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Cymber
United Kingdom
966 Posts |
 Posted - 30/01/2010 : 21:11:44
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I have just reread John Bolster's book Specials and find his comments on the engine of one of the Wharton Specials surprising. I quote:-
"A supercharged J4 MG 750cc engine is used, which has been persuaded to revolve at the breath-taking velocity of 8000 r.p.m. It is tolerably reliable, but made strange and expensive-sounding noises at the September Shelsley meeting, 1948, when it suffered a broken camshaft. Nothing appears to happen to the two-bearing crankshaft."
Did these engines really run to 8000 rpm?
The car had a modified late model Austin Seven chassis with LMB independent front suspension conversion. Would this really have been a better chassis than the original J4?
Maurice Blakey. |
Edited by - Cymber on 30/01/2010 21:13:33 |
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Peter Green
United Kingdom
1682 Posts |
Posted - 30/01/2010 : 21:39:46
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Maurice,
Yes a 750cc J4 engine could and would rev to 8000 rpm. I know that Barry Foster revs his C type engine to at least 8000 rpm.
Peter. |
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Cymber
United Kingdom
966 Posts |
Posted - 30/01/2010 : 22:11:38
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On original cranks?
Maurice. |
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George Eagle
United Kingdom
3238 Posts |
Posted - 31/01/2010 : 11:21:05
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I can recall a photo taken of the rev counter taken out of Barry Foster's C type, the instrument had broken with the needle at 8500 rpm!! 
George Eagle |
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MaGic_GV
United Kingdom
868 Posts |
Posted - 31/01/2010 : 12:53:44
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Geoff Coles campaigned the special for a while. In the yearbook for 2000 Michael Coles briefly describes this period - handling was frightening, and apparently Ken Wharton said '...well I built the thing so I had to drive it!' The picture in the article shows a somewhat crude device, of the sort the VSCC (and MGCC?) would probably not accept today - most specials still racing look far more professional than their original pictures show!
Cheers,
Graham |
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David Allison
United Kingdom
665 Posts |
Posted - 01/02/2010 : 12:01:48
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The standard J4 crank will go to 8000 rpm and beyond - but it is NOT to be confused with a standard J crank.
The bent wire crank is reasonably safe to 5500-6000 as long as was brand new.
MG very quickly fell foul of the 80 mph J2 and a lot of engines were burst trying to repeat the feat!
The J4 has a fully counter balanced steel crank and 8000 rpm although not condoned by the works (the rev limit relayed to Hamilton was 7000 rpm) was accepted (probably because Hammy never looked at the rev counter).
The J4 was a very free revving engine most of the C types and J's that have raced seriously are revved very hard indeed - if you go much beyond 7000 rpm though on any MMM engine however then the risk of problems increases a great deal.
Fine for a racing car - not really for road use!
Regards David |
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MDP
United Kingdom
35 Posts |
Posted - 01/02/2010 : 13:08:27
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The R went beyond 8000 rpm, but not with original crank, rods etc. The problem was that the rev counter ran out of numbers & I was more concerned with looking at the fast approaching corner...
It would be good to find an old 'historic' 4 cylinder car that needs rebuilding to see what is the absolute maximum power that can be achieved from one of these engines. I'm convinced that a well built 4 cylinder single seater MG would keep up with the ERA's.
Mark |
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David Allison
United Kingdom
665 Posts |
Posted - 01/02/2010 : 15:55:19
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The standard valve gear is ok to around 4500 rpm (9000 crank speed) - but lubrication gets a bit critical beyond 8000 rpm.
A story from early post war was that an R type led the allcomers from the exit of Club corner on lap 1 until the exit of Becketts of the same lap - Bill Moss who was driving Remus (ERA) reported the "noisy little thing was pulling away like a train!" then the blower drive broke.
Until a certain MDP got his car running a couple of years ago a 4 cylinder car never went so well again.
Dick Last got the Parnell K3 running very well a couple of years ago and put a cat among the pidgeons and Sid Beer finished the Seaman in third place back in the 60's - Sweets K single seater used to finish in the top 6 regularly and Dick Summers K single seater got FTD at Prescott.
I would love to see an R type fully developed and am sure that on 16 inch tyres that ERA's would struggle around a circuit like Silverstone or Cadwell particularly in the wet.
My dad always says that you struggle on really long straights against the ERA's because they accelarate so fast and are able to get their power down.
Seriously I have always thought that a 750 blowing at 30 plus should give around 160 bhp at the wheels and be reasonably reliable too - in sprint races (VSCC scratch 10-15 lappers) if an R type can make a good start I think it is capable of staying in front.
Tom Dark drove the R very well in the wet at MGCC Silverstone a couple of years ago and would have won if the rear brake balance had been wound off a bit.
I still think the car is sett up too soft and the tyres are way too narrow to make the most of the extra grip and road holding available from the suspension though.
Maybe its time to start again Mark?
But I aint paying for it!
Regards David |
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MDP
United Kingdom
35 Posts |
Posted - 01/02/2010 : 17:33:28
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My old R (a fantastic thing it is) lifted one if not two wheels on the fairly narrow 19" tyres we used. I don't think wide 16" ones would be a good idea - not without anti-roll bars anyway (& they're not allowed!). It did need stiffer torsion bars, but we didn't get around to that.
