I swapped it with a guy in South Africa for some parts. They’re a bit tricky to find now as most of them got turned into 1275 engines

There will be little progress in the next few months for obvious reasons, the next couple of stages are:
Buy some A+ conrods, get them refurbed & buy new crank bearings
Take the block for a dry build and get it decked to suit the shorter stroke
Once that’s done I’ll get the short block completed and then work on the head

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Hen's teeth now.
I sold two to a fella from Warwick a while back and my stock numbers are very low.

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The bitterness of poor quality (or Crappy Workmanship) remains LONG AFTER the Sweet Taste of Low Price is forgotten.

I tracked down some A+ rods from a running engine. They look like they’ve had an easy life as they still have factory standard size pistons and bearings fitted. They definitely are much lighter than the 1100S ones with the big lumpy caps, and are apparently lighter than the Innocenti ones too

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any reason not to have the journals machined down and use S type rods?

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did I tell you that I won a trophy?

why?

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The bitterness of poor quality (or Crappy Workmanship) remains LONG AFTER the Sweet Taste of Low Price is forgotten.

I guess that's probably a good question... and I can assume the answer to my previous question is "because there's no need to"? unless you wanted to shorten the stroke even further? edit: -3mm stroke = 1024cc

I didn't realise there was so much difference between A+ rods and 1100S-type large journal rods

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did I tell you that I won a trophy?

I don't think that you should shorten the stroke on the crank. Leave it good and strong as is. I think that if you want a 1024cc ish, then bore a 998 and put a 1275 head on it.

I think that a big bore using the stock stroke of the SA crank is a better way to go. 1250ish would be better than the 1024cc.

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The bitterness of poor quality (or Crappy Workmanship) remains LONG AFTER the Sweet Taste of Low Price is forgotten.

I'll be using polished Innocenti rods.

In standard form;
Innocenti made from EN19 and weigh 675grams,
1100S large journal made from EN16 at 750 grams,
A+ made from EN15 at 650 grams

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The bitterness of poor quality (or Crappy Workmanship) remains LONG AFTER the Sweet Taste of Low Price is forgotten.

I had thought about swapping to the smaller journal rods, but all the guys in the UK run the 1.75" ones, and I didn't really see any good reason to get the crank ground that much. Maybe on the 3rd or 4th rebuild I might have to consider it! I think that more surface area on the bearings will give more service life too. I also don't have any S type rods, and these were probably cheaper than an S rod in similar condition.

Vizard's book has the stock Cooper S small journal rods at 690g, so heavier than the A+ and a bit more than the Innocenti ones (of course they were also made with a higher grade of material than the regular 1275 rods).

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Agreed Timmy.

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The bitterness of poor quality (or Crappy Workmanship) remains LONG AFTER the Sweet Taste of Low Price is forgotten.

thanks guys, sorry for the ignorant questions/comments - I've only ever worked with small journal 1275 engines... I heard about the south african cranks a few years ago but didn't have any detail

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did I tell you that I won a trophy?

Don’t stop with the questions! I’ve got a very limited knowledge or these engines too, and I’m learning as I go

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Totally agree Timmy, don't stop the questions! I'm learning heaps out of this and would absolutely love one of those cranks. I will have to keep an eye out for one.
PS great work on your other engine. Looks spot on!

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1963 Morris 850 Smoke Grey
1963 Morris 850 Shadow Blue
1965 Morris Mini Smooth Van
1966 Morris Mini Van
1969 Morris Mini Deluxe Resto
5/72 Clubman Gt

Hi Timmy
If you are going to build a short stroke engine you will have to rev it to make it go, as the 970 1071 engines really don't make a lot of power.
If you want to build a strong short stroke engine de stroke a big journal down to 1.625 size this gives you less surface area less friction, and a lot less weight to turn around at rpm.
Bore the motor to 73.5 mm this will give you 1328 cc I have built a few of these engines for people and they perform really well good torque and power.
Don't put a 1275 head on a small bore engine as they are to big for the little engines, on my formula junior race car 1100cc I have a 202 head on that making 121 HP and 93 ft lb of torque much better spread of power than the 1275 head.
Graham Russell

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"It's better to be not informed than ill-informed"

Thank you GR.
Yes we know that the engine will like a rev. that's why we are building them. Cam choice and head etc also will come into play here in regard to power/torque band.

I certainly wouldn't be de-stroking or using small journal rods with my engine. If we want to reduce weight at RPMs I guess a lightened flywheel will do the job.

Oh you most certainly can run a 1275 head on a small bore Mini (note: not a Formula Junior race car) with great results. Nice and usable around town too.

EDIT: "there was a one-off type of engine, of which only around 40 were made, built for John Cooper’s Formula Junior race cars. It is not well known, but worth having a look at. This was based on a 950cc A-series block, with a bore of 2.661” (67.6mm) and stroke of 3” (76.2mm) – giving a capacity of 1095cc – and produced 98 hp at 7,800 rpm with a 40mm Weber. The first version used a smaller cam and twin SU carbs, and produced 94hp.

It was dry-sumped and had special rods, but the best part was the cylinder head. This engine had a small-bore head (with two casting numbers – AEA626 and 12A185) which was almost the same as the 12G295 head"

Thank you again GR

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The bitterness of poor quality (or Crappy Workmanship) remains LONG AFTER the Sweet Taste of Low Price is forgotten.