Cam timing change, vintage bike engine

[Truckedup]

pcnsd ,Wow you were busy, thanks.... I have a few comments...On the dyno as the engine is now, the best power was with the short intake length. I tried longer intakes and it made no difference in peak power ...And the long intakes made it impossible for the rider to get into a proper tuck because the splayed intake forced his knee's outward.
On the cam,I have considered the Sifton 460 or the Johnson ...Megacycle has a 510-2x that falls in between the Sifton 390 and 460...In my dual engine Triumph I have a Web Cam 330 grind that's close to the 510-2X.
With the current Sifton 390 intake intake at 102 degree lobe center the intake valves left witness marks on the piston valve reliefs...I cut the reliefs a bit deeper but can't go any deeper..So I have to be careful to keep intake lobe centers to at least 105 degrees...
The bike has the two individual pipes because that's what all the other guys use Most of the Brit Bike lSR racers use megaphones on what appears to be a 36 -40 inch head pipes. No two megaphone set ups are the same diameter. length or taper some open ended, some have reverse cones..

This bike has made about 15 dyno pulls...I never tried different ignition timing or exhaust lengths, only intake changes and jetting..

Thanks again...Things to think about..........

[twl]

We have successfully modified vintage rocker arms similar to yours at virtually no cost except the labor.
The pushrod end of the rocker arm can typically be shortened by 10% or even more, yielding more lift and area under the curve. Get a very good welder to put the tip back on, and try it out.
Bet you'll love it!
If not, just put some stock rocker arms back in.

Worked great for us. We went from 1:1 to 1.2 :1 on our first experiment. Picked up about 4hp.

Try to set up the cut/joint in a way that is not likely to shear. Our first try with a weak weld lasted 1100 miles before it broke. Our later efforts have never broken. We then moved to rollers when going to much higher lifts, but the regular ones are still working. It is a real low cost way to bump the power.