be gained from getting the head sent away and ported? I know when you change cams/turbos/intake manifold you can get reasonable results. The specs are (SR20 of course):
hks t300 turbo, hks exhaust manifold, hks wastegate, toda step 1 cams, subzero 80mm sub zero throttle body, sub zero plenum, wesico forged pistons, gapless rings, arp rod bolts, plus all fueling/exhaust/cooling mods.
Has anyone done any back to back tests with a standard, then a modified head? Also the car has a 3" exhaust, would that be causing any restriction?
It's only worth cleaning up any casting marks and match porting the intake side only.
Making an overall port larger will only give a power gain up high in a narrow rpm band.
You need to keep the overall velocity high in intake ports.
I meant to add debur any sharp edges in the combustion chamber, it doesn't need to be polished. A slightly finer finish used in the intake ports would help.
Polish the exhaust ports all you like, generally you can grind down excess material around the valve guide boss. Don't match port the exhaust to the manifold either.
Ideally you want to make the floor of the ports as flat as you can, another technique is to reshape and shrink the port slightly using an aluminium epoxy to provide the flat floor and ensure a high intake velocity, higher than a std head.
Take a look at this page, it makes sense:
They talk about motor bike engines, but the theory is the same on any engine.
wants Sloan clone
Contact JHH for info about a bolt-on head... they seem to have very good results from what I have heard, I had a thread about them a little while back on here too if u'd like to search for it.