948 tuning

[Fentuz]

I finally received the Vizard bible... in the 850/948 tuning part, he seems to think the triple camshaft white bearing is required from 265-270 duration, not an issue with 250 which is good to know.... but as I had to refurb the carbs, i m not going to fit a camshaft, follower and possibly oil pump just yet....

So I ordered the rebuild carb kit from mini spare with AN an H6 needles. will fit AN and red spring to start with. For similar config, it seems to be either AN red or H6/M blue... I ll get the car going and at some point, i ll go to tipton garage...

Now, pulley, i like the idea of the 1275 dampered pulley however, i read something about timing marks being different. What are the differences and how do you work around this issue?

Thanks

[oliver90owner]

he seems to think the triple camshaft white bearing is required from 265-270 duration, not an issue with 250

Yes, lift is not the only criterion for a camshaft - there is the rate of increase which is also a factor to consider - think here of the effort required while walking up a gentle slope, to the same height, in comparison to a really steep one. With camshafts, that increase in height might be the same but the time to make the lift is different.

Change the timing mark or move the static pointer is the solution to your pulley pointer problem.

[Fentuz]

Yes, i thought about putting both pulley on a bench and transfer the mark from the 948 on the 1275.

However, i was wondering what the difference is in degree.
If i was the use the 1275 marking on a 948, is it advanced or retarded and by how much?

[Declan_Burns]

You can fit this timing mark. Set the engine up to TDC on no 1 cylinder on the compression stroke and mark the damper accordingly.
Regards
Declan

[Mike Wood]

Hi

This is a very useful thread, thank you.

I’ve got a rough project 1961 948cc Austin Healey Sprite MkII slowly getting back on the road which I will eventually be planning an engine rebuild, as well as refresh the clutch. Long term it will be a 9cg engine (rebuildable one found), plus 30 948cc Sprite NOS high compression pistons with a 9 spring clutch (NOS) smoothcase gearbox rebuilt and modified for 1098cc Sprite internals. Checked so it is FIA compliant.

This would replace an unknown 948cc with an unknown origin smoothcase gearbox with apparently 1098cc clutch and flywheel (but the old engine could end up as a fun budget-ish build using 998cc plus 60 pistons, modified flywheel and appropriate clutch to fit a 1275 Midget gearbox).

Some of the excellent references in this thread have popped up on the web as downloads:

https://www.scottysretroworkshop.co.uk/ ... -akd1021c/

https://www.scottysretroworkshop.co.uk/ ... KD5097.pdf

https://www.scottysretroworkshop.co.uk/ ... S-CARS.pdf

For someone else, anyone please know of a source of good quality new replacement Mini Cooper 998 standard bore pistons? So far, I can only locate these Powertune pistons in standard 998 bore size from Somerford Mini: https://www.somerfordmini.co.uk/piston- ... 8cc-cooper (also see: https://www.somerfordmini.co.uk/interna ... and-1098cc). Anyone used them and can comment on quality?

Unless you have some NOS 998 Mini Cooper D top pistons in standard bore lurking in a cupboard looking for a new home...

Cheers
Mike

[liammonty]

It's been 10 years since I rebuilt my 948 engine to 998 + 40 thou (1030) and I had the machining done by Rob Walker Engineering in New Yatt near Witney. He sourced Nural pistons, which are flat topped rather than domed - I recall at the time that he said flat top pistons were available but domed ones no longer were. It meant we had to take a little bit more still of the 12G295 head I was using, but we were able to compensate for the use of flat top pistons over domed with no trouble.

[philthehill]

These are the type of 998cc pistons I had in my modified 998cc Minor engine.
https://www.ebay.co.uk/itm/BMC-MINI-COO ... XQLbVRaA9c
Now they are too expensive - the 948cc engine I have & intend to rebuild to 998cc will use very good S/H 998cc 3 ring Mini pistons with floating knuckle pins secured with circlips. They will have new rings fitted. Whilst they are not Powermax pistons these 998cc Mini pistons are well capable of doing the job for very little expense.
The 998cc pistons with the 'D' shaped dome are not required and are no longer available. BMC soon reverted to flat top pistons instead.