info on camshaft PD-R 2-1 B/742 WEC

Dear Norton adepts,
I've tried to race last season with my Domi 500cc with a camshaft that was wangled me : PD-R 2-1 B/742 WEC
I had to fit neelde bearings and a oil feed and 3 inch radiused followers.
Torque felt good but it seems not wanting to rev what ever I tried over the season. Timing forward and backwards, ignitiontiming forward and backward, small diam carbs, big diam carbs.

does anybody know something about this cam, what was it used for, what is the proper timing for it.
I think it is for a big cc MX or (MX) sidecar application and not really suitable for a 500 twin.

PD prefix sounds like it may have something to do with Paul Dunstall ??
Perhaps some of their old catalogs may show up what it was intended for.

Have you tried a degree wheel on it, to see what the cam timings are like ?
There is a thread here a while back, where JohnM outlined his 500 (road) racer in NZ.
And using a dyno and some steady development to get good results.

We see that PW3 cams are avilable for dommies (Peter Williams developed version of racing cam),
that sounds like a more viable and known and proven version....

I think Rohan is on the right track. It's most likely a Paul Dunstall "R" race cam prepped for needle roller bearings

thanks guys so far, I could degreewheel it, but without timing info the curves wouldnot really help me. And if the profiles are meant for a "tractor" than it is if no use anyway in a 500 twin. I fitted needlebearings (it will not fit in the regular bushings), made oilfeed to the lobes and used radiused followers and ran it a season. I've lengtened my inlets to 400 mm. Loads of torque but no top end power. I was hoping for some details and info where it was made for.

Hi

I dont recognise the numbers but if you did measure it you could compare it to the large collection of curves on Dave Comeau site (Dyno Dave)

http://atlanticgreen.com/camsurvey.htm

This would enable you to compare it to a wide range of cams, possibly identify it and if you find a similar cam, give you a good idea about timing.

Measure the cam profile from the top of the push rod. I measure at least every 5 degree over the base circle and every degree on the quietening curve and the profile.

As Rohan mentioned I have used the PW3 curve for 10 years. I recomend buying it from Mike Hemmings as he has the PW3 on a real Dommie core not a modified Commando one. This gives a more robust timing sprocket mounting. Be aware these cams are made of cast iron so DO NOT OVER TORQUE the sprocket nut. 20 ft lb with blue locktite. If you lean too hard on it you will snap it. This cam will easily rev out over 8000 if you try but 7200 is ample and should give you a good 50 bhp at the rear wheel if you have everything right.

The 500 is more difficult to tune for good horsepower and wide power curve than the 750s. The best present you can give a racing 500 Dommie is a 5 or 6 speed gearbox !!

Cheers

John

You can get that running to tight a clearance . DO YOU have the Valve Clearance SPECS ??

lot of race cams run 12 to 16 thou . Tight can mean it gets lame touring when warm .

Is it a road or track machine .

With having to use radius followers you might have a full races cam, which has not been designed to go in a 500. What is the amount of valve lift inlet & exhaust?
You also need to check timings with a degree disc, and you might have to use a ridiculous amount of ignition advance,(as quoted by Paul Dunstall on the ex-works Lowboy 500 Domiracer he acquired)
A manually operated K2F magneto might be an advantage as you can ajust the ignition timing while you ride to find the “sweet spot”!

With this race cam, are the valve springs becoming "coil bound" on full lift :?:

Carb & bore port size is also critical- are you using a large valve downdraught inlet and splayed exhaust port cylinder head :?: - or the earlier head :?:

Clearance inlet and outlet is at 0,010" or 0,25 mm as I m more used to metric being Dutch
Best result I got were with 1 1/8" (28,5mm) carbs at 32 degree ignition advance
(before this cam I was at 28 degree advance on a 4S lobe grind)

If it won't rev out and give top end, it might be due to the exhaust system you are using. When I had my short stroke 500cc Triumph, the problem was in getting enough torque to get decent lap times. What you have is not a bad problem, at least the bike would be sane and ridable. I'd also check to see that you are not getting frothing in the carbs which can richen the mixture and cause the motor to slow, especially if you are using petrol. Are you permitted to use methanol fuel ? I suggest whatever cam you use, it should be possible to get reasonably decent top end , it is just that some give more than others. One way of knowing what is happening, is by noting where the 'cam spot' occurs. In a 500cc racing motor if it is very low in the rev range or you don't have one, there is something wrong. If you are using an open exhaust it should occur strongly somewhere around 4000 RPM. A muffler can stifle the cam.