ET: Engine (Twin) Equal lift at 4 degrees

[litnman]

What's a few degrees between friends anyway? While factory timing figures are simply what the manufacturer found to work 'best' with the engine when new, much has changed including fuel, exhaust etc. .... so live and let live I say.

For what it's worth, by experimentation on many engines, I've always found that advancing the cam timing so that you've got no less than 0.030" piston to valve clearance works well with any cam profile for power at higher engine speeds while retarding the cam makes it pull well from low rpm. Just like ignition timing this is simply another tuning parameter rather than rigid dogma.

Have I been doing this wrong all this time? I retard cams for high speed power and advance for low speed power.
http://www.webcamshafts.com/index_blank.html?pages/cam_glossary.html

 

[Vincent Brake]

My road Comet was timed at 99.8 mph and my road Twin 141.9 mph, How fast does yours go ?. Cheers bill.

Very good indeed Bill, and I bet its not only down to the eye!

 

[Bill Thomas]

Very good indeed Bill, and I bet its not only down to the eye!

Vincent, You are right,It's always more than one thing,With the Twin it was a home made 2 into 1 exhaust plus 36mm Delorto pumper Carb's, With the Comet, I nicked a cylinder head and Delorto carb' Off the Twin for a short time, Oh and I forgot !, Both days had a nice Tail wind !!. Cheers Bill.

 

[passenger0_0]

Have I been doing this wrong all this time? I retard cams for high speed power and advance for low speed power.
http://www.webcamshafts.com/index_blank.html?pages/cam_glossary.html

No, not at all. You're agreeing that cam timing can be varied as a tuning parameter and that different engines and configurations of exhaust/inlet etc. ... all have an effect. No one is either right or wrong if we feel we get an improvement with this change, either on the dyno or 'seat of the pants'.

 

[fogrider]

In one of the well known books ( Richardson ?) there is advice that if you're on Mk3 cams and the bike feels sluggish, move the cam timing one tooth - which I think is 7.5 degrees. How scientific is that for cam timing !