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Fitting a new camshaft on a 3A


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Am hoping that someone can help me out with this one 

Essentially i have the cam lubed up and in the  bloc, the Vernier cog is fitted loosely   but  its the next part I'm checking on, The information  from moss is listed below ...

So would be correct in assuming  that once i have confirmed TDC, I then  advance the crank by 103 degrees at which point the no 1 Inlet valve  should be at maximum lift. its worth mentioning that the head off and i do have dial gauges and mag stan ..   have  got this completely wrong .The crank gear was worn so the gears and chain have been replaced.

 

Profile: Fast Road

Inlet Timing: 37-63

Exhaust Timing: 73-37

Camshaft Duration: 280˚

Lift: 0.300”

Install Figure: 103˚

Inlet Valve Clearance: 0.022”

Exhaust Valve Clearance: 0.024”

Power Band: 2500-5500

 

Al;l the best

steve

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Read this article from Macy’s Garage.  
Very simple and straightforward.  

Only time consuming issue may be making the plate and dummy push rods.  

This is precisely the system I use 

https://www.macysgarage.com/cam degree.htm

 

Peter W

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The Macy's kit looks the business but I was a bit more agricultural.  I placed the appropriate cam follower in No1 inlet with another follower upside down on top so that I had a flat surface to place the dial gauge on.  I had already determined TDC on the engine using an old spark plug with the centre drilled out and tapped for a piece of studding.

I did exactly as you suggest, set the engine to TDC, advance it to the desired setting (103 deg in your case) and then set the camshaft at max lift on No.1 inlet.  I didn't have a vernier camshaft chain wheel so I played around with the one i had to find the best setting, remembering to keep the chain tensioned.

I fixed the camshaft setting protractor to the crankshaft by drilling and tapping the end of the crankshaft pulley bolt to accept a small setscrew.

Rgds Ian

Edited by Ian Vincent
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That's  great news, I really appreciate  the help the forum provides, so many thanks to you all.  Ian one last question though,  is the degree disc secured to the cam so that you can check against movement ?? 

all

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2 hours ago, Nobbysr said:

That's  great news, I really appreciate  the help the forum provides, so many thanks to you all.  Ian one last question though,  is the degree disc secured to the cam so that you can check against movement ?? 

all

Hi Nobby,

Apologies for a major senior moment - the degree disc was secured to the crankshaft not the camshaft - doh!  See attached:

Rgds Ian

(PS my cam was a Newman PH1 which needed to be set at 110 deg.)

 

IMG_3162.jpeg

Edited by Ian Vincent
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thumbnail_IMG_5158.thumb.jpg.4c46ad6f92be43e26da571d94fd2c924.jpgThat's great  thanks for the clarification  ... knocked up a pointer at the weekend   and have some alloy plate awaiting delivery  to make a piston TDC lock

so should be good to go, will send a few pics of the rig

I  really appreciate  your help it would have been a real challenge without it  so thanks again Gents 

cheers

Steve

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Final question i hope....   is the  cam installation  figure of 103 degrees ATDC or BTDC , assuming  a clockwise rotation ??? 

hopefully that makes sense

cheers

Steve

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Clockwise rotation when viewed from the front.

ATDC 103 degrees is centre of the inlet lobe.

Use the link I gave above and fill in the info for your cam that you gave at the start of this thread.  You will get the following printable image.

 

Cheers

Peter W

 

4E31AF41-AB43-419B-949B-0738C20A3F9A.jpeg

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3 hours ago, Nobbysr said:

Final question i hope....   is the  cam installation  figure of 103 degrees ATDC or BTDC , assuming  a clockwise rotation ??? 

hopefully that makes sense

cheers

Steve

It is the number of degrees after top dead centre (no1 piston or no 4 as they are at tdc at the same time) when no1 inlet valve is at max lift. 

If you look end on the direction of rotation is clear - the timing chain tensioner is on the slack side of the chain when rotating.

I tend to time the cam before putting the head on. I use 2 old cam followers stuck together on a bolt to make identifying max lift with a dial gauge easier.

It also makes sense to mark / verify your front pulley’s TDC mark.

251D5ABC-3E6C-4A17-942F-2FE727E4F145.jpeg

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PS  Remember No 1 inlet is the second cam lobe counting from the front.  The front cam lobe is exhaust.

Peter W

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I have to say Peter that I find the camshaft timing protractor that you have shown quite confusing. With the one shown in mine or Bob’s photos it is very much clearer, set the camshaft to maximum lift on no 1 inlet and have the crank at 110 (or 103) after TDC. 

Rgds Ian 

PS. Remembering all the stuff about tensioning the chain etc. 

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1 hour ago, Ian Vincent said:

I have to say Peter that I find the camshaft timing protractor that you have shown quite confusing. With the one shown in mine or Bob’s photos it is very much clearer, set the camshaft to maximum lift on no 1 inlet and have the crank at 110 (or 103) after TDC. 

Rgds Ian 

PS. Remembering all the stuff about tensioning the chain etc. 

It is the text on the printed page that was important.  It confirmed that the 103 was inlet After Top Dead Centre.

The other gubbins on  the disc merely shews valve duration as coloured bars.

Peter W

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s

God i like you Guys   you are Princes among men    will let you know how it goes

all the best 

Steve

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