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Old 29 Jun 2007, 12:06 (Ref:1949643)   #1
Frank de Jong
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Frank de Jong should be qualifying in the top 10 on the gridFrank de Jong should be qualifying in the top 10 on the grid
Cooper S 1275 - when did it go 1293 cc?

I've just finished researching the 1964 BSCC (BTCC) for my site. This was the year that the 1275 Mini Cooper S was first raced. In early programmes, some entries were 1293 cc, but later in the season every entrant seemed to stick to 1275 cc.
I'm sure I read somewhere that Broadspeed actually was the first one to be able to increase the bore to get 1293 cc, but I can't remember where I read that.
Does anybody know here if in 1964 1293 cc engines were used at all?
It's a tiny detail of motorsport history of course (just 18 cc...) but I'd like to get my data right.
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Old 29 Jun 2007, 14:23 (Ref:1949746)   #2
SidewaysFeltham
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The 1275 Cooper s was on standard bores: boring to plus 60 thou gave a swept volume of 1293.

Homologation allowed re-boring to within standard factory recommended limits.

Since the then saloon class limit was 1300 c.c and as every little helped, most competitive race and rally cars were 1293.

All of our 1275 s cars were run at 1293 c.c.
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Old 29 Jun 2007, 14:33 (Ref:1949757)   #3
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Frank de Jong should be qualifying in the top 10 on the gridFrank de Jong should be qualifying in the top 10 on the grid
I know the cars could be re-bored, but my question is was that been done from the start in 1964 or was it later?
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Old 29 Jun 2007, 16:22 (Ref:1949844)   #4
SidewaysFeltham
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Race programmes are not in fact always a very accurate reference source!

The actual official size of the Cooper s in this official configuration was 1,275 c.c.

However, most race and rally engine builders over-bored to +20 thou as a matter of course. (n.b. Correction to earlier post, 1293 c.c. is +20 thou, not 60 as I stated earlier: it's been a few years!).

I can try and find out for you as my best friend (and oldest one too, as we have been chums since we were at school in the early 50s!) is one of the leading figures in the official heritage Mini Cooper Register.

As to when, exactly, that the first tuner discovered the slightly extra bore size would have probably been the first day +20 pistons became available!

It is worth remembering that the Cooper s engine was based on the works XSP dry sump. 1,000 c.c. Formula 3 engine, which used forged steel crank and rods, duplex timing chain and the extra stud in the head, which was a special casting to accomodate the larger inlet valves.

From memory, forged pistons were an homologated option for the s, in all three sizes.

In all probability, privateers would have had to wait until Hepolite (e.g.) came up with suitably strengthened +20 thou pistons to allow the extra swept volume; whereas Abingdon would have used them on competition cars from day one.
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Old 30 Jun 2007, 07:38 (Ref:1950259)   #5
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zefarelly should be qualifying in the top 5 on the gridzefarelly should be qualifying in the top 5 on the gridzefarelly should be qualifying in the top 5 on the grid
the capacity hike is the same principal as Fords engines, the twink was 1558 but most where overbored 20 thou to 1598cc . . .squeeze every little drop under the 1600cc class limit
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Old 30 Jun 2007, 08:12 (Ref:1950285)   #6
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275 GTB-4 should be qualifying in the top 10 on the grid275 GTB-4 should be qualifying in the top 10 on the grid
Overbores

Plus 20 = 1293
Plus 40 = 1312
Plus 60 = 1330

From what I've read, and generally speaking, 1310 (1312cc) was a much more popular capacity (other than works cars).....in the period
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Old 30 Jun 2007, 12:41 (Ref:1950463)   #7
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Excepting, of course it would have then been outside the class limits (1,300 cc.) for both saloons and rally cars.

Many people tried some amazingly silly things!

Like taking standard mini blocks to 1,700 c.c..

I saw some interesting blocks which would have probably been classed as air-cooled! Some strange shaped con-rods and some amazingly Daliesque pistons...............

The core problems with the whole A series was the three main bearings; the siamesed centre inlet ports and the fairly poor block castings and thin walls.

That's why Ford became supreme. Plus the basic over-square nature of the 105E onwards range, of course.

