5 replies to this topic

[dave-88_123]

hi ive got a 1979 mini special i plan on keeping the 1100 engine and tune it im trying to find out if 1275 con rods would fit

[Guess-Works.com]

no they wont, wrong big end size

[Dan]

The 1100 uses 998 con rods.

[Cooper-202S]

hi ive got a 1979 mini special i plan on keeping the 1100 engine and tune it im trying to find out if 1275 con rods would fit
[/quote]

The Big end size is 1.625" opposed to the 1.750" of the large bore engines,
if you are looking at new rods then there seem to be 3 main options
Cooper S rods from Mini spares at £100 each
Arrow forged rods at just shy of £200 each
Or a similar forged rod from Specialist Components at £90 each.

I've no running experiance of any of the above but will be using the latter in a 1100 twin carb project after the My Cooper rebuild is done.
Hope the above is of use.

[Sprocket]

Cooper S rods are not a straight swap and are not easy to assemble on the engine. The benefits of using these rods for anything other than a 9000rpm screamer are pretty small.

The standard 998/ 1098 rods are more than adequate for 99% of aplications.

Why all the extra cost just to run a different rod? Money would be better spent elsewhere on the engine

[Dan]

Cooper S rods from Mini spares at £100 each
Arrow forged rods at just shy of £200 each
Or a similar forged rod from Specialist Components at £90 each.

There's more to a rod than the big end size. Small bore engines must use small bore rods, the 998 and 1098 rods are exactly the same and will interchange but no rods designed for a large bore will work whatever size the big end is. Small bore rods are cut on an angle rather than straight accross the big end and are offset both tangenitally and laterally from the big end. All this is to clear the cam and the webs in the block. Also they are a different length. Don't buy any SC or other large bore rods and hope they'll work in a small bore engine. As Sprocket says, adapting a large bore rod to fit is not all that straightforward.

Edited by Dan, 02 January 2009 - 09:45 PM.