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BeezaBryan
BeezaBryan
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Hi,
I am in the process of fitting my timing gears/wheels to my 1966 T120 engine and have found the “Intermediate timing gear” is very tight on the CAM timing gears.
It should slot into the cam gears fairly easily, but I would have to force it to fit (not good).
The part number on my Intermediate gear is 70-6159. The cam gears are older and do not have numbers. They both have 50 teeth.

Does anyone have any suggestions to solve this problem?

1. Have I got the wrong intermediate gear? 2.7190 thou diameter.
2. Have I got the wrong cam gears? 2.8825 thou diameter.

Any help would be greatly appreciated.

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Have you got the top end of the engine fitted? If the valves are being operated, then it will be difficult fitting the idler gear. I have several sets of gears, but they are at my workshop some 15 miles away, can't check 'til tomorrow

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Presumably the intermediate wheel you are attempting to fit is a newly acquired item?

Do you still have the original one?

Are other 3 gears (the 2 camwheels and the crank wheel) original to the engine?

A bit more of the history would be helpful. What have you recently done to the engine that may be pertinent eg new cam bushes etc?

The new intermediate pinion possibly may be machined too large, if that is the only new wheel, and if so then try the original pinion.
The more usual issue is clattery slop between the gears.

I would suggest removing all the pinions, then first check that the intermediate wheel slips easily and freely on its spindle (ie the bush isn’t tight on the spindle).

Then install the crank pinion and see if the intermediate still fits easily. If its tight, the problem has to be with one or both of these pinions.
If free fitting, remove the crank pinion.

Then install one cam pinion and test fit the intermediate gear. If its ok, fit the other cam pinion only, and test.

Hopefully this will identify 1 or more tight contacts, which will inform what the problem is.

I have made the assumption that the timing side cam bushes/cam journals are good.
If they are worn, and the cylinder head/rocker boxes are installed, then the valve spring pressure will tend to close the clearances between the cam pinions and the intermediate pinion.

Over many years of use, the cam bushes do wear (mainly at their lower surface) bringing the cam gears closer to the intermediate wheel. Over more years those gears will wear a little together. A new (correctly sized) intermediate gear then will not fit comfortably.

Best of.

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I agree that slop is the more common problem, in fact I've never found a tight intermediate wheel. I would suggest finding a new intermediate wheel somewhere, or better still, a complete set of T140/TR7 gears. They're heavier, better made, usually much quieter in operation, and I'm sure they'll fit without slop or bind.

SR

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When I first purchased my 67 T100R, the spindle for the intermediate wheel was half missing and the timing cover repaired as the engine had been in a mishap. I replaced it and the timing cover that had been chewed up by the half and loose spindle, locktited it and it held. 20 plus years later when rebuilding the engine after over 30,000 miles on a used engine, I had to get the hole for the spindle repaired and a new spindle installed. The machine shop was sure they had got it right but fitting the intermediate wheel was tight as there seemed to be a slight shift from the original position. My solution was that from the drawer of gears from parts engines I had purchased over the years, I found a gear that fitted nicely and is now fine. I saw a film from the 50's showing the assembly of Triumph engines at the factory and the guy doing it had a box of gears and just tried different gears until he got a nice fit. Made me glad to have the spares and that I had purchased engines/parts when they were easier to find. Someone near you must have a few of these in a box.

Cheers, Wilf


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I measured some gearwheels, and the idler gear measured 2.723" (more than yours) and camwheels 2.790" (less than yours). That said, the O/D's are not what matters, it is how deep the gears are cut. As Stein Roger has said, I use the T140 gears in my engines anyway, though I do have sets of the early ones too.


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