Thought I would throw up a few pictures in case anyone had any advice. Here is the stock port...




The ported version it looks like the valve seat is overhanging the bowl but it's not. The seat and the bowl where they meet is flush. Same camera angle as above, same lighting...




I believe that just under the seat is supposed to be 90% of the diameter right at the seat, that is hard to create because of the void in the casting that caused the shadow you can see in the stock picture. That part of the port is quite a bit underneath the seat so I just tried to blend that as best I could. Didn't know what else to do there really....I could fill it w/epoxy, but I don't think that really aligns with the fact that I'm using 113 heads -and their limits. The ported version it looks like the valve seat is overhanging the bowl but it's not. The seat and the bowl, where they meet is flush.








Still need to finish the surface w/a sanding roll, plan to blend the ridge in the combustion chamber outside the seats. IDK, this is my first head porting endeavor.

 

A couple of things things come to mind based on the pics.
Is that the valve job that'll be used or will it get a going over after you touch up the topside?
First the thing that was addressed on my aftermarket Vortecs and the re-re-done valve job was to smooth out the transition into the bowl area.

There'll be lots more I'm sure but this gets the conversation going.
Good, bad or indifferent opinions exist on David Vizard's tutorial on porting the L98 113 aluminum Vette heads.

 

Thanks for replying. IDK why I never posted back. My plan was to use the valve seat that is present in the pics...but now that I've gotten ~2.5 cylinders and combustion chambers done, it's obvious to me that there is no way in hell I'll get through all of 'em w/out messing up and zipping across a valve seat at some point. Adding to that, it's a 1 angle valve job, so...

One thing that's bugging me is the bowl-to-seat ratio. The way that the casting us "under cut" on the outside radius makes it essentially impossible to have the bowl end up 90% of the seat OD. I've tried to smooth/blend that abomination as best I can, but the outside radius HAS to taper inward before the bottom of the seat...unless I fill that area w/epoxy. Which I've considered.

I wanted to do this b/c I've never done heads before....only intakes, I wanted to try it. Also, they're 113 heads, so no big loss if I F'em up IMO. At this point though, I feel that I've learned that it's not worth it. I guess that's a personal thing; if you have zero money....it's totally worth it. But from MY perspective, I'll be lucky to get 220 CFM out of these things, and I could spend $800 on a cheapy Ching-Chong-China head that would do 240-250. So...if I were doing it again, I'd probably just do that.

 

I did a set of big valve 128s yrs ago, swapped em with iron and picked up 1/2 second in 1/4 mile.

 

Might you be thinking of the throat to seat ratio of 90% and not the bowl to seat ratio? The throat being the area directly below the bottom cut of the valve seat.
Charles Servedio (Servedio Cylinder Head Development) has done some work on these (although pictures and or videos are scarce) and he mentions, as you do that it's not worth the time. Other than for one's own edification I suppose.




This is the only Servedio example i could find although there's a decent thread about these and similar heads on Speed-Talk. His username there is carnut1.
https://www.speed-talk.com/forum/viewtopic.php?t=55055
You might be interested in his YT channel if you haven't come across it already.
https://www.youtube.com/@servediocylinderheads

He has an extensive ST thread about porting 083's. Not the same I know but I believe there are similarities that carry over.
https://www.speed-talk.com/forum/viewtopic.php?t=55886

Any just about any inquiry on these heads comes around to Vizard's book on how to modify Chevy heads.
https://books.google.ca/books/about/...EC&redir_esc=y

 

I believe it. Porting these is dumb...but I wanted to try it and see what I could do w/'em....and I won't be crushed if I ruin them in the process, and I won't be crushed if they limit power....I already know that they're going to be the #1 limiting factor. In todays world, with <$1000, 250 cfm heads, they're a disposable head, IMO.



Perhaps. I was under the impression that the "cross sectional goal" is essentially an inverted velocity stack....that has a valve at the "mouth"/exit. If the only important aspect is actually the throat to seat ratio, that is doable....but having that hollowed out area under the throat and 'hump' near the top of the bowl on the outside radius doesn't seem ideal.

