In summary, polishing works and at the same time it doesn't work. Now, wasn't that a lot easier to say than all of that engineer speak?

 

yeah, I guess....

 

It doesnt work. Period.

No more from me, I am done.


KP

 

"""It doesnt work. Period"""



hmmm...nothing in this world is absolute.

 

Yeah, and ALL generalizations-- every single one of them-- are false.

 

I just finished one exhaust port on a 8V head, these things are a travisty. After about 2 hours of work it looks hugely better, but I still think a bit more can be done in the cross section. I tend to polish the exhaust side a bit but not to the point of cross buff shinny, and leave the intake a bit rough, about 80 grit. But this head is being done for a very patient guy and will have the exhaust runners/bowl and chamber thermal coated, so the shinny will be sand blasted anyway.

11 more to go.....

 

Unless I missed it, no one ever explained the reason you wont get 2.2 HP per CFM on a Diesel VS a GASSER. That extra air on a gasser is also carrying fuel, unlike the Diesel that is air only.

Porting gives little power addition on our trucks, but it IS needed after 500 or so HP on the 12 Valves and VP44 24 Valves. The Echo can go out a bit further.

At 600HP the porting begins to help performance in the mid range. At 700, you really get a boost and at 830 HP, porting and a big camshaft REALLY shines on HP production.

Don~

 

I'm hoping some headwork will carry me into the 500's, and still keep valet mode towable!

Chris

 

DonM, you are right that extra air doesnt do much without the extra fuel, but allowing more air in allows more fuel to be added in the proper quantities for a good mixture for the best burn. I look at it like this if you at making say 300 h.p. at 30 psi on a unported head and 300 h.p. at 25 psi with a ported head, your that much more efficient, not to mention being able to get the spent gasses to the turbine for quicker spool.