Little and large A series

[251 ENG]

Just an example of BMC diversity

[251 ENG]

Another picture

[cpr1]

Haha imagine what power could have been achieved with the Hemi, and those single leading front brakes = plenty of fun.

[Tupers]

I’ve seen the 2 cylinder before but not the hemi. What’s the story in that?

[iain1967s]

Is the hemi serviceable? Would make an interesting build for someone - if they could figure out how to do the rockers with the pushrods all on one side.

[251 ENG]

I believe the hemi was developed in very early 1960,s for possible use on FJ engines . That would have required it to be fitted to a production road car , Obviously that never happened.

I do have a picture of one in a very early cooper fitted with webers

The head had the bore spacing of a cooper s block

What confuses me is that I bought it with a 998 type block with special domed intruder pistons !!

Also came with a manifold and a pair of HS4,s that will never fit under a std mini bonnet

[251 ENG]

Early coopet

[mk1]

Great Pics. Thanks for sharing them Simon.

Anyone would think you weren't at work at the moment

[251 ENG]

Ha ha been over 5 weeks now mark

Rod and Colin still in finishing of a few engines that had all the machining done and some that want refreshing .

I just trying to clear out stuff at home


Would really like to know some history on the head

[andy1071]

Nice pictures.
Always interesting to see development / proto-type project parts.

I don't think the hemi would have produced particularly good power compared to a good 5-port, and definitely nothing like as good as the 'normal' 8-ports.

Hemi heads tend to 'suffer' from too much surface area in the chamber (the hemispherical chamber needs a domed piston to get a reasonable compression-ratio), so you get a 'slow' mixture burn as the flame-front has to travel so far, you see this from the amount of ignition advance they tend to need.
Also this doesn't appear to have any squish area, so this would tend to make the mixture burn worse as well...

-And the spark plug stuck right over on one side doesn't help...
On the Alfa twin-cam they had to go to twin-plugs to get reasonable power (haven't heard of Jag using twin-plugs on the XK engine -in the D Type or racing E Types. -Anybody know?)

-Now when I say 'hemi heads' I mean the ones with very wide valve angle, typically 90 deg. Such as the Afla twin-cam and Jaguar XK engine mentioned.

If you want a good hemi, you should look at the Lotus twin-cam, which is more of a 'semi-hemi'... -Of course it was designed by Harry Mundy and developed by Keith Duckworth (Cosworth).
-A race-spec Lotus gives 170hp or more from 1.6 Lt, and the Alfa struggles to get much more than that with 2.0 Lt (with single plug)...

[251 ENG]

The best race 1600 twin cams are now making a lot more than that

[andy1071]

Thanks for confirming that, Simon.

[251 ENG]

After a very interesting phone conversation with an older gentleman that was there at the time , it appears that Dowton did have at least one of these hemi heads .

So could the cooper in the photo be anything to do with them ?

The inlet manifolds look more " Downton " than factory BMC

[agricola]

I think most people would give their eye teeth to see the rocker gear,
With vertical push-rod holes must have been an engineering marvel. Russ Carpenter got some very good horsepower out of NA and supercharged hemi headed Daimler v8s but then Edward Turner was a brilliant designer. Now if Jaguar had put the 4.5 litre majestic major engine in the Etype then Cobras might have got a big shock!

[Hipwell]

Google Hemi valve gear. Be interesting to see.

[251 ENG]

Only bits I have

[251 ENG]

The posts are the righr thing but rockers may be off something else

[Supersonic]

Nice pictures.
Always interesting to see development / proto-type project parts.

I don't think the hemi would have produced particularly good power compared to a good 5-port, and definitely nothing like as good as the 'normal' 8-ports.

Hemi heads tend to 'suffer' from too much surface area in the chamber (the hemispherical chamber needs a domed piston to get a reasonable compression-ratio), so you get a 'slow' mixture burn as the flame-front has to travel so far, you see this from the amount of ignition advance they tend to need.
Also this doesn't appear to have any squish area, so this would tend to make the mixture burn worse as well...

-And the spark plug stuck right over on one side doesn't help...
On the Alfa twin-cam they had to go to twin-plugs to get reasonable power (haven't heard of Jag using twin-plugs on the XK engine -in the D Type or racing E Types. -Anybody know?)

-Now when I say 'hemi heads' I mean the ones with very wide valve angle, typically 90 deg. Such as the Afla twin-cam and Jaguar XK engine mentioned.

If you want a good hemi, you should look at the Lotus twin-cam, which is more of a 'semi-hemi'... -Of course it was designed by Harry Mundy and developed by Keith Duckworth (Cosworth).
-A race-spec Lotus gives 170hp or more from 1.6 Lt, and the Alfa struggles to get much more than that with 2.0 Lt (with single plug)...

Andy, I’m so proud to say I met the great Keith Duckworth and Frank Williams when they were over here visiting their friend J.N. Brown in Ballynahinch. James Norman Brown was an extraordinary engineer who did development work on the David Brown tractor and was passionate about cylinder head development in motor cycle 4-stroke racing.

I remember going to the chip shop to get these three great men food when they were in cylinder head discussion. Unique individuals all three gentlemen were without question. I’m also very proud to say J.N. Brown helped me with my racing and his knowledge proved to me that racing is won in the workshop

Alan

[agricola]

fabulous
twin shaft and very different rocker ratios so camshaft would be interesting

[251 ENG]

This is carbs and manifold that came with it.
Fitts head but not a round nose mini !!