I've give that guy's YT channel a look. Thanks for sharing!

 

As I have said in the past the 113s GM put on the ZZ4s went 240-250 cfm with minimal additional work. Lingenfelter got 260-270 cfm out of the production 113s via CNC porting. Those offshore heads will have a ~200cc port and flow about 244 @ 0.500 out of the box. With a good valve job and minimal cleanup they will go about 265-270 cfm @ 0.600. Lloyd Elliot ported a set of the Assault castings for me that flow just under 300 cfm @ 0.600" using a GM Fastburn intake gasket dimension.

 

Just to qualify my comment above, it's a 90% diameter ratio we're looking for. The word area may have entered the mix and that would be incorrect on my part.

 

Yep, I got you. I know/knew what you mean.


I haven't seen or heard of numbers better than ~220 for a ported 113 in my searching. I'd expect my porting to produce less results than LIngenfelter's CNC machine, Lloyd Elliot, or anyone else who knows what they're doing. I'm basically trying to do what Eric Weingartner shares, and doubt that my results would be as good as his.

 

My ported 113s off a ZZ4 with 1.94/1.55 valves flowed 229/188 @ 0.500" and 238/193 @ 0.600" sitting on top of a flow choking 3.75" bore fixture. They were flowed on a 4.000" fixture and gained about 10-15# on each side through most of the curve. The biggest gains were actually at low lift with the larger bore being simulated.

Here are some other ported 113 head flow numbers.

https://www.thirdgen.org/forums/tech...num-vette.html

https://www.corvetteforum.com/forums...rs-are-in.html

A good common upgrade path on 113s atleast a number of years ago would be a good set of used GM LT4/Fastburn/CT350 2.00/1.55 valves. A lot of racers cheating to win races have them rebuilt with undercover modifications. Those "Sealed" crate engine builders often substitute 2.00/1.55 Manley Race valves into them that are even lighter than the sodium filled hollow stem LT4 valves they came with. That is where the 1.55 exhaust valves in mine came from.

I really like the 113s for 305s and other small cubic inch small blocks. The runners start out tiny and can really be improved on shape and flow wise maintaining port velocity on the smaller engines. At one point I built a 302 with atandard bore 880 casting Vortec 350 block, L99 265 crank and 5.94" rods. Topped it with Vortec heads, it was absolutely lazy compared to the 113 headed 312 I built. The 350 Vortec heads killed the low-midrange port velocity and cylinder filling. Looking back that engine needed a 3.75" or 3.875" stroke in it and it would have performed drastically better everywhere torque and horsepower wise.

 

I posted a question over at Speed-Talk regarding info on these 113 heads (did I already mention that?). There's been a substantial follow up to that via email and texts from a professional engine builder who for whatever reason has shared pages of information regarding porting in general. Not 113 specific but the guidelines to follow when developing a port.
Here's an example of an intake port with some critical dimensions. I understand it's 14° Pontiac head although things like the short side radius and roof axis relative to the throat diameter all carry over.




In my case, the RHS Vortecs have a 1.8" throat and a 2.02" intake valve. So in or around 89%. Close to the 90% value that's considered a target.
Although I had never intended to do a deeper dive on these heads, as in a full port job, that 1.80" throat means that a .900" radius for the short side (50% of the throat) and the roof axis is (throat and SSR combined) for 2.7".
It was further explained to me that templates are designed to ensure those values are held true.






That's for the same Pontiac head but could be modified and applied to the 113's.

FTR: I've done my fair share of cylinder head research over the years but can't say I've done a full porting job. Plenty of reading and viewing and acquiring bits of data, like throat diameter, MCSA, port length and volume has at least allowed for a decent spec for the 357. As interested as @Tom 400 CFI is (or was as the case might be) it's also piqued mine. I just may make porting them a retirement project.

Anyway, just throwing this out there. That engine builder keeps sending info and if there's interest I can relay any part of it.

 

I'm interested.....and thanks for the drawing. I'm going to finish what I started and see what she'll do.

