Great information - now just how does one actually install a Rover six cylinder camshaft in a Vincent??
ET: Engine (Twin) valve timing for Gary Robinson 105 cams
- Thread starter Restoration Man
- Start date
Start from the rear and work your way forward..............
It was intended to show that such timings can be used to good effect.
Please excuse my ignorance. What does this value of 105, or 107 one 110 refer to. If it is the angle between the cams then on a Vincent with lever cam followers and inclined push rods etc. one could not just transfer a cam. Yours confusedly.
You certainly can time an engine at max lift, it is just not as accurate as timing it at equal lift because equal lift happens at on very narrow place. Max lift occurs over the largest space possible if you are lucky.
I know that the confusion of using the term 105 has caused at least on maker of Mk2 cams to use 105 as the LSA (lobe separation angle) and not max lift. That is why I was surprised the term was used when the cam debuted. I don't think it is necessarily wrong, but I think it is poor practice because it causes confusion. The LSA on a Mk2 is usually around 97 degrees.
David
Any one please explan how to set up Terry prince Mk 2 105 cams in plan English using lift figures ,using dial gauage on top of the valves .
Terry said get the rear cyl at tdc and turn his cam till you got .170 lift and slide the ider gear in at this . Then turn the engine 360 and 50 degree and then slide the front cam in with the same .170 lift on the inlet . But when I do it this way and turn the engine over a few times I get .165 lift on inlet at the rear cyl at tdc and at tdc on the front cyl I then get .170 lift at 43 degrees ATDC ?
Terry said get the rear cyl at tdc and turn his cam till you got .170 lift and slide the ider gear in at this . Then turn the engine 360 and 50 degree and then slide the front cam in with the same .170 lift on the inlet . But when I do it this way and turn the engine over a few times I get .165 lift on inlet at the rear cyl at tdc and at tdc on the front cyl I then get .170 lift at 43 degrees ATDC ?
One of the problem you face is that there is no such thing as a 'standard' Terry Prince Camshaft profile. Add to this that with Terrys cams the amount of valve lift has also been known to vary from canshaft to camshaft.
I would suggest you aim for EQUAL lift of the inlet and exhaust at 4 BTDC on BOTH cylinders. Highly unlikley you will get it exactly the same on both but get as close as you can to having them the same. You may need compromise a tad and try positions of equal lift anywhere between 4 BTDC and 2 BTDC - but be sure to check then double check for clearances INSIDE the head between the faces of the valve and the top of the piston - you need AT LEAST 1/16" . Modelling clay or like material may be of use.
You will also need to make sure there is sufficient clearances around the valve lifter parts, inside the rocker tunnels in the head and also sufficient clearance of valve movement - at the point of maximiun valve lift) there needs to be at least 1/16 inch of additional travel available.
Please keep us up to date with your progress.
Good Luck!
thanks , equal lift ? how much worth big a good figure to try to get?
Vincent,
The cam will tell you what the figure of equal lift is. On the cam there is only one place where the intake and the ex cross paths and are at the exact same distance off the seats. If you look at the timing chest with the cams installed that place of equal lift should be where the front cam slot is straight down and the rear cam slot is pointing to 11 O'clock. If you had all the Factory timing marks that were good they would all be lined up at this same place (the Factory made it happen at 4 degrees).
The equal height might be a little different on the two cams because they may be ground differently. But, if you turn the cam 360 degrees you will find the spot where the two dial indicators show the same absolute value, maybe around .166", for example. If you turn the other cam the valves may be equal at .168", for example. It is very easy to find this spot on the cam if you use digital dial indicators.
The Factory set the equal lift spot at 4 degrees BTC. Many I know set it at TDC with no problems, so close is good, but it is a target.
David
The cam will tell you what the figure of equal lift is. On the cam there is only one place where the intake and the ex cross paths and are at the exact same distance off the seats. If you look at the timing chest with the cams installed that place of equal lift should be where the front cam slot is straight down and the rear cam slot is pointing to 11 O'clock. If you had all the Factory timing marks that were good they would all be lined up at this same place (the Factory made it happen at 4 degrees).
The equal height might be a little different on the two cams because they may be ground differently. But, if you turn the cam 360 degrees you will find the spot where the two dial indicators show the same absolute value, maybe around .166", for example. If you turn the other cam the valves may be equal at .168", for example. It is very easy to find this spot on the cam if you use digital dial indicators.
The Factory set the equal lift spot at 4 degrees BTC. Many I know set it at TDC with no problems, so close is good, but it is a target.
David
If you look at what he is saying, he is not far out on the rear and about 7 degrees out on the front. My guess is the rear is close enough, and on the front cam you will need to press the cam out of the pinion and retard the cam a bit. This may take several goes to get right, and I generally only press the cam on about half way and try it. Once you arrive at a good figure, then press the cam on fully and check again. On a twin, for the rear cam you can shift the position of the half time pinion on the crank to arrive at a good figure, but on the front cam you can only adjust by moving the cam in the pinion. I have set up many of Terry's cams and got the figures spot on without too much difficulty. I feel on Terry's cams you are better off to have them slightly advanced as opposed to being retarded, as the inlets close very late, with the piston at least half way up on the compression stroke. If this is an engine with stock carburetors and kick start only, you will find the engine hard to start and it may be difficult to achieve a good idle.