Cam Timing Using Lift In Mm At Tdc Method

[leeroy_25]

Can anyone who uses the mm lift at TDC method for cam timing please reply here or better still pm as I dont seem to be getting any notifications at the moment!

I would really like a couple of points about a general base setup and maximum difference between inlet and exhaust lift to avoid collisions.

Thank you

Lee

[discopotato03]

I don't know of any mm lift at top dead center method . That sounds like an ah alternative way of setting the cam timing based on overlap and not my first choice .

There is a way of looking at duration at 50 thou lift to work out how agressive some cam profiles are .

If you use std pulleys I'd set them up as std and with adjustable ones start out with them zero'd . If the valves are hitting the pistons then the cams have too much lift or the cam timing is a long way out .

[leeroy_25]

Thanks for the reply.. I have some info also from HKS about the duration of the cams at 1mm.. From this I could roughly say the for instance the exhaust cam should be just under 1mm open at TDC. When My cam pulley was set to 0 I had nearly 2mm lift at this point! I had similar on the inlet cam but again going by the 1mm valve lift info from HKS the valve would be just over a mm at TDC?

It appears looking at my cam pulleys that the exhaust cam sits about half tooth out anyway? is this common with RB30 conversions? Maybe the belts have a slightly different pitch? Or maybe my eyes are just out!

As it is I will go an play with it on a dyno tomorrow and dial it back towards the zero marks and see what I get. I presume to get a valve and piston collision on stock lift or very mild cams the cam timing would have to be further out that the possible adjustment? I.e a couple or teeth? What about valve to valve collision? Is that possible?

Cheers

Lee