And later on the cross flow heads.
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Old 30 Jun 2007, 18:48 (Ref:1950726)   #8
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zefarelly should be qualifying in the top 5 on the gridzefarelly should be qualifying in the top 5 on the gridzefarelly should be qualifying in the top 5 on the grid
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Originally Posted by Michael C Felth
And later on the cross flow heads.
better gas flow maybe but all the best ones still used chambered heads !

precrossflow rules . . .like the dinosours
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Old 30 Jun 2007, 19:28 (Ref:1950759)   #9
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I agree! Not in the ethos of the original car.

I used to run what was then the fastest non-crossflow 999 c.c. Cooper s in the UK!

Originally the car of the US driver, Ed McDonough and I gave the lump to my chum, arch Fordie and FVA/FVC engine builder, all round eccentric, ex-Lotus Klingon, Bruce Rennie to sort. After huffing and puffing and throwing stuff around his 'shop as he was wont to (Don't you just hate these prima donna engine builders until you go quicker than everyone else?), and swearing about siamesed ports and "S*****g BMC Crap, he magically transformed it!

Milled the ports right out; gummed in a block of mild steel a la downdraft MAE, and split two DCOE 45s and made up a slide throttle.

Boy! Did that jump along! The addition of a Norman Abbot beam axle was the final bit.

If I can find some time later this weekend (probably next week!) I'll scan a pic or two.
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Old 16 Jan 2017, 20:51 (Ref:3703025)   #10
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hi, this is a complete shot in the dark but, having looked at your site over many years as an excellent source of research, but do you have a list of the colours of the cars used in the back 1964 season.

I am building the complete set of vehicles used in 1/43 scale.

Regards

Pete
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Old 17 Jan 2017, 20:56 (Ref:3703248)   #11
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So when did the 1380 become popular and was it ever homologated?
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Old 17 Jan 2017, 23:14 (Ref:3703269)   #12
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I don't think it's homologatrd. We were running 1380 and 1399 in the late 70s and early 80s and I have no reason to believe that it was a new idea even then. I even tried a long stroke 1380 which was something like 1460 (????? I can't remember) but kept burning pistons out around the original Combe.

AFAIK the only homologation it carries is Goodwood's!

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Old 18 Jan 2017, 09:08 (Ref:3703316)   #13
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So when did the 1380 become popular and was it ever homologated?
Manufacturers and thus Works Teams only Homologated (With the FIA), an, if you like, Wish List, for competition use at the time.

This was predicated on class regulations then ruling.

Cooper s specs were set to compete in circuit racing and international rallying, mainly.

Also remember, at this time (1960 to 1975: may well have changed quite a bit after I retired totally from the sport), homologated specifications were "Works Options"; i.e. in theory, anyone could order the optional bits or even a car built to the "optional" spec for competition.

One would have a hard job persuading works teams to fulfil such orders, as the factory was focused on its own team!

As I then ran three MG Midgets (in Modsports), we did manage to obtain a copy of the Midget/Sprite homologation papers.

Made yer hair curl!

Such esoteric delights as wide mag wheels; five-speed box, twinWeber 40DCOES (And naturally a four inlet port head); Lim-Slip diff; etc.

As Lord Nuffield, by this time, became extremely hostile to using motor sport to promoted his brands and had also become increasingly curmudgeonly and more focused on his charity foundation etc, his intervention starved Special Tuning Depart, at Abingdon of adequate funding. The earlier sad death of "Kim" (Cecil Kimber: The founder of MG sporting activities) in 1945, led to a gradual disassociation of BMC and Motor Sport.

Thus developments stalled.

In any case, the old BMC A Series was "far too long in the tooth", but Nuffield refused absolutely to invest in a new range of power plants, thus BMC were stuck with the A, B and C series; which was one of the core crisis points in the whole business and much contributed to its eventual demise.

Some members might be interested to read my analysis of the travails and misfortunes of what was the greatest British motor industry business, in an earlier age.

Here:

(N.B. Seems a software bug is scrambling the punctuation on that site; ignore!)

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Old 18 Jan 2017, 21:04 (Ref:3703430)   #14
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The reason for the overbore was to allow for taking a production and remachining o your own racing accuracy. The maximum over bore for homologation was 0.040". So it's for Cooper S 970 + 0.040" = 999. 1071+ 0.040" =1098, 1275+.020"=1293. For Ford twin cam it's 1558+0.040"= 1598. the Ford sizing is why there were Elan 1500s. The other Ford tweak was to take the max tolerance sizes on a 1600 BDA and getting 1601 cc, which allowed the engine to be bored out to around 1800cc as the class entered was then 1601 to 2000cc
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