26 replies to this topic

[bmcecosse]

Ahhh - you said 'S' rods !! I don't think these are S rods ? You will obviously need to get the gudgeon pins out. But I am surprised - because these 1275 rods are made for the larger big-end bearings - so do you have a very special 998 crank - with large big-end bearings ??

Edited by bmcecosse, 24 September 2009 - 07:21 PM.

[rofert]

No idea if the crank is a special as it was all in an engine that i bought. It was a very good small bore before it started burning oil due to the knackered bore.

Will have to measure up the journals to see what they are.

[bmcecosse]

I think they probably ARE 'S' rods - looks like a nicely built engine too!

[rofert]

It is a nice engine except for the scoring to No2, when it was rolling roaded it had just shy of 70bhp at the crank.

Spec is
998 pocketed block with 20thou overbore
MG metro cam
295 Slark BVH
45 Weber
Straight cut drops and box
3:44 FD

I've gone back to what I know which is an MED 1380, was either going to rebuild the 998 or sell on the bits if I can get the last 3 pistons out.

[Dan]

With the piston as it is in the photo, half out the bottom of the bore, can you not rotate it another 30 - 40 degrees clockwise and get at the gudgeon pin?

Ahhh - you said 'S' rods !! I don't think these are S rods ?

I think they probably ARE 'S' rods

They have to be S rods (or what are known as S rods among the Mini community). The big end of a Cooper S rod is 1 5/8", the same as small bore rods. Non S rods have 1 3/4" big ends, that's the very reason so many different re-stroking options are available in large bore engines.

[bmcecosse]

Yes - after studying the picture I realised it could not be a special crank with large big-ends - hence must be S rods (maybe AEG 625 Spridget rods rather than genuine AEG 177 S rods) to suit the small big-end. Still leaves the gudgeon pin problem!

[benpopham]

Hey
If you do decide to sell this, how much would you like for the SC drops? Very interested!

[Calver ST]

Where S rods are used in a 998 block (very common in Mini Miglia when I first started racing) you have to push the pistons up out of the top of the block, remove the pistin rings, then pull the pistons/rods out of the bottom of the bores/block. But this was with Cosworth forged slipper type pistons. Somebody has really made an effort to make things difficult in your case... The obvious statement of 'well, they went in, they must come out' doesn't help I know. The rods must have been bushed at the small end to take what appears to be Powermax 998 pistons... Either the pistonmust move out far enough at TDC or BDC to get the wrist pin circlips out, or the piston needs rotating in thye bore.... Very weird one - congratulations...

[Paul Wiginton]

Must be awkward assembly on that - if you need to rotate the pistons you cant guarantee where the gaps are

Paul

[Cooperman]

Maybe the pistons were put onto the rods without their rings. Then the piston/rod ass'y was pushed right up the bore until the top of the piston stuck out of the block deck revealing the ring grooves and the rings were then fitted and the piston dropped back down.
That's a novel way of building a short engine.

[Paul Wiginton]

Novel indeed.

Were S rods used because theyre longer? so there's less 'swinging' motion?

Paul

[Calver ST]

No Paul - they were used because they were believed to be stronger (shortage of decent quality big end bolts for the 998 rods at that time). Plus, the Cosworth Miglia pistons were made to fit S wrist pin sizes, not the smaller Powermax/998 ones.