[Mgs] Piston Broke (was Picking a head)

[The Roxter]

Eric Erickson wrote:
> On 15/02/2008, at 1:09 AM, WSpohn4 at aol.com wrote:
>
>   
>> I doubt you had a piston problem due to RPM, Eric. There are lots  
>> of people that rev MG engines much higher than you do without  
>> incident.  I'd look to something else.  Were you getting  
>> detonation?  I'd worry about timing and mixture.
>>
>>     
>
> Well it looks like the issue was caused by a broken top ring (the  
> rings on the JE pistons are pretty fine) - and using AVGAS with the  
> high compression generally mean no detonation.  I will try and take  
> some shots but the damage was pretty certainly done by the broken ring.
>
> As far as over revving - on the track I take that thing regularly up  
> to 5500 to 6000+ revs but can remember the odd "issue" (missed gear  
> related, or high-speed "off"... ) where it has gone well over that on  
> a couple of occasions.
>
> I was told she could handle 7000 revs but never really found any  
> advantage going much over 5500 - it was only the odd error that would  
> see the needle bounce that far past the old redline.
>
> Anyway - I have a lead for some flat-tops and I will be chasing that  
> on Friday.
Good luck on that.

I have had broken rings before on a racing mill, back in the 60's. I think what caused that was a new cam and an increase in revs that resulted. I had run long enough with a 6000 rpm redline that a slight step had developed in the cylinder walls. When the new cam called for 7000 rpm top, the step broke the top ring on one of the pistons.

-The Roxter
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