BMC A-series guru help please
Discussion
Peter Burgess sometimes post here, you could always contact him: http://www.peter-burgess.com/indexstart.html
It's a small bore head and both motors are small bore, the 1098 being very long stroke and a good 'torque pump', so it would work with either but you need to check the compression ratio.
The 12G940 is a big bore head (bore spacings are different) but it can be made to work on a small bore by pocketing the block.
The period head to have would be a 12G295 (998 cooper head) which had bigger valves and better porting and chambers - in fact the 1098 received this head in MG1100 guise.
The 12G940 is a big bore head (bore spacings are different) but it can be made to work on a small bore by pocketing the block.
The period head to have would be a 12G295 (998 cooper head) which had bigger valves and better porting and chambers - in fact the 1098 received this head in MG1100 guise.
bnseven said:
Aren't there two 1098 units as well with the later type having bigger main bearings so being more durable for tuning?
Or has my Vizard book been in loft too long as well??
No, you're remembering right. Or has my Vizard book been in loft too long as well??
The "10CG" 1098cc engine had 1.75" main bearings (same as the 848cc and 948cc engines). From some time in 1964 the "10CC" 1098cc engine came along with 2" main bearings - as continued onto the 1275cc engines - fitted to the Midget Mk2/Sprite Mk3 and no other production models. The Spridgets needed the stronger bottom end because of their low gearing and the fact that they got ragged more, and upgrading the bearings/block allowed BMC to homologate the parts for Formula Junior cars.
The 1098cc has the longest stroke of all the standard A-Series sizes, so tends to hammer its bottom end when tuned and and driven hard, but also has some of the best possible cylinder/valve size combinations, so the 10CC engines are somewhat prized.
The 1098 can make a nice engine, even with it's long stroke. Keith Calver championed them a few years ago
With special pistons 1215 is possible - a friend had one built (by Calver) for this 1962 Mini and with the right compression and a decent head (a worked 12G295) it's a lovely engine and probably close to a std 1275 S performance wise and certainly a lot smoother.
With special pistons 1215 is possible - a friend had one built (by Calver) for this 1962 Mini and with the right compression and a decent head (a worked 12G295) it's a lovely engine and probably close to a std 1275 S performance wise and certainly a lot smoother.
As far as i remember the 12g295 head for the long stroke engines needed a fair chunk milling off to sort the compression ratio if fitting to a 998 engine. |So a 998 head on a 1098 will be a bit high on compression. Is the 948 engine a long stroke as well? I think it might be. 30 years ago I would have known, and probably would have known exactly how much machining was needed in each case.
Remembering back to the 1100 Mini I tweaked I used Diddy Visards book for Cylinder head work. I used the stock head as the desireable 998 cooper type was in short supply and I was poor. The work was mostly changing chamber shape and skimming the head the maximum the casting depth to water jacket would allow, I (didnt) err on the side of caution and used the max figure listed and didnt break through the head surface. I also used a modded HIF 1 3/4 SU on a decent inlet /exhaust manifords with the obligatory at the time RC40 exhaust. Cant recall If I swapped the cam, suspect not but still got a decent HP at the wheels on the local dyno and an easy 110mph not on the public highway. It was faster than a stock 1275GT and probably the Rover Coopers in stock carb trim, though these werent that quick IMO (owned one that I blew up the transfer gears and box so rebuilt it as a 1400).
If any of you BMC A Series fans are looking for Vizard's book I have a hard cover edition with dust jacket which I could be parted from. It is the black cover version issued June 86 and apart from my late father's signature on the flyleaf it is mint, no creases, oily fingerprints, turned corners or, at a quick glance, pencilled notes in the margin. PM me if interested.
LimSlip said:
I had an 1100 Mini Special (Belgium import) for a number of years and with a DIY ported head, 266 cam and the usual LCB it went exceptionally well. Unfortunately so did the sills...
I had one of those as well. Great Cibie headlights as standard and I seem to recall it still had LHD wipers! It was a sort of tomato soup orange with a black vinyl roof and Mini clubman rear bumpers front and rear.It threw a rod whilst I was heading home down the A45 (now A14) and I managed to coast into a lay-by near Newmarket. The rod punched the oil filter out of the block, same with the fuel pump, put a big hole in the gearbox casing and cracked all the way around the diff casing. The flywheel sheered off the locating washer.
After fitting three different engines from the local scrap yard ( all knackered!) I eventually got a gold seal engine out of an Allegro, it had totally the wrong diff ratio in it, so I could do 0 - 60 in about 3 seconds, but it would red line at 65!
Great for traffic light Grand Prix, but really crap for the 300 mile journey from East Anglia to South Wales! Eventually I salvaged the crown wheel and pinion out of my scrap gearbox and it was back to being a lovely car again.I ended up selling it when I got my Mini Jem on the road as my everyday car.
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