Zongshen GS250 - Clutch + other issues

[SpudRider]

Originally Posted by culcune

I wonder how much trouble it would be to put one of these engines in a Sierra ?

I believe the ZS172MM engine in the Zongshen GS250 has the same stroke (55.7mm), but a larger bore (72.5mm) than the ZS167FML engine of the TW200/ZS200GY-2 engine, which has a bore of 67.0mm.

You could bolt the entire ZS172MM engine in the Sierra's frame, but you would have problems with the exhaust header. Personally, I wouldn't want to mess with it. Because the GS250 engine has a larger bore, you can't put the smaller cylinder head of the TW200/Sierra on the ZS172MM engine.

[Weldangrind]

Originally Posted by SpudRider

Because the GS250 engine has a larger bore, you can't put the smaller cylinder head of the TW200/Sierra on the ZS172MM engine.

Please explain. I don't understand why the Sierra head is incompatible with the larger bore, given the same frame of architecture (FOE). The small block Chevrolet SBC) engine will allow any head to interchange with any block, from 265ci to 400ci. The only real difference is cylinder head volume. The bolt spacing remains the same.

The only real issue that comes into play with the SBC is that the FOE is such that the valves are shrouded with anything less than a 4" bore, but the engine will still run properly.

A larger bore in the Zong engine would give the valves even more space. I doubt that the cylinder volume is dissimilar between the two heads. As long as the dowels line up, I can't see a problem.