22 replies to this topic

[Fordy]

I have recently purchased a mini engine off ebay for a first mini project, it was advertised as a 1275gt engine. I have tried doing some research on the engine to confirm that it is definitely a 1275gt as stated. I have listed below various numbers/identifications that I have found on different parts. I have already done some research on the internet, but so far unable to find anything which matches up exactly to what I have got. If anyone could help me identify that would be great.

 

Engine: BHM1442N

 

Cylinder head: 12G940

 

Flywheel housing: 22G 1921    D1268

 

Gearbox casing: A/BZ 4           DAM

                           BC&M            3220

 

Crank: DAM 6232

 

Differential crown wheel: 22 A 411      

                                        18/62  

 

Laygear shaft: G 927

 

I also believe the carburetor is a HS4 from comparing it to photographs online.

 

Thanks,

 

Fordy

[RHDmini74]

http://www.minimania...on_Data_UPDATED

This page has some good info. I know the 12g940 head is a big bore 1275 head.

[Spider]

I don't have a listing for that particular Engine No. however it is a Silver or Gold Seal Engine, meaning it's been reconditioned (at some point!) by the factory, though with the BHM prefix, I'd say it's post 82.

 

The Gearbox Case is likely 1275GT approx 77 - 78-ish, and not reknown for be strong, they crack through the centre web, and it doesn't have the GT gearset.

[Fordy]

Does this mean the gearbox and engine are separate and were never ran together? And shouldn't be ran together? I cant see any obvious signs of cracking on the centre web, thanks for the heads up though.

 

Also found out that the diff ratio is 3.44:1 and the engine bores measured 70.61mm

Edited by Fordy, 10 January 2016 - 09:45 PM.

[Spider]

They were likely separated when the engine was fitted, but could well have run together since. As long as it has the matching set of drop gears, there shouldn't be an issue there and it would stand out like the proverbial if they were the wrong drop gears.

 

Seems to be a standard bore size, ie, not over size, though it may have had sleeves fitted (and nothing wrong with that).

[Fordy]

Ok thanks I shall check the drop gears and make sure that they are a matching set. The bores don't looks like they have sleeves fitted, I did get told that they had been honed when purchased.

Should I work off the basis that it is a 1275gt for any parts I may need to buy? And other components such as carb, ignition, etc?

Appreciate the help and advice as it is my first mini engine rebuild!

[Spider]

The 1275GT Engine was an ordinary 1275 Engine, ie, nothing particularly special over any other 1275 Engines, except for the Cooper S ones. I mention this because some may try to take advantage if they suspect you don't realise that they are the same, eg, "Oh, you need this one, it's Genuine GT" for example. It should be Pre-A+, though the last of them were A+.

 

The 1275GT Engine spec was 8.1:1 CR, 33 / 29 mm Valves in the head, 12G940 Head Casting, Simplex Timing Gears (though I think the early ones were duplex), fairly tame Camshaft (same as 1100 engine in profile), Single HS4 Carb, early ones were fitted with a 3.76 Final Drive, though about 73 they changed to 3.44:1 (which is what you have, but then so did every other Mini by then), then in 74, they uped the wheels from 10's to 12's, though the engine and gearbox remained the same. Fairly tame engine, but a very solid base to build a good engine from. The 1275 blocks from around 76 to 78 were (just before the A+) - in my opinion - the best of any of the 1275 blocks.

 

The Gearset you have are Pre-A+ and just ordinary Mini Ratios, the GTs were factory Fitted with Helical Cut, Close ratio, same as post 68 Cooper S, but that's not what you have, the Lay Gear should have a no. 22G1040 or DAM3168 (these particular ones are quite rare).

Edited by Moke Spider, 11 January 2016 - 02:37 AM.

[Fordy]

Ok thanks for the heads up on the GT title to stop people taking advantage like you said, and all the information on the engine.

The block itself has the webbing on which I have read online that this means it is an A+ block, is this true?

And if that is true then does this make a difference with the gear set being pre A+, or is it all dependant on the lay gear? Also could you run an A+ block with a pre A+ gear set?

I shall check out the part number of my lay gear and see if it matches up, if I remember correct I did get 2 lay gears because the engine did come with some other spare parts.

