mk1-forum.net

Here is a very helpful chart for anyone thinking modifying an engine with different pistons etc. I wonder what is the best combo???

A useful table.

But, what crank has a 66mm stroke?

Also some of the colour coding is a bit misleading.

No one has used Imp pistons in a mini for years.

M

Answers

1. Stroked crank
2. Change the colours if you want
3. So what!!!

it doesn't have the SA1100 crank stroke(s) on it either, so you need to add 68.26 & 70.00 to take into account both variations

3. So what!!!

That's my favourite answer

Well done.

M

Your just lucky I did use the word Imp in one of my answers

Anyway my point to this was to kick off a discussion on what combo's people have used in the past etc etc failures and successes!

Back in the 70s yes imp pistons were used along with triumph PI and what they called Devon pistons ( BMC ) but as special piston sizes were produced ie 73.5 etc they melted away into the distant past , possibly literately .

Having owned and built a couple of 1480 cc race engines , this would be my choice . You can't beat the tourque of the extra cc . They may not rev as high a a short stroke but a lot less chance of a blow up ...... Ken

rich@minispares.com wrote:it doesn't have the SA1100 crank stroke(s) on it either, so you need to add 68.26 & 70.00 to take into account both variations

Isn't the third column from the left 68.26????

Went the 1149 route on a Mk1 Cooper many years ago, wasn't really worth the effort and a gudgeon pin came loose trashing the block. Did a 1341 which revved nicely and produced 108bhp but just didn't have the b*ll*cks that my 1426 had in my Vita-ish Cooper S. Had so much torque that it didn't really recognise the steepest gradients!

I have always been a fan of the short stroke revers. I have built a 970 crank / 73.5mm screamer for my brother which went like the clappers & easily revved to 9,500+, it did however get through head gaskets like I get through underpants.

I have built many, many 1070 /SA1100 cranks with various standard overbores, usually plus 40 or 60, these always go very well & give a smooth & beautifully behaved road engine.

I have never liked the lumpy bumpy nature of the 1275 engine, but the short stroke 1299 in the Hornet was a bit of an eye opener, no where near as smooth as a true short stroker, but it gave excellent power, well until Rich blew it up it did anyway

I am currently building an all steel appendix K 1293 for it, so we will see what that is like won't we.

I have over the years built many other engines both small & latrge bore, but the above ones are my favourites.

M

Weren't "Devon" Pistons from one of these?


Austin A40 Devon

mk1 wrote:, but it gave excellent power, well until Rich blew it up it did anyway

these car breaking works drivers eh............

Last A series I built was a 16v 73.5x86mm 1460. Now I'm building the other end off the spectrum with an 8 port 970 at +40. Not sure what I'll prefer but I suspect the high rever is likely to tick more boxes for me.