Evolution of Victor Gen 2 chamber

"Stuff" swirling around inside my quasi-empty head...

E Victor Gen 2 (72 cc advertised) chamber & seats OOB

Same heads w/ Brian at IMM's valve seat rework

Hughes CNC chamber modification, and my additional extending of the exhaust transition into the quench pad

Why do they leave all of those sharp edges?
It's the cheapest way to do it.

I wanted to clean up around the valve seats but never got too it or the chamber unshrouding

Here’s the “heads with valves” vs the “bare heads”.

With the bare heads the seats are left uncut.
The ID of the seats/diameter of the bowl where the relief cut ends/OD of the as delivered 45* angle that’s made into the seat insert:
In - 1.970/1.770/2.100
Ex - 1.575/1.420/1.700

They're kind of ugly either way... no magic wand is going to turn them into functional pieces, regardless.

Depends on what shape the burr is at the end of the wand.

My "wand" is made by Makita... but it's not magic.

Very curious to see how both style of chambers look after the new seats are cut... Feel free to post "after" pics, too.

Update: Not sure if Dwayne took any additional pics than the ones he sent me after the seat cutting was done, so I'll post what I received FWIW.

Two different views from the intake sides, showing both the "bare" 77919 head and the disassembled 77929 head together. They're not "identical", but there are less big differences in their appearance after the new seats. Dwayne also pointed out some things and recommended measuring same-position chambers on both heads to see how close -- or not -- they are.

This is a 35/45/60/75 seat config. I drove Dwayne (and myself) nutz going back and forth on angles, etc., until settling on this.

Exhaust seats for both heads.

Also, these seats aren't actually "finished" and will be given one final "touch" after the chamber work & porting is done. Dwayne suggested -- with good reason -- that I hold off on the final seat work and head surface milling until I've gotten past all my "Ooops!" and "Oh, sh!t!" moments working around the seats.

What was the bare head looks like the area around the seats in the chamber is more filled in.
As they are in those pics, the valve drop between the two heads is within a couple thou.

I know there are people thinking: "Big deal, it's just a valve job..."

Yes, yes it is.

However, there's been something of a learning curve w/ this style of head (Victors and the Procomp "clone"). Therefore, the goal w/ this set is to start off w/ the least amount of material removed from the as-cast chambers to have a basically "unmolested" chamber as a baseline.

Brad, are these a science experiment or actually going on your engine? I am wondering where your going with this?
It looks like on the previous heads, you have unshrouded the chamber to the gasket line. I have not found any mid to high flow gains by doing that, although I've never worked a set of Victors.
You can start conservatively by scribing the actual bore line onto the heads, the Victor chambers look small enough to try that.

This will be part science experiment AND the heads are expected to be used on a live engine. "When" depends upon which century they get finished.

Ideally, they'd be done in time to do a swap w/ the current heads on my RB 452 to see what's what. Otherwise, they'll be tested on my RB 451 build that will eventually replace the RB 452 that's been through multiple rebuilds / freshen-ups over the years.

The current heads' chambers being opened up to gasket line as shown is the result of Hughes Engines CNC chamber program, which I had Hughes do after getting the heads from Brian at IMM (member ou812).

I'd prefer to not have any overhang at all, if possible, but won't know how far to take it until I finally get around to porting & flow-testing. One hypothesis about why the current heads back up starting about .750" is because this CNC'd chamber program takes too much out between the intake valve and the adjacent bore, as well as removes too much material from the plug-side of the chamber (too concave). So, that's where the "science experiment" part of this factors in. Also, I've never notched the top of my blocks' bores, so maybe this is one of those scenarios where the head is "happier" if the chamber is pushed out a bit beyond the bore, as long as the bore is notched to eliminate the resulting ledge.

There are a couple of beliefs I've seen debated on engine tech forums such as SpeedTalk. One is (basically) that improving the area below the curve of the peak valve lift is the goal, even if the port stalls or backs up (flows less) at lifts higher than the cam being used. The other is that having a port that is more stable across the lift curve and continues to increase in flow well after the peak valve lift will help power across the RPM range, even if the flow #s that fall under the valve lift curve aren't as good as a head that fits into that first category.

My current head seems to fit pretty well into that first category w/ solid flow #s, but backs up starting around .100" above peak valve lift. My desire for the second set of heads is to come up w/ something that fits into that second category. An apples-to-apples comparison of both sets of heads would be very interesting... well, at least to a few(?) people.

At one time, I considered notching the bore fixture for my flow bench. My bore fixture has removeable sleeves from 4.100" to 4.500", so to gauge the effectiveness of bore notching, I compared the flow between a 4.350" and 4.500" bore on a well ported BB RPM head. This was a long time ago, but I was surprised to discover the large bore was worth nothing flow wise, at least on that head! So, I never notched my bore fixture.

I have also tried opening up the chambers similar to the Victors on the plug side, and again found little to nothing on an RPM style head.

Back in the bad old days of 516, 915, and 906 iron head porting, I subscribed to that first theory, mostly because I couldn't keep them from stalling at high lifts anyway! They still ran good for what they were.

Nowadays I'm all about consistent port areas and air speeds, which favors the latter theory. These heads run better, but they are higher flowing, better heads to start with.

Don't know about anybody else, but very interesting to me indeed! Reminds me of when I used to build in-line four drag bikes, I built two cylinder heads for a 1327cc GS Suzuki, one epoxied dump port style, and one tumble port. They each had their strengths, but the best head ended up being a hybrid of the two.

My next cylinder head project is a set of Stealths. A preliminary look reveals significant chamber shift, with some valves much more shrouded than others. Sounds like these are a prime candidate to duplicate your science experiment!

I'm going to notch the top of my flow bench fixture to have the option of testing both ways.

I notched mine many years ago & it did make a difference, I don't remember how much .