What diameter do I cut around stg 1 valves?

oops , lets try that again

 

This angle shows how large t pocket could be with out the valve guide.

 

Really this is the first set I've ever done. I've invested lots of reading time into this. Smoky Yunick books are good for this. Although much of his referances are from high rpm small chevy stuff, It still applies in almost every aspect. there is a post from charlies evens that keeps popping up that pretty much covers the basics. You kind of have to learn from there.

I may screw this up yet. The first piece of advice smokey gives, is to take your heads to a good port shop! The way I am going about this is probably very inefficient, but that's alright. This is an educational experience. I plan to learn

Here is the post from Mr. Evans

1. Bowl Blend. Blend the bottom of your machined throat cut with the cast part of your bowl. Gently enlarge your bowl down deep in the bowl around the valve
guide area.
2. Valve Guides. Grind on them and reduce their size quite a bit. They are sitting smack in the middle of one of the most critical areas of the port. On the
intakes they dont hurt you too much because the direction of the flow is with the gentle, natural shape of the guide boss. On the exhaust they hurt you
because the first thing the air sees is that abrupt flat machined surface at the top of the guide boss. Reduce it but dont completely remove it.
3. Short Side Radius. Lay it back, lay it back, lay it back!! With your fingertip you should be able to gently slide it from the seat all the way around to
the crest of the floor and feel no sharp edges or abrupt changes. This should be a smooth natural roll or turn.
4. Crest Of The Floor. At the apex, or crest, you may want to reduce it some. Generally, grinding a little of the top here greatly increases your
cross-sectional area, probably at the most critical point of the window.
5. On the intakes, youll want to grind on the head bolt boss some to thin it and again increase your cross-sectional area.
6. Also on the intakes, youll want to grind on the pushrod side quite a bit and roll that short side WALL around and down gently to the seat. This is where
your air flow velocity is the greatest.
7. Steps 5 and 6 are usually roughed in using a Bridgeport in an engine shop, then finished by hand.
8. On the exhaust, dont even touch that ugly reverse pocket in the bowl. Im talking about that area where the heat riser passages are on the two center
ports. Every time you fill them in with clay on the flow bench, the flow picks up. So dont grind in there and make it worse.
9. As much as I would like for it to be a pure science, there is still an element of Black Magic to the feel for porting. It is somewhaT AN ART.
10. I will tell you that Newtons Laws of Motion certianly apply, especially the Law of Inertia with regards to wet flow. Also, Bernoullis Principle
(Daniel 1700 1782) APPLIES. Study them.
11. If you decide to port your own heads, it would still be good to send them to a shop that has the capability to flow a Buick head accurately
(mot all do), when you get done and have them checked and flowed.
12. porting takes time. Lots of it. $800 ought to give you a lot of head porting time and a good flowing set of heads.

Written and submitted by:
Charlie Evans, GSCA Member
Automotive Machine & Performance
6235 Highway 54
Philpot, KY 42366
888-624-3848

 

Picts are of stock, unported 455 heads. Not exactly sure which year.