Chamber Mods vs Gains

[skinny z]

I've posted here regarding my iron heads. Presently they're in great shape and could go back into service anytime.
That said, something I've also posted previously was the somewhat messy combustion chamber. In particular the abrupt cutter lines from a previous re-work.

Mine.jpg

Similarly, Weingartner has touched on this as well.

Weingartner.jpg

So, for the chambers to be cleaned up the opinion is that I'd lose between 1 and 2 cc's of material (although 2 cc's seems excessive). That would mean a revisit to the mill to get the CR back to spec.
The question is, what can be expected in terms of CFM gains if the results were similar to these pictures below?

How much gain.jpg

How much gain 2.jpg

I'd imagine the greatest gains would be in the low lift regions. In particular during the overlap phase.
I'm confining my question and any additional work to just that area immediately around the top cut and the adjacent surface.
For what I'm doing (and that direction won't be finalized until sort through things like this), it may prove a measurable benefit in terms of engine output.
Then again, it might not be worth it
While I'd like to squeeze the last bit of goodness out of the current collection of parts, what's the reward to cost ($ and labour) outlook?
Does anyone have flow bench data to support one point of view over another?

[Dave B]

In iron heads you for sure don't want any sharp lines.Allot of guys think low lift means nothing.I think it's all important in getting a good burn pattern in combustion chamber.It can be tough to get a good texture in a iron head.In iron heads we prep area just under seat and above it differently than what we do with most aluminum.It just depends on how it will be used and also fuel type.Imo slow burn rate fuels need way different approach than quick lite fuels.

[Dave B]

It's going to be hard to make anything work nice with heads in pics imo.Huge lazy chamber with poor plug location.Angle Mill the crap out of them is best hope there.Intake bowl walls are just flat after the guide .The air needs to be turning before the guide .You need to go in and address ssr in ex side.You have big gouge flat spot in left hand upper corner.You want a nice round tongue shape there.Your throats roll right into your bowls.Bowl area or volume should always be different than your throat area.You are going to have a fuel pool mess that is going to just make black tar blodges in chamber instead of nice even burn pattern.You will not achieve nice b.s.f.c numbers with all the issues that need addressed.

[skinny z]

It's going to be hard to make anything work nice with heads in pics imo.Huge lazy chamber with poor plug location.Angle Mill the crap out of them is best hope there.Intake bowl walls are just flat after the guide .The air needs to be turning before the guide .You need to go in and address ssr in ex side.You have big gouge flat spot in left hand upper corner.You want a nice round tongue shape there.Your throats roll right into your bowls.Bowl area or volume should always be different than your throat area.You are going to have a fuel pool mess that is going to just make black tar blodges in chamber instead of nice even burn pattern.You will not achieve nice b.s.f.c numbers with all the issues that need addressed.

The 1st picture with the circled areas is mine. It's a Vortec chamber copied by RHS. 64cc as cast.
By all accounts it's a good design.
The other pictures are examples of the chamber mods I'm inquiring bout.
The issue I'm addressing is the nearly flat top cut that transitions the valve job to the chamber. It was done after the fact in an attempt to take a few cc's out of the chamber. End result was ~ 67cc. After milling during the lastest valve job, they're now 65.4cc.

My example is not as intense as the one shown in the shown picture which is Weingartner's Brodix IK 200.
The other pictures are of unknown brand.

[BOOT]

In my opinion it depends on the cam & use, whether you wanna just break the edge or put more work into that area.

[skinny z]

In my opinion it depends on the cam & use, whether you wanna just break the edge or put more work into that area.

Under consideration: 282/282, 236/236, 108 LSA, 104 ICL, .575".
Drag racing. Some street and long distance highway.
Break the edge only.

For what it's worth, compared to an OOTB Brodix IK 200, which has a similarly abrupt transition (but more pronounced on the Brodix) I'm better off in CFM up to .400"-.500". This is the same sized 2.02" valve. 170cc port though.

Looking back at Weingartner's video, I'm already ahead of the game.

https://www.youtube.com/watch?v=iVR0BctDhjM

He goes on the say his Profiler's 195's are about 230@.400" which is the same as my bench results (Both 4.030" fixture bores but obviously different benches).
Makes me think to leave well enough alone.

[Dave B]

It's going to be hard to make anything work nice with heads in pics imo.Huge lazy chamber with poor plug location.Angle Mill the crap out of them is best hope there.Intake bowl walls are just flat after the guide .The air needs to be turning before the guide .You need to go in and address ssr in ex side.You have big gouge flat spot in left hand upper corner.You want a nice round tongue shape there.Your throats roll right into your bowls.Bowl area or volume should always be different than your throat area.You are going to have a fuel pool mess that is going to just make black tar blodges in chamber instead of nice even burn pattern.You will not achieve nice b.s.f.c numbers with all the issues that need addressed.

