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Discussion Starter #1
Would appreciate some help on this one. I have a 2007 Heritage and 2 weeks ago had a 103 kit installed. I broke it in carefully and had over 900 miles on the new pistons when the rear cylinder head gasket blew. It has performance heads and 204 cams. I noticed that the rear cylinder compression release was sticking sometimes and had planned to have it looked at this weekend. When the head gasket blew, I thought it might be the compression release sticking. I immediately lost power when the gasket blew and pulled off the road. I knew there was an HD dealer (not the one that did the work) about 5 miles away.
I have two questions. First did it cause any engine damage by riding it at about 50mph with the blown head gasket to that dealer that was 5 miles away? Second, could the blown head gasket be related to the sticking compression release? Any help would be appreciated. Thanks.
 

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If I understand you correctly, you have the SE performance heads in combination with the SE flat top pistons and the SE 204 cam on a 103" build. It should run around 10.6 static compression, which appears very high for a 204 cam to begin with, but this is very likely not the reason for the head gasket blowing out. Typically it's an installation problem (head bolt torquing procedure etc.). You should not see any significant damage to the head or cylinder surfaces as the operating time was short. If there's anything, a little machining will take care of it.
Who for Pete's sake selected the cam?

PS: The comp release is closed during operation of the engine, no worries about that being the root cause.........
 

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Discussion Starter #3
Thanks Vienna Hog. I hope no damage occurred. The cam was a combination of my own choice, the dealer, and following the Joe Minton philosophy of mild cams for big low end torque. On American Rider's website, Minton recommends the 204s as a good cam for the 103 inch motor. The low end and mid-range torque is great(or was before the blown head gasket). You raise a good point about maybe those cams building up too much compression. I appreciate your comments.
 

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Head Gasket

Cometic head gaskets will handle a ton, and not let go.
 

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Seasoned Wrench
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Optimum compression for SE 204 cams is 9.8:1

Use a thicker head gasket to lower the compression and you will have a much easier cranking motor and you'll gain the full potiential of the 204's. This will also negate the need to use the compression releases each time you start the motor.

just my 2 cents worth...

peace--
 

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Discussion Starter #7
Thanks for all the replies. When they took the engine apart they found a broken head bolt which in turn resulted in the blown gasket. Veteran mechanic said it was the first time he had found a broken head bolt. A different mechanic did the repair than did the original work. Fortunately, no damage was done to anything else in the engine.
 
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