Next on the list for the engine was the CAM timing. The first problem that I came across was actually measuring the lift. The problem being that the valve is below the CAM, now when we do Porsche timing, as there is a rocker, there is no problem with access to the valve to measure lift. However as with the busa the CAM is above the valve you need a special curved probe to bend around the CAM. However nothing a bit of welding rod couldn’t sort, but then it was a little tricky keeping it in the same place on the valve bucket as the probe was now not really attached at either end and could slip, but with a bit of care it was sorted!
The next issueette was a small problem of turning the CAM the wrong way on the sprocket. The CAMs a a vernier pulley but obviously if when you throw the CAMs in you are a tooth out on the chain you need to turn it. Not too hard you might think, and really its not, except when you think you need to turn it clockwise but then turn it anticlockwise!!! Hence an hour job turned out to take more like a lifetime! Nevermind!
The last difference, which took about 10 minutes to understand was that the timing was done on the remaining lift on the exhaust CAM, whereas on the Porsche it is done with the initial lift (ie as the CAM lift is reducing not increasing). This is probably the norm but on a Porsche the way I normally do it it on cylinders 1 and 4 which are exactly opposite. However a little thought soon sorted out why it was different, and then I was much happier! I thought it was right, but I just couldn’t see why up to that point!
As I have changed the chain to a roller chain I needed to modify the chain ramp that sits above the 2 CAMS. This was done on the mill and fortunately came out really well.
Then the chain tensioner was bolted on and done up. However the instructions for this said to give about 10mm of chain movement using only finger pressure. But, being a pedantic whatnot, what is finger pressure? Anyway, I just sort of guessed what a thought was about right and then bolted on the ramp. The timing was then rechecked and adjusted ever so slightly now that the chain was all nice and tight.
Tags: Engine
