Comsidering all 12 port heads what is the approximate HP gain by using one? Raw numbers? percentages? I'm talking actual street HP for a GMC, the 261 and the 292. I'm wondering what it would be for a non temperamental, regular hot rod motor for the street, not something you always gotta tune and mess with to get it right so you can drive it to the next rod run.
Anyone with any thoughts?
Geez, thats more than I thought. take a 261 and go from 160 to 200 hp is 4 grand??? Wow!!! why do people use them??? I saw some discussion on 12 ports and was just wondering the cost/benefit for streetable HP.
Wow, thats lots more than I thought!
It's the "wow" factor: "Wow, you spent all that money, and you could have done 3 times better with a $600 nitrous kit!".
I use nitrous every day!!
In my opinion one would go to a 12 port for is looks and ego appeal. At 2500 to 3000 RPM driving a street rod on a rod run it would make little difference. People and street rodders do things because they want to not because they need to.
If I was building a street rod I'd use a 270 GMC because in 1953 no one had heard about a 302 and they make approximately the same torque which is what pushes you down the road. I'd also use a small port head because of it's velocity when the valve opens and it's would have no stumbling when starting and who needs 5000 RPM. Even tho gaskets are better there always some problems with aluminum to cast iron especially with long inline engines.
If it's a 12 port GMC you are looking for you can contact the Fergusons in Wilmington Ca. they have most of the patterns for the various GMC 12 ports and Joe Fontana has a few Skinners available. Most of these were designed for racing so intakes are not to choicey
It's always a choice; sometimes it's money and like I said "EGO" plays a part....Good luck and have fun with what you are wanting to do..................
Opps forgot. As stock HP goes a 302 GMC is 160; a 270 is 140. I make close to 400 with my 311" stock head GMC but could not run it on the street. Skinners injected on gasoline made 525 hp in race trim over 6000 RPM and 750 hp on nitro at 5500.
Just about everything about hot rodding is somewhat irrational, at least from an economist's point of view. A 12 port head certainly makes a street rod more interesting, at least to those who are aware of the early days, when the Wayne Horning heads made the Chevy sixes very competitive. If $100/HP for a 12 port head is not a good deal, how does one justify spending $200 for a cast aluminum valve cover, which does not add any horsepower to the engine? (Tom, please do not take this seriously!) I paid $405 for my
the 12 port head that is on my 261 , but even in this economy I do not believe that any one would offer enough to tempt me into selling it.
From a historical standpoint I would love to own an older 12 Port,particularly a Skinner since I'm from the area they were first designed and built. I don't know if I'd even install it. Probably just brag I own one.
I'll never be able to afford one, but man it would be cool if I did.
Just about everything about hot rodding is somewhat irrational, at least from an economist's point of view. A 12 port head certainly makes a street rod more interesting, at least to those who are aware of the early days, when the Wayne Horning heads made the Chevy sixes very competitive. If $100/HP for a 12 port head is not a good deal, how does one justify spending $200 for a cast aluminum valve cover, which does not add any horsepower to the engine? (Tom, please do not take this seriously!) I paid $405 for my
the 12 port head that is on my 261 , but even in this economy I do not believe that any one would offer enough to tempt me into selling it.
Hey, no offense taken. But I should clarify the valve cover issue for you. We ran test after test and this valve cover actually gives 30 HP to an otherwise stock inline. So, buy away!!!
All I am trying to do is get my head around this - I'd like to get 300 HP on the street and not sure the best way to do it. My preference is still the 235/261 but its looking like a lump in a 292 may where I am headed. A guy cant break the bank to do it. I'm thinking 40 hp for $4 grand might not be the best buy. I seriously thought it would be more like 100 hp for a x-flow head....
It is 100 hp - if the engine has max mods and can pull high RPM.
There's nothing un-streetable about a 12 port, except that some of them are not quench and you have to watch the spark and mixture.
A 2 × 2 Weber 5200 etc. and a mild cam should be a calm as a stock V8.
The current 12 ports for the 250/292 are highly developed, those for the 235/261 were already obsolete when produced (read Huntington). Vertical valves, open chambers, and low downdraft angles are inferior to the better modern L6 engines such as the Slant 6, AMC 258, Ford 300. They're just better than the original heads.
Irrational!!! Right on Hoyt! Here I set with a nicson aluminum head- valve cover- long side plate- 2 carb intake & a couple of gas pedals [ALL NICSON]. Although I would love to build an early 235 using this stuff, will I? Doubt it. How about an early track T with this stuff? Thats my dream. But,I already have more projects in the shop than I have construtive life left. Has anybody ever been around a running NICSON engine? 1 OL REDNECK
Previous quote: " [/quote] All I am trying to do is get my head around this - I'd like to get 300 HP on the street and not sure the best way to do it. My preference is still the 235/261 but its looking like a lump in a 292 may where I am headed. A guy cant break the bank to do it. I'm thinking 40 hp for $4 grand might not be the best buy. I seriously thought it would be more like 100 hp for a x-flow head.... [/quote]
It would be so simple to install a turbo & if you source parts carefully ,it can be done very cheaply.
