Moto Grand Prix
Moto Grand Prix
Main Motorcycle: Triumph Bonneville
Join Date: Oct 2008
Location: Bordeaux, France
Other Motorcycle: Triumph Speedtriple
|Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.|
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A standard Bonneville doesn't make maximum torque with those 3134 cams until you reach 5500 rpm.So really,you're losing out below that because of too much duration;especially late intake closing.
So it depends what rpm you normally ride at,and where you want the response.
If you spend a lot of time between 5500 and 7500 rpm,use more duration;something like T140 intake .
More lift is always good,you can't get enough lift to get full flow from a standard intake port.
You're a bit limited if you still have the '69 timed breather,you can only use cams with a breather hole.
According to Phil Irving's book "Tuning for speed" you should be looking for cams with a duration of:
Inlet Opens at 35° Before TDC
Inlet Closes at 60° After BTC
Exhaust Opens at 65° Before BDC
Exhaust Closes at 30° After TDC
The problem is this book was written in 1952!
You might also note that Phil mentions after you have set up the 3134 cams at the checking clearance of 0.020",the "actual timing" becomes 59/80 on the intake at running clearance.
These are not really slow cams.Its easy enough to be on the wrong side of 7000 or 7500 rpm if you don't pay attention to the tacho.
I think there is something to be gained by using the timings that the T100R used with the same cam profiles.
Like I said,more lift is better.I've used cams with 0.360" lift (0.400" at the valve);and if I could get 0.500" valve-lift,I would use it (currently working on that).
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