Triumph TR3 drawing


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Triumph TR3 FAQ page

TR2-4A Lifters

>Further to your concern about proper springs, I recently installed three-
>part valve springs in my TR3A engine along with new tappets, push rods and
>a 280 degree cam ( and some other things). The springs tested at aprox.
>105# cold. Within 1500 miles both the cam and the tappets were destroyed.
>I've gone back to stock springs ( from Moss) which tested at 76 - 79# cold.
>At operating temperature, these values should degrade - - perhaps to aprox.
>70#. Time will tell if this setup will endure.
>Dick Ames
>Triumph Register of Southern California

The most likely reason that your cam and lifters went bad is that the lifters were not hard enough. We hardness test ALL lifters that we use in our engines, especially NEW ONES. In the last 2 years I returned at least 10 lifters to the TRF that were under Rockwell 50 hardness. I have also returned many to Moss that were too soft. Original lifters were always harder than 53 and sometimes they went as hard as 57. I have received some new ones that checked at 19! The criterion that we use is 50 to 53 for a stock engine with stock spring pressures, 54 and above for anything with higher spring pressures than stock.

For a full race engine with 135# on the seat and 225# or more at full open we sort out sets that check at 56 and above. We also have all our cams ground with tapered lobes to match the radius on the base of the tappets. The original stock cams did not have a taper and that contributed to their early failure.

We have not had a cam or tappet failure that I am aware of in the last 15 years . Of course we always is Molybdenum disulfide assembly lube paste on all tappets and lifters.

Regards, Greg Solow

Also:  The factory spec for cam shafts is a Rockwell hardness of c90 or above.

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