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#92693 - 10/17/17 11:40 AM Can I divide my head for six injectors on a 235?
Larry Callahan Offline
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Will this work or am I missing something? I am new to this engine so I could use some help.

I am modernizing my 235 in my '55 Bel Air. The end goal is to make it look like GM made it today.

I have installed a T5 and now it's time to work on the engine.

I picked up a Clifford intake and a set of Williams cast exhaust manifolds.

Can I divide the intake ports and put 6 fuel injectors on the intake?

Does anyone make dividers or do I need to make them myself if it's possible?

My plan is to use the Holley EFI elbow with a GM throttle body and throttle by wire using a Holley Dominator ECU.

I have already ditched the distributor for indavidual coils and a crank trigger also by Holley.

I also plan to add a little boost with a turbo and I am working on a serpentine pulley system. Nothing crazy as I know the rods won't hold up and are like a mile long.

My day job is at an aerospace machine shop so the machine work and welding does not worry me.

Thanks everyone for the help

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#92694 - 10/17/17 12:53 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
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That is a fairly tricky issue. At one time Algon made a three port mechanical injector. They are very very rare. One of the older inliners owned one and may still own it. I understand that it was a tricky business because of the Siamese intake ports. There were injectors made for the 12 port heads but those heads had individual intake ports designed into the head. Trying to divide the intake ports on a stock 235 head is equally tricky. First, the intake port itself was designed so that the entire port would be used when each of the paired cylinders was on its individual intake stroke. So if all you do is divide them, you are reducing the overall volume of the port. So you would have to somehow enlarge the intake ports after they are divided. As to the division, if you try to make a divided rectangle or oval on the stock intake/exhaust side of the head, you will likely hit a water jacket or two. May be resolvable with the kind of welding you have access to. You might also be able to do it easier by dividing the intake runner and port, (so that one cylinder uses the stock intake runner) then install an additional intake runner through the top of the head for the other newly divided chamber like the Palomino head. You will still, however, have to enlarge the actual ports to gain enough volume. Another approach would be to use the exhaust ports as the intake ports, enlarge and divide the center siamesed exhaust ports, then use the intake as the exhaust port, adding an additional exhaust outlet through the top of the head like the Palomino heads did except those heads used the new tubes through the top of the head for an additional intake)so that you have sufficient exhaust volume. again, a great deal of welding involved. I am sure there are other approaches. I used to have these conversations with Charlie Baker prior to his death. We even talked about whether a land rover head would swap over. We eventually agreed that there was no truly easy solution or approach but you never know, there are much cleverer minds around then mine, lol.


Edited by mdonohue05 (10/17/17 01:01 PM)

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#92695 - 10/17/17 03:59 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
panic Offline
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The existing intake port is too small.
Dividing them makes them half of too small.

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#92697 - 10/18/17 04:05 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
70Nova Offline
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just a thought... why not have two injectors per intake port, only one would fire at a time, but you would be able to use a normal 6 cyl controller firing in the correct firing order. The port/chamber doesn't know or care where the fuel is coming from. Fuel is fuel whether it came from a carburetor 12 inches away or an injector 2 inches away. You would gain better metering and atomization. You could even aim the injector towards the port you want to feed. The two intake valves in the shared port are not open at the same time.

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#92699 - 10/18/17 06:40 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
THE FRENCHTOWN FLYER Offline
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I've seen this done on home built intakes. My only reservation would be that I have read somewhere that the siamesed port tends to favor the first of the siamesed cylinders in terms of fuel biasing, leaving the second one on the lean side. I am sure your idea will work, but from an optimum standpoint it may be feasible to individually tailor each injector pulse width, as some of the more sophisticated drivers can do.
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#92701 - 10/18/17 07:40 AM Re: Can I divide my head for six injectors on a 235? [Re: THE FRENCHTOWN FLYER]
stock49 Offline

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Originally Posted By: THE FRENCHTOWN FLYER
My only reservation would be that I have read somewhere that the siamesed port tends to favor the first of the siamesed cylinders in terms of fuel biasing, leaving the second one on the lean side.


