Identifying 1275 engine

[andrew.searston]

Hi there
I’m ordering parts to build my 1275 engine, I’ll be doing a rebore, so that I get the right parts could some identify what I have. If the pistons have been oversized. And what size pistons I can go to without offsetting the bore
Thanks

[philthehill]

The engine looks to be from a Marina. I cannot make out if there is any additional ribbing on the block making it an 'A' Plus engine.

I see that the engine number tag is still in place so knowing the engine number would be a good start.

I would suggest that plus 0.60" is about the limit.

If you offset bore right from the start you will have a few more bites of the cherry as regards re-boring.

If you have the Vizard book 'Tuning the A Series' all the details and measurements are set out in Fig:14.3. Page 387.

My own 1380 A Plus block has been offset bored to 73.5mm bore and that gives me a second chance of a re-bore to 74mm.

My other 1275cc Midget engine has been offset re-bored to 74mm giving a engine size of 1400cc.

I have found one of these parts lists to be invaluable in identifying and sourcing parts.
https://www.ebay.co.uk/itm/NEW-MORRIS-M ... Sw9WBeYP10

The BL Marina workshop manual is especially helpful. The Ital section was issued as supplements.
I have BL Marina wksp manual AKD7555. I have kept it up to date with the factory revisions and there are a lot of them.
I also have Ital supplement AKM 4580/1 1980 onwards to be used with operation manual AKM4580.
Plus supplement AKM3660/1
and BL / Churchill Special service tools supplement. VLD/1126/2/71.
I do have the 2.0 ltr supplement AKM4580/2 but that is outside the scope of this thread.

[ampwhu]

here's the 1275 i'm going to be building

1275.JPG (70.32 KiB) Viewed 1922 times

1275a.JPG (59.12 KiB) Viewed 1922 times

1275b.JPG (54 KiB) Viewed 1922 times

it's a midget engine thats been lined and is standard bore. its now been stripped and is ready to go to Southern Rebore to be machined. I've already spoken to them and when there's some freedom to move, i'll be down there for a chat. According to Vizard's book, i have cooper S con rods. (whatever that is).

i've gone for a rebore, skim the block, new camshaft bearings and they supply new pistons and rings.

it's going on my van with a full maniflow system, Hif 44 carb (I already have these) and whatever Phil recommends going forward

i was going to start a new thread when its back from the machine shop.

[RobThomas]

If it has S rods then it may also have an EN40B crankshaft. One on Ebay recently for £1200 (not entirely realistic?) Other version will have EN16T on it, IIRC. Worth having a look.

[les]

——- Cooper S con rods, you’ve got to be a lot older to know what that is!

[ampwhu]

con rods say AEG 521 on them. according to vizards book, on page 377 it's says there cooper S con rods. now i'm stupid but I know that anything mentioned with the word "cooper" is going to be half decent.

i'll check the crankshaft later...……..

[ampwhu]

——- Cooper S con rods, you’ve got to be a lot older to know what that is!

i'm an old git, don't worry!

[ampwhu]

https://www.cckhistoric.com/1380cc-race-engine-build/

CCK historic own southern rebore. I guess they know what they are doing. They come recommended.

[philthehill]

The Cooper S was fitted with two different sets of conrods.
The first type were made from EN24V (forging numbers AEG177/Aeg521) and are the best BMC factory/production rods ever produced.

The second type were made from EN21 (forging number ARG625) which whilst good was not as good as the EN24V rods.

The very early 1275cc Midgets had EN40 crankshafts and were nitrited (pickled in other words) the same material as the 1275cc Cooper S.

The production costs of the Nitrited crankshafts and EN24V con rods put paid to long term production and both the Cooper S and the Midget fell back on the EN21 conrods and EN16T crankshafts. Some crankshafts were heat treated and some were not.

[andrew.searston]

Thanks guys real help, here is the engine number if it helps, looking at the pics of the pistons are they standard.

[philthehill]

Andrew
1275cc Marina engine prefixed 12V with High compression pistons.

A good engine to base a rebuild on.

Phil

[andrew.searston]

Has anyone used and recommend these rods

[andrew.searston]

Thanks phil that’s good to know I can’t see any oversize marks on the pistons so assuming there standard size. Would any mini high compression pistons work?

[ampwhu]

yes, I have the EN40B crankshaft. it is stamped with 12G 1321.

[philthehill]

The rods above appear to be for 1.625" big end journals.

The Marina has 1.75" big end journals.

If you do purchase this type of rod the pistons have to be matched and the gudgen pin fitted otherwise the gudgen pin can move sideways and score the bore.

Mini pistons will fit but the gudgen pins are a pressed fit in the small end of the rod on 1275cc engines so an engineering shop will have to fit them.

[philthehill]

EN40B crankshaft is good.

[andrew.searston]

I’ll stick to the original Conrods to keep cost down haha. So high compression mini pistons on marina rods need to be fitted at machine shop not just a straight swap over?

[philthehill]

Have a look at this you tube video.
This is how most machine shops remove and fit interference gudgen pins from 1275cc rods.

https://www.youtube.com/watch?v=HvS3K3HYpvQ

[ampwhu]

cheers phil. me being stupid, tried to remove the pistons from the rods. I couldn't and stopped before I made a mess..

[andrew.searston]

I have to rebore and machine the crank anyway, as it’s a budget build what would be a nice cam to fit. Thinking fast road. Already have maniflow exhaust and hif carb. Think there standard pistons so what would be a worth while size to bore it to? 1340, 1360, 1380. It will have the standard head back on