The valve seats are nearly 1cm "tall"....which in my observations makes the lower part of the seat....the "throat". Yes? No?

 

In the following picture, as it's difficult to tell, where would you say the bottom cut of the valve job is? I recall it being mentioned that it's a "one angle" valve seat although somewhere below that angle has to be some transition.



The throat is described as being the smallest area below the valve job. Whether that's an angle cut in and then radiused from there or in my case, the casting below the seat continues to neck down, is where that measurement would be taken.



There are a couple of angles below the shiny seat (although it's difficult to see as these pictures are of the heads fresh from being removed from the engine prior to cleaning) but what is obvious is that there's untouched casting below the bottom cut. This is where I pulled the 1.8" across from and is the narrowest part. While I'm very close to the 90% objective this is where I would direct my cutter to size appropriately.

 

That all makes sense to me. Thanks for sharing.

Since I'm confident that I'll f-up a seat before I'm done, and need a seat grind, I added that "some transition" myself, using highly sophisticated tooling; a drum brake cylinder hone. So the actual "bottom cut" is where you can see the dull looking seat, transition into my fresh grinding marked taper, from the brake cylinder hone.

In Tom's perfect seat, the bowl>throat>seat>chamber were be just like the mouth of a velocity stack. Of course, that wouldn't seal for chit with the valve -you need an actual seat. But multi angle valve jobs are tying to accomplish that very feature (a smooth "radius" from the throat to the chamber). So why no try to just radius it to the seat, and then after the seat?

 

As long as you're measuring the smallest area below the valve then whatever it is, is what you're after.
The velocity stack analogy, from my understanding, is what one is going for with an intake port. That also includes the intake manifold runner. A continuous taper from the entrance in the plenum to the throat and then from there it enters the domain of the valve job itself. Seat angles and the quantity, again from what I've read and inquired about, play a role in how and when the flow is initiated and then directed. The angles too, as opposed to a radius, impact fuel shear and that helps keeping the air fuel mix moving the right way. The exhaust port on the other hand often utilizes a radius (as mine did until it got fubared by one hack or another) as there's no fuel to deal with.
This isn't to discount the importance of port shape, included the various radii, and volume and the velocity that results from all of that. That to me is whole other level although my grasp on the science is just enough to understand it.

I like your DYI approach and if a brake hone helps you get there, who am I to argue?
The f'ed up valve seat is what kept me from cleaning those ridges in the chamber in the picture posted above. I just kinda knew that I'd skip across some sensitive area and then off to the machine shop I go for the 3rd time! You've probably never seen such an expensive average iron cylinder head as what I've got! And after participating in this thread, and then initiating another, all of this has me thinking maybe one more time!

Anyway, there's probably more to come from my new engine guy. Seems like there's some value in it (aside from me) so I'll post back.

 

THanks for the props on the brake hone....I think it's a cool idea....I'm sure some are rolling their eyes!

LOL!! That was hilarious!! I'm in danger of being there too. I already spent ~250 on these junkers, getting them chopped and drilled for steam holes. After all the work I'm doing, I can't leave the one-angle valve job, so whatever that's going to cost, now. They'll probably be $500 heads by the time I'm done w/'em....if they make 400 hp on a this 400, I'll be luke warm about that.

WRT the ridge around the valve seat, Eric is all about that area. He claims that more power is made at and around the seat than all other typical porting. I believe it since the space between the valve and seat is where the air speed is the highest in the entire system...thus, and turbulence/restriction in that area will likely have a profound effect.



Go for it! It's an "essential car-guy experience"!


Finally, I'm done with one head!...






Here is the intake bowl, seat and combustion chamber as it sat in some dealership, in '89. Junk....




Here is the same view, after my efforts. Could this be worth 25 CFM?....





Here is that ridge above the seat...





Same ridge after tapering. This was tedious and you can see I was dipping into the seat sealing surface.





Also gasket matched the intake side, cleaned up the exhaust, shaved down the guide stands and tips, and sanding rolled the rest of everything including the chambers. Sure wish that I could find someone to flow these things, here in UT.

