Sport bottom-end differences

[foy9999]

Hi there.

Are there any things you can examine to establish if you have an original Sport bottom-end, as opposed to standard Imp?

The ones I can offer so far are as follows but some of them are just suggestions from other people and some are practically impossible to measure:

• block has (1/2 BSP) thread tapped for oil-drain
• gear on crank and oil-pump differ. possibly Tutrified on Sport or perhaps different number of teeth
• compression-height of Sport pistons is different (so small that it's hard to measure)
• gudgeon-pin thicker-walled

Obv there are a few situations where these things would apply to Sport and STD engines...

Afaik the stronger gudgeon-pin later became standard fit and late engines with L4 head would have the oil-drain tapping. I don't believe there is any way to date a block either so there's not that much to go on but would be interested if anyone has any thoughts on this

Graham

[John A. Ross]

You have pretty much nailed it I think Graham as far as I know anyway

Actual early HC pistons are like rocking horse whatsit, only ever seen them in mk1s that are very early, ours goes like the devil.

The piston height was really marginal if I also recall correctly something ridiculous like 0.1mm

It was aid to me blocks from L4 onwards were pretty much same as "sport" bottom end.

Dave Dave Lane might have more infor in his mega parts records

John

[foy9999]

Thanks John

Yes I got the data about the piston dimensions from the WSM and as you say the difference is very small so measuring the height from middle of pin to top of piston is not really going to be accurate as there's no way to pin-point exactly the middle.

The actual length of the piston is also slightly different. Easier to measure too.

I was thinking Sport pistons might have different number cast inside. Mine seem to have N12 and ?101025

Graham