The Stovebolt Site Forums The Shop Area Engine Shop Replacement Cylinder Head- 55.2 235

More changes = more power = more money = fewer sales.
A stock replacement head with only a small compression increase will add very little power.

It will have more than compression improvements added to it that will boost its power potential, and they won't add any more cost to the development of it, or the final cost of it. With this cylinder head, the design engineer, the CAD draftsman, the CAM programmer, the patternmaker, the foundry man and the machinist are all the same person....me! With a large company like Brodix or World Products, it takes close to a dozen people to do the same thing, so yes, any small change can snowball into more cost because it requires so many different people to have to do more work to make the change.

12 Port-

As long as you don't develop a hexa-polar disorder, that is a very good point about minimalizing costs, and where those development costs are usually incurred. Production tasks cost money- plain and simple.

Once you get the pencil on paper and rough-order magnitude of the project, there should be a decent amount of support from here and elsewhere.

In reviewing several material change projects over the past three years, there is one huge factor that is probably on your side that you didn't mention- time. In every one of those projects, more often than not the desire (or requirement) to have a component ready for 'plug & play' application on a set date accelerated each of the duties of the team members. This can create more than one "snowball" to keep in check.

I already know my answer to this question, but it is also thought provoking: At what point would a cylinder head 'redesign' or 'modification' totally reconfigure the engine's specifications to the point that it is no longer considered the same engine? My question is subjective, I think it's an eye-of-beholder scenario, and I'm not really sure except to re-phrase it as, "will these hypothetical cylinder heads, if installed, make the engine not be a Stovebolt 235?"

Whatever the thoughts are, the fact still remains that good OEM cylinder heads are becoming harder and harder to find. I think you're on the right track.

Brad

Claude, I keep going back to the GMC engine and all the similarities it shares with the Stovebolt. If you saw the two of them a few feet apart with only the long blocks being visible, at first blush one would have to study them over a bit to tell which was which. Especially if the GMC engine didn't have the valve cover on it that says "GMC". I've ported a few GMC heads for some nostalgia racer guys and they have done some impressive things with them. The same mods performed to a Stovebolt head just wouldn't yield near the same results.

So my solution would be to blend the better attributes of the GMC head, which would be its intake and exhaust ports, and merge them with the Stovebolt head footprint yielding the same Stovebolt look, and allowing it to retain the common intake, exhaust and valve cover it already has. Then tweak the chamber design and voila!

That would be my plan of attack initially, and if any revisions need to be made afterward, then they would be addressed at that time to fine tune the design.

So back to your original question about the point at which you loose the Stovebolt look. From the aesthetic standpoint, a head with the GMC ports in it will fool anyone looking at it, other than the fact its aluminum. For those seeking to go above and beyond and desire a 12 Port head, then maybe at that point you will lose some of the nostalgic look of it because you will then have a crossflow design head and more racy looking accessories that may stray from the original. So maybe at that point it will.

Now you don't have a replacement head, you have a replacement head and a new manifold, which (I'm guessing) does not exist yet. The current GMC manifolds have the new port size, but unless you want to re-align at least 2 ports it won't fit the head. The 1st to last cylinder center distances are 21-5/16" (235) and 22-1/4" (302).
I agree that the GMC head is an improvement, but not compared to anything 1955-*. The original 12 port heads are retro vs. the better OEM engines of that time.
The "tweak" I recommend is what has already been done many times: make a wedge out of it, and use SBC parts.

There's also a latin phrase that I believe applies here: materiem superabat opus.

It would retain the original Stovebolt port spacings on both the intake and exhaust ports. Also, the ports don't have to be as large as the 302 head to be an improvement. The fact that the GMC has a "Y" shaped intake port runner over the Stovebolt's "T" shaped port is a huge flow improvement by itself. And yes, a modern heart-shaped wedge chamber is planned. I already have posted pics of a 3D model and a prototype already machined for my 12 Port Head patterns on a couple of other forums. A new intake manifold is also not out of the question either if needed, I have already designed and made patterns to cast a new 2 bbl intake for the Chevy 194-292 engines. Those pics are also posted on several other inline forums as well.
Chamber

Intake

The 2 brl manifold for the 194-292 engines. Does it work with the stock exhaust manifold? Might be something to consider for t5he 230 in the Nova...... What 2 brl is recommended to use with it?

John

the GMC has a "Y" shaped intake port runner over the Stovebolt's "T" shaped port is a huge flow improvement

I agree - that's a big step.

Another mod that's easy to do, and nice to have: increase the ID of the pushrod clearance holes so that 3/8" OD clears.

If the head thickness (top to bottom) should resemble the 235, you have about 1" of extra valve stem height that allows you to raise the entire port wall and make the ports downdraft.

The carb for this manifold is the Rochester 2gc. I actually had a lot of guys with the 194 and 230 engines want something a little more suited for the smaller cubic inch engines that were more to the stock side than heavily modified. But its still right at home on the 250's and 292's also. And some just weren't comfortable jumping all the way to a 4 bbl and still wanted good low speed driving manners. It will be water heated, and is intended to work with stock exhaust manifolds. Some road testing is still needed to see that it fits all the parameters it was designed for.

So it doesn't pickup it heat for the carb from the heat riser in the exhaust manifold?? I wonder if there would be problems working the Powerglide with a 2 brl?

John

No, its common for all aftermarket intakes like Clifford and Offy to have a plate that attaches to the bottom of the intake to be plumbed for water to heat it. Shouldn't be any issues regardless of the carb used to operate in conjunction with the Powerglide.

Fenton headers have ports,one in each header,for heating the (stock) manifold,but 12 Port's correct. Water heat is more efficient than exhaust heat. Very interesting thread!! THANK you,12 Port!!

While we're on the subject,would it be possible to incorporate the steam holes,(261), passages, into the "mass-produced" larger-market 235 heads?? Just throwin'it out there,for us that own 261's. Thanks!!

If using the Fenton's, the buyer could determine if they preferred water of exhaust to plumb into the plate. The steam holes could also be an option that could be performed at the time of purchase for the 261 guys.

The source of heat for the intake manifold is a personal preference - but, heat is necessary in almost all situations (at least, on my engines, where I live/drive).

I have used coolant heat and exhaust header heat (all with Fentons) - they both work fine. I now use Fenton exhaust header heat because it heats more quickly and I do not ever have to worry about coolant leaks.

Regarding the need/use for the extra coolant passages in a 235 head to match the coolant passages in the 261: someone has posted a link to how to drill these holes in the 235 head.

http://www.inliners.org/ubbthreads/ubbthreads.php?ubb=showflat&Number=51987