Racing Valve clearances!

Champy72

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Nov 30, 2018

Messages

109

• Jan 3, 2020

• #1

I have modified an 850 to a 750cc unit to move into a more competitive class.
A Maney stage 2 head is installed, along with a P3 cam.
Anyone have any ideas as to the valve clearance I should set?

Many thanks

 

Matchless

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Dec 23, 2010

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1,183

• Jan 3, 2020

• #2

If you mean PW3 cam the clearance is .011" inl. & exh. with iron barrels & standard ally pushrods.

Martyn.

 

SteveA

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• Jan 3, 2020

• #3

Matchless said:

If you mean PW3 cam the clearance is .011" inl. & exh. with iron barrels & standard ally pushrods.

Martyn.

Click to expand...

The capacity change will make no difference, if it is the cam and pushrods you used before, no change.

But if you have Maney (or other) steel pushrods....go for half that, around 6 thou does fine.

But if in changing capacity you went to alloy barrels....go down to 0 clearance with steel pushrods! You should just be able to rotate the pushrods with your fingers.

 

B

Bernhard

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Apr 20, 2011

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5,773

• Jan 3, 2020

• #4

You should be able to rotate the push rods when the engine is hot!!!!

 

Champy72

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Nov 30, 2018

Messages

109

• Jan 3, 2020

• #5

Yes, of course, I meant PW3 cam! Thanks so much, I had a notion when it was an 850 where the clearance should be, and yes, it is the same!

 

johnny Lagdon

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• Jan 1, 2021

• #6

I have pw3 cam standard alloy rods and Maney alloy barrels. Anyone advise correct tappet clearance?

 

SteveA

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• Jan 1, 2021

• #7

johnny Lagdon said:

I have pw3 cam standard alloy rods and Maney alloy barrels. Anyone advise correct tappet clearance?

Click to expand...

Following the logic noted a year ago, starting from your standard 0.011" with cast iron barrels and alloy pushrods, the greater expansion rate of the Maney barrels will reduce the required gap, go for 0.006" inlet and exhaust.

 

Fast Eddie

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• Jan 1, 2021

• #8

johnny Lagdon said:

I have pw3 cam standard alloy rods and Maney alloy barrels. Anyone advise correct tappet clearance?

Click to expand...

As mentioned by SteveA above. With that set up you should go for half the standard clearance specified for your particular cam. That’s what Mr Maney told me.

 

Last edited: Jan 1, 2021

johnny Lagdon

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Nov 18, 2016

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• Jan 1, 2021

• #9

Thanks, much appreciated!