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johnc

United Kingdom
212 Posts

Posted - 05 Feb 2010 :  13:08:58  Show Profile  Reply with Quote
I have a Series 4 with a 1725cc engine with dished pistons,engine number (B13200442 ODS HSO) this bears no relationship to Rapier numbers.When I aquired the car it came with a 1725cc recon.short engine (without numbers) from Grimes,which has never been fitted,this has flat top pistons.My question is why the difference? and I am curious as to what car the fitted engine origionates from.I propose to fit the recon.block using camshaft etc etc from the present engine.I know that the flat top pistons require a Holbay pattern head,which I have thanks to Howard Johnson.

johnc.

1922

United Kingdom
549 Posts

Posted - 10 Feb 2010 :  22:34:38  Show Profile  Visit 1922's Homepage  Reply with Quote
Hi,
B = After 1960
132 = Humber Sceptre II (1965 - 1967)
OD = Overdrive
HSO = Home Market, Saloon, Standard specification.

Have a look at http://www.team.net/www/rootes/chassis.html

The combustion chamber on the Holbay engine is a very different shape to standard engine. I guess this shape works better than the standard one (better breathing and better able to cope with the higher compression).

If you are lucky you have a Holbay cam in your short engine - if so I would use that, it will breath better than the Humber cam. You'll have to measure it to find out it, the H120 cam has a 320 thou lift.

One word of warning, the 1500 Minx/Hunter engine has flat top pistons, so you might want to make sure that's a 1725 before you put it in!

Regards,
Derek
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