Porting a Chy 340/360 head.

[jfholm]

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[jfholm]

You have read at the bottom of my posts:
"It is a wise man that learns from his mistakes, but it is a wiser man that learns from the mistakes of others."

I appreciate what you do.

John

[coulterracn]

[jfholm]

And just wait until you bolt an intake manifold on and it all changes again.

John

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Well port session #5 is done.

Opened up bowl area at mid point to 1.81"(approximately) but short changed the bowl area on the slow side.

Malvin, i may have just a little bit more metal in that area then you did, but not by much.........Hope it serves!!!!

Ray the top of the barrel look good but was afraid to drop it down enough to crate the bottom part.
One of the guys on speed talk warned me that i would find water if i when to 1.81 in the bottom, and after looking at Melvin cut up head, I would have to agree!

Straightened the prp wall(hi speed wall) a little bit more, rounded the ssr from the 70*cut all the way up to almost the seat. It's not rolled back just rounded all the way through.

so what did all this do? well the fast wall, at the ssr went UP from 338 to 350 fps. The middle of the ssr(the highest air speed in the port) stayed the same at 386, and the slow wall at ssr when down in fps form 350 to 310.

CFM?...... Well, gained 1 cfm from .100 to.300 2 cfm at .400 8cfm at .500 and 10 cfm at .600

Max cfm is still at .500 lift, and is at 267 cfm........which is grate! way more then my expectation!!!!!

Here is my problem. There is BIG turbulence above the ssr at ALL lifts.
I took a piece of mechanics wire, made a loop in the end of it, and feed about 3 inch of string out past the wire and tied several knots in it to create a ball.

In the entrance of the port it's smooth and runs down the center of the port, top to bottom.(the top of the roof is a little bit turbulence) Just past the prp (about a inch inside the port) the string pulls off center towards the prp wall and is turbulence any were from there to the ssr area.
all the ssr, the string is smooth all the way down toward the valve.
Any were else, in that area, the string become a complete blurr as i move it from left to right.
If i force it to the wall past the guide, its calm again and go's straight done.

My question is, how do i recognize areas of the port creating turbulence.
I realize this is not a cut and dry answer, by any means. But, any ideas of what to look out for would Help.

Thanks.

[200cfm]

This is what Barnhouse says. "If the flow is deflected, the air may separate from the wall and cause turbulence. High and low pressure areas will form..." He gives an illustration with air flowing over a bump or physical deflection. As air hits the bump it piles up and becomes turbulent. The result is an increase in pressure. Air passing over the backside of the bump also tumbles but the pressure is decreasing. The highest pressure is at the peak of the bump. He doesn't say it but I interpret the bump as either a guide protrusion, or a headbolt turn or a pushrod turn.

I would think that anywhere the CSA is changing, the air is experiencing some deflection and eddie currents of air tumble are "born."

[coulterracn]

Gorden

After reading Tom's post about air turbulence over a bump or protrusion I am curious how using clay before and after the head bolt boss would affect air flow and velocity? If your concerned removing the boss inside the port will weaken the head then maybe filling this area will help both cfm and port velocity.

Any ideas on this?

Ray

[Flash]

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[blaktopr]

Man, these old low entrance castings seem to give the same problems, regardless who makes them. Gordon, was the oil on the half under the SSR side? Good thing for you is the intake valve size/throat. Small enough to massage the rest of the port to fit. Check the areas after the pinch with your mold. That can be smaller with the floor/roof convergence. That can drive up the speeds before the SSR. The valve job makes a difference too. Try to mess a little with that before grinding too much out. Unfortunately, I changed the seat angles after I was progressing before then trying to rework the ssr. I went from 5 back to three and ruined the port with that one change. So be careful not to chase your tail. I did it and is frustrating.

[Flash]

[blaktopr]

Check the mold for the csa after the pinch, and as it approaches the SSR apex. You can sit there getting your pinch right and still have a problem and snap guages are not too accurate, IMO, in getting the measurements. Especially when reaching around the PRP buldge.

As for the 5 to three..
I went from a 3 angle VJ with a 45 seat to a 5 angle VJ. Playing with angles and learning some effects for the SSR. The port was doing really well with a little turbulence. Before I took a mold to see some true CSA's, I changed it back to a 3 angle VJ at a different depth and messed with the SSR shape and killed the progress. I should have took the mold, reworked a few areas like I did later and then retried it before messing with the VJ.
Basically, ........don't jump the gun and get as much info as you can before changes.

[blaktopr]

Oh, and Gordon, no hints on the VJ. I see too many different things in these ports to give you any "hard" numbers. Plus, I wouldn't want to steer you wrong.

[Flash]

Chris You had to go and jink me, didn't you!

Wow...........

OK, un-shrouded the intake valve to day. Had a stone that would cut a 38/52* and top it of with a straight top cut in the combustion chamber wall.
Worked grate too................Until i realized that my 38* had taken my narrow 45 seat out at the top were my valve was setting :angry:

Had to sink the valve about .007" to fix my problem.

Flow test showed a 3 cfm gain at .100 lift and bad #### all the rest of the way threw.
By .500 lift i had lost a bunch!!! When for 267cfm to 232 :p

When i turned the bench on I new I had screwed up!
.100 lift, sound like it's got water running threw it,.....again. All the rest of the lift setting, had a screeching noise...............kind a sound like a car's tire locking up at 60 mph.

Chry said o Not Sing the Valve for any reason as you will loose power............SURE DID!!!

Actually, I'm not sure if the loss is due to the valve sinking or the change in seat top cut. Before there was enough 30* to just see it, now is much wider due to stone cutting it when i was widening the combustion are at the valve.

the string also tell me there is NO calm spot in the hole port now.

I thing the un shrouding of the valve was a success. Can force the string to exit out that side..........

Was going to take my head to work tomorrow and do another porting session on it. Laying back the ssr.............now i don't know what to do.

cc'd my intake port to night. i started out with 161cc now I'm at 187cc