The, "May", combustion chamber ??

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pdq67
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The, "May", combustion chamber ??

Post by pdq67 »

I flat don't know so have to ask??

Is the, "May" chamber design just the old flat-headed Chevy, "W", and Ford, "MEL" heads?

If not, then would somebody explain what a, "May" chamber is.

Thanks,

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Re: The, "May", combustion chamber ??

Post by Stan Weiss »

I think this should in the "Vintage/Classic/Historical Engine Tech"

That said the best that I can remember. The Jaguar was a flat head. I believe this is what a "May" head looked like.

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Re: The, "May", combustion chamber ??

Post by pdq67 »

If so, then please C & P this to it.

And thanks Stan.

I always figured that the, "May head", was either flat with the chamber in the piston or flat with the chamber recessed in a valve pocket.

Stand-up valves of course.

Is there a link to a picture of the, "May head", combustion chamber???

If so, would you or somebody else please post the link up.

Thanks,

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Re: The, "May", combustion chamber ??

Post by Stan Weiss »

I don't have any links. That picture and this picture have been on my computer for a number of years. My memory is not what it used to be as I believed I had a few more picture of this.

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Re: The, "May", combustion chamber ??

Post by chevyfreak »

Dont know if it is a "may" chamber but the chevy gen 2 235/261 inline sixes had such a design. And a image that i have.
Im thinking some leyland engine also had a head like that, not too sure on that.

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Re: The, "May", combustion chamber ??

Post by Stan Weiss »

Stan Weiss wrote: Thu Aug 13, 2020 12:05 pm I don't have any links. That picture and this picture have been on my computer for a number of years. My memory is not what it used to be as I believed I had a few more picture of this.

Stan
OK. The memory is only partially shoot. :lol: Over the years as computers have crashed and I move thing forward they have sometimes been placed in the wrong folders.

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Re: The, "May", combustion chamber ??

Post by BCjohnny »

chevyfreak, yes it is ..... or at least the fundamental concept

'Leyland' ..... can't recall any other model using it, apart from the Jag V12 HE ...... Jaguar being part of 'British Leyland' as a group, so maybe that's what you're thinking of

Mercedes used it in the 280/300 sixes, and I would imagine possibly other manufacturers too

One of the benefits of the design, lean mixtures, was pretty much lost when OE had to mostly go stoic, hence it's fall from favour

Prompted a lot of Larry Widmer's 'softhead' research, that IIRC is still ongoing in the Honda heads, although it's more subtle in the 4v stuff

Stan's post outlines the concept

[edit : grammar]
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Re: The, "May", combustion chamber ??

Post by pdq67 »

After looking at the, "May", head combustion chamber, why did the Chevy small block engine go with the wedge?? And I know about the old Chevy, "stove-bolt", 6-banger engine heads chamber.

Wasn't the old 318" engine's poli-head chamber about the best FOR THE TIME as there was except for the way more expensive early '50's hemi??

Way later MOPAR designed a, "ball/stud", hemi, "concept", head so the rocker shaft's should NOT have been a problem for Chevy early-on due to them and Pontiac, (I think??), coming up with the, "ball/stud", in the 1st place if not mistaken(??) and as always, JMHO..

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Re: The, "May", combustion chamber ??

Post by pdq67 »

After looking at the, "May", head combustion chamber, why did the Chevy small block engine go with the wedge?? And I know about the old Chevy, "stove-bolt", 6-banger engine heads chamber.

Wasn't the old 318" engine's poli-head chamber about the best FOR THE TIME as there was except for the way more expensive early '50's hemi??

Way later MOPAR designed a, "ball/stud", hemi, "concept", head so the rocker shaft's should NOT have been a problem for Chevy early-on due to them and Pontiac, (I think??), coming up with the, "ball/stud", in the 1st place if not mistaken(??) and as always, JMHO..

PLEASE LETS CONTINUE THIS THREAD SO I CAN LEARN MORE!!

And I really like the Jeep Tornado 6-banger SOHC head design.

Oh, and btw, why did the, "modern", Jeep go back to, (I think?), the May chamber design for very short time and then dropped it???

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Re: The, "May", combustion chamber ??

Post by modok »

The May "fireball" chamber had the exhaust valve sunk deep in a round pocket, idea being the charge would be swirling and hot.
It works but it flows terrible.
At least the chevy "blue flame" design the exhaust is offset to the side, allowing larger valves.

A decent fast burn design is a "Heron head"
The head is FLAT, and there is a bowl in the piston. like a diesel. Most diesels are made this way.
it still flows bad, but you can use four valves.
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Re: The, "May", combustion chamber ??

Post by frnkeore »

modok wrote: Thu Aug 13, 2020 8:51 pm A decent fast burn design is a "Heron head"
The head is FLAT, and there is a bowl in the piston. like a diesel. Most diesels are made this way.
it still flows bad, but you can use four valves.
Allis Chalmers has use that style of combustion chamber since about 1939 and used it until, at least 1973, in all their 4 cyl gas engines.

Their first model, used FT pistons but, in '53, they opened it up from 201 CI, to 226 CI (4 x 4.5), added a spherical cup to the piston and started calling it the "Power Crater" combustion chamber. Later, they changed to a tapered cup piston.
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Re: The, "May", combustion chamber ??

Post by BCjohnny »

The 'Heron' design was another technological blind alley when used in petrol engines

Relatively high surface ratio, not volumetrically the most efficient, bad emissions and heavy, heavy pistons ...... to name a few

Ford went mad with them over here ...... almost everything they made for pass cars in the early sixties to mid seventies ..... Pre-crossflow, X-Flow 'Kent' & 'Essex' V4 / V6

In the most common, the X-Flow 'Kent' OHV engine, widely used in many racing Formulae such as FF, everyone who can does everything possible, if rules allow, to go to flat top pistons and use the low comp 'van head' which has a vestigial chamber, if they want to be competitive

Same with the 'Essex' V6 ..... which Cosworth eventually put a 4v pent roof on and went Capri racing in F5000, beating the 302 Chevys, with just 3.4 litres ..... but I digress

Works well in diesels but a terrible petrol design

[N.B. The British 'Essex' V6 and Amercian engines are different designs]
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Re: The, "May", combustion chamber ??

Post by Sparksalot »

Yes, the ball, stud and stamped rocker design was first used in Chevy and Pontiac engines in 1955. IIRC the design was originated by Pontiac engineers.
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Re: The, "May", combustion chamber ??

Post by BCjohnny »

IIRC ....... GM claimed patent on the ball stud design in the early 50s (Pontiac)

But a sharp eyed Ford engineer remembered seeing a much earlier design, maybe 20s, in text and claimed 'prior art'

Thus saving Henry millions in royalties
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Re: The, "May", combustion chamber ??

Post by Truckedup »

The Chevy W ,348 and 409 were Heron heads as was the Ford MEL engines. Several Italian bikes including Guzzi used Heron heads on some engines.
I used to mess around with Chevy 235-261 inline 6's in the 1990's as a nostalgia hot rod thing. The squish part of the chamber is actually tilted the wrong way...But milling the head some, zero deck flat top pistons, a moderate cam with a Rochester two barrel and a short tube header could run away from a modified Ford flat V8...
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
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