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Geofftaylor

Camshaft timing

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Good day,

I have just replaced the camshaft in my 3A and am in the process of setting up the valve timing. I have used the time honoured method utilising a timing wheel and mechanical stop to exactly determine No1 TDC. I now intend to set No1 inlet at max lift and install the chain. My question / issue is: the valve timing diagram I have from the manual shows the inlet valve opening 15 degrees BTDC and closing 55 degrees ABDC. Thus a duration of 250 degrees. This means the cam lobe for No1 inlet is at its highest 110 degrees ATDC. The new cam spec, which is sold as a basic road cam, has a duration of 278 degrees and thus to maintain the max lift point at 110 degrees ATDC the No1 inlet valve starts to open 14 degrees earlier at 29 degrees BTDC. Can anybody confirm my maths as I only want to do this once. 

Thanks in advance Geoff

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If the cam supplier says the installation figure is 110 deg After Top Dead Centre, follow their instructions and install that way.  Check the cam supplier's rocker clearances for that cam as they could well be different to what you have previously used.  Use those rocker clearances when running.

Cheers

Peter W

 

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Your maths is correct but usually with a new cam they will give you a timing installation figure.  As Peter says, set it to that figure.

Rgds Ian

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Agree with both of the above posts, cam manufacturers will squirm at the  slightest opportunity if something goes wrong "post installation".

The best advice would be to follow their instructions to the letter.....their install  angle, their cam followers, their cam lube, etc etc. They can't squirm then.

Iain

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Thanks everyone for your input but I finally tracked down the cam information on the moss website. Nothing came with the cam. The inlet timing is 31 before TDC 67 ABDC and the install point is 108 degrees ATDC. I will be going ahead using this data.

Cheers Geoff 

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On the Moss Europe Web Site.

 

https://www.moss-europe.co.uk/camshaft-road-new-tt1104n.html

 

TT1104N

Profile: Road

Inlet Timing: 31-67

Exhaust Timing: 67-31

Camshaft Duration: 278˚

Lift: 0.260”

Install Figure: 108˚

Inlet Valve Clearance: 0.013”

Exhaust Valve Clearance: 0.013”

Power Band: 1000-5000

 

Peter W

Edited by BlueTR3A-5EKT

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Geoff

I made my own Cam degree wheel from this https://www.blocklayer.com/degree-wheel.aspx

Enter Cam spec, select wheel size and print. I used a diameter of 200mm which seemed to be about the max useable size and stuck it to a disc cut from 2mm thick aluminium sheet

 

Phil

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To enable me to fix the timing disc to my crankshaft, I drilled and tapped the centre of the pulley retaining bolt for a 2BA set screw.

Rgds Ian

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