6 replies to this topic

[Gremlin]

I've got my reprofiled Piper 255 cam back today and started working out what woodruff key I would need, and after several checks I am delighted and amazed to be able to say that a normal straight woddfruff key is perfect, we worked it out to be 0.3 degrees out. We then checked that the inlet valve started to open 25 degrees before TDC, only to discover that the pushrod started to lift at about 57 degrees BTDC. We realise that the initial pushrod movement will not cause valve movement until the tappet clearance (0.3mm) is taken up. Are the camshafts profiled so that the initial 32 degrees (roughly) of movement is to take up the tappet clearance? Thanks for anyone's help, I'm going to ring Piper tomorrow to see what they have to say

[Gremlin]

Anybody? ACdodd? Cooperman?

[Gr4h4m]

My piper Reground cam was also bang on and didn't need any offset keys. I can't help with the other question

[ACDodd]

Check the timing at the valve timing checking clearance for the cam call piper for the chhecking clearance. Failing that install the cam such that both intake and exhaust valves are at equal lift 2 degrees BTDC.

 

 

 

AC

Edited by ACDodd, 18 January 2014 - 12:33 AM.

[Gremlin]

Double post

Edited by Gremlin, 18 January 2014 - 01:07 AM.

[Gremlin]

If checking clearance and valve clearance all mean the same thing, it's 0.3mm (off the piper website for this cam). If all else fails I'll set it to both at equal lift at 2 degrees BTDC. I'm going to call piper tomorrow anyway just to make sure that this is normal and what they have designed, other wise it works out that I have 330 degrees of inlet duration!!

[Gremlin]

Ok I've gone and done some measuring, the first 0.24mm of lift is before 25 degrees BTDC. 0.24mm is the tappet gap when you take into account the standard rocker ratio of 1.25:1. It would appear that there is a lot more to the profile than I initially thought, we were initially expecting the cam to start lifting at 25 degrees BTDC, and was therefore suprised that it actually started lifting at roughly 57 degrees BTDC. This is all very clever but what if you've got different ratio rockers?