PW3 Camfshaft

Hello Tim....

I used a PW3 in my racing featherbed commando .. I had the crank re-balanced to 83 % and it would rev like a turbine to 8000rpm.

Check this attachment out :..........

I used one for two years and 7000 miles. That was a 750, Combat head, 9.7:1, intake ports well opened up and the usual 32mm Mk1's. Yes it would rev but there was little low down oomph and even the mid range was disappointing (claimed in some articles to be improved). Set up to spec with a timing wheel it also made the exhaust very loud (subjectively) and blatty. Set using the std marks it was better and lost little in perceived performance. For me it wasn't a success. I think it would probably be useful in an 850 with the greater capacity or a 750 on which you don't mind wringing it's neck. With the stupid ports done by a previous owner it just wasn't nice and works a lot better with the std cam. If you have a Combat cam installed you will miss the rush at 4500rpm but PW3 is less peaky. It all depends what you want or expect really. Apologies if it sounds like I'm putting a dampener on it but it just didn't work in my engine.

Hello,i have also on my MK3 PW3 cam,very easy to start and running nice idle speed.I have also Mikuni VM36 single carburettor and seems that very difficult to find correct adjustments for Mikuni.I have also some "universal" exhaust pipes,last autum i took silencer out from pipes and it helps,before back pressure in the pipes was too high but now engine running very smooth.

Hello Tim,

I have PW3's in all my Commandos, mainly because they are only slightly more expensive than the standard cam and they are supposed to be a better cam. However, I would agree with some of the previous replys that the overall performance is little improved over the standard cam in a standard engine but it does change the characteristics of the engine and makes it more willing to rev but can run a bit rough at very slow speeds at 30mph or below (I only found this out trying to follow in line at one of the Norton rallys) but this could be more of a fault of the standard 4 speed box where at this speed top is too high and 3rd too low! The other problem I have come across with fitting PW3 cams is that on some early Commandos and Domi's you have might have to modify the crancases and barrels to get sufficient clearance and if you have a high compression head or one that has been heavily skimmed, you need to check carefully that the valve springs are not going coil bound on full lift. None of these issues are beyond a reasonably capable home mechanic but if your not confident in your abilities I would play safe and replace the cam like for like,

Peter Austin

Previously tim_nolan wrote:

I have just stripped my Combat motor down and the camshaft looks fine, but I'm considering fitting a new PW3 camshaft. I would be interested on members views to see whether its worthwhile.

I'm sure this subject would have been raised in the past, but cannot find much information about it.

Many thanks

Tim

The 2S was the Combat motor cam, whilst the 3S was fitted to the 750 Production Racer. It looks as though someone has been in there before you....

Interesting that there is little information on the 3S, only intake lift figures at TDC from the NOC technical pages on cams. It shows greater than 2S but less than 4S. No timing data though. Norvil sell it and state it is the original PR cam.

That is correct, as Norvil say.

If you want to know the timing data for the 3S, it is as follows:-

Inlet opens 59 deg btdc

Inlet closes 89 deg abdc

Maximum lift 0.396"

Exhaust opens 88 deg bbdc

Exhaust closes 60 deg atdc

Maximum lift 0.352"

Those figures are the same as the 2S (Combat) cam, except the lift, 0.006" greater on the 3S. The latter also differs in that it has higher acceleration and a 0.016" ramp rather than a 0.010" of the 2S.

As it happens I have a Proddie Racer, at present stripped for rebuild, and as the cam is worn out, I have a PW3 to go back in; when I get round to it!

The PW3 has alot of overlap and I was advised by Mick Hemmings that to get the best from it more compression than standard (850 in my case) is needed. Against his advice for fear of starting problems I went for standard C/R an am now (when it get warmer in garage) going to try the JS Motor sport 3 thou thick head gasket to see if it helps. I have read many reports since that raising the compression made all the difference to other users of this cam.