[Spider]

The ribbing on the block does sound like it's an A+ Block. They were introduced in 79 and the last of the GTs had them.

 

From the number on the Laygear ((22)G927) you posted up earlier and also the number that's cast on to the casing (DAM 3220), the Gearbox is not A+.

 

You can run an A+ Engine on Pre-A+ Gearbox no trouble.

Edited by Moke Spider, 11 January 2016 - 10:21 AM.

[nicklouse]

easiest way to tell blocks apart is the dizzy mount.

 

goes around with pinch bolt A

 

clamps over no pinch bolt A+

 

and as above either box will fit and work.

 

often GT is used to help shift a 1275 engine even though it may actually be from a Austin 1300 or a Metro ( or even originally from Midgets and other RWD cars).

 

but this only really matters if you are going for 100% original build.

[gazza82]

1275 Midget won't have the right crank or rear bearing housing. The way to tell from just a block is the three small bolt holes in the back of the block above the main bearing.

 

The 1.3 A+ was found in the Marina/Ital in RWD, and I think Maestro with FWD and possibly like the Metro. (but my experience of Maestro was with the MG version with 1.6 engine and that had a VW gearbox .. much easier to change clutch though!). Ital/Marina will have wrong crank for Mini as it was a standard flywheel/clutch on those.

[Fordy]

So I would be okay working off the engine block being a 1275 between 1979 and 1985ish?

And I shall then work off the basis of the gearbox being a pre A+. When I took the lays haft out I did notice that it was a 2 step which I didn't think was an A+.

Not going for a 100% original build so that will be fine thanks for help and information.

And is there no way of exactly saying which car the 1275 engine would have been from? Again it's not an issue just curious as to what the engine would fit in.

[Spider]

Being A+ you need to pop the Main Bearing Caps to narrow down a year range. On the Caps themselves, the early A+ ones have a machine finished tunnel and the tang slot for the bearing shell is off set to one side, the later ones have Hone Finished Caps and the Tang for the Bearing Shell is in the centre line of the bearing.

 

On the gearbox, yes, it's Pre A+.   Though, if I can suggest and if the funds will stretch, find a late A+ Gearbox, with it's Transfer Housing and Drop Gears. These really are so much better than the eariler boxes. These have a casting No. DAM5262.

 

Without the original Engine No. it's hard to really narrow down the block to a specific car model.

[Fordy]

I have attached some photos below if this helps to identify.

 

Unsure if this would help but the numbers on top of the main bearing caps are: 12G 1433 QB, 12G 1430 and 12G 1429

 

In what way are the later A+ gearboxes better than the pre A+ gearboxes? Can they handle more torque, power, smoother? But that is something I will deliberate dependent on funds, and benefits of getting one. If I do decide to I shall use that number thanks.

 

And in response to a post from earlier I have just looked and can't see the 3 small holes above the main bearing on the back of the block. 

 

 

Attached Files

•  20160111_192705.gif   204.76K   12 downloads

[Spider]

Cheers on the photo, though what we really need to see is the bearing that's actually in the cap, not the one in the block.

 

In short, the A+ Gearboxes will last considerably longer than their older brothers, though there were a few incarnations of them, it's only the last of them (roughly 83 on), identified with the DAM 5262 Casting Number that's worth chasing up.

 

What makes them different?  Lots!

 

Bigger Idler Gear Bearings, though granted they do have an increased Helix Angle on the drop gears too, though I'm yet to see a worn Idler Gear Bearing from an A+, yet just about every other Pre-A+ Gearbox I've stripped down, the bearings have just about disintegrated, especially the real early ones. The Increased Helix does have an up side of making these gears much quieter. One down side though is that the thrusts have less contact area and do seem to wear more on the A+. I can live with that.

 

The Main Shaft Nose Bearing is much bigger on the A+. These were a real issue with the early boxes.

 

The Layshaft Small End is bigger. On the early boxes, these wear pretty bad. I'm yet to see an A+ that's worn here,though they do tend to wear on the big end, but overall last much better.

 

The Gearcase that I've mentioned would be about the strongest type they made. While it may seem like overkill going for 'the strongest' I've seen plenty of stock 998's break all the early gearboxes - I've got enough to make a house out of! Well, nearly!!  The breakage has little to do with the engine that's fitted and more to do with the weight of the car.