Inliners International Forums General Discussion Hi Performance 12 port

Anyone interested in a Arias/Howard GMC 302 12 port solid head.

Like the old saying goes..."if you have to ask , you can't afford it"
I have to ask though , what are the details?

Would love to find a 12 Port Chevy head.....

They're out there, but there are many that won't help.
Many were only made for 15 bolt blocks.
Both iron and aluminum.
Some can use a reground or aftermarket stock cam, some need a billet cam.
Both manifolds are very tough to find and identify.
Head gasket?
Some have 12 ports, but the chamber was obsolete 80 years ago, and need $$$ pistons for any compression.
Any aluminum part may have corrosion damage.

$5,000 will get you started

Let me expand on that thought.
Of all the 12 port heads made back in the day, not one uses current varieties of chamber design, given here in order of technology:
1. 4 valve, pent roof
2. hemi
3. multi-angle, quench (BBC, Cleveland, 429)
4. wedge, closed chamber, parallel valves, quench (almost everything else from 1955-70)

This means that an engine built using these heads will produce less power than any modern design (Atlas, Barra, 2JZ, Ford 300).

So where does this reasoning stop? One can buy a Tesla electric motor with SBC motor mounts and a Spicer universal joint hookup . . .
https://www.autoblog.com/2020/10/02/ev-west-tesla-motor-conversion-chevy-ls-sbc-mount/

People build to a period; a dream; a desire. To each his own. So be it.

Sorry, it's not reasoning. I confined my remarks to "what can be done to a Chevrolet engine", not "what other engines can fit a Chevrolet".
I hate to see owners viewing 80 year old $5,000 parts as rocket science that will get another 100 hp out of their 235.

This is why we need a NEW speed manual about these old Chevy & GMC sixes. A lot of new tech has come along since 1954. I know they won't compete with the 4200 but they can do better. When California Bill's nook was written small block Chevys didn't exist so neither did the valves & springs commonly used today.

The paths diverge.
The 235 is more popular, cheaper, more spares available, fits cars up to 1962.
The GMC (at least the 270 and 302) have more potential, good position for XO with a 325" limit. No auto installs without mods.
The lower ends are almost identical as to design and function, but the heads are completely different.
We still have no clues on a possible 235 "hybrid" head. Santucci had a running start because both the 292 and SBC have the same bore pitch.
IMHO there is still no market volume for complex $$$ speed equipment (there is still no Ford 300 alloy head), few owners have that big a hit in their budget.
A modified 235 can be much faster, certainly faster than the mods of 1955, but the car is still not fast compared o street cars today.
The 235 cam is too close to the rod path to make the rod or stroke much longer (the 250, 292 cam is moved out of the way).

What would you buy if available?

So they won't out run a new Honda, we should just $#!% can the whole thing.What's the point?

I think much of the problem with the Stovebolt was the fact that for the time, the GMC offered many advantages over it. The GMC had a better platform to build on with the 270 and 302 with more cubic inch. It was a fairly easy swap into Chevy cars and trucks. The GMC had full flow oiling on all its engines since they were created, while the Stovebolt had Babbitt rods until 1953 and after that finally offered a full flow design. But by then the V8 Chevy was right around the corner and the interest in inlines soon shifted to V8's.

What I think is "asleep at the switch" is that the GMC made 4 different heads, and all bad.
Even if keeping the siamese ports and same manifolds, a new head using the 1949 chamber design (Cadillac 331, Olds 303 with closed quench chamber, angled & parallel valves) would have improved power and mileage. None of the GMC 12 port heads do this AFAIK.

These are the kinds of ideas that need to be discussed and gathered. So much has changed since the last book was written about these engines. Even if they will never again set real world records there are plenty of places where they can compete successfully and getting more from them is fun. Expensive but fun. Fun is reason enough it does not have to be reasonable or financially sound.

I personally don't care about the actual speed/performance. I am into inline 6's for the sweet sounds they make,and am even weird enough I am into Ford flat 6's. Have a finned aluminum head and a 3x1 intake to put in the flat 6 in my 51 business coupe,and am looking for a set of cast iron headers and a street cam that is a little "rumpy".

My left leg is now useless due to cancer,so I am going to put a FOM in it. Bought one last summer from a guy that claims he pulled it out of a 51 he used to drive years ago and totaled,and got it all,from the flex plate to the driveshaft. Waiting to recover a little better before I start work on it.

