Lister Engines > Listeroid Engines

6/1-8/1 650 VS 850 RPM and Iron VS Alu. pistons

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I've seen the warnings "do not exceed 650 RPM with a cast iron piston", or "if you're intending to run 850 rpm, better have an aluminum piston fitted"....etc.
Could someone please explain this requirement in detail?


The cast iron pistons are much heavier that the aluminum version.
As such, the cast piston creates greater reversing inertial loads each time it's stoke comes to a stop and reverses direction, thus limited to 650 rpm.
The reversing loads created by the lighter aluminum pistons are less, and can tolerate 850 rpm (or even 1000 rpm on some engines)



So then can an Alu. piston be retrofitted into an engine that had a CI one?  Re-balancing required I suppose...

Hugh Conway:
I think the higher speed engines have non-spoke flywheels.
A spoked flywheel (especially a listeroid flywheel) may become shrapnel in an overspeed  situation.
Personally, wouldn't attempt replacement with Al piston, rebalance, then higher rpm
Maybe some more informed members will add their .02

It is as Veggie said, the forces involved quickly go up with RPM. Even with the lighter piston the 8/1 engines had a change to the same H-D bronze backed babbit shell that was used on the heavy flywheel engines.  A cast iron piston engine is not going to fly apart at 850 RPM but the service life of both the big and small end bearings will be quite short
I have never seen an over balanced CS or India clone, they are all under balanced thus a change to an aluminum pistion will always smooth them out some,, in my experience.


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