Mark |
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Ray Masters
United Kingdom
568 Posts |
Posted - 02/02/2010 : 16:15:08
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| The lifting of one rear wheel was 'designed out' in my Q engined single seater by the fitting of a De Dion rear axle. This was designed & built by the then owner Geoff Monk & his pal Alan Bell; but still incorporation a PA diff. & drive shafts made from P-type prop. shafts! Regarding engine revs, we always limited those to the original limit of 7200 rpm even though it had a rather special Robin Jackson crank & Bonneville rods. I could give the ERAs a good run of the line but they soon pulled away after that!. In the (then) 20 lap Seaman Trophy Race at Oulton Park we used to reckon on being lapped twice, even so I was topped up with fuel on the start line in the 15 gallon tank. It used to do about 3 1/2 mpg when racing.It won the handicap section of the race a few times. The car was on 15 inch wheels from its original design as a 500ccs F3 car. These were possibly the first 15 in. wheels made by Dunlop . |
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McEvoy
United Kingdom
252 Posts |
Posted - 02/02/2010 : 16:56:34
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This topic has certainly encouraged me with the building of my 4 pot 750cc s/c MG special knowing the sort of power and revs obtainable at a price!
Mark & Tom's exploits with the R have given me some of my best motor racing moments and only increase the regret I have in not achieving something with 0257 & 8 in the 50's & 60's - continually moving home & job didn't help.
The previous owner of 0258 told me that he achieved a lap time on the old Silverstone Club Circuit in I think the early '60's of 1min 12secs a time I believe in the ERA area. I have no evidence of this I don't know if this was recorded in a race or practice and it would be nice to know if any one can shed any light on it. At that time the car was fitted with the McEvoy twin cam head a single stage rootes blower and on the SU Carburetters dyno in Birmingham recorded 120BHP at the back wheels.
Mark is right the suspension is too soft and on 0257 we fitted an additional transverse leaf spring with snubbers rather like the Coopers of the late 50's. This springing medium with interlinked wishbone connections was considered by MG as shown on some of their drawings.
Maybe a slip of the finger Mark, you mention 19" tyres the originals were 18" but whatever the car was a credit to all concerned and what a shame that you could not continue and develop it, just hope it is going to be used in the same way with the new owners.
Bob |
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Colin Butchers
United Kingdom
1487 Posts |
Posted - 02/02/2010 : 18:03:42
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The engine referred to by Ray was developed by Robin Jackson for Dr A R Samuel's QA0256 in 1934/5 and the crank was made by Jackson to the design of Sinbad Milledge. It was fully counterbalanced and nitrided and the special rods - also designed by Milledge, were made from Hiduminium RR56 forgings and only machined at the small and big ends with the main H section being polished. The rods ran direct on to the crank journals without any white metal shells This produced rods which were lighter than the standard M.G. Q-type items. In this form, Jackson managed to get QA0256 round the Outer Circuit at Brooklands at 124 mph with a maximum speed of 138 mph when coming off the Banking and crossing the Fork on full throttle at 135 mph at 7200 rpm.
The engine was removed from QA0256 in 1938 when the car was sold to Australia and eventually it found its way into the rebuilt and much lightened QA0251 after the war when it was owned firstly by David Murray and then by Geoff Lant. Lant competed regularly with QA0251 until the early 50s and frequently took the revs up to 8000. I am not aware of any problems he had with the bottom end but initially the head would lift through stretching of the head studs. This was cured when Geff was able to obtain some magic aero quality steel, but the difficulties then moved to the valve stems where circlips or collets (he tried both methods) constantly broke. These problems were never cured and the constant stream of new valves which he had to fit eventually caused him to remove the engine in the early 50s. And that is how Geoff Monk managed to obtain the engine for his single seater.
Colin B. |
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Ray Masters
United Kingdom
568 Posts |
Posted - 02/02/2010 : 20:14:08
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| Thank you, Colin, for your input. I still have the special con-rods but one is slightly damaged as a result of one breaking & damaging another ( there was a spare one when Geoff Monk bought the engine from Geoff Lant.) Triumph Bonneville rods replaced the originals. The head lifting was cured by Geoff M. (an A.V.Roe employee) by having special studs made, rolled threads, heat treated,de-embrittled etc. etc. at work. |
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Cymber
United Kingdom
966 Posts |
Posted - 04/02/2010 : 20:47:11
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This topic turned out much more interesting than I anticipated, thank you everyone.
I had assumed that all MMM cars originally had bent wire crankshafts as possibly did Bolster although I would have expected him to have been better informed than that.
Maurice Blakey. |
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David Allison
United Kingdom
665 Posts |
Posted - 08/02/2010 : 10:17:01
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John Bolster was a great journalist and motoring writer - however his technical knowlege was limited - there is a tale of him instructing his mechanics to change a spark plug to cure a misfire, when the bonnet was opened a rod was hanging akimbo!
He refused to listen (probably deafened by the ERA's engine) until the plug had been changed.
Regards David |
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