Ported Dart pro 1 pre platinum

[MELWAY]

The chamber it's self will not be except down low in most cases but it can become a hindrance as the port gets better if it's not sized/shaped properly for the valve size you are running. The chamber/pressure recovery is part of the intake system and has to work together with the port, if the air can not get over the valve and between the valve and chamber wall efficiently then how can it get out of the port?

Judson with S.A.M gave an example of a highly developed head they had, they decided to raise the compression on the engine by angle milling the head 1 degree and lost over 20 CFM because of the effect it had on the chamber.

EDIT! If you have a test head it would be worth wile to test different chamber shapes and lifts.

So did it make more or less power angle milling and loosing 20cfm??

[zums]

The chamber it's self will not be except down low in most cases but it can become a hindrance as the port gets better if it's not sized/shaped properly for the valve size you are running. The chamber/pressure recovery is part of the intake system and has to work together with the port, if the air can not get over the valve and between the valve and chamber wall efficiently then how can it get out of the port?

Judson with S.A.M gave an example of a highly developed head they had, they decided to raise the compression on the engine by angle milling the head 1 degree and lost over 20 CFM because of the effect it had on the chamber.

EDIT! If you have a test head it would be worth wile to test different chamber shapes and lifts.

The chamber can be sensitive in that situation, usually in a totally different area many chase cfm from

[JoePorting]

I've found that the reason you lose CFM when you do any type of milling to a head is not because of the combustion chamber shape, but because you are cutting into the top 30 degree valve job angle at the surface of the head. That 30 or 35 degree angle above the 45 degree seat is very important for max flow. Also, that part of the valve job is the most sensitive since the majority of flow passes through the short side radius (ssr).

This is why milling the head to raise compression is a zero sum game. Any gain you get from the raised compression will be lost in reduced flow. If you want more compression, use a larger domed piston.

[GARY C]

The chamber it's self will not be except down low in most cases but it can become a hindrance as the port gets better if it's not sized/shaped properly for the valve size you are running. The chamber/pressure recovery is part of the intake system and has to work together with the port, if the air can not get over the valve and between the valve and chamber wall efficiently then how can it get out of the port?

Judson with S.A.M gave an example of a highly developed head they had, they decided to raise the compression on the engine by angle milling the head 1 degree and lost over 20 CFM because of the effect it had on the chamber.

EDIT! If you have a test head it would be worth wile to test different chamber shapes and lifts.

So did it make more or less power angle milling and loosing 20cfm??

It lost power, the cfm lose wast just an example he used to show how a change in the chamber can effect what happens in the runner, the discussion was about angle milling a head without addressing the chamber in relation to the new angle.
As I recall they reworked the chamber to get the head back to where it was and even though they ended back at basically the same compression they gained power due to the new valve angle.

[GARY C]

I was trying to find the info he gave but have not found it yet but here is another example he gives. "The goal is to keep velocity even all around the valve." If the chambers aren't optimized, the penalties can be severe. "On one of our race heads, we cut 1-2 cc of material out of the chambers to get some extra piston clearance for the aluminum rods we were running. Our flow dropped from 410 to 385 cfm. It just goes to show you every little thing on today's heads is so much more critical than on the junk heads we had 15 years ago."

He covers most areas being discussed in this thread here.
http://www.superchevy.com/how-to/0607-c ... der-heads/

[Carnut1]

0115171847.jpg

Port #2 flow progression peaks. I did these ports in a different order to see where the gains and losses are. These are not similar to the first port I have done. These are ported more like what an average porter could expect with some metal removal. Not bad for used heads with some work in them. Thanks, Charlie

[GARY C]

Good thread, I like seeing the progression.

[Carnut1]

0115171847.jpg

Port #2 flow progression peaks. I did these ports in a different order to see where the gains and losses are. These are not similar to the first port I have done. These are ported more like what an average porter could expect with some metal removal. Not bad for used heads with some work in them. Thanks, Charlie

I forgot to include the last test pushed the pinch size as well.

[randy331]

I did these ports in a different order to see where the gains and losses are.

You'll find the gains and losses will differ depending on what you do first. Basically as far as cfm gains you're always up against the weakest link, or whatever the restriction is.

Like if you open up the pushrod area first but if it was only flowing 125 cfm/per inch of area at that location before it was opened, it's likely not gonna gain cfm because that location wasn't the problem. Like wise if the first thing you work on is the st, but the pushrod area is already moving 145 cfm per inch of area, it's not likely the st modification will net a gain.

Interesting to the changes in stages anyway.

Randy

[Biteme]

Interesting following this thread thank you Charlie.
The ssr work you're doing is to the profile you showed earlier isn't it?
Are you able to do a comparison between the intake without the ssr modified vs with it modified?
I'm interested to see how the factory ssr holds up turbulence wise.

[Carnut1]

Interesting following this thread thank you Charlie.
The ssr work you're doing is to the profile you showed earlier isn't it?
Are you able to do a comparison between the intake without the ssr modified vs with it modified?


I'm interested to see how the factory ssr holds up turbulence wise.

Port #2 and port #8 have less radical ssr shape than the first port. They also have higher airspeeds and lower cfm flows.. The stock intake ssr works well up to .5" lift and stalls, which is fine for a street only hot rod application. Lowering the airspeed and getting the airspeed similar across the width of the ssr seems to only help in the higher lift flows. I have a few more virgin ports if you like I can work up a set with everything else done but the ssr just to see what happens. Thanks, Charlie

[mag2555]

The effect of mill on chamber depth can effect the pressure recovery factor,and good pressure recovery is a very high thing on my list of good things for making the best power with a given amount of air flow.
I am not saying this is cut in stone as some chamber designs realize the power gains you would expect with every 1/2 point of compression increase!

[Biteme]

Interesting following this thread thank you Charlie.
The ssr work you're doing is to the profile you showed earlier isn't it?
Are you able to do a comparison between the intake without the ssr modified vs with it modified?


I'm interested to see how the factory ssr holds up turbulence wise.

Port #2 and port #8 have less radical ssr shape than the first port. They also have higher airspeeds and lower cfm flows.. The stock intake ssr works well up to .5" lift and stalls, which is fine for a street only hot rod application. Lowering the airspeed and getting the airspeed similar across the width of the ssr seems to only help in the higher lift flows. I have a few more virgin ports if you like I can work up a set with everything else done but the ssr just to see what happens. Thanks, Charlie

If you could please that would be awesome!

My thinking is that the factory ssr may be best for a flat tappet cam, whereas a solid roller that spends a lot of time at .500+ would benefit from the layed back ssr.

[mag2555]

Gary, did that chamber mod allow the flow to shift more towards the cylinder wall?

[Carnut1]

Interesting following this thread thank you Charlie.
The ssr work you're doing is to the profile you showed earlier isn't it?
Are you able to do a comparison between the intake without the ssr modified vs with it modified?


I'm interested to see how the factory ssr holds up turbulence wise.

Port #2 and port #8 have less radical ssr shape than the first port. They also have higher airspeeds and lower cfm flows.. The stock intake ssr works well up to .5" lift and stalls, which is fine for a street only hot rod application. Lowering the airspeed and getting the airspeed similar across the width of the ssr seems to only help in the higher lift flows. I have a few more virgin ports if you like I can work up a set with everything else done but the ssr just to see what happens. Thanks, Charlie

If you could please that would be awesome!

My thinking is that the factory ssr may be best for a flat tappet cam, whereas a solid roller that spends a lot of time at .500+ would benefit from the layed back ssr.

Working on it. I decided to take this pic for guys who may not know how much metal needs to be removed in a project like this.