Just a little part needed of fabbing up some parts.
Mainly the pipe to attach the exhaust manifold to the turbo & the downpipe/exit pipe from the turbo into your exhaust system.
You do need need a great flowing cylinder head to produce a lot of torque when using a turbo.
Unless you have no room for a turbo?
Just a thought.
Remember what the dyno tests of that makeshift turbo install that Tlowe did on the 250,& that was by no means a great timely mannered/great install,just some pipes hooked up to see what a blow through turbo set-up could do .
It did pretty good considering what he was working with.
MBHD
X2 - the first turbo mod produces amazing results per dollar spent, doesn't have to be anything special.
It is 100 hp - if the engine has max mods and can pull high RPM.
There's nothing un-streetable about a 12 port, except that some of them are not quench and you have to watch the spark and mixture.
A 2 × 2 Weber 5200 etc. and a mild cam should be a calm as a stock V8.
The current 12 ports for the 250/292 are highly developed, those for the 235/261 were already obsolete when produced (read Huntington). Vertical valves, open chambers, and low downdraft angles are inferior to the better modern L6 engines such as the Slant 6, AMC 258, Ford 300. They're just better than the original heads.
I recall reading or hearing that Wayne Horning used the Winfileld head for the Model A engines as a guide for his head design for the Chevy six, starting the design work prior to World War 2. The open combustion chamber design and spark plug location are certainly not desirable for a high performance engine. It seems to need a lot of spark advance (more than 40 degrees total) and a rich mixture to run well. I'm about to install two wide-band O2 sensors to measure the AFR.
Panic: How is the downdraft angle defined?
Quote:" [/quote]I'm about to install two wide-band O2 sensors to measure the AFR. [/quote]
Smart man,no reason to guess your A/F ratios nowadays w/todays lower cost A/F wideband readers.
MBHD
A line bisecting the port runner vs. the valve stem axis.
A less acute (110° rather than 90°) angle promotes flow, but requires a taller casting, more weight, more hood clearance, longer pushrods, longer stems, etc.
In addition, the stem angle to the bore axis has an effect, and influences shrouding.
A vertical valve can't make a wedge, but it can make a good closed chamber (BMC Mini). The wedge only began high volume production in 1948 for the Cadillac engine. An existing vertical valve like the GMC, Buick L8 etc. can be improved quite a bit by closing off the chamber, but cast iron welding is not fun.
There have been closed chambers with non-vertical valves tilted in the other axis (along the crank) like the Australia Chrysler L6.
If you don't like the turbo plumbing, how about a M-90 Eaton off a Supercoupe or one of the Blower Pontiacs? (speaking for the 235 / 261, a 270 / 302 would likely want a M-112)
Might not make 300 Hp, but the torque would be there (you would have to wind the engine some more for the Hp, requiring cam & head work to optimise).
As far as $ per Hp, none of the stuff we discuss on this forum makes any economical sense.
IIRC Fontanna has a parts assembly (dare I say "kit") that's supposed to make 300+ (320~340 I think) out of an otherwise "stock" Jimmy 302 (12 port head assembly, intake, exhaust, rockers, pushrods, tappets and cam) for $7000 ish (maybe $9000 now that the dollar is further down
).
I was told that was the "street" tune (single 4V, & Iron Manifolds) but that was from a 3rd party, not from the orriginal source so the numbers may be out of date (I hate it when my numbers get old
).
The main problem when using a super charger.
The snout will not line up(too short) for the blower to be centered on the intake manifold,it does not have to be,but would nice if it could.
B&M used to make all kinds of length blower snouts that were used w/there blower.
Second draw back or should I say hard to line up,,,,you need to make sure your belt is lined up perfect,or else the belt will get thrown off or move a few ribs when using serpentine belt.
Here is a manifold to bolt onto the 194-292 engines,but I am not sure B&M makes the blowers that used to work on these manifolds.
http://prostores1.carrierzone.com/servle...manifold/Detailhttp://www.34-chevy.com/ pic is to the right
I only seen one guy here in SoCal that ran a B&M supercharger.
IIRC, Mel Petterson ,worked for SOCal edison.
He had made an adaptor plate & used the Clifford intake manifold.
The B&M was the 144 CI one.
It was in a very nice 5 speed manual 1966 Red Nova maybe 67? ,Been in a car craft magazine for a street car shoot out.