I've read the same - but it was in the context of an I4 The MG Experience where the sequential firing order 1-3-4-2 causes a lean condition in 2 cylinders as RPM rises.

With the distance-between and sequence-of firings in an I6 the effect is likely less pronounced.

Perhaps someone can speak from experience.

regards,
stock49

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#92706 - 10/18/17 11:00 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
panic Offline
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The sequence in the 1-2 and 5-6 pair is highly offset: 240-480-240.
Only the center 3-4 pair has regular 360-360 firing.
Even 3 X 1 carburetors such as the Jaguar 3.8 etc. require different jetting between the end and center SUs.

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#92708 - 10/18/17 11:25 AM Re: Can I divide my head for six injectors on a 235? [Re: panic]
stock49 Offline

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Originally Posted By: panic
Even 3 X 1 carburetors such as the Jaguar 3.8 etc. require different jetting between the end and center SUs.


That's interesting. The triple Carter YH setup on the corvette used three identical carbs with the same jetting.

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#92709 - 10/18/17 12:49 PM Re: Can I divide my head for six injectors on a 235? [Re: stock49]
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The Jag isn't siamese port either, so it may be an apple to oranges comparison to these engines.
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#92715 - 10/18/17 04:59 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
panic Offline
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But the ports are siamese as far as the carburetors go.

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#92744 - 10/24/17 11:40 AM Re: Can I divide my head for six injectors on a 235? [Re: panic]
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these same jetting differences occur with the Bristol engined A/C cars too (The Bristol engine was a Siamese ported six cylinder engine also)--Panic--check it out in a '62, or '68 edition of Philip Smith's book "
The scientific design of intake & exhaust systems" --Stock 49--I believe Bristol's jetting differences were only to the order of about 0.003" between the end carbs vs. the middle carb--so perhaps in the rpm range touched by these motors GM, with the Corvette, chose the more economic route of not having to deal with multiple different carburetors for a very low volume production run (but I'm not opposed of stealing knowledge gained by a competitor!)...playing fair is square!


Edited by preacher-no choir (10/24/17 12:03 PM)

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#92745 - 10/24/17 05:17 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
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A better way is to run a GM TBI off of a 4.3 or 305. This way you get the same fuel distribution as a carb. without the flow sensitivity. If you are ok with making a wiring harness then suggest looking at megasquirt 2 - its runs a TBI no problem and a lot less $ than a holley box.
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#92746 - 10/25/17 06:22 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
THE FRENCHTOWN FLYER Offline
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I never did like TBI in general. I'll explain why. You can discount my experience, since there are many cars running around with a TBI and they seem to function OK, but there is a reason TBI was short-lived and replaced with the more complex, more expensive multi port EFI systems.

The injectors are designed to have a conical spray pattern such that most of the fuel is in the outer ring of the cone and delivered to the outer periphery of the throttle plates where the shearing action of the airflow helps to further break up and disperse the fuel droplets coming from the injectors mounted above the throttle plates. All well and good at low throttle openings. At high airflow like WOT the air velocity "pulls" the conical pattern down, compressing it into a more "pencil-like" stream centered in the middle of the throttle body bore. Again, no problem, if you are at WOT. The pencil stream hits the opened throttle blade(s) and gets dispersed into the intake manifold. The problem is when the throttle is near to WOT but not all the way there. At that condition there is still enough airflow to pull the conical spray down into a pencil-like stream, BUT, since the throttle is slightly closed the stream impinges onto the top of the plate, gets deflected by the plate (in the case of the 2V-V6 engine I was dyno testing) and most of the fuel gets diverted into the cylinders at the rear of the engine. I noticed at 90% of throttle opening the air/fuel ratios on each individual cylinder varied by as much as five air/fuel ratios! That means a rear cylinder had a A/F ratio of, say, 10:1 while a front cylinder had a ratio of 15:1 at the same time. I confirmed my A/F readings by taking high speed movies of the injectors on a running engine.

