Camshaft Timing

[Ian Vincent]

I have just finished replacing the camshaft on my engine. I have had the cam re-profiled by Piper Cams to 'Fast Road' Spec and installed it according to the data sheet that came with it at 110 deg ATDC.

 

I was very surprised to find that I used the same fixing holes for the cam gear as on the original camshaft before I had it reprofiled. To me this suggests that the timing for the standard cam is also 110 degrees but I can't find that information anywhere.

 

So back to the original question, does anyone out there know what the timing should be on a standard TR3a camshaft as supplied by the factory?

 

Rgds Ian

[Mk1PI]

Pretty sure all Triumph Cams were 110 ATDC, apart from TR5 "150bhp" which is 105 ATDC

[Celtic2]

This might help.

 

Triumph Cams

 

gary

[Ian Vincent]

This might help.

 

Triumph Cams

 

gary

 

 

Many thanks Gary, it took a bit of reading to get my head around it but I think I finally worked out that a lobe separation of 110 degrees and 0 deg advance means that a stock Triumph cam is timed at 110 degrees on the crank.

 

Rgds Ian

[john.r.davies]

Are any Triumph camshafts, except possibly some of the really wild ones, non-symmetrical?

Meaning that the two cams for each cylinder have the same shape, and are equally set either side of TDC?

And designed for an engine that has pairs of pistons, moving up and down together.

 

Because any cam that is symmetrical can be set without any need for that magic angle.

If the crank is set to TDC on No.1 bore then the other bore that matches No.1 cyclinder - No.6 in a six cylinder Triumph, No.4 in a four - should have both valves open, overlapping as that cylinder moves from the end of one Otto cycle to the beginning of the next. If both valves are lifted equally, then the cam is correctly set.

 

This is the "Equal lift on overlap" method.

 

John