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TR2/3/3A Stock Valve Lift

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CJD

CJD

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I'm finalizing the head assembly. All I lack is knowing what the valve lift is at the valves. I have hashed the manual, which gives just about any measurement you could dream of...but I cannot find a mention of valve lift anywhere. Odd!?! I measure .260" at the lifter, but I don't know if there is a ratio through the rocker arms.

So, if anyone knows the TR2/3 valve lift off hand...it would save me a lotta assembly just to measure it.
 
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Kind of a muddy topic, when you start trying to take all factors into account. The nominal rocker ratio is 1.5:1, but actual is usually slightly less than that (around 1.46:1). TR4 workshop manual gives the lift at the cam as .260" (and is supposed to be the same 301466 cam as the TR2-3). So, theoretical lift at the valve would be .260 * 1.5 - .010" (for valve lash). But there is some flex in components, so actual will likely be somewhat less. Of course it also goes back up a little when the valve gets hot, since the lash closes up.

If that's not confusing enough, there are multiple specs at
https://www.tildentechnologies.com/Cams/TriumphCams.html
 
Yep, a bit confusing. I think I'll end up taking actual measurements to make sure I don't get coil bind. I didn't think it would be an issue using the stock springs and cam, but it looks like it will be. I figure the lift to be at least .375" if the rockers are 1.5 ratio, and a bit more if they are 1.6.

If I set the springs to the service manual seat pressures of 38lb outer, 33lb inner, and 10lb for the stabilizer spring...then I've only got about .4" and change before the inners start to bind. That's getting too close not to measure the final assembly.

That is an interesting link, Randall. There have been a lot of iterations on cams for these old engines. Mine looks to be an early generation, but seems to have more lift. I don't know if my re-grinder added it or it was a bit hotter than stock to begin with. I'll update when I run the measurements later in the build...
 
Final follow-up...going back and closing out all my threads for the TR2...

I think my grinder went with a later, performance grind on the cam. It's been too long now to expect him to remember, but the engine has more torque than the TR3 did, even though it has less displacement and smaller carbs. I used .4" valve lift as the magic number. With shims and such, most of the valves could tolerate a bit more, but the limiting valve will accept .4" before it binds. I used the stock springs, but went through, like 40 or so old springs to choose the 8 best. Some were weak, and others had actually collapsed in sitting height.

Cheers!
 
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