MG Motorsports Forum

Delete.



Edited 1 time(s). Last edit at 2015-01-28 10:05 PM by Rick Starkweather.

My first impression is the worst case of detonation I've seen since one of my engines!

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Rick

You might be a racer if;
You consider the redline as a "conservative suggestion" and the rev limiter a "fun limiter".

What fuel, what timing? May have broken a ring which caused piston to run hot leading to detonation.

First guess, major ring land failure.

Pics on the web always leave more to be desired, is the piston near ring land failure, broken, or burned away, if the latter, then my guess is too lean, too much advanced timing, or both.

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com

Did you have the advance turned up to 11?

"We had a little trouble getting the rings in, but a few good whacks with a hammer took care of it"
Hap got it, rings/lands bust.

I have a set of Spitfire pistons, which progressively show the effects of broken top rings; the worst one is about half this bad, but looks exactly like that. In this case, it is clear that at some point the car sat and the top rings were rusted to the bores. Somebody before my customer got it free, so we were able to start it up (not knowing it had been stuck) and it ran fine, for a few months driven by a "little old lady". Finally the ring bits on one hole ate through the top land; Still drove in though. The busted ring fragments in the squish area sure did make a racket & a mess.

Doesn't really look like the melting you see in severe detonation - I have an AA/Mini 1275 that did that, and it is very obvious - the wrist pin is melted as by an oxy-acet torch, and molten aluminum spatters everywhere. Rings still intact, running across the melted missing area. Caused by running out of water on a screwed up race start, 1/2 hr pissing around on the hottest day of the year, then they dropped the green, melted 3&4 at the siamese section.

FRM