Camshaft advice

[ranton_rambler]

I thought I'd put my camshaft progress in the same thread rather than have 2 separate ones.
I got the guy to measure the lift of both of the ones he had (see photo) and dug out the measurements of mine. As far as I can tell from the lift measurements and eyeballing the profiles, the right-hand one in the picture is the same as what I already have. Standard cam for 175/200, which has 7.5mm lift on both lobes at the cam. I believe lift at the valve stem is about 92% of lift at cam from my own and Jim's measurements.
The other has 8.6mm on the inlet and 7.9mm on the exhaust, and exhaust looks to have a bit more duration, so he's sending me that one. Moderate increase in lift compared to some on Jim's sheets.
Once it's here I will fit it and put the head back on, measure the timing and check clearance to piston. The piston is already a higher compression version with reasonable pockets in the crown.
If all seems sensible I'll give it a try, although I suppose I'll need to revisit the carburettor settings all over again.
If it doesn't work it looks like the camshaft can be changed with the head in place, although I'm sure someone will put me right! I could try adjusting the timing by a tooth either way, or put the old camshaft back in. I think the bevel shimming is set by the gear and the bearing so should be preserved.
Hopefully get a chance to zoom up and down the lane before they start chucking salt down.

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[George]

Have you got timing figures for existing cam. It would be good to be able to compare with new cam to check open and closed degrees.

[ranton_rambler]

Have you got timing figures for existing cam. It would be good to be able to compare with new cam to check open and closed degrees.

Yes, measured mine when I built the engine.

[George]

Might be a good idea to check compression ratio while waiting for new cam. Mine had to be adjusted via barrel gasket. Clearance checked after. Sorry for stating the obvious don't mean to offend

[ranton_rambler]

Camshaft will probably be here before the head comes back from having its guides sorted. That’s one of the things I took a chance on but it does smoke a little and uses a bit of oil....
I could measure the compression ratio with a bit of improvisation but I don’t know if I have enough knowledge to interpret what I get...
It should be 8:1 with the parts in there. I did a compression test before taking it apart and seems about right at 135-140psi.
The camshaft isn’t costing me much so I won’t be too upset if I don’t use it.

[ranton_rambler]

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Old and new camshaft profiles comparison. Got some domestic tasks allocated today but will try and get it put back together during the week after work.
Ian

[ranton_rambler]

All back together yesterday afternoon, and first start this evening. Got a day’s holiday on Wednesday so if weather alright I’ll put the tank on and give it a run up the lane. I imagine a bit of carb tweaking will be needed.
Ian

[LaceyDucati]

Ian

I did have a quick look at your info and was going to reply to your email, maybe give me a call. My guess is the cam is a "sports" cam rather than a race cam as such. I don't have enough 175/200 reference info to identify it as a particular cam. My basic observation is the "new" cam is advanced by about 15 to 20 degrees from where I would think it was supposed to be timed. Maybe a tooth out at the crank around 17 degrees.

By indexing the gears top and bottom you can get about 8.5 degrees, so you could try all these variations, finer changes have to be done via stepped keys either in the top or bottom bevels. My general experience is that changes of 3 degrees are generally not that significant/noticable. Certainly changes of 3 degrees off optimum would not be detectable on the road and only just on a dyno. Obviously you will need to check the valve to piston clearance at these positions, but it sounds like you have loads at the moment. My guess is, as set it won't perform at it's best, but as it's safe it's worth a try just out of interest for reference.

Regards Nigel

[ranton_rambler]

Initial impression after a few trips up and down the lane this morning - can’t tell much difference.
I’ve had to drop the main jet size from 112 to 100 to get it to run at full throttle, which seems opposite to what I expected.
Need a proper ride really but not sure when that fits in the schedule.
Will also try adjusting cam timing as per Nigel’s suggestion.
Ian

[double diamond]

Ian, what sort of device did you use to get the graphs of you cam profiles? I’ve wanted to determine the specifications of several cams I have. Your graphs are just what I need.

Matt