18 replies to this topic

[minim@t]

Evening All...

started to gather parts to repair the mini after the conrod insident on the M1 last week,

so far ive aquired a 1000cc block, gearbox and head, im not fussed about it being a 1275 at the mo so wanted to put an engine together that will be reliable....

basically im wondering what parts im going to need to get ahold of that wont fit from the poorly 1275 lump,

I know that if i wanted to use the 1275 head i need to have the block ported, so ive gone for a standard 1ltr head, though its missing the rockers, would the 1275 head rockers fit? I know the push rods are different too so am sourcing some new ones.

also, the 1ltr has a breather from the tappet chest, the 1275 hasnt got this but its on the flywheel housing, which would be best to fit as im using the 1275 flyweel and clutch assembly?

I know theres got to be other problems ive missed so im after any advice as this is my first engine build, i understand the basics but as im mashing the 2 engines togther i think ive missed something,


cheers for any help in advance

Matt

[Big_Adam]

Got to remember, BMC where cheap. Very very cheap.

Why make different parts for cars when you can have 1 thats fits 8 cars.

From you're 1275 you can use straight off alternator, carb, manifolds, clutch side breather. Gearbox has a different final drive so not sure on that one.

Push rods on a 1275 are longer so they are out. As for the head, you can use it if you pocket the block (take chunks out of the block to leave space for the valves to come down).

Rockers will fit either engine, might want to check the cam in the 1275, might be better than the 1000cc but you might end up needing new cam bearings.

BUT!

I wouldn't take too much off. 1275's go for a fair bit on ebay and 998/1000cc parts are cheap. So you might want to look into that.

[1984mini25]

Rockers are the same and are interchangeable.

I’d stick with the 998’s tappet chest breather as the 1275’s normally have 2, one on the flywheel housing and another at the timing cover end.

1275 Push rods are longer by about 10mm, so you need the shorter 998 ones.

Other things I can think of are the top radiator brackets different, top hose, water pump pulley and fan belt. The rest of the auxiliaries can pretty much just be swapped over.

[danrock101]

So 998A+ and 1275 A+ have the same journal size?

[1984mini25]

So 998A+ and 1275 A+ have the same journal size?

No, well the cam bearings are, but the 998 using a different one at the oil pump end.

But were does it say that he’s swapping the guts of the engine/s over?

[danrock101]

I meant big end journal, people are saying the rods wont fit because of length, that's the least of your worrys lol
That's if I'm right in thinking 998 rods have 1.625 big end journals, don't think they're 1.75

[1984mini25]

I meant big end journal, people are saying the rods wont fit because of length, that's the least of your worrys lol
That's if I'm right in thinking 998 rods have 1.625 big end journals, don't think they're 1.75

The pushrods, i.e. the link between the cam/followers and the rockers aren’t interchangeable and are of different lengths between the 998 and 127's.

Completely different to the length of the con rods you’re thinking of.

Edited by 1984mini25, 07 November 2010 - 06:30 PM.

[danrock101]

HAHA , I read it as con rods Early bed time for me

[bmcecosse]

You need the 998 primary gear - the 1275 one won't fit - and of course drop gears to match the angle of whatever primary gear you use. You only need to sink the exhaust valves of the 1275 head to give 320 thou clearance - far easier tahn block pockets!

[minim@t]

Thanks for the replys guys,

so hopefully its as straight forward as i originaly had hoped, phew

will post some pics of the build as im gonna try tweaking the head as David Vizards "how to modify your mini" book suggests

Matt

[bmcecosse]

Don't waste time 'tweaking' the standard 998 Mini head........ it's useless!

[Big_Adam]

Don't waste time 'tweaking' the standard 998 Mini head........ it's useless!

Eh?

Its so badly done, you do anything its an improvement. So why not learn a bit on one.

[irish.yobbo]

If you're planning to work the 998 head, go for an 1098 head. If they're the same as they are in aus, the 1098 heads are the same as some of the cooper heads - the number is 12G202 I think. They don't need as much modification as the 1275 heads and are much cheaper.

Usual procedure is to skim it to bring the compression ratio up to about 10:1, and give it a bit of a polish to help the flow. You can up the valves and port it if you're really interested, but just raising the comp ratio will make the most difference.

[minim@t]

Right,

finally managed to get it all built up and under the bonnet,

998 block, cam,head + box, think around an 88

1275 metro fly, clutch, timing chain gear etc, electric dizzy, and a hif38 carb, around 88 same ish year

thing is i cant get it to start,
it turns over, plugs get wet so fuel is getting through, plugs are sparking (tried different plugs+coil), timings bang on, plenty of compression in all 4 chambers

still wont start >

any ideas, starting to really annoy me now,

any ideas?

[minim@t]

Just thought, ive used the 1275 rockers too,
could this be the cause????