 

I wish I could find a better picture of what GM did with the 113s used on the ZZ4s for your porting effort. They did not have that massive lip, just a nice smooth bowl entry to the seat, very similar to how you have revised yours. They flowed considerably better and required minimal cleanup and a larger exhaust valve to get even more flow. This is not the clearest image but it was the only one I was able to find on the interwebs of the intake bowls in the ZZ4 113s part number 12556463.

 

I think that pic is pretty good. Of course it would be nice if it were bigger, but it shows what they've done. I wonder how they did it? I can't imagine that they pay hand porters to port ZZ4 heads?? It doesn't look hand ported, it looks machine finished.

Anyway, it looks like that ridge is there above/outside the seat, although it looks far less prominent. The casting looks better than mine did starting off. The guide stand looks as "fat" as mine did originally...IDK...I think if I did the right things, my head should be better than that one. Thanks for posting that.

 

Not sure you feel about Vizard or his books. He does however devote about a dozen paragraphs to the L98 aluminum Vette heads in his How to Build Max Performance SBC's on a Budget. I believe it's still in print.
No specifics though. Just a generalization and things to watch out for. A couple of diagrams too in addition to before and after flow charts.
It would be easy enough to scan the couple of pages and post it up. As long as the copyright police aren't watching!

 

I like Vizard, and certainly respect his knowledge. IDK if I want to buy, wait for the book...I want to move on but if anyone wants to scan and post, I'm sure no one will be offended, and I could compare what I've done to what he says and make adjustments if necessary.

I got some inside calipers last night and measured the throat (bottom of the valve seat insert) to top of the face seat face, and got 1.7272 at the throat, and 1.90" at the top of the seat face; 90.9 %.

 

Timing is everything. This just in front my engine guy.
Not sure how deep you'll get into these although it does sound like you intend to give it a thorough go.

Here's how to make two of the templates.

I use old valves and sheet plastic from a hobby shop or even 1/8" or 1/4" sheet aluminum.

A old valve is the way to since until you get use to using these templates you drop them into the guide to really judge where meat needs to be removed.

I now use adjustable cutters for installing replacement seats which really saves a ton of grinding time and keeps the throat concentric to the valve.

So you take a used valve that's bigger then what your starting off with for a throat size and on your bench grinder bring it down to a OD that's .010" less then what you really want.

Next you grind a flat equal to 94% of the throat size your shooting for.

So in terms of a 1.80" throat that flat would be 1.69".

Next the sharp change in OD left from grinding that flat needs to radiused off some.

As a throat diameter gets increased this flat gets used to keep the roof width / flow path to no wider then that 94%.
It's also used in some cases to make a D shape on the short turn when needed to control air speed when flow regression takes place if the proper short turn radius fails to do so.

A couple of diagrams.





As for where you're measuring the throat, as long as it's the narrowest point prior to the valve (recalling your velocity stack analogy) then that's what it is. I'm guessing that's after the brake hone exercise?

Keep going. This is interesting to watch.

 

Back in the late 80s early 90s I ported a set of 113 castings mind you I was young but followed direction pretty decently. My assignment was to gasket match, go into each port about 2" and be gentle in the pockets. Remove flash from around the guides after 3 weeks of work on my end due to work I finally bolted them on my L98 with felpro blue stripe thin gasketsnot sure of thickness. Mind you this Z had an SLP cam 495/510, 1.6 rockers and TPIS miniram, 700r4 and 2800 stall. Hooker 1-5/8 shorty which were NEW to the market back then, 3.42 rear on street radials fastest avg time at HRP was 12.70 my home ported heads with 2.00 1.56 valves brought me down to 12.4 to me it felt the same as previous with a little more mph. I want to say the larger valves did most of the improvement maybe more than my unprofessional port job who really knows. Back then we had very little support in the aftermarket world.
****I made an error,****
this L98 did not have the SLP cam it had the ZZ9 cam in it

 

Thanks. That's a lot to absorb, but I'll re-read a few times and see if I can follow his directions.