Like I said, many cars are using TBI, and it was definitely a step up from the problems associated with a carburetor, but if you are going to go with a computer controlled system why not get one (multi-port) that functions well - under all conditions.
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#92757 - 10/25/17 02:30 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
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^^^^^^^ this above info is great to know. just wondering if the body can be rotated and the primary and secondaries run sideways and not front to back would this still be an issue?
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#92759 - 10/25/17 05:53 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
panic Offline
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I agree, TBI manifolds were developed to minimize these problems and adapting one to a carburetor-based design may not be satisfactory.

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#92769 - 10/25/17 09:11 PM Re: Can I divide my head for six injectors on a 235? [Re: THE FRENCHTOWN FLYER]
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Originally Posted By: THE FRENCHTOWN FLYER
SNIP
Like I said, many cars are using TBI, and it was definitely a step up from the problems associated with a carburetor, but if you are going to go with a computer controlled system why not get one (multi-port) that functions well - under all conditions.


Main reason to run TBI is you avoid the tough fuel distribution issues when running a simeazed intake port. With port injection 1 of the pair will run lean.
The engine "sees" the TBI with its central fuel metering like a carb.
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#92771 - 10/26/17 07:04 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
70Nova Offline
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Anyone have any data of how a stock 250 family engine distributes fuel? Individual exhaust port mixture or exhaust temp. Would be interesting to see how close they are. Pricey... 6 egt probes or O2 sensors and a way to read them simultaneously laugh


What's the thread size on the air injection ports in the exhaust ports? Convenient hole for egt probes... I just found a bunch on ebay for less than $5 a piece!! This would be easy and cheap to try if you found matching threads. Then just read the probes with a multimeter, maybe fab a switch panel for quick switching between the 6 signals. Something to do before I toss the stock carb.... hmmm...


Edited by 70Nova (10/26/17 07:09 AM)

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#92774 - 10/26/17 08:18 AM Re: Can I divide my head for six injectors on a 235? [Re: THE FRENCHTOWN FLYER]
stock49 Offline

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These engines were designed with a wet manifold - so why not array the injectors near the hot spot?

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#92777 - 10/26/17 01:05 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
panic Offline
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The fuel is going to be supplied every 120 degrees, but (except for the center 3-4 pair with 360-360 degree intervals) the air supply is quite irregular, at intervals of 240-480-240 degrees.

Few factory carbureted manifolds have the precision of A/F mixture as port injection system, and the cylinder-to-cylinder variation varies with engine and air temperature, RPM, and load (engine vacuum).

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#92792 - 10/27/17 05:47 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
gbauer Offline
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I was going to go down this road until I talked with Tom Langdon for about 30-45 minutes. GM tried to do individual injectors and tinkered with port dividers but couldn't make them work properly. Figured if GM couldn't do it (and they were going down the same road I had planned) I wasn't likely to do it either.

Tom was a GM engineer for these engines during the end of their life run.

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#92796 - 10/27/17 09:08 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
70Nova Offline
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guys, there is a simple solution to all of this. Make the engine run backwards. ;D

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#92799 - 10/27/17 10:39 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
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I know this was originally a post for a 235, but, I have an idea for a 250-292.

Why not take two 181 Mercmarine 4 cylinder 8-port heads and cut one cylinder off each end. Then weld back together.

Bigger valves, individual intake ports, all bolts line up and maybe even working water passages for the street. Not cheap, but probably cheaper than an aluminum head and looks stock on the street.

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#92800 - 10/27/17 10:47 AM Re: Can I divide my head for six injectors on a 235? [Re: 70Nova]
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Originally Posted By: 70Nova
guys, there is a simple solution to all of this. Make the engine run backwards. ;D


Or just run the cross flow 12 port GM inline 6.. cool


Edited by efi-diy (10/27/17 10:48 AM)
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#92801 - 10/27/17 01:31 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
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Or a 4.2 DOC. laugh
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#92803 - 10/28/17 06:09 AM Re: Can I divide my head for six injectors on a 235? [Re: gbauer]
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Originally Posted By: gbauer
I was going to go down this road until I talked with Tom Langdon for about 30-45 minutes. GM tried to do individual injectors and tinkered with port dividers but couldn't make them work properly. Figured if GM couldn't do it (and they were going down the same road I had planned) I wasn't likely to do it either.

Tom was a GM engineer for these engines during the end of their life run.


