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Tunebug engine diagnosis, thoughts anyone?

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A follow up on this, Steve sent the head to me, and I did find the #1 intake valve to be leaking, so all the valve seats in the head wil be cut with carbide angle seat cutter on a valve and guide machine, putting three fresh new angles on the seat, 30/45/60, and I will document this here on the forum with pictures of the actual machine work, and hand lapping of the valves. it's a good chance to show the forum what goes in to a valve job.

I also found the combustion chamber to look like they had a bit of rich burn to them, so I'll be sending Steve back some leaner HS2 needles to install in the carbs.

Updates and pics soon.
 
Any thoughts on what could have caused this, Hap? I'm curious (from a learning prospective) to know if something I did or didn't do might have had a hand in this problem.
 
drooartz said:
Any thoughts on what could have caused this, Hap? I'm curious (from a learning prospective) to know if something I did or didn't do might have had a hand in this problem.
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No, I don't blame any this on you Drew. Only thing I can come with is there was alot of sooty rich deposits in the combustion chamber and on that valve, in the seating area. Cutting the seat again with the carbide cutter is a hi-end appraoch, but one I want to take, then hand lap to confirm seal, then reassemble, and the new leaner carb needles should correct the rich fuel mixture condition.
 
Darwin said:
Sounds like a bit of carbon on the valve seat. Or in the valve guide. You could try the old trick of squirting water in the carbs to free it up but that can be danerous as it could cause even more damage. May have to tear down the head to fix it.
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Wondering the same thing. Sticky valve.
 
Hap Waldrop said:
No, I don't blame any this on you Drew. Only thing I can come with is there was alot of sooty rich deposits in the combustion chamber and on that valve, in the seating area. Cutting the seat again with the carbide cutter is a hi-end appraoch, but one I want to take, then hand lap to confirm seal, then reassemble, and the new leaner carb needles should correct the rich fuel mixture condition.
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That's good to know (though I hope you would tell me if I *had* done something wrong). If nothing else I've now learned that I need to add the compression test to my mix of troubleshooting tools.
 
Boink said:
Darwin said:
Sounds like a bit of carbon on the valve seat. Or in the valve guide. You could try the old trick of squirting water in the carbs to free it up but that can be danerous as it could cause even more damage. May have to tear down the head to fix it.
Click to expand...

Wondering the same thing. Sticky valve.
Click to expand...


Nah, the guides clearence are good. I already did the valve seat three angle cutting on the head on thre DSunnen machine and hand lapped everything to comfirm seat seal on both the valve and seats, and have pictures of everyhting, I've been waiting on new shop computer to get done, so I could download the pictures on it rather than the temp computer I've been using, and I got the new computer yesterday, so picutres will be posted here next week, as I get the new hot rod up and running :smile:


The valve probably seated and sealed fine for a while, then started getting leakage, it could have been extra deposits from being rich, but who knows, bottom line, it was easy fix.
 
Glad it turned out to be a simple fix. I was always struggling with getting it dialed in here (we're at 5550' elevation) so I was certainly running a bit rich.
 
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