Chevrolet 235 12 Port Head

annd--- the basis for this is?

 

I don't have my books for record but compare
302 v8 ford-to-300 ford inline
283 chevy to a 292
You look at most of the inline engines and they have a long stroke and smaller bore. Heads on the older engines are the weakness. With the taller block the heads suffered with poor port angles. Most were 90 degrees to the valves. Anyone who has expearience with head porting knows what the "short side" of a port is. Well the 235 and 250 have a very poor short side. The 235 has real problems with exhaust valve shrouding.

I have to do a couple 235 engines in the next couple months. I have stared at the heads and I just want to cut holes in one and make new ports. Then I had anouther thought. I wonder how it would work to run a blower and swap the ports. Make the exhaust intake and the intake exhaust. On a blower motor it's good to have a free flowing exhaust. You would have that. Plus you would have the intake coming in right by the sparkplug. Sure the exhaust are pathetic, but just throw boost to it until it starts to ping and back it off. You may end up running 25psi boost before you have troubles. Biggest problem would be the cam.

 

Simese ports on the intake may preclude this free flowing requirement of swapping the ports.

I know of no-one doing this, so give it a go, and the get back to us, please.

 

The 235 exhaust valve sits in a pocket in the combustion chamber,not much room for anything bigger than the stock 1-1/2 inch valve .Running boost will see a lot of pressure cause of the poor breathing.And the intake side of the head has less coolant flow around it than the exhaust.
Like other vintage engines there are severe limitations to power even when supercharged.
Like the guys who splice together two V-8 heads for use on the 292 Chevy,maybe that's the answer.

 

It's that "laws of physics" thing - perhaps you've heard of it?

"Inline engines have more torque" is simply not true. It's entirely based on how the engine is designed, there is no inherent advantage to V, in-line, boxer, etc. that changes the power characteristics.
What they DO NOT have is torque at higher engine speed. That's called horsepower.
A V8 engine fitted with a 1 bbl, small cam, small valves, and small ports mysteriously becomes a "torque motor".

In a practical sense when someone remarks (every 5 seconds) about the power potential of some ancient of cast iron from 1956 is that "they produce a lot of torque",
No, they don't. They have a power curve biased to low speed power, because that's all they have. An engine with more cam, bigger ports etc. has reduced low speed power ("torque"), and greater high speed power regardless of V, in-line etc.

Small bore/long stroke engines don't develop more torque - they simply can't make as much peak power due to small valves and low maximum RPM, so (if properly designed) the port size etc. is suitable only for low to mid-range. Again: low speed power is all they have, and it's not based on the bore to stroke, V, in-line etc. That information was already discarded by engine developers in 1930.

 

Regarding the "law of physics thing"

Torque: product of force and the lever arm
Force: agent that results in accelerating or deforming an object
Horsepower: 745 Watts

I didnt make these definitions up - they came from the physics dictionary. So, it seems to me like long stroke indeed has something to do with developing more torque.

 

So, it seems to me like long stroke indeed has something to do with developing more torque.

Only if the bore is the same size.
And torque is also increased when the force applied (pressure to the piston surface area) is increased.

 

Good points panic. Air flow is critical for horsepower and torque. If an engine is starved for air and choked down it will not have power. I have a feeling that's why Colonel Ingus started this post, and others took intrest. To improve the performance of the stovebolt and still have an engine that looks "period". That's what the HAMB is all about.

 

I find making your own parts to be the pinnacle of hot rod work. Adapting a head from another engine is a huge project, and I applaud anyone brave enough to try it. I just try to offer comments where it looks like a bad path may be chosen (i.e., more work than it appears).
If you get past the "I can do surgery" part, chunks from a useful engine with as few as 1 or 2 chambers can be used (where the bore spacing error is less important) - it's just even more work.
The best possibility that's been offered so far is the comment as to similarity between a Buick V6 and the 235. Few auto makers throw away any tooling or fixtures, and it may not be coincidence if the bore centers are the same. Either the V6 or the Buick/Olds/Pontiac/Rover small V8 (215 etc.) are possible donors, but of course both heads have to be used in all cases and at least 1 welded joint. I suggested the Buick 300 or Rover V8 since aluminum is easier to weld, nice weight saving, and can be repaired without going back to square 1.

