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MG Midget and Sprite Technical - 73mm pistons

Has anybody tried the 73mm dia pistons offered on Keith Calvers website?

http://www.calverst.com/shop1/index.php?main_page=popup_image&pID=85

I have a spare motor to refurbish for my '68. Its on +040 at the moment and I don't think another 020" will be enough to sort it.
At this diameter, does the boring need to be offset, as per DV and 1380's, or will standard spacing do the job?
If offsetting is needed, is there anybody in the Preston Lancs area thats recommended to do the machining?

Ta Mark
M Crossley

73mm pistons give 1362cc and do not require to be offset bored. This will allow you to (eventually) overbore to 73.5mm (1380cc).

A 1380 itself does not need to be offset bored, but if it isn't you can't overbore further to 74mm because this size DOES require off-setting.

Note: Not all blocks will take 74mm bore.
Deborah Evans

73mm bore and pistons are not usual and most go for 73.5 or like my spare engine 74mm and 1400cc. If I were doing a 1380 I would definately offset bore the block to give it a good chance. That said anything over normal rebore would IMO be far better off by being offset bored.
Robert (Bob) Midget Turbo

as said 73,5 does not need to be offset bored.
And if you can get away with out it then i would not.

I would how ever get a 73 of 73.5mm bore centered on the type of gasket you are going to use.
Originaly the centers can be a bit all around the place and centering the bores on the gasket will improve gasket life.

Alex M has had several kind of 73mm pistons fitted hopefully he will be along shortly.

But why not liner the block?
Onno Könemann

73mm is the way to go!! (?)
Don't get the EVO pistons from minispares, they are not very good. Get a set of Hypatecs from australia or a set of the other Australian guy, can't remember his name. No problems with the BK450 gasket.
Alex G Matla

This is probably your best place in Aust. to pick up the Hypatecs -- They also have the Graham Russel 7 Omega piston sets

http://www.minisport.com.au/category5_1.htm

Cheers Willy
William Revit

Graham Russel! That's the one!
At the time I needed them they where out of stock worldwide! luckily a fellow BBS'r in the states (thanks again Jim) had a set to spare. So my pistons already had some flying miles on them before installation.
Alex G Matla

Thanks Again Chaps,
Shopping list time again.
Regards,
Mark
M Crossley

This thread was discussed between 30/04/2011 and 03/05/2011

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