3S Cam timing information

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Feb 20, 2006
Hi there,

I'm looking to to establish lift at TDC, or opening position at a set clearance for a factory 3S cam - can't find the information anywhere, and I'm sure someone out there will have it!

Many thanks,

Found this in my files if it's of any help...........
Just to cause confusion, another SS cam, henceforth known as the 2S, was introduced for the 750cc Combat engine. This cam had more lift and duration and virtually equal overlap, i.e. no lead. The result was more power at the top end at the expense of bottom end torque. The 2S was also recommended for 850cc Stage 1 tuning, i.e. fast road work. There was another grind known as the 3S which had the same timing as the 2S but more acceleration, and 0.016" ramps instead of 0.010". The 2S and 3S cams may be advanced up to 3o to restore some lead and presumably result in a less peaky power curve. Advance by 5o as above, then file a tiny step on the camshaft key to turn the sprocket 1o anticlockwise. The net advance is then 3o.
Best check with Les Emery, he'll have the data for lift at TDC. An educated guess says it's a little higher than 2S with the faster accelerating ramps. 2S is around 4.5mm nominal but they do vary. My own std cam was way out and I had to advance it 5 deg. Do you have a degree wheel ?that's the only way to do it properly then you can set up the inlet side near as poss to specs.
Inlet opens 59 deg BTDC
Inlet closes 89 deg ATDC
Exhaust opens 88 deg BBDC
Exhaust closes 60 deg ATDC

Measured with 0.016" clearance using a 0.003" feeler.


Thanks for that - I am indeed armed with a degree wheel and DTI - I've also read that whilst the relationship between the lobes on factory cams was pretty accurate, the relationship between the lobes and the keyway could be 'variable'!

Cash - Thanks again - all I need now is lift at the collet at TDC and I'll be able to sleep at night.
I can't find my cam data sheets, but I'm pretty sure the valve lift is the same on both exhaust and inlet, and same as the inlet lift on an SS Combat cam. Lucky pehaps, I have found a note on an old timing disc that looks like '0.384" lift SS inlet' .
If I do find the data I'll get in contact.

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