Yes, that is after the brake cylinder hone experiment.

 

There are a couple of key items it seems. The one comes up the most (and it'll be included in Vizard scan when I can manage it) is the 2.00 intake vvalve.

That is another example of which appear to be many.
Not sure of your chamber volume although I seem to recall your calculations for the compression ratio with those L98 heads on a 400. It might have been in there. One thing to keep in mind, should you go the route of the 2.00" valve (and why wouldn't you when you've mentioned being committed, or very nearly so, to a better valve job) and that's the chamber shrouding that's going to be likely. Some relief around the cylinder wall side of the chamber would certainly help. And if the compression is creeping up while still maintaining a reasonable quench, it would pull out a few cc's and might be helpful in that regard as well. But unshrouding would be key with the larger valve regardless of the CR. There's more low lift flow for you.

On a side note, a million years ago when I assembled my first serious SBC, which is discounting the 307 previous to that, it too was a 400. On it I plunked a set of double hump heads and IIRC, they were 64 cc. Pistons were stock cast dish. I don't recall the CR although I had pretty good college professors and I'm sure I was guided to something reasonable. One of those teachers advised me to keep the 1.94" intake but up the exhaust to 1.6". Cam was short but not too short. Again, time has erased the exact numbers but that spec undoubtedly came from the "How to Hot Rod SBC's. which was a racers bible at that time. No Vizard. I'll say one thing. For a late 70's street racer it won it's fair share of rolling start to the top of 2nd gear races.
Nothing quite like C.I.D.
It reminds me quite a bit of your build direction. I




Published in 1972! I just may get an e-bay copy.

 

I've been struggling with a wonky scanner so I've resorted to taking pictures of a few choice drawings.
Maybe there's something to be gleaned from these couple of pictures. What they show is the form targeted for chevy ports in general although there's a specific reference to those drawings in the 113 section.
More to follow...

 

My engine guy has been sending texts on techniques and targets.
If the interest is still there, I'll compile them into a word document and stick it here.

Here's another graph from Vizard ion the meantime.

 

Sorry for the slow reply! Been up in Banff since Friday, doing some of this:









Thanks again for posting more Vizard.

I can't tell which line is the "light blue" line and which is the dark blue? There is one blue line that is what I would call "blue" or "medium blue"....maybe the white line is the light blue line? If that is the case, that doesn't look good for my efforts!
I do not want to change valve size however, simply b/c that's going down a road that'll end up with $1000, $200 heads.

I'm still interested in reading whatever you're willing to share, though!

 

Saw this old article and thought of your build. Kind of interesting to see what John Lingenfelter was playing around with when these engines were new.

https://www.hotrod.com/features/tune...-982-1350-86-1

 

The factory valve size of 1.94 and 1.50 are not quite enough for performance that is why LPE chose to cut down 2.02, 1.60s down to 2.00 1.55 along with portwork, create that upgraded performance without a lot of extra tuning.

 

Great read. I liked the writing style too with the Dr/Patient angle.

One take away (for me) was the reference to the 113 heads and the work needed. This refers to Tom's endeavour specifically.
"Significant flow improvements can be realized by pocket porting the heads, port matching the intake, and cleaning up the "very poor" short-turn radii."
And the key take away from that quote is the short turn.
Combine that short turn work with the larger intake valve and you're on to something in my estimation. I do understand the hesitancy (Tom's) to not go for bigger valves though. It's that lipstick on a pig thing more than anything. Lipstick equaling the dollars needed to a new valve job.
I still haven't foun d the full story with Vizards 113 exercise. It would probably need his cylinder head mods book (which I don't have). I do have more from my engine guy that I've assembled into a single document but I think it might be a little disjointed as it came to came to me in bits of texts with references to drawings also sent. I'll post that up at some point.