All that's really needed is a junk donor head (bad enough to band-saw up) to check for water, oil, bolts, blah. vs. the 235.
Even though cross-flow makes the manifolds much worse, it does provide a nice WOW. Although the max power will still be limited by the rods etc. the head should provide a big boost over anything that's been done to the 235.

 

Panic is right. Everything he said is true. I'm an engineer.

I thought the landcruiser motor was based on the later 6 cylinder. My father in law has one, a 68. All the cast dimensions were the standard, but all the fasteners were metric.

 

BTW I have an inline engine I shift at 8+. It's a 183cid (shudder) toyota engine, running 20# of boost. And it's in a 71 mustang.

 

something like this has crossed my mind before on siamese port engines, has anyone ever explored this? Hog the port hole out in the side of the head 'til you have a big oval, then put in your own port wall/divider to get the 6 intake ports?

 

I have a broken 848 head coming my way for just an evaluation....among other things. I think that there might be a possibility of striking water on several of the intake ports if you get too far off center. But in this day and time their isn't much that you can't make work with all little ingenuity and thought....

 

I'd be very interested in seeing what you come up with as far as the water passages, and port thicknesses are concerned.

I have had a good teacher discuss the fundamentals of porting the stock head, but the extra info would go down very well.

 

when talking about performance inlines there is one overriding factor on most of the mass produced american inlines and that is, they are 'built for torq' and 'thier rev,s are limited'. So even if you get a 4 valve pentroof superhetrodyne head you will be limited on rpms and havto overcome that factor. The straight 8 Bugatti,s solved that problem by taking the drive off the center main of the crank, thus splitting it into two 4 cylinder crankshafts. Also there is another factor thats involved and thats each rod has its own crankpin, thereby relieving it of any drag by another cylinder. and also specifically 6 cylinder inlines are inherantly balanced, which V6,s arent. theres no question that the manufacturers are going back to inline power and for a reason.

 

mopar, this has been done on the 250/292 chevy 6 and according to Leo Santucci,s , chevy 6 hi performance book an experimental head with the 6 individual intake ports had less power than the siamese'd ported heads. the siamese'd ports did pretty well with a 'lump ported head'. the welded up V8 heads are the way to go and you can get them in aluminum. its all in the book.

 

There is one thing you need to remember when concidering a siamese port. You have the valve opening once every two revolutions. I don't think a flowbench or anything could really explain what is going on in that port. The way I look at it would be the saimese ports have an advantage, they keep the air flowing helping volocity. on the 235 and any siamese port I think (with nothing to back it up) the best you can do is direct the flow to add swirl or turbulence to the mixture entering the port or bowl area.

To be blunt the heads on the stovebolt are fustrating. I'm a kid yet at 40. I've hopped up plenty of V-8's in my day and understand what it takes to make serious horsepower. This 235 head, It's like marrying a fat lady expecting her to change into a super-model in a year. Sorry if I offended anybody it's fustrating.

I would like an explaination why nobody makes a 12 port head aftermarket today, or do they? SBC aluminum heads are cheap enough. I know it's because of production numbers, supply and demand, development & cost of the molds etc.... It can not be because someone has patent rights. They expire, and it's to easy to get around. I would think people building these would step up and spend the $$$$.

Adapting a v-8 or a v-6 head would get power if it was an option, but then it wouldn't have the vintage look. I think that's what most of the people running these engines are after I think.

 

Doesn't Fontana make the Fisher head for Chevies? If a 12 port is all you want (as opposed to adapting a production head to a 235 etc.) they have been offered before. Finding one is the only problem.

If you had the later motor Sissel makes a 12 port for that (but it's not cross flow).