If I am unable to work on it this summer,I will pay someone else to do it. I already have a stock 51 Victoria with a stock FOM and flat V-8 in it that I can drive anytime I want,but it ain't the flat 6 hot rod business coupe of my dreams.

Not selling the Vicky until I get the coupe back on the road,though.

AND.......,once I do get it back on the road I flat do NOT care if some new OHC cylinder economy car is faster than my coupe. There is nothing the owner can do to make it sound as cool as my coupe will sound,or look as classy rolling down the road.

I build and work on cars to please ME. If they also happen to please someone else,it makes me happy to talk about it with them. If not,I honestly don't care.

I think some of you would be dismayed at the expectation expressed (Jalopy Journal, etc.) as to how much power will be added to a 235 by a 12 port head. I've seen guesstimates as high as 100 hp, with no details as to what other mods done.
Do a search, you'll see that the to-do list includes
high compression pistons (no ratio given, dome shape unknown, $$)
3/4 cam (I need not elaborate, meaningless)
high ratio rocker arms (no such thing exists currently TIKO)
individual manifolds (made to order)
magneto (because they used one in 1948)
tuned exhaust (made to order)
fully balanced (as opposed to)
H beam connecting rods (source, length, pin size?)

Note NO specifics, no dimensions, no data, just categories.

I applaud and encourage ANYONE modifying an obsolete engine because they want to.

I'm slowly accumulating a future article or book (depending on demand) on L6 flathead engines, including, Chrysler Spitfire, PlyDo, Pontiac 239, Hudson, Studebaker, Rambler, Olds. The block itself is remarkably similar in design with each other, and with OHV engines of the same period.

You are right panic, a lot of secondary parts and mods are required. Plus, depending on the era of 235 you choose, the early 15 bolt blocks are also babbitted and were usually subject to the GMC rod swap along with converting the block to full flow oiling.

Just out of curiousity,and because I have been missing from this board for a long time and missed any possible discussions about them,what do yall think about the 292 Chebby and the 302 GMC inline 6's?

I remember seeing a few "back in the day" that were stuffed into stuff like 38 Chevy coupes that would FLY. Granted,these were dedicated drag cars with mucho unknown to me modifications,but I am thinking this would still be a sweet combination for a moderately hot street car. Plus it would be different and sound different than all the cookie-cutter 350 smc crap.

Yeah,it would be cool to find and use one of the old 12 port heads and other serious drag parts that used to be readily available,but I am thinking you could still build a fast and fun driver today without having to go crazy spending money. These and the Ford 300 inline 6 Ford make plenty of torque and horsepower for a hot rod daily driver,and it might even be more fun to put a 300 Ford in a Chevy and a 292 or 302 GM in a Ford.

I know the 292's and especially the 302's and speed equipment for tnem are getting hard to find these days,but it's still possible to get lucky. While they are harder to find these days,there are a lot fewer people looking to buy them.

The SCTA rules separate 302 (pre-1956) from 292 (post) because the power potential difference is large.
The Ford 300 leads the pack (which includes AMC 258) in max power, speed equipment is available.
I'd like to see one of the bigger Japanese L6 engines converted to distributor and carburetor. Even the little (183") Toyota 2JZ is 225 hp in stock form. The 273" FZ is cheap in JY, the Nissan TB is 290".
I know, the V6s are hotter, but they look wrong (to me) and sound terrible!

Sometimes playing with & adding to history is more appealing than climbing on the newer tech wagon. There is value in the visual and there is comfort in memories. My 270 will go faster than I need it to.

Not to be a complete trouble maker, but shouldn't a moderator move this discussion out of the Swap Meet? LOL!

I"m really starting to like this place and how laid back it is.

Carry on...

The 12 Port Head design was first on the drawing board in 1939. As panic pointed out, there were other better combustion chamber designs already being used by other manufacturers, but whether Wayne or Horning actually realized those other designs were better, they for some reason created the 12 Port head in the open chamber style design. If a modern approach was put on that head today, it would likely be capable of much higher power levels similar to a Sissell or Duggan 12 Port head.

If a modern approach was put on that head today, it would likely be capable of much higher power levels similar to a Sissell or Duggan 12 Port head.

This^^^!

Can anyone here share any images of the Kirby-Sissell and/or Duggan combustion chambers?

I don't have them, but it's a closed wedge (like 100 other designs) like to the SBC, with the outline of the open area modified.
They may not be nearly as good as the LS, although the shapes are similar.

I owned the casting patterns for one version of the Duggan head and Sissell ended up with the other one. I'll dig through my pics and post some.

