We suffered a cam timing jump on our Evo 5...resulting in bent valves and cylinder head redo.

It appears repairable and would like to upgrade while it is apart - certainly more entertaining than going back with the same HP.

We run a mild combination - Evo 9 turbo (updating to HTA71 along ported FP exhaust manifold), GSC S1 cams, good intake and exhaust with OEM intercooler with 23 psi boost. It produced close to 400 CHP on the dyno with a pro-tuned Link ECU. Pretty happy for the last 20,000 miles.

The head was just shipped to Head Games for the fix. I compared the OEM cylinder head ports to the gasket that fits the FP manifold perfectly and see the dramatic difference. Admittedly the flow is going the best direction (small to big)...but seems like some HP is lost along this path...


Will we lose anything going with either their stage II pocket port or even their full CNC porting? On other applications, ported heads are always a plus. I can see us limited boost to 25 psi, but investing in the head considering the task to shipping across the world and the like - maybe the $2000 porting service isn't so bad.

BL: what might the HP gain (or loss)?

 

Likely this has been discussed a time or two in the past. My searches didn't yield anything conclusive other than the porting will help, but there are other more cost effective options (better turbo/more boost).

Thanks!

 

There should be no downside to a properly done porting job to match the gaskets or a quality full cnc port. At the end of the day the engine is still an air pump and anything you do to remove restrictions and help it pump more efficiently will improve performance. The only real risk to porting is that the job isn't done properly.

You will likely only get a slight bump in hp maybe 5%-10% at the crank. That's simply because with the stock turbo/intercooler the head ports are not the biggest restriction on the system. At 400 crank hp you're near the maximum power that the stock ix turbo can push, once you replace it the porting will be a bigger deal. Might as well do it now.

Just an aside, when I got the heads ported on my car when still running the stock ix turbo, my boost pressure went down a few psi because the head was flowing more air. This might help you if you're limited to 25psi. After my heads were done the stock ix turbo tapered to 19psi by redline. Couldn't physically push more air.

 

Headgames says that their removal of the quench pads included with their pocket port R and CNC port services helps prevent detonation and allows pump gas cars to make more power. If your head is already with them I think the pocket port R is worth looking into.

Regarding "more cost effective options" are you asking for advice on parts selection? Are you trying to make more power?