Rally 180 rebore

has anyone any experience with boreing out a Rally 180 to take a P200 piston?
Is it a straight forward rebore, and can I use the P200 head?
Thanks for your help.

Thanks Juank,
that is very useful, really appreciated.
All the best.

Hasn’t the 180SS piston-timing, and the P2 crank-timing? And isn’t it a port on the P2 piston just where the 180SS piston-timing is?


[:dance1:] [:dance1:]

Okay,I was thinking about this yesterday so I sought advice from someone more in the know than me.Here we go…


A lad on the SIP board is asking.

I was thinking about this today and I reckon there will be a differance in the exhaust ports so the P2 piston won’t be a straightforward conversion.


Its still a straightforward conversion. Port sizes and shapes are slightly different, but timings are pretty much the same.
The P2 has bigger ports…basically it’ll work,and will be at a guess slightly down on power just as a straight bolt-on compared to a P2.However it’ll still be a good performance boost for the Rally 180, and lets face it, what else can you do with a rally 180 barrel?.. Could always tune the barrel further…

The alternative is opening the crankcase mouth to accept a 200 barrel,or any P2 kit.

The P2 head is a straight bolt on. Stud spacing is identical.

Tell him to dump the 20mm carb too…

I’ve never tried it but I see no reason why you can’t.I know it is possible to use a P2 piston modified for piston ported motors on the GS160 and SS180 to replicate the Grimstead Hurricane 200 conversion so a Rally should be relatively straight forward to convert.

Yes Leif.

It does mean welding up the port and then modifying the piston to suit.Unless you can find a NOS correct item.