Maney cam timing

Can anyone tell me the figures to check the cam timing of a Maney cam, lift @TDC preferably?

I have this cam in my 1968 750. When I asked Steve what timing figures to use he said to time it to the standard marks as there was virtually nothing to be gained by deviating from them.

I don’t intend to deviate Martin, I just wanted to check it.

For someone more used to Edward Tuners finest, it has an awful lot of lift at TDC !

If my memory serves me correctly I think the figures for lift at TDC are very similar to a 4S profile.

Matchless said:

When I asked Steve what timing figures to use he said to time it to the standard marks as there was virtually nothing to be gained by deviating from them.

Click to expand...

Hi Nigel, I asked the same question to Steve and got the same answer , and so that's what I did.

Martin and Martyn,

Yes, after some discussion with various folk I got a concensus that 4S timing is what it should be, and it is pretty cock on.

So we’re all good.

Onto the next job! (Which you can see in my build thread if yer interested)

With any cam, I'd install it to the marks and put a degree disc on it and see what I get. If the duration is longer, you can either equalise the difference or adjust the cam position to suit your exhaust system. There is plenty of information in 'Tuning For Speed' to help you make a judgement about where the timings should be. If you are using a 2 into 1 exhaust or mufflers, I would move the cam forward.

Chaps,

So, a Maney cam should be timed as per a 4S cam I am told. These cams are all new to me, so I’m still a tad unsure if my set up is ok or not.

I had been measuring the lift at TDC with .016” tappet clearance, and have been told this is incorrect.

When I measure the lift on the cam follower I’m getting a different situation.

Lift at TDC measured on the follower should be .1885” according to RGM and .189” according to NOC.

I’m getting .1885” lift 2 degrees on the timing side and 3 degrees early on the drive side.

So, at least Al should be happy as it seems to be a tad advanced !

My question is, what effect will this have?

And also, is it worth correcting?

Assuming there are no issues with valve tangle & piston clearance, advancing the cam will shift the powerband down a tad, and retarding will move it up. Depending on your situation this may be desirable or not, in my case it (street), I was advised to aim for around 5 degrees advance, but ended up with about 3 degrees using RGM's new cam sprocket...

Were you able to plot out your lobe centers? I found it helpful to figure out the separation angle of the lobes on my cam and compare them to manufacturer specs, I too took these measurements off the lifter and found them to be different than those taken off the valve retainer.

Thanks for that. I’ll see what Steve Maney has to say when he’s back in UK, but I’m leaning towards leaving it be at present.

Fast Eddie said:

Can anyone tell me the figures to check the cam timing of a Maney cam, lift @TDC preferably?

Click to expand...

http://www.gearhead-racing.at/Workshop/Project 850cc/Project 850cc.htm

• Steve Maney S4
• Inlet valve opens 46° BTDC, closes 76° ATDC
• Exhaust valve opens 76° BTDC, closes 45° ATDC
• Intake lift 10,1 mm
• Exhaust lift 8.9 mm

Thanks for that, I find opening and closing figures very difficult to establish accurately though and much prefer lift @ TDC for set up.

Are you running flat or radiused lifters? Is that cam designed for flat or radiused lifters? Depending on the scenario, establishing the opening and closing values may be moot. I've got 4" radiused lifters and a cam designed for flats, so the opening and closing values provided by the manufacturer won't help. That's why I think it's more advantageous to simply establish lobe centers to help figure out where the cam actually is in relation to the crank... tweak to suit your needs from there.

This guide was very helpful, as were some tips from both "Jim's" on the forum (a few degrees of advance etc.)

https://www.accessnorton.com/NortonCommando/cam-timing-101-2011.9927/
https://www.accessnorton.com/NortonCommando/pw3-cam-timing.14255/
http://www.faliconcranks.com/pdf/degreeing_In_your_camshaft.pdf

Thanks, there’s some good info in those threads!

I have flat followers, which is what the cam is designed for.

• Steve Maney S4
• Inlet valve opens 46° BTDC,
closes 76° ATDC
• Exhaust valve opens 76° BTDC,
closes 45° ATDC

Above does not make any sense to me?


The spec sheet that Mick Hemmings supplies gives the following timings:
Inlet opens 50degrees before TDC
Inlet closes 82 degrees after BDC
Exhaust opens 84 degrees before BDC
Exhaust closes 48 degrees after BDC
Mick's terminology above works for me.
Yes these are for different cams but the 4 stroke timing concept is still the same.

Which ever cam you use, the optimum timings will change with the type of exhaust system you use. If you are using all of Maney's recommendations, you still won't know if you have something which suits your local circuits, until you actually use the bike. Then a number of things come into play. If you make the motor pull harder, you will probably raise the overall gearing. A lot depends on whether the local race circuits are 'power circuits' or 'riders' circuits'. For a 'power circuit', you might use separate pipes with megaphones, the cam timings which suit that are different from what you would use with a 2 into 1 pipe on a 'rider's circuit'. What I usually do with an unfamiliar cam, is start advancing it in 5 degree steps, and keep testing. With Triumph motors, it is sometimes necessary to advance the exhaust cam when you fit a 2 into 1 pipe.
If you are timing the motor and getting a couple of degree differences from what is prescribed, I would not worry. But I would tend to advance the cam rather than retard it. In the end whatever cam you are using has probably been developed by somebody facing the same considerations as yourself. Even if they raced for years using that cam, it might never have been fully optimised to suit any particular situation. When you race, most things are a compromise - gearing, exhaust system and steering geometry included. The problems only come when you get so many things wrong that you tie yourself in knots trying to adjust your riding to accommodate the bike.

You comment about the lift interests me. I still have that 2S combat cam, the lift seems to be extremely high. I also played with Triumphs for many years. In comparison, the 2S cam appears to be horrendous. And I am still of two minds about whether to use it.