Race Engine Forum UK

I have reviewed the topic "Doing the cam timing - Single overhead cam"

However I would like to know how I can accurately measure some specifications of a camshaft of unknown origin. The tools that I have at my disposal are minimal. However by bolting the head to a bench and using a dial gauge I am hoping to be able to measure something. Perhaps the following for the exhaust and inlet lobes.

Clearance should of course be considered and when to start measuring on the dial gauge. I have tried once or twice but I think I got all muddled with when to start measuring and the calculations.

• Lift at TDC
  Overlap
  Peak Angle
  Cam Lift
  Timing
  Duration

Could you advise?

I also have some old software called "cam analyzer" but I have not had the time to work out how to use it yet. I'm hoping that it might be able to tell me the more interesting details like acceleration, ramp etc

Pretty well impossible for you to do with rocker valve train - best send to Piper or Kent and let them do it.

GC

Pretty well impossible for you to do with rocker valve train - best send to Piper or Kent and let them do it.

Ok I haven't asked but I can only imagine that would cost an arm and a leg if they even want to do it.

What about if I:

• Attach the rocker assembly to the head.
  Screw it down to the bench below using large screw acting as headbolts
  Set the clearances as normal
  Measure from the rocker and not the cam lobe

Chris, hi

Well, I just spoke to Kent, and mapping in and ex lobes by degrees is about ‚£25 per lobe measured plus carr and vat. Which is nothing really. However that won't tell you valve list and to do that they'd have to build part of the head and would be a fair bit more, costed by the hour I imagine. If you subtract valve lift from cam lift you can work out rocker ratio...

You could part build and measure lift (mm) by degree of rotation but you'd need the actual cam and rockers fully set up at running clearance that you're going to run - or the rocker ratio is going to be wrong and the measurements are going to be meaningless. I know your head and your rockers will need to be replaced due to wear, (they would damage any new cam), and I think you have some damage on the old cam lobes too, corrosion esp. so that combo won't last long.

All the cam timing springs from the duration of the lift event. The full lift position, valve open/close phases can all be deduced from that. I can do that easily for you. Essentially, to do the simple calcs I'd have to decide where you want full lift.

GC