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Ian Grace
USA
661 Posts |
 Posted - 23/01/2021 : 18:37:16
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A VMR member has unearthed this cylinder block and head in New Zealand. The head has been copper plated - any ideas why? But the block is of more interest. The number is 2382A, but if this were an OHC Minor block, it would be an early one compatible with the small dynamo, but this block has the concave front compatible with the later dynamos. Under the number is 'J72'. Is this possibly a J2 block?
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Oz34
United Kingdom
2546 Posts |
Posted - 23/01/2021 : 18:55:58
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Ian, this is indeed a J2 block. J2 engines up to 2500AJ had the "type number" 72 and beyond that, 117 thus 2382AJ 72, the A I think signifying that it is standard bore, but I await being shot down on that!
Dave |
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Onno
Netherlands
1046 Posts |
Posted - 23/01/2021 : 19:07:46
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I have read the copper plating was “popular” in period to up performance.
The actual benefits might have been questionable but it looks good
Onno "J,D" Könemann |
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Simon Johnston
United Kingdom
6145 Posts |
Posted - 23/01/2021 : 19:09:50
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As Dave says, a J2 block originally in J3451, a black swept wing car with green upholstery first registered on 4 August 1933 to a G.W. Fenwick of Thorpe St Andrew, Norfolk and seemingly not heard of since.
However, on checking my engine number, there’s no sign of the '72' And what looks to be a different font as well.
Simon J
J3437
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Edited by - Simon Johnston on 23/01/2021 19:26:30 |
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sam christie
United Kingdom
3108 Posts |
Posted - 23/01/2021 : 19:53:26
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If you have difficulty obtaining an original OHC Minor block a J2 block will do for the purpose although it offers no great advantage.
This one came from J 3097 . The number is something like 1920 CJ 72 and it is now with an OHC Minor.
Sam |
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Ian Grace
USA
661 Posts |
Posted - 23/01/2021 : 20:20:18
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Sincere thanks for the immediate and fascinating information. Do we know the registration number?
Regarding the A suffix, I can quote from a post I put on the VMR forum many moons ago. Minor blocks (both OHC and SV) are nearly all A, some B and I have come across one or two C's. While the following is specific to pistons and not blocks, I feel confident that the suffix letters are closely related.
"Down in New Zealand, Alex Dempster has been stripping down a SV engine which still retained its original standard pistons and was wondering about the markings on the piston crowns. Here is what the Morris Owner of June 1932 had to say on the subject:
Regarding the markings adopted for Morris pistons, the complete range of pistons comprises five groups, of which "A" is the nominal or standard size. The remainder are considered oversize and the increase in diameter between each group is 0.25 mm. They are designated B, C, D and E, the latter being obtainable only to special order.
Each group is then divided into twenty-four individual piston sizes ranging from -13 to +10. These figures refer to hundredths of a millimeter, and not thousandths of an inch as is commonly supposed. Consequently, the variation in diameter between two consecutive pistons is only 0.01 mm or rather less than half a thousandth of an inch. For example, size A-10 would indicate a standard 57 mm piston with a diameter equal to that of the bore minus 0.1 mm.
In selecting a piston at the works, the following example can be taken: The piston clearance (which incidentally, should always be measured at the skirt) for the Minor is 0.11 mm to 0.12 mm. Assuming that piston A-10 is fitted and as a result of wear the skirt clearance has increased to 0.18 mm, then the following deduction applies:
A-10 piston fitted
Skirt clearance 0.18 mm
Skirt clearance required 0.11 mm
Difference 0.07 mm
Therefore A-10 piston plus 0.07 mm equals A-3 piston needed. Naturally, it is impossible to accurately forecast the piston size which will be needed after reboring, since this is entirely dependent upon the size of the cylinder bore when cleaned up. Careful micrometer readings should be taken of each bore, when after deducting the requisite clearance, you will arrive at the piston size. The letter "P" on the piston crown indicates that the piston is of the Morris parallel type" |
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Ian Grace
USA
661 Posts |
Posted - 23/01/2021 : 20:28:56
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And I just realised that there is a casting date - 5 4 33. Does that tie in?