 

Racers have De-Siamesed Ports and found enough Power to get De-Siamesing outlawed in certain Racing Classes.

It places two Valves really close together ( much less port length than what a good tuned Port Length would be )
And they are usually not spaced a full rotation apart ( which would give a even spacing of the pulses )

One of my Favorite Engines has Siamesed Intake Ports.
But Siamesing Ports is still a Crappy way of doing things, IMO.

I cant think of any reason to do this, except for cutting production costs ( and maybe squeezing in a Port where there is no room for 2 )

 

I think there are a couple of things to look at relative to the end ports of these engines (fireing order, fuel delivery and cam timing).

The end cyls. have a uneven fireing pattern. There is a short then long spacing in the order of happenings that doesn't make for good air flow. It also does funny things to the A/F mixture (rich, lean) of these cyls. The first cyl. in the order gets a good A/F mixture, while the second is a little on the lean side do to port robing by the first cyl.. There is not enough time to refill the port properly between these happenings. Center cyls., No Problem, better pulse spaceing.

There has been some work done by people out there on the cam timeing thing to try to improve this problem. Although no one at this time will come forward with any solid info. on what works and what doesn't, it has been said that that progress has been made in the lift (area under the curve) of the second happening in this cycle.

Just some food for thought. What say you?

 

Absolutely Stovebolt, I will be glad to share any and all results with you that I discover. If you have any ideas on other things you want me to check or investigate while I am cutting, sawing, milling and sectioning this head, just let me know as well. I'll even send or post pics if you would like. Thanks for the interest and response....

 

Yes, you are correct about Fontana producing a 12 port for the 235, im not sure of its origin, but its on their website and looks pretty sweet! Also in the mid-80's, a company called Duggan also made a head for the 250/292 late engines also, I think they were based in Australia. Dont know if they are still around, or if that is how Sissel has theirs.Maybe they merged or he bought them out??

 

"why nobody makes a 12 port head aftermarket today"

Only 1 reason: not enough volume × purchase price to make it a sound business decision.
10 heads is $$$$$$$$$$$$, billet CAD/CAM is cheaper than casting
100 heads is only a bad idea that will take several years to make and several more to get your money back - after that some profit
1000 heads = Vic Edelbrock

 

Fontana producing a 12 port for the 235

Nothing on their site but the GMC head.

 

Yes, some very serious research work has been done to engines with siamese intake ports.
Read Vizard's book on the Mini.

 

Sorry, my bad....I remembered seeing it some time back and just remembered the 12 port head and not realizing it was for the GMC instead of the 235!

 

I cant think of any reason to do this, except for cutting production costs ( and maybe squeezing in a Port where there is no room for 2 )[/quote] Well, you have to think that back in the early 1930's when these engines and other similar manufactorers were developing them, that engines in general were a new concept in the industry. They didn't have but just a few dozen years of experience to draw from to know how to make better changes for power and other changes that the public wanted. If the Wayne head hadn't have boosted the interest in the inlines in the late 30's and early 40's when it was concieved, other heads for those engines such as the Fisher, Horning and some others may never have been created at all either. They truly are an improvement over the siamese production head. But also, guys like Ferguson have had incredible success even with them as well as the 12 port.....

 

A well known Inliners International member and I went to Duggans a few years ago, whilst he was out here visiting. boy was that a great day!!!

Frank Duggan sold all his stuff to Kay Sissell - all except for a prototype engine he was building, and it made 400hp out of a 292, bloody brilliant. We saw the SBC heads he made too, as well as the twin turbo SBC setup going into one of his sones Mazde RX3's

Unfortunatley Frank wasn't there that day, but his son had a wealth of knowledge he imparted upon us.

 

Anyone got access to a Nicson head for the 216 - it had different combustion chambers to the stock head, and may be the first place to look when figuring out a better head for the 235/261 - repop this and all you have to make is the head, and not the valves, rockers, valve cover. and.....