Author Topic: Piper Cams / valve clearance  (Read 2648 times)

pschiii

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Piper Cams / valve clearance
« on: 22:04, Mon 28 November 2011 »
Hi ,
I have just fitted a Piper Cams to KTR spec ( it is the modified 260) . The engine is running fine , no problem .
Today I wanted to double check the valve clearance and realised that the valve clearance given by Piper was the following : 0.37 for the inlet and 0.42 for the exhaust . I just thought WOA that's huge . I took the ETAI document and realised the Renault one for a standard camshaft was 0.20 for the inlet and 0.25 for the exhaust .
The Piper valve clearance to respect is about twice more than the Renault one .
So my question is why ? what clearance do you have/adjust when running with this particular camshaft ?
What is the valve clearance to have when running with a Piper 270 or 285 ... is it even more than these ones ?
The first idea I had was probably to avoid a contact between the pistons and valves at high RPM since the springs to use are the standard ones .
Cheers .

Ash-Lee

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Re: Piper Cams / valve clearance
« Reply #1 on: 22:32, Mon 28 November 2011 »
The measurements do seem a bit on the large side.  :?

I still use the standard cam, but i'm sure someone who uses uprated cams will come along and advise you on what to do.

markey mark (bd)

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Re: Piper Cams / valve clearance
« Reply #2 on: 22:33, Mon 28 November 2011 »
On standard cams i've run .20 on inlet and exhaust, with uprated cams i have done them to .20 on both with no problems but if not set them to .20 inlet and .25 exhaust.
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pschiii

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Re: Piper Cams / valve clearance
« Reply #3 on: 21:45, Wed 14 December 2011 »
Right , so I continued searching and  made a comparison between different camshafts to try to find a coherent explanation .
what I could notice is that the more the lobe is sharp ie the minimum degree/shortest time the valve is opened when it is totally opened , the fewer clearance is required . on the opposite , the fewer sharp the lobe is , the bigger clearance is required .
At the moment the car is running with the clearance Piper are recommending , and it's perfect .
What do you think ?

James5

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Re: Piper Cams / valve clearance
« Reply #4 on: 13:02, Thu 15 December 2011 »
Quote from: "markey mark (bd)"
On standard cams i've run .20 on inlet and exhaust, with uprated cams i have done them to .20 on both with no problems but if not set them to .20 inlet and .25 exhaust.

Perosonally I do the same as Mark and never had problems :D