It did not fare well in the 1/4 mile in the mag test,had problems, about 14.3 in the 1/4.
It also was bad in the salom course,typical of a standard Nova those years w/stock suspension.
I have the Car Craft mag somewhere & this info is from the top of my head.
I had talked w/him @ a local Car hop Named Kevins burgers ,nice guy Mel.
MBHD
Magnuson supposedly makes nose drives in different lengths for the M series, bu they're pretty expensive. Some GM ar really long, but of course not the correct length, and can be shortened and the bearing moved.
An alternative is a jack-shaft in parallel (as used on the Ford Super Coupe) to have 1 pulley align with the engine/damper, and the other with the M90 nose.
More: read my article:
http://victorylibrary.com/mopar/blower-drive4.htm
Maybe Larrowe & sons have superchargers for there manifolds or they know where to get them?
MBHD
It's also possible to make a centrifugal supercharger from the compressor side of a turbo, and belt-drive it. This needs a jackshaft (multiple ratios) just to get the wheel spinning fast enough.
The downside is that (like a centrifugal) it doesn't produce boost at low speed.
Hey, no offense taken. But I should clarify the valve cover issue for you. We ran test after test and this valve cover actually gives 30 HP to an otherwise stock inline. So, buy away!!!
How does a different valve cover add power? It has absolutely NO EFFECT on valve operation, oil pressure, Drag on any components, ECT. You could run one without a cover, but you could/would get contaminants in the oil and/or loose oil (splash)...
Not saying it isn't true, just wondering how?
Hey, no offense taken. But I should clarify the valve cover issue for you. We ran test after test and this valve cover actually gives 30 HP to an otherwise stock inline. So, buy away!!!
How does a different valve cover add power? It has absolutely NO EFFECT on valve operation, oil pressure, Drag on any components, ECT. You could run one without a cover, but you could/would get contaminants in the oil and/or loose oil (splash)...
Not saying it isn't true, just wondering how?
He's pulling your leg.....
I figured it was some kind of inside joke or something, Just wondering...
If anyone want a 12 port - there is one for sale on the HAMB
If anyone want a 12 port - there is one for sale on the HAMB
A link is always helpfull & faster.
MBHD
...beat me to it!
We all appreciate a "heads up", but no one enjoys searching for something you already found.
For those who are not familiar, go here
http://tinyurl.com/#toolbarWhen you're on a useful page, just click the toolbar button, and post the link.
And a link to the other pictures mentioned in the advert.
http://s495.photobucket.com/albums/rr317/TruckBoatTruck/Wayne%20head/Thats all the info I have at this point.
So who is going to step up and buy it, and when you do - I need all the info on it for the 12 port register???
Here is what is for sale - $15K.
Hey this is fun!!!
Yeah........
That's more like it! ;-)
MBHD
That's a 15 bolt head, which reduces it's usefulness a bit.
It's a first series (10XX) head. The first two series (10XX and 11XX) were for 15 bolt blocks.
It wasn't until Bob Toros came out with the 12XX series, and the I'll-fated Wayne Mfg Co heads that you could get an 18 bolt head.
Mark,
I recall seeing head #1054 (if I recall) on ebay a few years ago; the high bid was about $4800, but did not meet the reserve. Pat Swanson contacted the seller. Did any of that information make the registry? Mine has been running for about three years now, and has not sprung a water leak. The final head repair by Bob Toros seems to have worked.
Here is a cutaway drawing of the intake and exhaust flow path of the Horning head. I still seem to be confused over the definition of downdraft angle and why the downdraft angle of the Horning head is not good. Based on various sources (e.g.,
Vizard,
Heywood, and others, the head looks pretty good. The spark plug location and combustion chamber shape are certainly not the best, however. The real chambers do not have as much quench as the artist's drawing shows.
I believe in most scenarios, a downdraft intake port is always better.
Look @ most all motorcycle cylinder heads of the newer style bikes,there all down drafts.
It makes for a great loooong short turn radius.
Not sure why the Wayne head is not good as a down draft?
A port w/a short 90 degree bend is not good, like the stock Chevy 6's.
I know Mike Kirby told me the earlier Duggan/Sissle aluminum 12 port head ,like Tlowe owns,,,,said that particular intake port flows less the a siamesed port head, & those were down draft ports w/a square inlet. 194-292 series engines .
Maybe Tlowe has some flow numbers of those heads?
MBHD
Not sure why the Wayne head is not good as a down draft?
Looks good to me, the port isn't the problem - it's the vertical valve, which is usually inclined another 10-20° to ease the SSR even more, and permit one side of the chamber to be closed completely into a wedge (as Cadillac and Oldsmobile had just done for 1949).
