Cam Chain Tunnel / Tensioner PICS

[OakBehringer]

For those of you that have a 1974 or later motor that has the slipper/shoe type cam chain tensioner (not a wheel), could you let me know if this is how your cam chain tunnel looks? As you can see, the tunnel in my 1973 head has some nubs that prevent the tensioner from going all the way forward. In this pic, I'm installing a late model tensioner in an early ('73) head, and I'm not sure if the late model head had these nubs. I can't imagine that the tensioner would ever push this far forward, but I want to be sure.

THANKS!
Adam

 

[OakBehringer]

Found this pic on the internets, maybe the later models do protrude as well??? I can't tell if it's the same amount, though.

Help! I want to torque down my head in a couple hours

Thanks,
Adam

 

[cpt137]

looks like thy are part of the casting and not really "nubs" for anything. I don't think your tensioner would ever come that far forward with the cam in anyhow.

 

[OakBehringer]

looks like thy are part of the casting and not really "nubs" for anything. I don't think your tensioner would ever come that far forward with the cam in anyhow.

Yeah, I noticed that when I saw the other pic. Hard to tell if they're larger on the early head. I'm hoping someone has a later model head they can measure?

I also am inclined to think that the chain will never slack that far forward. But if I'm wrong I could be tearing the whole motor apart, and this is my daily rider!

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[OakBehringer]

This is the measurement I'm dying for on a 1974 or later model head. Thanks!

 

[OakBehringer]

Come on.. someone has to have a head out they can measure for me!!!

 

[5twins]

About 15mm in the head, 18mm in the cylinder. The tensioner blade is a little over 15mm wide, maybe 15.5mm. Obviously, the blade is never supposed to go in that far or it would get jammed in there.

 

[OakBehringer]

THANKS. Same as mine. What year head was that?

 

[5twins]

Early '80s.

 

[OakBehringer]

Thanks again. Ready to GTFO of work and install my cam!

 

[XSLeo]

Those "nubs" are there as part of the casting that supports the headgasket. If they are any smaller you would be more apt to blow the gasket, this will lead to oil leaking into the combustion chamber and loss of compression pressure.
Leo

 

[OakBehringer]

Those "nubs" are there as part of the casting that supports the headgasket. If they are any smaller you would be more apt to blow the gasket, this will lead to oil leaking into the combustion chamber and loss of compression pressure.
Leo

Yes, I realized what they were when I saw the head from the bottom. It wasn't obvious to me looking down the tunnel. I didn't want to pull the head off b/c I had a healthy coating of copper spray on the head gasket, which was already sandwiched in place.

Head is back together, torqued down. Looking forward to finishing up the clutch today. Maybe even putting it back in the frame!

 

[XSLeo]

On my 75 when the chain got extremely worn the tensioner was screwed in so there was hardly any threads to put the cap on. This let the tensioner slap the chain against those nubs. Made a lot of noise. Kinda like a bell clanging.
A new chain and front guide as well as the damper on the plunger stopped all the noise. Using the elephant foot valve adjusters with all good parts inside and the engine is so guiet you have to stop and listen close at idle to hear it run.
The clutch and tranny make more noise. Guess I'll have to pull that right cover and check it out closer next oil change.
Leo