Here is a pic of a Duggan older design head. It used shaft mount rockers and a canted valve arrangement. will see if i can also get some of a newer Deppe head. The cost of professionally designed and casting a New head is about 100K.
And pic of a Sissell street head also a 12port with a straight valve arrangement

The chamber reliefs leaving the seats are a big improvement, the pattern is based on how flow leave/enters the valve curtain and runner. Probably not possible to older (smaller, more regular) chambers without hitting water, etc.

tlowe,

Wow! Thank you for posting those. What an improvement. I could see a chamber design like the ones shared so far really helping even the mild street engine. The Sissell chamber has what looks like a "Fast Burn" design to it.

So I guess I can add my name to the list of people who wishes someone could come up with a more modern and cost effective cylinder head. The Sissell "Street Head" at $3500 is not a bad price. Just too rich for my pockets.

I have seen some interesting heads produced in two pieces on CNC machines. This would skip the whole foundry thing and allow for some pretty cheap production. Of course the heads I've seen were for flathead engines that don't have the ports or valve train. Someone with a 3-D printer will step up and print patterns for a lost wax/plastic casting. It would not take a huge foundry to pour a head. If you can think it you can print it.

Due to low production volume, they have to amortize their R&D costs ($$$) over a small number of sales, hence the price.
You're paying for his development of the head to produce power, hold the gaskets, not overheat or leak water, minimal port to port flow differences, not just a product.
Making a head in house is only Step 2.
Do you really want to do flow bench, then dyno on a fresh engine back-to-back to see if it works?
No one gets it right the first time. Look at the list of 235 factory heads.

Beater, this is a multi stepped process to complete. First, it requires 3D software to create a model to then import into either the 3D printer or CNC mill. So that usually requires involving numerous people into the equation which increases costs. I have both, 3D software(Solidworks)and a CNC. But then, it requires a CAM package to create the CNC program, which I also have. So in my case, all that can be done in house, while others may only have one part of the puzzle.

But I think any head you made in a 12 Port configuration would be a vast improvement over the stock siamese Stovebolt head, and maybe better that the Wayne or Horning heads just by virtue of incorporating modern thinking into the design.

Yeah Scott, I know it's not line printing a plastic wrench but I know it could be done in a way to make small runs attractive. Going back to tweak a computer program would be much easier than creating a whole net set of patterns if updates were needed. My son and a couple of his friends have the capability but are otherwise involved right now. They don't owe me enough yet.

The part with the largest "luck" component is the creation of the flow path (position, size, shape, intake/exhaust bias). Intake port face > runner > bowl > valve seat > chamber > valve seat > bowl > runner > exhaust port face
Many failures, few successes, and no explanation of why: LS, 2JZ work far better than their designers' expectations.

Here is the 8 port head, the 12 Port's baby brother. It has an inline valve configuration.

There are MANY companies now that can directly 3D Print both the sand cores and sand molds. You assemble the printings and pour!

Here is one of many:

https://hoosierpattern.com/additive-manufacturing/3d-sand-printing

Neither Chevrolet nor Toyota anticipated the finished product.
Toyota, so far, has been unable to duplicate any features of the 2JZ with the same results.
Those heads produce power disproportionate to their flow bench testing.

Not all that long ago, the Chevrolet "W" engine (348, 409, 427), and Ford MEL (Mercury, Edsel, Lincoln 383, 410, 430, 462) were thought to be leaps into the future, consuming millions in development, and both failed.

Before spending tens of thousands of dollars, how do you know how your model will behave?

Advanced 3D modeling software such as Solidworks can perform stress analysis simulations as well as FEA simulations to highlight issues that may be in flow paths, and can even approximate flow rates in ports based on size and shape and other parameters embedded into the model. It also allows you to create assemblies from numerous parts you created, like a complete engine and show simulations of all the parts moving together to evaluate stress in the individual parts and as a complete assembly. Other 3D modeling software can as well, but Solidworks is an engineering standard for 3D modeling software the world over. My package cost a little over $20K 15 years ago, if that gives you an idea about its capabilities.

Here's a 3D model I made with my 3D printer I had about 7 years ago before I started getting them cast. This is just one section of the triple side draft 6 cylinder intake. I also cast a 4 cylinder version as well. No flanges were added, I did them separately, but just this piece took 8 hours to print.

At the time of his passing John Erb was working on a new Studebaker V8 head that he described to me as Studebaker on the outside and LS on the inside. He owned the patterns for Lionel Stones R3 heads and knew why they didn't work. I hope someone carries on with that.