Let's see those ported Predator heads!

[braaaaap]

Gonna be doing some porting on my 18cc Predator head soon. New to porting, never done it before but I have a general understanding of what the process involves and the tools needed. It is to my knowledge that it is hard to mess up these heads (unless you have Parkinsons or something) with regards to the flow of the factory ports. I pretty much want to clean up the sharp edges, and probably radius the short side of the intake emphasizing on the corners of the port. Might go a little farther into it if I'm confident after that.

Of course this is along with the usual slew of upgrades including the typical Al rod and flywheel, box stock race carb, header pipe, BP2 cam, 18 lb springs, all that good stuff. Just want to take it a step further.

Been doing a little research into this and I want to see what you guys have done. I want some expert hot rodder input here!

 

[rugblaster]

Up front, I have no experience with modifying Predator engines. I did have a VW drag car that ran a best of 10.32 @ 122 mph back in the '80s......I got the heads for it from a well known cylinder head shop in California. It was aircooled too.

There is 5 things I can think of:

All out race heads don't work on the street.

Without a flowbench, it's just guesswork.

Small, well designed ports can flow more air at rpm ranges common to most engines. (I'm thinking of Vortec chevy heads versus traditional camel hump 2.02 heads)

Some of the most effective porting doesn't involve the ports at all, but rather in the combustion chamber in the area around the valves (unshrouding the valves)

The absence of a good, three or four angle valve job.

 

[Moedog07]

Gasket match the ports and bench race with friends over which is better on the street smooth or textured port walls.

 

[ole4]

I'm in rugblaster's camp. The most important area is a half inch above and below the valve and the valve seat and valve itself. A eyeopener for me was a head I tested (flowed) for misfit who installed a 32mm intake and 27mm exhaust with bowl work to match the seat and radius the SSR and some port bowl blending but the runner itself up to the bowl area was untouched (stock) and that head flowed a lot of air up till coil bind, more than any clone head I had tested before. It showed me that enlarging the runner was not necessary for enough flow for a 212cc motor and by keeping it stock it kept velocity up.

 

[braaaaap]

Seeing as this bike is going to be a street bike I thinking now I might not go too far into it then. Probably just radius the short side on the intake a hair and match that radius on the valve guide to induce flow downwards, clean up all the sharp edges and possibly do an intake match up. Going to go a head and polish the exhaust port and rough polish the intake a little bit. This should be my safest bet for a street bike I'm thinkin.

 

[rugblaster]

That is the key, keeping the port velocity up. If you have a blower or turbo you don't have to worry about it so much. The air gets stuffed in there anyway. Another thought, I might even back cut the valves 30 degrees on the stem side of the 45 degree seat face. Just knock that little lip off.

I'm building a bike for the build-off, and when I removed the stock exhaust from my Predator the exhaust gasket was protruding out in the port a eighth of an inch all around the port. That is obviously not what you want.