Linered bores

[youngun]

Upon dismantling my engine (goldseal 948) I've found that the bores have had liners fitted......now as ive got it all in bits, is this good or bad? Or does it make no difference as i would think would be most likely?

Oh and seeing as its in bits, what needs to be replaced/modified?

cheers,
YG

[bmcecosse]

Well - it's v unusual to liner a 948 - just not worth it! As long as the bores are not worn - just use it - with perhaps new rings on the pistons - but they are expensive and if there was nothing wrong before - just use them as they are. It may have been linered because of porous block problem - so if it's need reboring i would just look for another block. In which case - get a 1098 block and use your crank with standard Mini pistons - and now you have a 998 engine. Of course - a complete 1098 engine will be better still if you get one at the right price. Big end and main bearings should be renewed if any signes of wear - and if there is lots of obvious wear then measure up the crank journals to see if it needs re-grinding - and then suitable oversize bearing shells will be needed. Consider a new oil pump and a new timing chain - and this is a v good time to consider fitting a much better camshaft in that engine - even a standard cam from a 1098 engine (AEA 630) will be well worth fitting - but better still is an MG Metro camshaft if you can find one at the right price.

[youngun]

luckily the bores are perfect, the big end shells need to be replaced though as a couple are scoured..........ill measure the crank journals for good measure as well.
As for cams, i dont really want to get into changing bearings etc....so will the Metro and 1098 cams jus slot straight in as it were? And can they just be used with the standard 948 head?

[bmcecosse]

Yes - just replace the standard cam - but MG would need a modern oil pump (which is a much better pump) however the AEA 630 (1098) would match the existing pump. They will run with standard head - although full benefit will appear with better head - however it's easy enough to swap heads later, the cam change is best done now.

[youngun]

Ive been offered an MG cam, where can i get a corresponding pump? Is it just an A+ engine pump?

[bmcecosse]

Yes - the 'spade' drive pump - but there are two lengths of drive shaft - for a 1098 engine you will need the short shaft - also sold for the 998 Mini engine. 1275 engines are v slightly longer in the block and they use a longer shaft on the pump to engage in the camshaft tail. The MG cam is excellent - you won't be disappointed, but to get the best from it you really need a well modified head with larger valves - and of course carb and exhaust to suit. But these can be added later in stages as funds permit.
And Minisport or MOSS or similar will supply a pump.

[youngun]

right, so im guessing i need the Short shaft pump for my 948 engine?

Im planning to fit the cam straight in now, but use the standard head. But with Howley manifold and LCB branch exhaust manifold. I have a unmodified 12g940 head, and when time and money permit i will get the valves sunk and have it ported polished etc.

[bmcecosse]

Good choice - although that head would make SUCH a difference - do you not know anyone with a pillar drill and a 45 degree countersink - who could sink these valves ? It really only takes 10 minutes.

[youngun]

Well i have a pillar drill, lathe etc.....i guess i lack the confidence to do it myself.
Ideally i need some pictures/good instructions to do it.

[bmcecosse]

Dead easy - but you do need a 45 degree countersink wide enough to hit the exhaust valve seats! Centre the seat under the countersink and just 'touch' it - set the stop on the pillar drill for a further 40 thou of down travel - and at slow speed allow the countersink to machine the seat for that 40 thou. The head is not clamped down to the table, and only light pressure is applied. It really did only take 10 minutes to do all 4 seats on my head. The lad who did the job (it was at work) had a 'tip' to stop chatter - he put a little square of wet/dry paper between the countersink and the seat - and certainly he came up with absolutely perfect seats which needed only the lightest of hand grinding. Dunno if it's important or not - but it worked for him - the cutter obviously went straight through the paper but it was dragged round with the cutter and the seats were perfect.

[alex_holden]

That's assuming your pillar drill has a decent quality depth stop - the cheapo DIY drills have plastic stops that flex by way more than 40 thou when you apply any pressure to them.

[bmcecosse]

Ah well - you could of course just machine -stop-measure - machine again etc etc. It's not got to be deadly accurate!! A few thou here and there won't matter.

[youngun]

so is it all the valves that have to be sunk, or just the inlets/exhausts?

[bigginger]

Inlet and exhaust - isn't that all the valves? I imagine you'd have to do both, but I don't *know*

[bmcecosse]

Just the exhausts. If you do both you will increase the combustion chamber volume too much and drop the comp ratio below optimum.

[youngun]

righto,

Im a bit concerned about doing all this work, im not going to have serious problems when it comes to timing and running the engine am I? Oh and with the MG cam, does the timing have to be set differently?

[bmcecosse]

No - it will run fine - just time the cam same as any other - dot to dot on the chain sprockets.
BTW - I have a spare brand new short shaft oil pump if you still need one - PM me if interested.