Pointers on Porting...

[darkfa8]

- Is it optimal, in terms of airflow volume and velocity improvements to take more material out of the upper portion of the intake ports on both the head and intake manifold?

- Is deshrouding the valves out to the cylinder wall beneficial in the turbo application?

- With a 5-angle valve job, what kind of back cut would be optimal on the valves?

- Is a land-to-face radius on the exhaust valve wothwhile for the turbo application?

- From what I've read, it might be wasted time enlarging the ports to a gasket when airflow typically sticks to the upper portion of the port.. so is just making the side and lower edges of the port clean and square (on both the head and manifold)?

- Does it pay off to leave a bit of a ridge (~ 1/8") at the bottom of the intake port on the head side in order to reintroduce fuel into the upper airstream?

Seems that the most gains are to be had by raising the upper portion of the port and taking out as much material from the port opening on back.

- Is it true that if you open up the ports to the gasket, that despite them being physically bigger, they consequently lose velocity?

- Are the exhaust port/valve face coatings available from Techline or somewhere similar?

thanks for any insight,

 

[Quick6'n'-K.C.]

im going to be porting a set of heads soon too, i dont have any info to add

im just wanting to read the info tomorrow when i get home from work

 

[darkfa8]

my readings..

i've been reading the Powerpro Series: How to Build & Modify Chevrolet Small-Block V-8 Cylinder Heads by David Vizard

 

[UNGN]

I think you are correct in not wanting to remove any material from the bottom of the ports. The intake port floors are already too low for "Ideal Flow".

I don't like "gasket matching" because opening a port cross section only to have it close back down again distrupts the flow.

A better way would be to match the actual ports (intake manifold to head, head to header), concentrating on the roofs of the ports and walls of the ports. The transition of the floor of the ports will suck anyway. Epoxying the floor of the head would probably improve it a bunch, but I'll save that for the pro's.

I wouldn't try to increase the port size all that much, but concentrate on improving the shape (smoothing the short side radii, smoothing the pushrod pinch, minimize and smooth the valve guide bosses so air happily flows to the back side of the valves)

 

[Crazi]

I ported my own using a bunch of info from the standard abrasives site and from reading a bunch of small block stuff. I talked to Jack Merkel when I picked up my shortblock about ported heads and he told some key points are the short side, the bowl area, and definitely... NEW VALVES!!

Here is a cross section the helped me out some
http://www.sa-motorsports.com/portdiy/portdy20.jpg

I mainly concentrated on the bowl area and tried to smooth the guides and that area around them as much as possible. I had some other pictures that gave you a clear shot but can't find them now...

Found them!!
http://gmhightechperformance.com/tech/0209gmhtp_buick03_zoom.jpg
http://gmhightechperformance.com/tech/0209gmhtp_buick05_zoom.jpg
This is all Jack's handiwork. I only wish mine looked that good!