[crm318]

They all measures 1.53 right under the seat where it is perfectly concentric with one outer port measuring 1.54. Further down, where it starts to taper into the rough casting, it measures 1.41 on all of them (bit of casting flash in each. Here is an intake valve I ground per the specs on the McCarthy video: 1.7 diameter with a 1.56 flat spot (92% of 1.7). 230 cfm on the intake would be good. I'm trying to get over 400 hp with my set up (in my sig)

[steve25]

Here's two shots of a 6X converted to a 1.77" Valve.
The first shot shows a 1.456" template ( notice where the light is passing around it ) right at the transistion where the bigger top Throat necks down fully to the sub Throat / real restriction.
The second shot is the short turn rework done even though this shot is of a center Exh port.
This center port flows well over 190 cfm due to the full flow path being reworked .
Note that it is only gasket matched on the top to a stock steel Flange gasket.

[crm318]

I spoke with the shop owner today and we discussed game plan. He said he would need the valves before he could do any of the bowl hogging/seat enlargement could be done, which makes sense. I bought a set of 30° 5.1" 2.11 and 45° 5.09 1.77 stainless ferrea valves from Butler. After I made my 1.456 template, it basically fell into the exhaust bowl, only snagging some casting flash. I'll probably just clean those up, no need to enlarge. Seeing as there were shims under the springs, these heads have been gone through before and by the looks of these pics, have been bowl hugged. While waiting for the valves, I will get a set of cometic head gaskets. Should I get the 4.2 gaskets (my bore is 4.18)? I will also get a set of 1233 felpro ram air 4 gaskets.

[steve25]

Yes, that makes sence that your Exh Bowl Throat is bigger then 1.456" as that is the same basic 68 casting as the big valve 4bbl Head.
This is going to make for Exh flow numbers up in the 180 cfm range with just cleaning up the rest of the port, and without factoring in a added 4% more Exh flow above .400" lift created by a Header being bolted on.

180 cfm will support 240 cfm of Intake flow so a single pattern Cam is the way to fly for your motor it looks like!

No neeed for the 4.2" gasket as your just tossing away compression, fact you could unshroud the tight chamber side of the Intake valve in trade off for the smaller Head gasket!

Does your Block have Intake valve chamfers in the Bores?

There is no need to port out the Intake Flange to the 1233 gasket area as the stock height port area will support flow numbers of 265 cfm if the push rod budge is ground back 1/16" .

[crm318]

What head gaskets would you use? The only gaskets that I can find are either 4.16 or 4.2. There are small chamfers on this block. My block has a .013 deck height if I remember right, so I'm trying to go with a small compressed thickness. The heads are also being resurfaced. I assume .040 is the target quench?

[steve25]

Since your milling go with a Fel Pro 1016 , it should be cheaper then the cometics I believe too.
The Fel pros compress down to .039" so with a .013" deck your hood.

Be sure that after milling you polish over the edge of chamber, the Eyebrow lips and any sharp edges near the Spark plug, a 1/32" roll over is all you need

[crm318]

Cleaned up an outer exhaust ports today. Blended the smog bump and cleaned up casting flash. Made sure not to get rid of the bump towards the intake valve. 1.456 template fits snug against it. Also blended the ridge at the short turn, making sure to not remove any portion floor. Not much material other than the smog bump was removed. New valves come in tomorrow and valves will be inlarged.

[steve25]

The nub on the crown of the Exh port floor needs to be ground out of there.

I do that removal work from the Exh flange side with a 6" long cone shape Burr.

To polish it out tare off a 10 inch long 3/8" wide strip of the finest grit belt sanding paper you can get, of if you have tapered Cartridge sanding rolls screw then on the mandrel back wards and then go onto the crown from both the bowl and flange side to polish it out.

[crm318]

I'm sorry, I'm not sure what the crown is. This is the port floor at the moment with the 1.456 template.

[steve25]

The crown is another term for the highest point of the short turn, sorry!

[crm318]

Got my heads back from the shop. I had the valves enlarged, hardened seats installed, studs removed and threaded and new valve guides. As you see, there is quite a bit of lip in the intake bowl. It measures 1.52 at that ridge. The intake valve that I have ground to 1.7 should be able to fall through the throat and turn up the short turn when I'm done (snuggly, of course). Also, my machinist, who is a Pontiac guy, says I should go with a 22° back cut on the exhaust valves instead of 30° because of the little material on the valve face. What do you think?

[steve25]

In the int bowl blend that lip out on the short turn, the common wall side and the back of the bowl , but only half way around to the Exh side of the bowl on the rear wall ,and do not polish out the blending work , leave it with the ruff texture of the cutter as long as it does not look like the suface of the Moon!

Exh valve back cutting wise, any where from a 20 to a 35 degree angle will produce some level of a low lift flow gain .
You have a nice 3 angle job in the chamber now which will pick things up so my main concern with applying a back cut would be to keep the main seat width to atleast .070" wide.

[crm318]

Are you saying that this area should remain untouched or that the 1.7 diameter should be kinda biased towards intake side (towards the right in the pic) of the cylinder, similar to leaving the hump on the intake side of the exhaust throat? This is how the valve sits. It only goes .25 in below the seat.

[steve25]

You want to have the greatest area / opening of the Throat on the straight wall side of the port, the straight wall side being opposite the side of the bowl from the Exh valve.

[crm318]

So, smooth the ridge, but have a bulge on the exhaust side while making the common wall straight? This is what the short turn looks like now vs what a 1.7 radius looks like. Should I mimic that radius? What I am doing now is making the common wall straight, which will bring it out close to the seat.

Sorry for all the questions. Much can be lost in translation in a process like this. I am very appreciative of this invaluable advice.

[74Grandville]

I would use a smaller template. 1.7 is pretty big and will get the head to flow ~250, but would start smaller and work up as needed.

when i did mine i went from 1.64 to 1.66 to 1.69.

Be careful cutting too deep on the roof of the bowl. I did that once and it killed flow as I probably lowered the velocity. I saw my mistake when I put clay back in and the flow picked up.

FYI, I AM NOT AN EXPERT ON THIS TOPIC. =)

[74Grandville]

As for a flow bench, I created something similar to what Dave Vizard had in his book. It’s a simple box that I connected a manometer and a shop vac too. It doesn't really tell me flow at 28", but it gives me an idea if I’m helping or hurting.

I have done some math to try and show numbers at 28", but i don't know how accurate it is. I use a stock 6x-8 and use Jim Hands numbers as a base after flowing my ported head.

excuse the messy garage.

[crm318]

I have worked the pushrod bulge back 1/16" making the opening at that point 1" wide and 2.03" tall. I notice that there is a coke bottle shape to the runner. Seeing as it's on the common wall side, shpuld it be straightened a bit? This is my bowl work thus far. It's 1.56" at this point with a venturi like hump towards the exhaust valve.

[steve25]

First off let's nail down some numbers, how much Intake flow at what lift are you looking for?
A 1.700" Throat could get him 250 cfm , but not without reworking the common walls Coke bottle area cut in as he put it.

[crm318]

Pretty cool! I haven't taken anything off of the floor or sides really, just casting and clean up. My bowl floor is just about flush with the seat. 230 cfm would be nice.