The 1st picture with the circled areas is mine. It's a Vortec chamber copied by RHS. 64cc as cast.
By all accounts it's a good design.
The other pictures are examples of the chamber mods I'm inquiring bout.
The issue I'm addressing is the nearly flat top cut that transitions the valve job to the chamber. It was done after the fact in an attempt to take a few cc's out of the chamber. End result was ~ 67cc. After milling during the lastest valve job, they're now 65.4cc.

My example is not as intense as the one shown in the shown picture which is Weingartner's Brodix IK 200.
The other pictures are of unknown brand.

It's the last 2 pics I'm referring to that look horrible.In first pic imo get rid of sharp edges and should be good to go .I really don't work with chambers in 23 heads that are bigger than 56cc.The engines I work with are all after compression,64-67 cc is terrible in what we are trying to do.We would get our asses handed to us leaving that much on the table.

[skinny z]

It's going to be hard to make anything work nice with heads in pics imo.Huge lazy chamber with poor plug location.Angle Mill the crap out of them is best hope there.Intake bowl walls are just flat after the guide .The air needs to be turning before the guide .You need to go in and address ssr in ex side.You have big gouge flat spot in left hand upper corner.You want a nice round tongue shape there.Your throats roll right into your bowls.Bowl area or volume should always be different than your throat area.You are going to have a fuel pool mess that is going to just make black tar blodges in chamber instead of nice even burn pattern.You will not achieve nice b.s.f.c numbers with all the issues that need addressed.

The 1st picture with the circled areas is mine. It's a Vortec chamber copied by RHS. 64cc as cast.
By all accounts it's a good design.
The other pictures are examples of the chamber mods I'm inquiring bout.
The issue I'm addressing is the nearly flat top cut that transitions the valve job to the chamber. It was done after the fact in an attempt to take a few cc's out of the chamber. End result was ~ 67cc. After milling during the lastest valve job, they're now 65.4cc.

My example is not as intense as the one shown in the shown picture which is Weingartner's Brodix IK 200.
The other pictures are of unknown brand.

It's the last 2 pics I'm referring to that look horrible.In first pic imo get rid of sharp edges and should be good to go .I really don't work with chambers in 23 heads that are bigger than 56cc.The engines I work with are all after compression,64-67 cc is terrible in what we are trying to do.We would get our asses handed to us leaving that much on the table.

Yeah. The last two pictures are of unknown brand although I'm pretty sure they belong to someone here.
The sharp edge is exactly what I'm talking about.
As for compression, it seems about 10.5:1 is the practical limit when all things are considered. I know that's nothing when the racing gets intense.

[Dave B]

Yes if your a street deal comp can be tricky.I still like tiny comb chambers then too.I would rather use some form of dish piston than a flat top then.We always get better burn patterns.I have never saw once that having complete even burn across chamber hurt power .

[panic]

#1 reason for sharp edges in prepared heads?
Highly $killed labor needed to finish them.
Once the piston drops ATDC, the huge shape & volume change disturbs flow into the cylinder.
Greatest effect @ low lift, helps most if the OL window (valve lift X degrees open) is too small.

[skinny z]

#1 reason for sharp edges in prepared heads?
Highly $killed labor needed to finish them.
Once the piston drops ATDC, the huge shape & volume change disturbs flow into the cylinder.
Greatest effect @ low lift, helps most if the OL window (valve lift X degrees open) is too small.

The reason for the sharp edge?
I'd asked a previous cylinder head guy to take a few cc's out of the chamber. My CR was too high for the intended use of these heads at that time. I'd expected he'd accomplish that with some grinding and sanding action but rather he used to what amounted to a flat cutter and cut a concentric ring around both valve seats. The result is what you see in the highlighted picture. That was 2011.
As for highly skilled labour...it's certainly within the scope of my skillsets to soften them up but the question asked is whether it's worth it. Any modification might mean another trip the mill but these have been cut 25 thou as it is.
Low lift flow isn't bad in comparison to some OOTB deals. What kind of gains are likely should I dress them up? 2 CFM? 5 CFM @ .200"?

Presently, on a 4.03" fixture. 170cc port. 2.02" valve.
0.100": 63/59
0.200": 121/108
0.300": 179/142
0.400": 230/167
0.500": 254/176
0.600": 247/179
0.700": 250/185

[panic]

Flow bench tests give results at all lift levels.
Do they test at every piston position 40 degrees B/ATDC with the actual piston in place? Then it won't show up on a test.

[skinny z]

Flow bench tests give results at all lift levels.
Do they test at every piston position 40 degrees B/ATDC with the actual piston in place? Then it won't show up on a test.

Does anybody? At least those that don't have a six figure R&D budget? (Think NASCAR or similar pro level racing).

[SoCalDave]

If you do it use an old intake valve and an old exhaust valve as you grind with a burr or even using a sanding roll. I've ported my own 243 LS heads and I used old valves when working near the valve seats to avoid nicking them.

[1980RS]

My peanut port heads have "big lazy chambers" and with only 8:1 compression I could only manage to run 11.16@118mph. I know that's pretty poor from a performance stand point.