Twin Cam lower end noise
Since I'm not seeing anything obvious I'm going to start measuring everything and see if I can find anything actually out of spec. I was oddly relieved when I found the connecting rod issue, but my wallet is happy that it's apparently normal. I'm still debating sending the lower end to Darkhorse to have the crank balanced and welded, and the bearings upgraded. It's only money, just have to convince the wife the kitchen remodel can wait another year...
I'm not 100% convinced that the carbon was the noise, but it's certainly possible. I swear the noise was on the low end, but maybe the piston noise was transferring down?? I'm going to check everything as well as I can, and if I don't find anything else I'll blame the carbon. I'm baffled why there was so much buildup, I ran Chevron Techron fairly regularly, but apparently I should have been more aggressive.
REW13, not sure what you mean by cam rest in the block? Where the rear cam bearings press in?
REW13, not sure what you mean by cam rest in the block? Where the rear cam bearings press in?
Originally Posted by bwoltz
Looks like you found your knock.. Too much carbon build up..
Seafoam in the intake would have fixed it..
Seafoam in the intake would have fixed it..
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Joined: Dec 2005
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From: poway
I'm not 100% convinced that the carbon was the noise, but it's certainly possible. I swear the noise was on the low end, but maybe the piston noise was transferring down?? I'm going to check everything as well as I can, and if I don't find anything else I'll blame the carbon. I'm baffled why there was so much buildup, I ran Chevron Techron fairly regularly, but apparently I should have been more aggressive.
REW13, not sure what you mean by cam rest in the block? Where the rear cam bearings press in?
REW13, not sure what you mean by cam rest in the block? Where the rear cam bearings press in?
The sound gets conducted down the rod to the lower end. I'm still not sure about it being carbon buildup as yours has more of a high pitched ring to it.. I would be more inclined to believe the sound is something in the exhaust system but you wrote the stethoscope led you to the lower end.. Did the stethoscope reflect the same ringing sound at the lower end as the recording? If so I'd suspect that carbon and maybe you've got more buildup than mine?. Anyway You have way too much carbon built up in the chamber. I suspect some of it is from poor oil control from the cylinders, Tune might all be a little rich. It keeps the buildup from being wet.. Have someone torque plate the cylinders and check for round. You can use seafoam to remove carbon from the head and piston tops. Drop them on a flat plate and sane the surfaces with some 220 wet and dry. You'll see little divots in the surface if the piston was hitting the head..
Here is an example..
This bike shredded valve guides.. Tight 0.030 setup..
I'm planning on sending the cylinders out to be bored out to 107", with new pistons. So that will solve that issue.
I wish I would have followed the advice given to me, and seafoamed it before I tore it down. At least then I'd know if that fixed the problem. Oh well.
I wish I would have followed the advice given to me, and seafoamed it before I tore it down. At least then I'd know if that fixed the problem. Oh well.
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Joined: Nov 2016
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From: South Carolina
See your top picture where your crank shaft comes out. Those two inlets aren't they were your cams go? One of mine has minor scaring where the cam rubbed do to vibration when the bearing came apart