Ok guys I have the basics of the P&P work and what I need to do to the I6 head... However i have a questions or two...

How rough to leave the intake runners?

I know to leave them a little rough but how rough? Smooth all the casting out and leave nothing but the 80grit scratches behind... Or just smooth the casting a little and take the big casting bugs out... Anyone have pics of how they should look?

 

I am far from an expert on this, but since nobody has chimed in yet, I put my $.02 in.

There are varying opinions on how rough the intake and exhaust ports should be. I have seen a lot of opinions on the internet. But narrowing that down to the opinions of people who do porting work for a living or for their own racing engines, what I have seen is as follows. I may be wrong about this.

A "mirror polished" port will flow about 1% better than a slightly rough port, where slightly rough means something finished with a coarse sanding wheel.

On an intake port, a slightly rough finish creates micro-turbulence at the boundary layer. This helps to keep fuel from clinging to the wall and dropping out of the air flow. Considering that the section of the intake port that is inside the head is hot (surrounded by 195 degree coolant) once the engine warms up, it is not likely that fuel will cling to that section of the wall. During cold operation, you might notice a difference. In the intake manifold, especially with the 300 where the runners are out in the air stream, you might notice significant difference in driveability between slightly rough versus mirror polished.

On the exhaust ports, you don't need the micro-turbulence. A mirror polish may slightly reduce the amount of heat soaked up by the port wall (maybe).

For a 1% difference, I wouldn't spend any time at all trying to mirror polish either side. I'd clean it up with a course sanding wheel and leave it at that.

Also, regarding the actually porting, keep in mind that the 300 head is a thin wall casting. You can't remove much metal anywhere without breaking into water or having it crack in operation. Also, the FI heads are thinner wall casting and are more prone to cracking.

 

That's kinda what I was thinking... I've done autobody work and when preping a bare metal fender for primer you always sand the bare metal to give it a "key" or "tooth" for the primer to stick to. So I figured that is what I was after... Smooth metal with a 80-120grit key or tooth in it but not "mirror" polished.

I do know the heads are thin walled... That's why I am using an 83 "non-FI" head. I plan to bevel the intake runners and smooth them back to gasket match the Mr.Gasket260. Then smooth the runners out all the way to the bowls...

Now for the next question. Do I want polished bowls???? or just smoothed up like the intake runners?

Oh and for those that might be stopping by to read this I will be posting pics of what and how I am doing this a little later once I get started... So stay tuned b/c my head should be back from the machinest any day now!

 

You can find a lot of info here about p&p. Theres a lot of good guys there, and they are very knowledgeable.
FORDSIX PERFORMANCE • View forum - 240-300 "Big Block" Six Performance not to step on anybody's toes or anything.