GM did figure it out over 20 years ago with the Brazilian 12 port head on their production 250 engines in that country. Surprisingly, those engines made more factory HP and torque than any GM production 250 siamese head engine did made in the USA, and has supported as much or more HP than most any siamese head race engine or performance apps ever produced in both N/A and forced induction.

There are aftermarket intake manifolds currently now available for the Brazilian head, so the ability for them to completely surpass the siamese head has arrived. The siamese port head design for GM dates back to before 1927, over 90 years ago, so why are we trying to hold onto it so vehemently when vastly superior technology exists and is available to replace it. So for most any application for street/strip use, the Brazilian head is a very good choice if not the better choice over the siamese head. And the cost for the Brazilian head is about the same as the siamese head when you buy the lumps and pay to have them installed. So not really any more cost involved to have a head that cures the ills of a siamese port design. And provides comparable or better performance to boot.

Myths and misinformation about what the Brazilian head is and isn't have placed it into a taboo category. But equally, myths and misinformation surround the siamese head as well about what it is and isn't also. Because better and proven choices exist that outshine it, but are still told siamese is better, when it truly isn't. Just look at what the Brazilian hot rodders have done and are still doing with their technology exceeds what the US hot rodders are doing with the siamese head technology, past or present.
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#92804 - 10/28/17 07:45 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
panic Offline
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Even though the Brazilian is still a non-crossflow head (all 12 ports are on one side) they made room for more port area by making the port shape a taller oval.


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#92805 - 10/28/17 10:26 AM Re: Can I divide my head for six injectors on a 235? [Re: panic]
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Panic,
You are correct with the text, but somewhat wrong with the picture. The one pictured is not a Brazillian head but instead one from Berta? in Peru?

Originally Posted By: panic
Even though the Brazilian is still a non-crossflow head (all 12 ports are on one side) they made room for more port area by making the port shape a taller oval.

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#92806 - 10/28/17 10:48 AM Re: Can I divide my head for six injectors on a 235? [Re: tlowe #1716]
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Yes, that's not the OEM factory GM Brazilian head. Berta was South America's version of a specialty racing head like the Sissell or Duggan.
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#92811 - 10/30/17 05:07 AM Re: Can I divide my head for six injectors on a 235? [Re: 70Nova]
gbauer Offline
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Originally Posted By: 70Nova
guys, there is a simple solution to all of this. Make the engine run backwards. ;D


But then you have to take the diff out and turn it upside down!

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#92813 - 10/30/17 07:33 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
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I have done that before... on an aircooled VW you can (some). 4 speeds in reverse..... LOL

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#92815 - 10/30/17 09:32 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
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Corvair to VW transaxle requires the diff to be flipped - 'Vair turns the wrong way.

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#92873 - 11/10/17 12:47 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
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Wow! Thanks everyone for the info.

I have picked up a Holley Dominator ECU, a throttle by wire throttle body from GM and three GM LS3 42lb injectors. I will put one injector at each port and fire each of them twice at the appropriate time as if there were six of them. There isn't room for two at each cylinder. I figure that with the limited RPM I will run that I can wire it so that the ECU thinks there are six injectors and I can adjust the amount of fuel needed for each cylinder.

I will also run individual ignition coils and will work in a cam position sensor so I can run a full sequential setup and not batch fire.

This weekend I will work on the location and angle for the injectors.

Thanks again everyone!

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#92876 - 11/10/17 07:01 PM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
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Suggest you read this.

http://www.starchak.ca/efi/siamese.htm

If you read Leo's book 1st ed. on page 87 he alludes to the cylinder timing issue, which the racers largely fixed by messing with lobe offsets.

There is a ton more article based on the mini cooper brit 4 banger. They suffer the same issues.
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#92878 - 11/11/17 06:38 AM Re: Can I divide my head for six injectors on a 235? [Re: Larry Callahan]
panic Offline
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Vizard suggested "scatter pattern" cams for the Mini, with different overlap and LSA depending on the firing interval difference.
Of course, the Mini has far more difference than the stovebolt due to L4 (180 degree separation) vs. L6 (120 degree separation).

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