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Don't forget you owe us pictures glad it's fixed though!!!

Oh for sure. Pics to follow!

sorry, repeat pics, trying to upload the bad head, but file is too big. Will try to post later !!!

Here is the crack at the plug hole in head #2

bad pic I know, but you can see the extent of the damage to the piston compared to the new one. My brother in law said it was the worst one he'd seen, and he has owned a shop for decades....I told him I was happy to provide new experience....

Glad to hear you are rolling again. Let me know when you might headed in the direction of the Hamilton Airport. I live close to it and the local Legion is a good place for lunch and a beverage.

Cheers, Clive

PS If we set a date with enough notice maybe the others in southern Ont. might join in. Any takers?

Could a crack like that be caused by using plugs that have too large a base or slightly wrong threads?

krick3tt wrote:Could a crack like that be caused by using plugs that have too large a base or slightly wrong threads?

While I'm no expert on this, I'm guessing high speeds/long distances could have generated enough heat to crack the head. I threaded the existing plug into the new head with no issues so I'm thinking that the plug thread/size was not the issue.

Tx Dave

63rover wrote:Glad to hear you are rolling again. Let me know when you might headed in the direction of the Hamilton Airport. I live close to it and the local Legion is a good place for lunch and a beverage.

Cheers, Clive

PS If we set a date with enough notice maybe the others in southern Ont. might join in. Any takers?

I'd be in for a meet for sure!

krick3tt wrote:Could a crack like that be caused by using plugs that have too large a base or slightly wrong threads?

Another thought was poor heat dissipation at an earlier time in it's life, possibly due to foreign objects such as we've seen in Scott's "let's keep them running" thread blocking the heat sinks. Always been clean since I've owned it, but who knows about the 35 or 40 years prior. I noticed minute hairline fissures in the #1 head also, not quite extending into the threads, so I will be keeping a close eye on my plugs to ensure they are snug at least once a week. Don't think I'll jump the gun and start replacing all the heads, but it's good to be aware.....

I'm thinking whatever part broke loose and hammered the cylinder wall could have also cracked the head through impacting. It's possible.

That's what I thought at first until I discovered the same, yet much less significant markings on the first head as well. The one thing that lead us to this conclusion as well was that the plug was immediately loose after the piston detonated. The damage to the cylinder and the piston line up perfectly with the plug hole. It would suggest that the cracks were pre existing and facilitated the loosening of the plug. Enter oxygen and Kaboom! That's the theory, anyway...... :idea: