DIY port matching

[S2_ITBVW]

Our local machine shop does everything we need to have done to build an IT head EXCEPT port matching. So, I have been practicing the art of "DIY port matching" on an old cylinder head and feel pretty confident that I can do this myself. But, I do have a couple questions . . .

How smooth does the finish need to be where I have cut away the material? My understanding is that the intake needs to be pretty smooth, and that the exhaust is not quite as important. Thoughts?

How does one cross the line between "port matching" and "polishing?"

Is there anything else I need to be worried about with this modification?

Thanks!

[JeffYoung]

I hand ported my first set of heads. Made decent power.

Thinks to think about:

1. Do some reading for your motor, but on mine, the thinking was you wanted a bit of roughness on the INTAKE side to get the intake charge to tumble and atomize. EXHAUST side is where you want it smooth for maximum flow.

2. Since you can port match in 1" I'm not sure there is any effective difference there between "porting" and "polishing."

3. The 1" is critical obviously. Have had folks at the ARRC DQ'ed over slight overruns.

4. You don't want the "python who just ate the watermelon" look meaning no matter how much room to port match you have with the gasket, you don't want the intake or exhaust runners to bulge and then narrow due to your grinding.

[seckerich]

Also keep in mind that alignment may not be perfect and you make both the same size and you create a ledge. Stay conservative on the intake side so it is a little smaller than the head ports. Very slick intake ports drop fuel out on the walls in most motors unless you have a wet flow bench to see how it acts.

[pfcs]

Usually the intake ports are perfectly matched-no need to modify.
And the exhaust ports, work pretty well just as they are. You will probably find that your headers are a good deal bigger than the exhaust ports. I would leave them alone unless you want to be married to one set of headers for the rest of your life.
Tell your self that the edge of port reflecting off the header is anti-reversionary. Maybe that's true. Fact is the short distance and steep angle you need to cut to match to those irregular header ports certainly does not improve airflow unless there is just a Little to be taken off the high side of the port. Fixing that would probably be appropriate.

[S2_ITBVW]

Thanks much. I'm firing up the Dremel and getting started in the morning.

DE