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+--- Thread: Query on port-heads (/showthread.php?tid=4280)
RE: Query on port-heads - Henry Harris - 30-04-2020
(30-04-2020, 06:27 PM)Hugh Barnes Wrote: So, Roger, are we suggesting that 750MC newsletters from (say) 1950 and 1951 might reveal further details of the story? The Archivist can't recall what date the magazines go back to and it may be a while, of course, before he can find out...The first printed 750 Motor Club Bulletin was June 1951...
From the July 1951 Bulletin.....
February 1954 Bulletin.....
RE: Query on port-heads - Chris KC - 30-04-2020
A fascinating read!
RE: Query on port-heads - Hugh Barnes - 01-05-2020
Great stuff, Henry! the Archivist tells me he likes your post very much....
RE: Query on port-heads - Bob Culver - 01-05-2020
Some may be wondering what all this is about.
Individual pipes are to harness momentum effects and pressure pulse reflections. Because adjacent cylinders fire just half a rev successively, and valves do not open and close at tdc, the next cylinder valve opening robs some beneficial positive pressure filling effect developed at end of suction stroke of its neighbour. Effects applicable mainly at wide throttle. By making the conditions of all cyls more similar, mixture does not have to be especially rich as determined by the weakest. Nonetheless very many cars had siamesed inlet ports. Can complicate smooth fast idle.
Similarly in the exhaust. Separation of successive firing cyls avoids a positive pressure from a neighbour arriving at end of exhaust stroke just as the last gas exits. This involves grouping the outer cyls and the inner, the latter can be siamesed as on Minis etc. Further separation is an attempt to better develop and harness various timely negative pressure reflections and concentrate these on one cylinder at a time. Somewhat rpm dependant, and resonant effects can be annoying
RE: Query on port-heads - Nick Lettington - 01-05-2020
I have unashamedly stolen a photograph from Dave Armstrong's Speedex exchange. May be of interest...
8 port block.jpg (Size: 34.47 KB / Downloads: 352)
RE: Query on port-heads - Rogerfrench - 01-05-2020
Thank you Henry.
I don't think Chapman admitted to his modification until later, and then only in part. The real 8-port block wasn't widely known until many years later.
I believe, and Holly would agree, that the Lotus would have been a winner even without that block. When it wasn't in trouble it was so far ahead of the rest in 1951 it was silly. But then, compared to most of the rest it was a well-engineered professional car, and expensive too.
RE: Query on port-heads - Lowespeed - 01-05-2020
Geoff Harrison is correct the Peter Ross book gives great detail of the modifications in the book "Lotus The early Years" It also shows the earlier block with the circular ports (8 0f them) and the manifold on page 44. It also gives a description of its production. I do have a copy; but copyright from 2004 is still in place so I can't illustrate here.
RE: Query on port-heads - Archivist - 01-05-2020
I've spoken to Andy about the book he refers to. Although it does have some specific Austin 7 information, it would seem to swiftly move on to the later cars that are increasingly removed from the Austin 7. I would like to acquire the book for the Archive, but given the volume of A7 content, I'm loathe to pay some of the figures I see on Ebay. Being careful with Archive funds, if anyone has a copy that they might care to donate or knows of a copy that could be acquired for a reasonable sum, please drop me a line to archivist@a7ca.org...
many thanks...
RE: Query on port-heads - Nate M - 02-05-2020
Thanks for the response as well as the fascinating read and information regarding what Lotus's Colin Chapman did with the Seven engine.
Bob Culver Wrote: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
Would it be accurate to say the Big Seven, Eight and Ten like the copycat Morris 8 all roughly had a similar latent enlargement potential as the Ford Sidevalve later OHV engines (as planned on the pre-war Taunus G93A in 1498cc SV form and later on the post-war Taunus P1/P2/P3 in 1498-1758cc OHV form
It is interesting to see the difference in outputs between the Morris Eight / Minor SV with both the Wolseley Eight OHV and Alta head Morris Minor OHV conversion.
(30-04-2020, 08:08 AM)Ritchie Wilson Wrote: 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.