It also got me thinking about any differences between the J2 and the Minor block. I think the cylinder head studs were larger diameter, and it looks like it took studs to attach the alloy sump, but perhaps these were the only differences?
So I'm thinking that some J2's (as well and M's and D's are fitted with Minor blocks these days? |
Edited by - Ian Grace on 23/01/2021 20:33:30 |
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Oz34
United Kingdom
2546 Posts |
Posted - 23/01/2021 : 20:39:12
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More fascination Ian in your mentioning that over-sizes were in hundredths of a millimetre. Presumably stems from the Hotchkiss origins of these units.
Onno, I also seem to remember reading something similar and I have a feeling that it was something like (strange as it may seem!) the head could stand a higher C/R. Is this something else on which I await being shot down?
Dave |
Edited by - Oz34 on 23/01/2021 20:42:23 |
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Ian Grace
USA
661 Posts |
Posted - 23/01/2021 : 20:43:11
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| Very probably, I should think. Anyway, I told the chap in NZ that he has the substantial beginnings of a J2 restoration! :-) |
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Simon Johnston
United Kingdom
6145 Posts |
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Chris Bucknell
Australia
107 Posts |
Posted - 24/01/2021 : 00:14:37
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| Yes I agree with Onno. Somewhere in the Forum Archive is a topic on bronze cylinder heads where the copper plating was also dicsussed. |
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LewPalmer
USA
3244 Posts |
Posted - 24/01/2021 : 02:16:41
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Perhaps the copper plating was to aid in the sealing of the head gasket. ???
Lew Palmer
PA1169, 2M1281, NA0651 |
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Onno
Netherlands
1046 Posts |
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Colin Butchers
United Kingdom
1487 Posts |
Posted - 24/01/2021 : 11:24:51
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It has already been established that
copper plating of cylinder heads was commercially available in the 30s and I am certain that it was to assist with heat transfer in an effort to prevent cylinder head cracking. Quite recently I was looking for something else and came across a Yearbook article titled "The post war history of EX127". In it there is reference to a German man who obtained parts of EX127 including the engine and a spare bronze head. In order to make a bit of money he decided to melt down the spare head and sell the block of copper, so he put it in a crucible and turned up the furnace. It did not melt, so he increased
the furnace temperature. Eventually the head exploded with a loud bang. It turned out to be standard cast iron head which had been copper plated !
I have also been puzzled why Harvey-Noble ran his single seater QA0258 with one of the bronze heads which Robin Jackson had persuaded Cecil Kimber to supply, but then removed it for several later events. Why should this be, when the bronze heads were so much better? I have now been told that Kimber pointed out to Robin Jackson that it was only on loan and he asked for it to be returned. It probably ended up with all the other spare bronze heads and other racing goodies stored in a basement away from the factory in Abingdon which was bombed during the war and simply filled in and eventually had a block of flats built over it.
Colin B.
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Ian Grace
USA
661 Posts |
Posted - 24/01/2021 : 16:13:38
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Gipsy engines - fitted to Gipsy Moths, Tiger Moths and many more aircraft originally had bronze heads, but later engine variants were fitted with alloy heads with steel valve seat inserts. The reason for the change was to save weight. The bronze heads were vastly heavier than the alloy ones. Bronze was probably used to dissipate heat in what was an air cooled engine. The heads were covered in cooling fins, as is common in air-cooled engines.
The problem with the alloy heads - apart from trouble with the valve seats coming loose, was that their lightness made the Moth very tail heavy. The design of the Moth is naturally slightly tail heavy anyway, requiring rigging to be done to bring the C of G as far forward as possible while keeping the centre section within defined rigging limits. So the alloy heads made the weight and balance situation more tricky.
How's that for thread creep?! |
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Oz34
United Kingdom
2546 Posts |
Posted - 24/01/2021 : 16:32:24
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Not sure if this is thread creep or not but, the "type number" of the early PA engine was 135 while the introduction of the second breather was a sufficiently major mod to warrant a change in number to 165.
Not knowing a great deal about J Type engines, was there an equivalent change from a "72" engine to a "117" engine?
Dave |
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