BTW: in the stock head shown, the inclined valve is the exhaust valve, the dotted (phantom) behind it is the nearly vertical intake valve with 90° (horizontal) port.
Wow. Some folks must really be into the nostagia craze to spend 15k.
It's a rare item, and it appears to be mostly complete, with several accessories, but i don't think it will sell at that price.
It might find a buyer at one-third of that price, but not much more.
God's Peace to you.
d
Inliner #1450
For those curious: this does not include the cam, because any original or replacement cam could be used. This is because the stock valve sequence (E-I-I-E-E-I-I-E-E-I-I-E) was used, although with individual cross-flow ports.
Some other manufacturers, such as Howard, changed the valve sequence to I-E-E-I-I-E-E-I-I-E, which requires a new cam.
This would be worth more as racing parts if for the GMC engine, since the 235 is far too small to be competitive in XXO.
That’s for sure. Hoyt that section view is priceless, Mark thanks for putting up the pic’s. and Tom thanks for bringing it up in the first place. Is there any reason it would not be possible to convert a 261 core to accept a 15 bolt head and/or how much different is the positioning? I think I would go as high as half the asking price at my weakest moment.
The 2 obviously extra bolts are between the rocker stands. I've read that it's possible, but you'd have to super-impose the head gaskets to see how far off, and there may be length differences in the bolt perch as well.
Which would be more practical-converting a 15 bolt head to 18 or a 18 bolt block to 15? Not having the engineering knowledge of many involved in the extreem performance world I thought this might be a good question. Wouldn't it be better to have 18 head bolts? I OL REDNECK
I've heard that Hank Lawshe had a modified 15-bolt head on a 261 in his coupe that set a Bonneville record a few years ago. Does our new historian have any more information in the archives? Jerry Weigt or Gary Cope would probably know what it takes to mix the heads and blocks.
And is the bottom line still just 40 HP?
I just made an overlay of both decks, and it appears that:
1. the 8 bolts in the row on the left (port) side are very close, if not the same
2. you have to add 2 bolts between rocker stands 1 & 2 and 5 & 6
3. the existing 15-bolt stand bolt between 3 & 4 is off quite a bit
4. there's a bolt missing midway along the pushrod side
5. there may be other errors on the pushrod side, but the other 6 bolts are pretty close
If you have P/Shop, e-mail me and I'll send you a .psd, you can slide the opacity control for the top layer to watch the bolt holes change.
Assuming that an early head + late block is the goal?
I would guess that the minimum is:
1. drill and tap the block for the 15-bolt center stand position
2. bore the head for the 2 extra stand bolts if it looks safe (enough material, no water underneath), otherwise leave them out and plug them in the block
3. plug the original 18-bolt center stand hole
What I don't know is where the water transfers. The early heads have 8 copper water nozzles pressed into the gasket surface to cool the exhaust valve seats, and I can't tell if they line up with the late block.
For what it's worth, I ran the flow characteristics (as best I know them) of the 12-port head through an engine simulator that had been tuned to match the results of the dyno tests by Frank McGurk in the May 1955 HRM. The results indicate that, if one has the nerve to take a stovebolt crankshaft and valve train to 6500-7000 rpm, the peak HP gain could be 60 to 100 HP.
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I have seen a few 15 bolt 12 ports on 18 bolt blocks, including those by Jerry Weigt, Hank Lawshe, and Keith Young. As I remember (it was quite a while ago) most head bolts line up, and the ones that don't (1 or 3?)in the block are plugged and redrilled to match. Only 15 head bolts are used.
As some scary Slant 6 motors have shown, 4 mains isn't automatically a low-speed engine.
Based on a GMC rod, light piston, and SFI-quality damper, 7,000 RPM is about 113,000 f/s/s, a very conservative figure for a race engine (lower stress than a SBC 350 with 5.7" rod at 7,377 due to lower piston weight).
The mean piston velocity is 4,594 - not good, but possible with a quality forging.
The RPM will require a steel cam for the spring pressure, and probably a fabricated rocker arm or welding and doubling to stiffen the original (which may turn out to be Buick L8 or GMC?).
So, all these years later, are there any 12 port heads for the 235/261 series??
I am sure if they were available cost would be around $4500-$5000 maybe more.
You are really going to want that cylinder head to pay that price.
Problem is there is even less demand for those engines than the 194-292 engines.
They weigh as much as a BBC & the potential performance gain is limited by the design of the engine.
Maybe I am wrong?
MBHD
Tom, I am in a position where I can/could very easily make one for these engines. The question is simply, who is going to spend $2000-$2500 just for a cylinder head, and then the other support components like intake, exhaust, etc for a Stovebolt anymore. If 10-15 people would step forward and raise their hands then that could get the ball rolling. Start a list and see who else will join in.