Taken together it would seem a Seven-derived engine that carried over the various improvements from BMW, American Bantam, Nissan D10, Reliant and Lotus, etc would potentially end up being a 860cc OHV unit with 4-to-8 port-heads of indeterminate output, since have seen claims of the SVs from Reliant, Rosengart and others claiming outputs of 20-24 hp when they were in reality only said to be putting out about 16 hp.
Also seem to recall a few Seven-based racers managing to displace as much as 900-950cc though not sure of the specifics companies and teams which did the work let alone would such mods could be productionized or be an improvement over the Big Seven and Eight engines.
Of the understanding the all-alloy Reliant OHV was basically slightly scaled down reverse engineered Standard SC engine used in the Standard Eight.
(30-04-2020, 03:31 PM)Rogerfrench Wrote: I have come to understand that the Mk III as raced by Lotus had a real, 8-port block with round inlet ports, and that Clive Chapman still has the block, which was planned to figure in the Mk V.
However, the Mk III as sold at the end of the 1951 season had indeed a couple of tongues projecting into enlarged inlet ports, as described above. That Australian Derek Jolly also de-siamesed a block seems beyond question, and that block made its way to Hornsey. Now, whether Chapman or Jolly did it first is debatable, we may never know.
There were several de-siamesed cars built after the 750mc relaxed the ban. My father owned one of them for a while, Complexity, whose engine lay almost on its side and had the manifold face of the block machined at an angle, removing metal from the lower edge so as to provide straighter inlet and exhaust ports.
Would have loved to have seen what a Lotus Mark V could have achieved given Chapman's belief a 100-mph road sports car could be developed using an un-supercharged Austin Seven engine that the Mark V was design for, even if it must have presumably laid the groundwork for the Mark VI and Seven.
RE: Query on port-heads - Jeff Taylor - 03-05-2020
Hi Nate M,
Unfortunately can't add anything at all to the interesting discussions above other than to say that I happen to own both a new old stock Morris Eight 'Military Tank' engine - (these were fitted to the Army's Centurion main battle tank powering a generator and are based on the 1951 / 53 Morris Series MM Minor SV engine block with the 'in water jacket' water pump / thermostat and external oil filter cartridge unit) - and a now seemingly rare 1946 to 48 Wolseley Eight OHV engine which is in many ways a scaled down version of the MG XPAG as both engines were designed by Claud Bailey. I don't unfortunately have an Alta OHV head conversion unit for the Morris 8 / MM Minor SV engine though I suspect the Wolseley 8 OHV would offer an improvement over the Alta OHV head especially if it were to be breathed upon as seen below. Of course the Wolseley 8 OHV uses a fibre camshaft timing gear / steel crank gear rather than the Renold duplex timing chain used in the Morris 8 / MM Minor SV engines.
The enclosed photo shows what is said to be 'high performance' 1946 Wolseley 8 OHV engine fitted to a 1938 Morris 8 Roadster Special over in Australia. Here's the build spec:
"This 1938 Morris 8/40 Roadster Special was originally built back in 1958 and powered by a 1946 Wolseley 8 OHV engine - one of only 4 Wolseley 8 engines in Australia at that time. The car has been completely restored / rebuilt in recent years reinstating the Wolseley 8 engine in place of a Toyota Corolla engine that had been fitted to the car in the early 1970's.
The chassis was welded and stiffened together with the fitting of telescopic shockers, 9" brakes and rack and pinion steering.
The current Wolseley 8 OHV engine was imported from the UK and rebuilt for high performance by Brian Sampson - bored to 1050cc, 9:1 compression ratio, special sports camshaft, twin 1.5" SU carbs, bespoke inlet manifold and exhaust extractors, 12v electrics and Tacho fitted.
The gearbox is a 4 speed Morris 8 Series E driving through a 4.8 Wolseley Hornet Diff."
The hope is that one of these days I may get round to dropping the Wolseley 8 engine into my 1936 Morris 8 Series I Tourer - would be even better if I could have its performance uprated to the above spec though I suspect that could prove rather expensive!
Screenshot 2020-05-03 at 14.03.33.png (Size: 1.02 MB / Downloads: 185)
Jeff.