 

Exactly. It seems that the number one thing to to do is increase the valve sizes. Followed in parallel with cleaning up the bowl and working the short side radius. I would imagine also that when installed on a 4.125" bore, there's a considerable unshrouding that could be done on the cylinder wall side of the combustion chamber.
A lot of work though considering you can buy (as an example) a pair of complete Chevy SB, 195 cc Intake Runner, 65cc Angle-Plug Chamber, 2.02 Intake Valve, 1.6 Exhaust Valve heads for about 1200 US bucks. I couldn't get a competition valve job (with the requisite new guides) for that kind of money!

 

You need more vertical!!

 

Fun reading that period, old timey stuff. I can't believe this, though!....



I'd have thought the thing would have done better on an engine dyno, than that. Weird order of mods, too. I was impressed that he got 27 hp from a ported stock base and runners....that's pretty good for no money. Slotting that value into my "10xthe tork take too" tests, it would have made 267 RWHP which is high value, and better than the Mini Ram.



Back to the heads. I've found a point of confusion. Most everywhere I've read that the Push Rod Pinch Point is not where to grind; little to no gains there. Also read above that the pinch point is offset by a taller port in that area. That could be true of the Pontiac head referenced above but it's not true of the Chev; the port-matched entrance is the same size as your intake manifold/runner. The pinch point is narrower but not taller, so that is a reduction in area. My throat is ~1.75" which is ~2.4 sq". The area of the port-matched entrance to the head is also, about 2.4sq". The area in the pinch point is only about 1.8sq"....so if our goal, is a "velocity stack"/tapered runner from the mouth of the runner in the intake, to the throat under the valve....the we got a pretty big problem at the pinch point, IMO. While it's not possible to get the pinch point to 2.4sq", I don't think....it's hard to understand how maximizing that space could be anything but beneficial. I'm measuring a wall thickness, after my porting, of about 3/16" at the pinch point on the pushrod side, so I could get after it more, right there..... Should I?

 

Regarding the pinch point: Typically in an SBC head, that's the pushrod area. Also called (as you know) the Minimum Cross Sectional Area and not to be confused with the actual throat which is the smallest area just below the valve seat. Wherever that lands.
The MCSA is totally dependent on engine bore, stroke and RPM desired.
http://www.wallaceracing.com/ca-calc.php
For a 4.125" x 3.75" engine wanting 5500 RPM, that pinch (below the gasket match) is about 2.02 sq. in. FTR: My heads are somewhat undersized at the pinch coming in at <1.9 sq. in. For the 357 to turn 6200 for peak HP RPM (although this cam is designed to extend beyond that for drag racing) I need more like 2 sq.in.
Working the SSR is the real bugger. Hard to do. Difficult to measure. But the results speak for themselves.

Wallace Racing MCSA calculator.
http://www.wallaceracing.com/ca-calc.php

 

Thanks for the additional posts, guys.


Ha ha ha...that wasn't bad there. Two days later, we skied an area at Sunshine Village, called Delirium Dive. I think ""delirium", b/c you have to be delirious to go into it? Anyway, it's a gated hike-to that requires beacon/shovel/probe and a knowledgable (about snow safety) partner. My best friend and I went into that, and that was where we found...."more vertical". It was the most intense terrain I've skied in years, maybe decades. STEEP, high exposure w/rock band/cliffs below aspect of the decent (no-fall, terrain), and it was long. Steep for a long way down. I'd guess about 1000' vert of persistent steep and rock band/cliffs. I was near my limit. We hiked out this ridge a little and skied off the looker's left shoulder of the ridge in the saddle....about where those ski tracks already are;




Second run, we dropped in here, just beyond where the dude in the blue jacket is....




Camera flattens out the slope, unfortunately, but I got one pic on the way down....








And we made it to the bottom w/o incident. What a rush.

 

I wish I had kept the pictures slotted in to the texts for better reference but here's what Magnotti has sent over the last couple of weeks.
Some pictures have been posted earlier. Bit of the text too but here's the whole works.

 

Makes my nose bleed just looking at it. I used to be an avid skier. Not a good one. But into it nonetheless. Those days, much like being a goalie (ice hockey) are long gone. That said, I may strap the boards on again and take my grandkids to the bunny hill in the local valley. As long as my medical insurance premiums are paid up!

