Ported Dart pro 1 pre platinum

[rewguy]

only had 3 pics.

[Carnut1]

Rewguy, any specs on these? Thanks for the pics. Charlie

[Carnut1]

1223160420a_HDR.jpg

My version of the same angle on port.

[rewguy]

I haven't poured the port......but Id guesstimate it around 215-220 tops. The first trip to the bench, the PR measured 2.28" (without subtracting radius). It was matched to a 1205 gasket at that point. The valve is a 2.02 and came original in the heads. I flowed it exactly this way and it gave up at 287, but showed no separation. Honestly, this was probably more than what the guy needed....as he has a nearly all stock 350 (+.040) short block, with the exception of good rod bolts and some heavy trw 2256f pistons. But we plan on spinning it up to about 7400 and living dangerously. So back to the grinder. The next move was we raised the roof only about .075" from the flange to behind the PR pinch, blending it in up to about he guide boss. At this point we got about another .020" in width out of the PR pinch. The new area at the pinch measured about 2.35" (without subtracting radius). I then just added a .060" wide 30 deg. back-cut to the same valve, and re-flowed. Those are the second set of numbers you saw. All I can think is that the lack of area upstream was really affecting the downstream.......so the area change / raised roof really woke it up. I'm sure the back-cut was what brought the .100"-.400" numbers up, but the area difference really helped feed the throat. The lack of cfm was strictly a volume issue and not a speed or separation issue in this case. One thing I will say......the short turn is layed back a pretty decent amount. The peak of the ssr is about 7/8" from the deck surface. I bet I must've taken .200 off of the apex in the process.

[rewguy]

From the picture at the same angle, it looks virtually identical, BUT....I can see a bit more ssr overhang. Id bet a million bucks it's in the short side.

[rewguy]

If you view the sideways view of the port that I posted.....And you take note of where the rocker stud hole is....in relation to where it is in your pic......I think you'll see how much I had to lay the ssr back. As soon as that is layed back......That 2.08" valve will blow right by my 2.02", and you wont have a problem getting that 310+ that you're after.

[Carnut1]

Good info and I think you are right in both instances. I have been easy raising the roof and keeping the 1204 opening and that ssr is a handful. At least the port doesn't start backing up at .6" lift anymore! Thanks for the help, Charlie

[rewguy]

Anytime! Good looking work, by the way!

[Carnut1]

Anytime! Good looking work, by the way!

Thanks, I appreciate that from a guy who does this for a living!

[user-612937456]

David Vizard said in his class that the rocker boss thread hole created a noticeable disturbance. It might be worthwhile filling w/clay and smoothing the hole just to see. It is worse on a BBC but it can affect the SBC port also

[mag2555]

Charlie I think one of the things that will help is to have a long sweeping radius on the roof starting off at Just before the the valve guide pops thru the roof, with the tallest at the short turn crown and then dropping back down at the flange .

I did not read all the way thru this string of post so I need to ask, what is your throat percentage at?

Are you flow gain percentages so far greater then your port volume percentage increase?

[user-612937456]

Also David talked about biasing the SSR on the common wall side to promote airspeed and swirl as it enters the chamber. Alternately by leaving material on the opposite side of the SSR slows the air speed down influenceing it to hug the radius allowing more air to enter the chamber on the side away from the spark plug further promoting chamber swirl instead of creating more of a disturbance underneath the valve counter to the flow coming from the common wall.

Please take my advice with scepticism I don't do this for a living just what I remember from DV's Seminar

[user-612937456]

Charlie I think one of the things that will help is to have a long sweeping radius on the roof starting off at Just before the the valve guide pops thru the roof, with the tallest at the short turn crown and then dropping back down at the flange .

I did not read all the way thru this string of post so I need to ask, what is your throat percentage at?

Are you flow gain percentages so far greater then your port volume percentage increase?

Yes DV said the same thing I remember some graphics in one of his slides also promoting velocity on the common wall side

[Carnut1]

David Vizard said in his class that the rocker boss thread hole created a noticeable disturbance. It might be worthwhile filling w/clay and smoothing the hole just to see. It is worse on a BBC but it can affect the SBC port also

I should at least check it. Thanks, Charlie

[Carnut1]

Charlie I think one of the things that will help is to have a long sweeping radius on the roof starting off at Just before the the valve guide pops thru the roof, with the tallest at the short turn crown and then dropping back down at the flange .

I did not read all the way thru this string of post so I need to ask, what is your throat percentage at?

Are you flow gain percentages so far greater then your port volume percentage increase?

I think I am at 90.5 % throat ratio on the intake. Thanks, Charlie