A follow up to the port flow stuff I have done since I got Mike's flow bench.
There are times when I think I would be much further along on the 68 Barracuda If I had not gotten that bench, as I have invested some time into it, but I have learned much and this is what I know.

The flow bench still calibrates to the to the manual requirements, which is a good thing. I have made a couple of improvements to the bench to reduce test variability.
I added dowels to the top plate that locate off two of the head bolt holes, that gets the combustion chamber centered to the test pipe the same way every time.
Mike used a set of large vise grips to clamp the head to the top plate, there was always some leakage that would need to be accounted for in the test results.
I drilled the top plate to allow the use of the four head bolts around the chamber being tested to clamp the head. That has taken the test leakage value to zero.


Through WV I have a Mike Jeffery ported head. That head is of no functional use as it is cracked between the seats in multiple cylinders. It looks like there was some kind of sealant added inside the water jacket. The cracks are tight enough they would not influence flow tests and would not interfere with using two part RTV to make molds of the port shapes.

There was an earlier post where the 30 degree seats were discussed. So I won't get back into that here other than to say that Mikes 30 degree seat recommendation was very much inline with what David Vizzard discussed in his port flow book. A nice summary of the David V port discussion is at the site linked below.

https://www.musclecardiy.com/cylinder-h ... ds-part-8/

I do have more information on the port shape. Two part RTV resin was used to make the molds, Low durometer rubber for flexability and a good shot of silicone release on the casting prior to pouring in the mix was required to get the molds to release from the port cavity.
The molds were of the intake and exhaust ports of the MJ ported head and a stock 1987 slant head. Compared the two with using caliper measurements and visual inspection. Dimensionally and visually it is obvious there was a lot of bowl work, almost no change in the port arms.
In the bowl itself I found that MJ raised the roof of the bowl .060 to .090 by cutting the inside of the valve guide boss. There was more removed from the intake than from the exhaust.
Photos of the port molds are below.

I did a test where I cleaned up the bowl very much like Mike did, added the 30 multi angle degree intake and 45 degree exhaust seats, and did not raise the roof. The ports flowed about the same as Mikes head until above .350 lift, then it dropped off. I made a fixture to hold the head on my drill press, bought a 3/4 inch end mill and cut the inside valve guide bosses by .070
Re tested the head and the flow came into the range of the MJ ported head across the higher lifts.

The charts below are of back to back test results ran last week of one intake port from the cracked MJ head and for two of the intake ports on the head that I ported duplicating what I found on the MJ ported head and describe above. The Exhaust test is one MJ port and one of my ports.

Keep in mind that this test bench tests at 10 inches of pressure, the over all results will be lower than a head tested at 20 or 26 inches. Testing a V8 head with large ports I bet this bench would run out of capacity at the higher lifts, but it still has test pressure capacity at high lifts on these slant heads.

You can see on the charts that ports I cut slightly out flow the MJ ports at lower lifts then it swaps with the MJ head flowing more at higher lifts. I don't know definitely as I have not tested this but visually Mike ran very narrow seats and as a result of that is the ID of the valve bowl at the seat is slightly larger. My though is that at large lifts the larger diameter will move more air. At lower lifts the larger diameter looses some velocity and the flow is less.

In support of the Slant Six community I wanted to share this info. I think the next quantum leap forward will take a significant change to the port shape, and that is possible.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Thanks for sharing this! Looking at the two molds it almost looks as if material may have been added to the short side radius of the intake port just above the seat. Of course I am just spit-ballin' here. Hard to tell from the photo. Interesting stuff none the less. Thanks again for sharing.

P.S. I reckon the larger valve seat would account for the change in shape of the short side radius without any material added there.

_________________
“Buy the ticket, take the ride.”
― Hunter S. Thompson

these is no visible evidence of material being added at the short side radius,
the blend is different because the bowl is physically bigger so the location where the radius joins the bowl is different

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

That makes sense and after thinking about the larger valve bowl I knew that could account for the change in contour. Thanks again.

_________________
“Buy the ticket, take the ride.”
― Hunter S. Thompson

if anyone wants to make their own port molds

I used US Composits Part A & B 74-30
and the mold release they recommended
ordered through their web site

I set a short section of wire with a hook on the molded end
into the liquid, so I could push on one end and pull on the other to
get the molded form out.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

This is GREAT info! Thanks for sharing!

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Woah.. its harry potter for slant 6 dudes and gals.

Cool stuff John!

Greg

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http://www.youtube.com/hyperpack

Did you make molds of the Exhaust ports?

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-MattMan
LEANED & MEAN

This is why I made sure to talk you into the bench John. If I would have kept it, it would be sitting in the Skunkworks collecting dust and spiders.

_________________
Official Cookie and Mater Tormentor.

Very cool. Thanks for posting, John.

Lou

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Home of Slant6-powered fun machines since 1988

additional intake views

notice that on the stock molds, the rubber duplicates the surface profile to the extent that one can see the
sand grain finish from the foundry sand cores used to make the port.
and on the rubber molds from the MJ heads the port surface is generally smooth and slick, so Mike did do some
smoothing of the port walls.

and remember these are stock sized valves in the stock ports and OS valves in the MJ ports, notice how on the MJ ports that the
diameter of the bowl goes right to the diameter of the seat.

The way the intake ports are splayed in slant six heads, the 1,2,3 intakes point one way, the 4,5,6 intakes point the opposite way.
I made a mold of the 3 and 4 MJ intakes to see if there was any difference between the two. I did not see any.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

photos of the exhaust molds
on the exhaust molds one can see the bowl sizing to match the seat diameter and the
general slickness of the MJ molds dues to the walls being smoothed.
As I mentioned earlier the major geometry of the port arms was not changed

the one thing that is shown in the exhaust mold is the slight bulge at the side of the
bowl. I attempted to duplicate that, but I did not test with and without.

When I get the head I am working currently completely finished I will make port molds
and see how they actually compare to the MJ molds that I have on hand.

This would all be so much quicker with a 3D scanning / layout device, but there are times when you
do with what you have.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Thanks so much for sharing this information, and putting in all of the time to do this study.

One thing this has done is clear up my confusion about some of the engine builds described here. I have seen builds listed as being in the 220 hp range yet the port flow numbers were quoted as being 199 cfm (if my memory is right- maybe I'm getting different builds confused). I would think a 199 cfm build could do 250+ hp.

Knowing that a well ported head flows about 105 cfm at 10" means it flows about 175 cfm at 28" - this is more in line with the ~220 hp number.

I saw an image years ago on this forum that had several heads shown in the 190-200 range. I wonder if this was accomplished by completely eliminating the valve guide boss, or if some of those numbers are the result of an improper flow conversion.

actually I think that port flow benches are a bit like engine dynamometers, they may repeat back to them self, but when you try to compare the test results from one machine to the test results from another machine, it gets a little fuzzy.

here is a post from a guy that says he gets a slant intake to flow 200+ (guess that is at 28 inches) by only working the floor and a little on the sides. (see post #26)

https://www.forabodiesonly.com/mopar/th ... ng.433131/

so like all things, it is likely there more than one way to do it.

Gary Bruner told me this one time and I do believe it, anything that helps you see the backside of the valve, when looking through the manifold face is going to help flow.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

You just keep doling out good info DT. I do appreciate it!

_________________
“Buy the ticket, take the ride.”
― Hunter S. Thompson