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Old 06-04-2018, 08:21 PM
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2006 MCX Engine Failure

Have a 2006 MCX small block Chevy with 1300 hours on it. Cylinder #7 had the spark plug electrode break off, or it was hit by a valve that may have failed . I need a new long block for a quick repair as it is now the beginning of summer. Who has recommendations on long block suppliers. Currently looking at Marine Engine Depot. Suggestions?


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Old 06-04-2018, 09:06 PM
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The automotive version of the MCX base is the L31-R I do believe.

You’d need the cam and injection system off the MCX. The only thing I’m unsure on is if both use the same pistons.

Just a starting point that will help save you some money if you can turn the wrenches.
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Old 06-04-2018, 09:07 PM
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Michigan Motors if you are just looking to buy a long block.
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Old 06-04-2018, 11:08 PM
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that doesn’t necessarily mean the engine is toast. how does the compression check out, oil?
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Old 06-05-2018, 10:13 PM
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Originally Posted by 1redTA View Post
that doesnít necessarily mean the engine is toast. how does the compression check out, oil?


Oil only has about 8 hours on it. Pulled dipstick and no foreign odor, no debris or water. Cylinder #7 has absolutely no compression. The electrode fragments did a good job of wiping out the rings or scoring the block. My initial guess is a lean burn condition ruined the plug during a full speed run the day before. Sunday, had a bit of a rough warmup, ran good for half the day. Started it up to head home from sandbar and that is when the plug failed and gave me my problems. At 1300 hours, Iím going long block and then rebuilding the old one over the next winter. Will have old long block ready for sale in the spring. Expensive lessons learned. I must listen to what the motor is telling me next time. Dammit....


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Old 06-06-2018, 02:00 PM
tommurtha tommurtha is offline
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Did you pull the head? Since you are planning to rebuild anyway ...It's maybe a long shot but you just might have a piece of the electrode stuck on the valve seat causing it not to seal thus no compression
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Old 06-06-2018, 02:17 PM
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Quote:
Originally Posted by tommurtha View Post
Did you pull the head? Since you are planning to rebuild anyway ...It's maybe a long shot but you just might have a piece of the electrode stuck on the valve seat causing it not to seal thus no compression
Pull the valve cover and manually turn the motor over and see if the valve closes?

Cheap scope to put down the plug hole to check out the top of the piston and cylinder wall?
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Old 06-06-2018, 02:22 PM
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Pull the valve cover and manually turn the motor over and see if the valve closes?

Cheap scope to put down the plug hole to check out the top of the piston and cylinder wall?


Yes, I did pull the cover and the valve is seating from what I can see from that side. I will pull head Thurs night, but I am sure I am going to be disappointed.


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Old 06-06-2018, 04:00 PM
tommurtha tommurtha is offline
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I really doubt the electrode could score the wall and damage rings enough for no compression. Most of the pieces or piece would likely get blown out the exhaust first. I hope I'm right and it's valve related, much cheaper quicker fix.
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Old 06-06-2018, 11:40 PM
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Originally Posted by tommurtha View Post
I really doubt the electrode could score the wall and damage rings enough for no compression. Most of the pieces or piece would likely get blown out the exhaust first. I hope I'm right and it's valve related, much cheaper quicker fix.


Actually, I am going to scope it tomorrow first. The plug actually has some witness marks in it as if something hit it first. Maybe a valve broke or the seat came off. Will report back, but ordered a long block from Indmar tonight to be prepared for the worst.


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