Exhaust ports

[Slavvy 0]

Hey all, in the course of my project I've grabbed some tubular headers for my m30. The problem is the headers are perfectly circular, while the m30 head has smaller, oval shaped exhaust ports. My question is if it's worth the trouble to grind away the outside of the port to match the exhaust. I say 'worth it' in that I've never ported a head before and I don't want the first time to be on my mint new head.

Red is the pipe, black is the port, grey is the area that would potentially be ground away. Any thoughts?

[turboprop 0]

Doing it yourself and not knowing what you are doing = not worth it.

Getting someone who knows what they are doing = possible marginal gains, but expensive. port work is tricky and takes along time to get right, its not just about making the ports bigger.

[bravo 34]

^^^ this.

If you don't know what you are doing, just leave as is. head porting is a fairly specialised field.

[*Glenn* 854]

Hey all, in the course of my project I've grabbed some tubular headers for my m30. The problem is the headers are perfectly circular, while the m30 head has smaller, oval shaped exhaust ports. My question is if it's worth the trouble to grind away the outside of the port to match the exhaust. I say 'worth it' in that I've never ported a head before and I don't want the first time to be on my mint new head.

Red is the pipe, black is the port, grey is the area that would potentially be ground away. Any thoughts?

Dont match exhaust ports. They need the back pressure at the outlet...only match induction ports. All extractor (header) manufacturers recommend a larger port overlapping an exhaust port like in your diagram

[Slavvy 0]

^^^ this.

If you don't know what you are doing, just leave as is. head porting is a fairly specialised field.

This was my first instinct, but it seems extremely messy for it to go from an oval port to a larger circular tube in an abrupt step haha

[Slavvy 0]

Dont match exhaust ports. They need the back pressure at the outlet...only match induction ports. All extractor (header) manufacturers recommend a larger port overlapping an exhaust port like in your diagram

Righto, leaving it alone.

[sp8s 1]

Seen someone try this and went straight into a water jacket

One good head gone.

[DRTDVL 0]

There was a diy head porting thread a while back that had some good information in it.

[*Glenn* 854]

Have a read here:

http://www.jdmuniverse.com/forums/how-tos-...ad-porting.html

[tibbs.james 1]

I opened up some ports on a nissan v6 a tiny bit but its easy to get carried away unless you are under instruction from an engine builder as I was