E: Engine Setting MkII Cams With No Timing Marks...Equal Setting?

[royrobertson]

Hi Jez, are you sure they are Mk 2s. They just don't look "lumpy" enough. I don't have the figures to hand but it's worth putting a "mic" over the lift and checking as Mk 2s have higher and longer lift than 3s and 1s. Someone on the forum will know.
roy the racer

 

[jim burgess]

I would like to thank you all, I felt assured that the level of my ignorance would reach new heights on this forum and I am not disappointed.

Vic, I love the workshop, the tools and the methodology "Forget all these funny numbers, they are not relevant" this really appeals and I will remember to quote it to my wife and bank manager. That's an awesome looking engine, very nice head steadies, what is it going into?

I don't think I'm going back to the stage of pulling of the half time pinion and starting all over, and from what you have all said I don't think I'm going to get much closer.

I agree about trying to time from the ramps, this is an old cam with a completely unknown history and picking out the exact points of operation has been quite difficult and at times vague, especially compared to the front cam, which is new, as is its wheel, and gives more definite results.
On the basis that there are more questions than answers, what are Andrews cams?
many thanks
Jim

 

[Bill Thomas]

Hi Jez, are you sure they are Mk 2s. They just don't look "lumpy" enough. I don't have the figures to hand but it's worth putting a "mic" over the lift and checking as Mk 2s have higher and longer lift than 3s and 1s. Someone on the forum will know.
roy the racer

A friend from Devon rang me some time ago , To ask how to tell the difference,
Between Mk1 and Mk2,
So I took this photo.

 

[bmetcalf]

Andrews was making Vin cams from the late ‘70’s, then sold the design to Megacycle. https://www.megacyclecams.com/catalog/index.pdf

 

[oexing]

Jim,
my projects started 30 years ago as a collection of boxes of Argentinian old iron from various bikes. So I knew then it would be a veeery long job, seeing lots of places wrecked. I don´t plan on racing the things but target is two B-Rapides with lots of "enhancements" we can do with modern tech for nice ride, like hydraulic steering damper, even on Bramptons. Or air shocks front and rear, crank and conrods homemade, with cranks and mainshafts one piece, 40mm press fit crank pin, and a lot more. And yes, mostly metric dimensions as so much easier for getting stuff in days from anywhere, in all kinds of shapes and material.
As to cam timing, I think the most critical matter for good engine performance is the overlap with equal lift. You have to see both valves are open in this situation and equal lift has to be within 10 degrees around TDC, else gasses will take unwanted directions when you don´t get this right. Really you want equal lift at exactly TDC for best power and torque combi. Vincents preferred 4 degrees before TDC for extra torque and a bit less max. power from this. Some like 5 degrees past TDC for maximum power at higher revs but less torque at same time. Racers here will be allright with my belief I think ? So that is why I am uninterested in funny numbers from handbooks as you cannot know the situation at overlap with your stored used components with unknown wear in various places. Better really check cams for equal lift, mark them for easy timing anytime later. All other strategies of timing the engine don´t promise to produce better results. Instead they rely on a lot of guesswork and a wide variation in readings on clocks at full lift, start of ramps or the like.

Vic

 

[litnman]

Vic,
Did you make your magneto gear?

 

[oexing]

You mean the alu gear for the Ronco 4 cyl. mag ? Yes, a story for itself as it has to accept the v-twin timing. So I had to keep 4 sparks per revolution , in consequence it produces two sparks going into the ht leads plus two "waisted" sparks under the distributor cap going to earth there. I tried the v-twin mod for just two sparks but then no sparks at all.

Vic

 

[vibrac]

Ben stuck with 4 deg BTDC at EO for the goodwood racer she did128 down the back straight and got the meeting lap record no fancy cams no high compression and we have no idea what the cam opening and closing figs are.

the equal opening will certainly get you to the next rally

 

[jim burgess]

Vic, fascinating project work and to a superb standard, how about an article for MPH? There must be much of interest for all members?
Please?
You make your own conrods? Really? What do you do in your spare time...?
While I agree with what has been said regarding overlap and valve timing, and I have leaned much, I have put the cams in with an opening at 55 degrees BTDC as I was happy with the front cylinder running with a new cam but not the rear, and I will see if it tries to break my leg again.
Cheers to all
jim

 

[Cyborg]

View attachment 58893

I’ve seen that photo before, but don’t recall noticing your stops on your home made G50 plate. That’s a good idea. I was probably focused on that display. Are those Sony probes or Chinese copies? I don’t think you’ve ever posted a photo of your mag. It would be interesting to see a couple.