Triumphrat

david_in_ky · 12-03-2009, 02:14 PM

Finally got new valves in for my 71 T120.. have them at the machinist to grind in the valves .. I need to know for him the nominal deck height of the assembled valves ... he is concerned if the valve seats need replacement.. anyone have the information on exhaust and intake ? I call this valve deck height, but it may be out dated.. basically from the head at the valve spring cup seat area to the top of the valve as assembled with springs and clips..

I have looked over my manuals and may have missed it ?

Thanks for any help on this ...

GrandPaulZ · 12-03-2009, 02:55 PM

72 (should be same as 71) 650cc

Valve spring fitted length (valve closed)

Intake Exhaust
Inner . . . . . . . . . 1-3/16" 1-1/8"

Outer . . . . . . . . . 1-7/32" 1-5/32"

david_in_ky · 12-03-2009, 03:29 PM

thanks Paul.. the machinist was concerned for the height at the end of the valve, but I explained if the assembled spring height was per your chart, the valve tip height was just a function of this plus the keeper collet fit up..

he will try it this way...

Mr.Pete · 08-21-2010, 08:32 PM

Quote:

Originally Posted by GrandPaulZ

72 (should be same as 71) 650cc

Valve spring fitted length (valve closed)

Intake Exhaust
Inner . . . . . . . . . 1-3/16" 1-1/8"

Outer . . . . . . . . . 1-7/32" 1-5/32"

This is not quite right,even though you see it in some manuals.The same manual gives outer valve-spring free length as 1-1/2",when I measure it at 1-5/8" (+1/32"/-0.0").
Those figures give seated loads at 75lbs INTAKE,87lbs EXHAUST,with the exhaust valve springs 0.060" from coil-bind.Its easy to get variations of 0.020" fitted length by just mixing up collets and spring collars,or swapping valves around.This would be dangerously close to coil-bind.

Standard production Triumphs used fitted lengths about 0.080" longer,and seated load approx 60lbs INTAKE,70lbs EXHAUST with these springs (Red spot inner,Green spot outer).

Personally I measure seated load with valves installed,using bathroom scales.I shim them to get 65lbs INTAKE,75lbs EXHAUST.
You can see 8000rpm with those loads,and I've done it with less.

GrandPaulZ · 08-23-2010, 10:19 AM

Personally, I wouldn't spin a Triumph big twin past 7,000 RPM for any reason.

There is no value in it. I've never seen a dyno chart of anything short of a $100,000 salt flat special that made any signifiant HP gains after 7,000 RPM.

jimmy bush · 08-23-2010, 11:33 AM

ever miss a shift in a drag race?