Welcome to our resource for MG Car Information.
Triumph TR6 - How to adjust a performance new cam?
|Speaking of winter overhaul,|
I received a brand new Performance camshaft from B.P.NW. having such specs.
270 degrees duration .415 lift intake .400 lift exhaust
Timing: Intake 22-70 Exhaust 62-28
Latest asymmetrical design profile using short duration opening, long duration closing intake and long duration opening short duration closing exhaust. No machining required, uses stock valve springs. Excellent bottom and mid-range with smooth idle.
But to install it, they mentioned I'll need a 360 deg indicator and dial indicator. With a strange procedure. Is there a web site explaining that procedure more in detail.
I remember replacing my spokets + timing chain was not so complicated few years ago.
I could follow that procedure but prefer to understand it.
|J. G. Catford|
I got the same CAM, i think. A set of instructions came with the cam.
It sounds a lot more complicated than it is. I assume it is a similar procedure to the Goodparts camshaft I installed a couple of years ago.
Basically all you have to do is synch the camshaft and crankshaft - that is, make the right valves open at the right time.
You will need the two tools they mention - firstly the 360 degree indicator is what I called a "timing wheel" - just a circular sheet of card with degree markings. You can buy them from car parts stores, but they are strangely expensive, in America at least(a few Pounds in England, $30 in America - no idea why!). I downloaded one, printed it and glued it onto a cereal box - let me know if you want a copy of the file and I will e-mail it to you. You also need a pointer, but that is easily made with a piece of stiff wire attached to the block somewhere.
You also need some way to accurately measure the point when the valve is at its maximum lift. That's what the dial gauge is for. I put in my lifters for no.1 cylinder and measured their movement with the dial gauge held to the top of the block with a magnetic base.
Attach the wheel to the front of the crankshaft and set the pointer so it points to TDC when the crankshaft is at TDC (I think I measured the point of TDC with the dial gauge). Then turn the crankshaft to the position for maximum lift of the inlet valve (no.1 cylinder), turn the camshaft until you get the maximum lift on no. 1 inlet and bolt the camshaft sprocket on in whichever orientation works best (there should be two sets of holes drilled so that turning the sprocket 90 degrees adjusts by 4 degrees, and if I recall correctly if you turn the sprocket front to back that gets the adjustment down to 2 degrees). You just need to make sure that the chain is tight on the right hand side (looking from the fron, with the block right way up). I found that I couldn't get it spot on. You could use an adjustable cam sprocket, but they are expensive. I actually spent a very long time on this job because it was the first time I had tried it, and I assumed that the grinding process would be spot on, so if the camshaft was supposed to reach maximum opening at 42 degrees BTDC (or wahtever) then I figured it would be spot on. It wasn't. I called Richard Good and he explained that it would be about right to a few degrees either way (not his exact words). You can also advance the setting a bit to move the peak power down the rev range a bit, or retard things a bit to get more top end power. I went with setting it up as close to the specified value as I could, but erring on the side of slightly advanced. The 22-70 degrees figures are (as I recall) the time the lift is over 0.010 (maybe 0.050?), and these were all over the place on mine.
Having done the job once I would say it could be easily accomplished in a couple of hours - in theory it should take 10 minutes, but where's the fun in that? I do remember wondering at the time how anyone could do the job with the engine in the car - the amount of leaning and stretching you would need to do seems crazy. You might want to book some time with your osteopath in advance...
Hard to say whether I set the timing up to give the optimum performance, and I am not about to take things apart to adjust it a degree or two! I am very happy with it, though I did a lot of other things at the same time, and my only basis for comparison was a very tired engine firing on 4 (occasionally 5) cylinders! For all I know I got it completely wrong and I am lucky it fires at all! Maybe the more experienced guys will correct my description in the morning.
|Thank you Alistair,|
I will try that with the engine out of the car and see how it behave.
|J. G. Catford|
|Alistair has pretty much outlined the process. Now that Crane Cams is back, so is the website. They have a pretty good set of instructions for degreeing camshafts.|
Try this URL for a *.pdf set of instructions for degreeing camshafts.
This thread was discussed between 15/10/2009 and 16/10/2009
Triumph TR6 index
This thread is from the archive. The Live Triumph TR6 BBS is active now.