Query on port-heads

[Nate M]

Recently read of the story where Colin Chapman effectively created a 4-port head for the Seven-based engine in the Lotus Mark III, is it known whether the BMW 3/20, American Austin / Bantam and Nissan / Datsun engines featured two-inlet ports or more as well as whether all were capable of featuring production 4-port or even 5-port+ heads like on the later A-Series?

As an aside was it within pre-war Austin's ability to develop an engine that carried over the various Seven-based innovations from BMW, American Austin / Bantam, Nissan / Datsun and others? Would it be accurate to say the Big Seven and Eight engines come close to fulfilling the brief apart from featuring SVs, curious to know what could have been feasibly done in retrospect to improve the Seven or later Big Seven and Eight engines?

While such a pre-war engine would be unlikely to butterfly away the post-war A-Series, am intrigued by the idea of Austin basically developing a fairly close pre-war similarly long production life analogue of the Renault Billiancourt engine (used in the 4CV) and the Fiat 100 Series engine (used in the 600) both of which were certainly capable of being eligible for the 750 Formula in terms of displacement.

Know that Alec Issigonis had the Austin Seven engine in mind when he included some design elements of the former in the 9X prototype engine, that does bring up the question of whether Austin or later BMC could have developed an earlier OHV precursor to slot below the later A-Series.

[Bob Culver]

The Big Seven is a very conventional monoblock engine much as established by the Model T and others and very similar the Ford A, 8, copycat morris 8, Austin 10  and very many others. Most cars had the main bearing caps bolted to the crankcase base but the Big Seven has the caps elegantly slotted into an extendedr crankcase. I gather this was carried on into BMC motors where the extra rigidity may have been helpful.
The Seven inlet ports are very large and it would seem practicable to divide, but when is a Seven not a Seven?
While c.r was below 7:1 and bores were small, ohv did not offer much advantage at normal rpm

[Ritchie Wilson]

Nate, in 1934 American Austin went belly-up. Bantam, which took over the operation, had the engine (a mirror image of the Austin Seven engine) redesigned. The obvious change was to the main bearings which were changed from ball and rollers to Babbitt.
Perhaps the motivation was to reduce manufacturing costs, perhaps to avoid paying royalties to Sir Herbert.

I gather from posts on here that Reliant, who made a copy of the A7 engine after Austin stopped making it, made a number of improvements before they turned to OHV.

[AustinWood]

I believe that Colin Chapman's modification was done by the inlet manifold which had a plate protruding into the siamesed inlet ports to divide them. Then inlet manifold was double and fed in pairs 1&4 and 2&3. It used a Ford V8 Stromberg carburetor which is a double unit. Effectively 2 units fed from one float chamber. Two barrels each with their own jets running in parallel. This gives better gas flow and allows each pair to be tuned separately.
I don't know where I got this from, possibly made it up?

[Mike Costigan]

Jim, I'm sure you are correct, although I don't know about the carburettor details. In the late 1960s the Pre War Austin Seven Club organised a trip to the new Lotus works at Hethel, and afterwards we went round to one of the directors' homes where a number of Seven spares were offered to us. I brought home a four-branch steel exhaust manifold which incorporated a full-length mounting flange; the original siamesed inlet ports each incorporated a steel tongue which fitted into the block to effectively create four separate ports. I didn't bother with the matching inlet manifold, which was indeed for a double-choke carburettor, as I couldn't see how I was going to use it - there was no carburettor to go with it   I'm pretty sure this was Chapman's original manifold which got banned from 750 racing and had just been cast aside.

[Renaud]

Found in my messy "archives":

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And Mike I hope you just put that manifold under a glass globe on your chimney?

[Austin in the Shed]

Years ago I bought a stromberg carb with a fabricated 4 port manifold,Unfortunately someone had cut the mounting flange off it. Whether it was a copy who knows.
I read Colin Chapman's biography,I believe he could still get 62 mph on 2 cylinders ?
I do wonder how  effective all of this is/was as when I owned a mini many years ago at that time I remember the 8 port heads available at the time only gave an extra 3 bhp or so when these engines could produce 120 bhp.
I also believe Frank Hernandes 4 ported one of his cars,I'm sure I saw it when on a rare occasion the bonnet was off in the paddock,cleverly hidden with exhaust wrapping tape.

[Alan]

Yes, but if you have 33bhp and the rest have 30, it makes it worth it. Doesn’t it?

[austin]

I'll let my dad do the rest of the description, but sounds like you are describing this:

[Mike Costigan]

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And Mike I hope you just put that manifold under a glass globe on your chimney?

Sadly, no; it went with a number of other random tuning bits when I had a clear-out in the '70s. The concept was as the one illustrated by austin, but the exhausts were long individual pipes (4 into 2 into 1, probably, I can't remember) and everything fabricated in thin steel rather than cast. The inlet was a separate assembly which, as I say, stayed behind in Norfolk. the tongues which projected into the block were probably no more than 1/16" thick, austin's version looks to be rather more substantial.