 

Thanks! I don't think it's possible to get the large a radius out of this casting...but I'll go down the the shop now and play w/it a little. Do some CAD; Cardboard Aided Design.

 

Copy that....that is great info. I got some extra work to do there, then.

What is SSR?

 

Do it. Hell yes. You're grandkids will never forget that time w/you. Never. I haven't forgotten the runs that I made with my grandfather....some 50 years ago!

Watch this, if not the whole thing, relevant is at:
7:35-8:05
31:08-31:20
34:03-end.
92 years old...showing us how it's done. F-yeah. *I* love it!!

 

The way that article was written it seemed like it had 128 heads. They alluded to the improved heads which would be the 113s for the next model year in that article.

 

Short Side Radius.

 

One thing that didn't copy over from Steve's tutorial was the use of solder wire to copy the form of the short side radius. Doing that and you can see what you have and then using the templates, go for what you're after.
He just laid a length of 1/8" solder and pushed it around the arc. Knowing the target radius is literally a matter of cut and paste. Keep checking against the template and solder "molds". Something I was told that my own heads would benefit from.

 

I was going on this:
"According to Lingenfelter, the ports on the '87 aluminum heads are not as good as the previous cast-iron design."
Did I wrongly assume that these were 113's?

EDIT: It seems that I did. A quick question asked on the www and in 87 the Vette heads were indeed the 128's.
Seems though that the approach is largely the same. Bigger valves. Better valve job. Short side radius and bowl work get the job done.

 

Yes the head's in the article were different heads. 128, I have 113s. I made myself a little radius Checker and lo and behold, I was pretty damn close....

 

Anyone know what the benefits are, or opening up the area in the combustion chamber around the intake (or exhaust too, I guess)? 5 CFM? 15? Is it worth it? There is room....according to the gasket....

 

Just saw these that had the bowls cleaned up a bit. I have long been told the most important area of a cylinder head port job is roughly 1" on each side of the valve seat. Meaning the chamber side is equally important to getting airflow through the most restrictive area which is the valve curtain area.

 

The more I re-read what Steven has sent (and since posted here) the more complex I realize the short side radius to be. A template is a worthwhile tool to be sure.
I requested the solder wire picture be re-sent as I had deleted it from my phone. I not only received it but also another page worth of instructions and directions.

The pictures below correspond to various parts of Steven's tutorial.
I'll post the text later but for now, the pictures.



Solder showing the before and after forms. (I think these are from a Ford but the concept is the same.)




Template demonstrating the shape of roof and walls. Details in the text to follow.

 

The short answer is that there is low lift to be gained.
The long answer, as with all things related to porting, is that there are guidelines and it's not a case of if a little clearance is good then a lot of clearance is better.
Vizard has demonstrated this with a flow ball (a ball bearing welded to a length of welding rod or stiff wire) the ball being a specific diameter (I believe he used 1/4" in his example), and used that maintain a specific distance between the valve and the seat relative to the valve and the chamber wall.
The link below is from his head porting series. He does a deep dive into Vortecs as well as others. The flow ball trick and the whys and wherefores are in the 23 video playlist!

 

^^^ Exactly this ^^^

Like my heads, which also need attention, the ridge just beyond the top cut of the valve seat needs to be smoothed over and blended into the chamber.




It's of less importance on the exhaust side (something also supported by Weingartner) but any sharp edge should addressed regardless.
My heads are a disaster in this regard and should they come off again, I'll be fixing that.

Below is what I have to deal with...



Multiple ridges from various cutting exercises. Also demonstrated is the subpar valve job.
This how the heads looked after just being removed a couple of years ago. The most I did after that was clean them as going in with sanding rolls ran the risk of 1) changing the chamber volume and subsequently the compression ratio and possibly cam spec. 2) The possibility of skipping across the valve seat and then being forced into getting a new valve job. And that would be major bucks as I'd go for new guides and a competition oriented valve seat and back cut intakes. I wasn't prepared to do that then so they went right back on.