The, "May", combustion chamber ??

[BCjohnny]

Neither the MEL nor Chevy W series engines were true 'bowl in piston' Heron designs

Each had an angle cut deck which formed most, or all of the combustion chamber volume

[Truckedup]

Neither the MEL nor Chevy W series engines were true 'bowl in piston' Heron designs

Each had an angle cut deck which formed most, or all of the combustion chamber volume

Yes, you got me there, but the heads are Heron design
Supposedly the W and MEL wedge shape piston chamber made better torque than a conventional wedge head..

[BCjohnny]

Truckedup

More your neck of the woods ...... IIRC the Morini 350 had a full Heron head / piston combo ......

[frnkeore]

Since we are on the Heron chamber design and since it was used in MC, how well does it work in a high performance engine?

As I said, AC used it for over 30 years and I do tractor pulls with the 226 engine (4x4.5). In my size engine, you can't get any real quench and we are limited to about 3000 rpm (stock is 1650) so, you can't get much above 10/1 (static) compression because of the cam timing. We are not limited on CI and although it's extremely expensive, some have opened this engine up to 403 CI (4.625x6) to gain HP.

What did the MC version do to make HP and what can you do to make TQ, in general with this chamber design?

This is what the chamber looks like on a early Power Crater engine, they later went to a tapered cup design.

[BCjohnny]

In my size engine, you can't get any real quench and we are limited to about 3000 rpm (stock is 1650) so, you can't get much above 10/1 (static) compression because of the cam timing.

I'd imagine with custom pistons you could get as much quench as you'd like

Being an older engine the pin is probably far enough down the piston to allow a fair depth of 'bowl in piston' chamber thus quench area ?

What did the MC version do to make HP and what can you do to make TQ, in general with this chamber design?

IANAE but the 2V Morini pushrod, for a MC engine, was in a fairly moderate state of tune ..... but the Heron concept was a blind alley

I'm certainly no cylinder head expert but aspects of a more conventional chambered head, such as pressure recovery influencing discharge co-efficient etc, are absent, and the piston is physically closer to the valve at low lift ..... none of the things are good for flow ?

[frnkeore]

I'd imagine with custom pistons you could get as much quench as you'd like

Being an older engine the pin is probably far enough down the piston to allow a fair depth of 'bowl in piston' chamber thus quench area ?

The picture I posted, is to scale. Note the relationship of the top of the rod and the inside diameter of the ring pack. From memory, the deck clearance is over 3/8" plus the head gasket. Not much available space to work with, within the piston crown.

Just as a guess, I don't think (on this AC engine) that you could get the piston any closer to the deck, than 1/8" plus the gasket and stay in the needed compression range of less than 10/1.

Maxing the cup volume and getting a good intake charge swirl is all the help I can see, at this point but, I can't see quench being available to help turbulence, at least like we do with other combustion chambers.

[pdq67]

IMHO, the best head would be one with 90 degree ports straight up in a flat head.

Put the chamber in the piston, and not the head.

But I am sure there are problems with doing so??

pdq67

[Truckedup]

Truckedup

More your neck of the woods ...... IIRC the Morini 350 had a full Heron head / piston combo ......

Yes... Moto Guzzi also had a series of 500 to 750 V Twins with real Heron top ends..In 2017 they went to a modified hemi because the Heron head could not pass European emissions.

[pdq67]

Sorry to digress here, but please post up both the MAY as well as the HERON chambers so I an keep track of them,..

Thanks,,

pdq67

[chevyfreak]

Heron chamber. Althou there are difference in design. Some a flat head , other has a small chamber in the head.
There was a discussion on ST about the jaguar v12 heads and the "may" head also in there. Just i cant find the topic link to paste it on here. Still figuring that one out.

Chevyfreak

[chevyfreak]

Got it. I hope.
Chevyfreak



viewtopic.php?f=15&t=28861

[BCjohnny]

please post up both the MAY as well as the HERON chambers so I an keep track of them,..

As these threads usually go we're talking about at least three different types of 'combustion chamber' types now :

1) The May design, heavily biasing the CC around the exhaust valve and mostly in the head itself ...... Jag V12 HE, Merc 280 & Chevy 235 etc

2) The 'angle cut' deck, where the CC is in the cavity left between the angled deck and the (mostly) flat top piston ...... MEL ,Chevy W etc

3) The true 'bowl in piston' Heron design where the CC is mostly in the piston itself,...... original Jag V12 etc, X-Flow etc

The first doesn't have a 'flat' head, the latter two do

I guess for relative completions sake mention should be made of the VW VR6 'design', which is mostly a hybrid of the latter two ...... 'angle cut' & 'Heron' ...... and with it's narrow angle block architecture heavily 'influenced' by the Fulvia V4 !

Obviously if you look further afield there will be many other designs share commonality, or attributes, of all of the above ....... lol ......

[pdq67]

I have to ask??

What does, "MC", stand for?

pdq67

[chevyfreak]

I have to ask??

What does, "MC", stand for?

pdq67

I would guess motor cycle in this case . seeing it was directed to truckedup.

Chevyfreak.

[pdq67]

"MC", motorcycle, make's since!

Thanks.

pdq67