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Old 12-04-2019, 07:54 PM
joes455 joes455 is offline
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Default Rpm intk porting

Rpm intk runners 8 and 2 having trouble getting them to flow any better than stock.So far porting has just been cleaning up entry ,widening ,plunum radious work.Both 8and2 flow 255 with intk bolted to head and carb installed.Jumps to 275 using a open spacer under carb and 274 just intk and head no spacer or carb.The port itself has not been touched except gasket match to a sce 28105.Will enlarging the port turn make a difference?I must say that the lower plane of ports flow much better than the upper plane.Especially that lower plane #6 it flowed almost 290.

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Old 12-04-2019, 08:43 PM
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Half-Inch Stud Half-Inch Stud is offline
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HIS

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Old 12-05-2019, 02:22 AM
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Jack Gifford Jack Gifford is offline
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I'm curious what the bare head ports flowed?

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Old 12-05-2019, 07:32 AM
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steve25 steve25 is offline
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Do I read you right here Joe?

Port 2 and 8 flow 255 with just the Carb bolted up.

The flow of 2 and 8 jumps to 275 with a spacer under the Carb.

Then you posted that both ports flow 274 with no spacer or Carb bolted on, do I read you right here?

If that's the case your seing the effect of high velocity air exiting out the bottom of the Carb not being able to take the path of least resistance thru the Plenum and make the turn into the runners like it can with no Carb bolted on!

I hope you have the hood clearance to run the spacer, as that added 20 cfm if it's in your Cams lift range could mean up to a additional 5 hp per cylinder.

What size Carb are you running, a as duel plane Intakes can run a 800 cfm Carb without much loss of bottom end power.

Also spreadbore Carbs tend to allow these Manifolds to flow better due to the slower air speed out the big secondarys!

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Old 12-05-2019, 05:10 PM
joes455 joes455 is offline
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Heads flow right a 300 cfm I have 1 head that i experiment with,it is installed on an old pontiac block that I sliced in half length wise.Anyways did some more testing velocity probing , that # 8 port just wants to suck the plane divider down its throat, airflow is being pulled over the top of it.I may test different divider heights.I've seen pics where 1/2 of the length was cut down to the floor .The ports cs can handle the extra flow its jusy not being available at the upper plenum

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Old 12-06-2019, 11:19 AM
KARGUY KARGUY is offline
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Joe, do you have any pictures of the porting?Thanks

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Old 12-07-2019, 07:47 AM
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Just so you know Joe, many moon's ago when I got my flow bench I made a perfectly streamlined orffice to go on my bench that had a entry area equal to that of a stock D- port gasket.

Once on the bench it would not flow more then 295 cfm!
This means that if any part of any runner does not have more area then a stock D-port then that can also be why that runner can not top 275 cfm.

At the point in which any runner in the Manifold curves at a rate of more then 45 degrees then at that point in the runner the amount offlow that can pass will act like there is now 25% less port area.

The outside walls of any runner in these locations need to have the outside wall of the curve in the runner kicked over as much as possible to gain back the port area and lesson the curve .

If you velocity probe deep in the runners you will find that a good part of each runner port area has far less flow passing thru it , so even though your 28105 gasket has close to 2.700 square inches of port area many areas of each port may be reacting like it only has 2.5. Square inches of port area.

Remember, high velocity air just like water will try to take the path of least resistance!
You may have the Manifold gasket matched to that 2.300" tall 28105 gasket, but does that area reduce down to less as the runner progresses back towards the Plenum?

This is how the divider should be reworked to help out the flow of ports 2 and 8.
The notch in the top of the divider should be equal to the width of the top of the entry into each runner from the Plenum.

The width of each notch at the bottom of the divider should be equal to 1/2 the width of what the top of the notch is.

When I flow test the base model Performer on average each runner flowed 225 cfm, with port 1 being the poorest coming in at 216 cfm.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!

Last edited by steve25; 12-07-2019 at 07:54 AM.
  #8  
Old 12-08-2019, 05:25 PM
joes455 joes455 is offline
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Nice feedback steve25,just port match is all thats been done to the sce gasket.I will focus on the outside wall.Ive already layed back the inside radius with no flow change I didnt lose anything thats good.Ill give u an update.

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