Porting a Chy 340/360 head.

[blaktopr]

I think it was 18 years ago when I played with one of those heads. Geez I'm getting...........................................................more mature

[Flash]

Chris, this is what i have noticed so far. the dark stain in you picture.............and in your video.

In your video, there is times when the droplets on the exhaust valve, are being drown or suck back into the intake.

almost, like that area, is so dead that there is no fuel there at all, but fuel returns back into the intake at that point because of the low pressure.

The liquid is spinning of the exh valve,running around the side of the opening and then drop in right were the stain is.

I never did see the valve change heights but it was interesting to see the swirl on in exhaust valve turn cw and then would turn cc further in to the video.

[blaktopr]

I think one of these days I will start a discussion in the wet flow area to get everyone's thoughts on those issues.

We'll stick to your head here and what can be done to help. The dark spot in the pic shows why even Dart is sticking the vanes behind the guide.

[coulterracn]

I like to shape the guide boss like a mini cone if possible. This allows the air to flow around the guide and keep air
moving in the long side radius.

The flat and small step behind the guide in your picture could be blended to the sides of the guide with a small ball type cutter 1/4" in diameter. The guide is shaped to get air flow past it but not behind it.

Sample picture

[blaktopr]

The "cone" term is better than my "fin" term. I would like to put epoxy there but am a little worried about loosing it. Ray, I wonder if the slight added area behind guide in your pic is enough to keep the pooling at bay.

[coulterracn]

Yes it will help. I started shaping my guides this way after noticing dust collection in this area while grinding the ports. I would blow air through the port to remove the dust and grinding particles. I would actually blow through the port with air from my mouth. Not a big blast of air from the compressor although that will work if you regulate it to be low pressure.

I have noticed the directional tail fins being used in intake ports. The question I'm asking my self is why? Could it be to help the air flow around the guide and help reduce reversion?

I have noticed on heads that flow higher cfm's the tail fins are smaller and less defined. I have ported both Trick Flow and Dart Pro 1 heads that have this tail fin. I reshaped the fin so it was less defined and made gains in the higher valve lifts.

Air velocity at the short side radius and roof on both heads is 332 - 350 fps.

Ray

[Flash]

[Flash]

Here's what my intake port look like now.........ssr is till were all the air want to go.................................. it did speed up the roof a little.










I took a air nozzle and sprayed it towards the ssr and the are came out the valve strong on the ssr.
Sprayed it on the roof and the came out the long side, but with less force.

This head really like the ssr ???

[200cfm]

Did you add a channel or were there two channels all ready in the roof?
Question? What would happen if you extended the cone shape all the way around the backside of the guide (facing the bowl). Are you able to flow test these changes?
On my port it seems the air favors the floor and SSR turn and is slow and not fast at all along the roof or on the backside of the long bowl. Would the flow increase if you lay back the eyebrows in the chamber some?

[Flash]

[200cfm]

Ok, I haven't tried that cut yet. I still have a semi shaped volcano cone on mine. But I think I will experiment and see what happens if I take that flat spot out that is between the guide and the long side of the bowl.

I did do this today and not sure how to interpret the discovery. I put together a sort of flow ball. Lead ball on the end of a wire string. Used wire string because I just wanted to see the primary direction of any turbulent twisting air and not just have a string twirling around like crazy. Well, when I placed the lead shot ball in that very area (the flat side of the volcano cone, the ball shot up and stuck to the flat portion. It was jerked up like a magnetic pull hit. And if I floated it down some (toward the valve stem) it would be grabbed by the air and pulled toward the back side of the valve. I'll see if I can't make a video to explain this better.

Be interesting to see if a complete wrap around cone for the quide takes that phenomena away. (tom c)

[coulterracn]

I'd like to see the results of your test after shaping the area behind the guide. You shouldn't have to remove allot of metal just blend it so air can get to the back side.

This is some interesting stuff. I love to learn!

Ray

[200cfm]

Ok, here is my first flow ball test on the experimental head.

Note how it sticks to the area of the bowl sort of directly behind the valve stem. (tom c)

[coulterracn]

The lead ball on the wire is an interesting tool. I like that idea and may have to make my own.

Totally awesome video.

Ray

[200cfm]

Got a question about bowl shape. Is there some CSA figuring involved in bowl work? I looked at my mold from the test port and concluded more spacing could be made on the long downward side of the bowl moving toward the seat. But don't know if de bowling the shape into more of a barrel shape up to the throat is good or bad.

Another question is the laying back of SSR. This port has rather thick flooring. A good .250" from entrance all the way down the SSR turn. So I could lay the SSR back alot in the sense of available metal. I moved it back some based on the bigger test valve (1.875) but that was to remove the over hang of the SSR. It now ends a few mm's from the start of the 60 cut but could be shifted back further.