03 Dropped Valve

Recently picked up another 03 Cobra, beautiful car. 2.9, E85, AODE, 20k Miles, perfect inside/out. Unfortunately, something happened. First time having it out I drove it roughly 115 miles. Heading home from dinner, sitting at an intersection the car starts acting up and sounding awful.

This plug came out of #1 (front driver side). Borescope fit last night to find out it had munched up a valve. So looks like Winter came early.

The car has already been 9s with the current set up (11:1, stock rods/crank). I’m looking to getting into a more stout short block. I have heard good things about MHS and they’re builds. Would that be the best option? Anyone had any issues? Lead time isn’t an issue. Just want something reliable that I won’t have to be concerned with on a street car.

Plans are to drop compression down to around 10:1, long tubes, crusher inlet and have the head obviously fixed and CNC’d.


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That blows. I’d have both heads gone through while it was apart with all the normal machine work done.


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SVT_Troy said:

That blows. I’d have both heads gone through while it was apart with all the normal machine work done.


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That’s the plan, for sure having heads done.


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at least you caught it early and dont have a scattered long block.
are the heads ported? now would be the time to do it.

makes me want to check all my plugs tonight and go over the whole car. ive been ragging on it pretty hard.

Sorry for your misfortune. Any idea on the root cause? Did it have old gas in it?

Was your air/fuel good?

Probably dropped a valve seat.

Don't lower the compression. Get a replacement piston and leave the rest.

Heads are not ported, planning on getting a complete valve job, and CNC porting. Not sure on root cause, I’m pulling it out next week and will begin tear down. My guess is dropped valve or seat. We shall see


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gt347mustang said:

Probably dropped a valve seat.

Don't lower the compression. Get a replacement piston and leave the rest.

Click to expand...

I’ll know more next week, we will see what it was. After thinking about it more, long as the walls are good on that cylinder, hoping to just slip a new piston in it and putting it back together. Really don’t want to drop the $5k for a short block right now.


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