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Camshaft notch

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Bobspit Avatar
Bobspit Bob Weddington
Lincoln, NE, USA   USA
Does anybody know what the purpose is of the notch on the end of the Spitfire camshaft pictured (the larger notch at approx 11:00)
When the chain sprocket is installed it lines up with one of the holes not used to attach sprocket to the cam.

My only thought is that it might be to allow oil to flow to the front side of the sprocket to lube the chain.

Trying to compare an original, factory camshaft to a new replacement shaft.

Thanks,
Bob

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Bobspit Avatar
Bobspit Bob Weddington
Lincoln, NE, USA   USA
Probably should have identified the chain sprocket as the Cam Gear.

Bob

tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
Centrifugal force would spin any oil outwards, not inwards.
Could it have been to index the shaft when it was ground?
JOhn

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clshore Carter Shore
Beverly Hills, FL, USA   USA
In reply to # 1592648 by Bobspit Probably should have identified the chain sprocket as the Cam Gear.

Bob

Why?
It IS a sprocket.
Folks who call them gears are WRONG.

I'm betting it's used when the factory assembled and timed the cams, they probably had a tool or fixture that set and held the
cam in position by the notch while the crank was positioned and the sprocket/chain was placed and bolted down.
The worker then made the marks on the sprocket, removed the tool, and the motor was sent down the line ...



Edited 1 time(s). Last edit at 2019-01-28 07:24 AM by clshore.

Jediscuba Avatar
Jediscuba Steven Spandorf
Southampton, NY, USA   USA
1963 Triumph Spitfire "Pussycat"
1970 Triumph Spitfire 1500 "PussyCat The 4th"
1972 Triumph GT6
1980 Triumph Spitfire 1500 "Pussy Cat"
I think John may have it right.
It looks like it's used to index and secure the blank when being ground

Steve

mtnwings Avatar
mtnwings Greg B
Ellenville, NY, USA   USA
Hello, Can anyone tell me how to identify the cam grind on the spit cam? There is someone selling a few cams but he has no idea what they are. Are there markings that identify what it is? Thanks

Jediscuba Avatar
Jediscuba Steven Spandorf
Southampton, NY, USA   USA
1963 Triumph Spitfire "Pussycat"
1970 Triumph Spitfire 1500 "PussyCat The 4th"
1972 Triumph GT6
1980 Triumph Spitfire 1500 "Pussy Cat"
Greg .....
It can be done but it "ain't" easy and for what you'd have to pay someone to calculate all the data from an unknown cam ...
It just isn't worth the time or money.
A good machinist would have to spin the unknown on a late at low rpm, using gauges he's have to measure the lift and angle duration.
At over $100 an hour for labor and about 2 hours of work, minimum, you could buy a brand new cam that is exactly what you want.

Even knowing the duration and lift, you still don't know that it's straight and of quality material to the proper hardness.
Pig in a poke is just that ...... I think you should pass ... even if it's FREE

Steve

tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
With some very simple tools and, yes, time, you can measure your own cams.
A friends did it by mounting his cam in his lathe, and turning it by hand while he used a dial guage indicator to take the cam lift mesaurements.

My lathe is too small, but I have a pair of V-blocks, available on UK eBay for £6 each, a dial guage indicator (DGI) with magnetic stand (about £20) and a circular protractor. The last is available form Crane, Burton etc. for about £15, but there are online versions. Print it out, glue to some card and she's good to go.

Bolt the protractor to the front of the cam using the two sprocket holes, and set up the cam on the V-blocks on a stout table. It's not heavy, you just don't want it all wafting about on folding card table.
Set up your DGI on its stand so that it bears on the cam. Unless your table is metal, it may be useful to use a piece of plate under the stand to weigh it down.
Arrange a pointer - I use a length of wire in a second DGI stand - onto the protractor, so that you can measure degrees.

Now you can measure the cam!
I start by finding the peak of the cam, noting the degees there and turning to the back 180 dgrees away. Then turn the cam, noting the degree position for each, say, 5 thou, lift of the cam.
Repeat for the other cam - make sure it one of the pair for a bore, or your timing will look very odd!
Put that data into Excel, and you can end up with this:



Edited 1 time(s). Last edit at 2019-02-05 05:43 AM by tapkaJohnD.


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clshore Carter Shore
Beverly Hills, FL, USA   USA
John is correct, although it's even easier to take measurements with the cam inserted into a motor if you have one handy ...
The block serves as an excellent stable platform for attaching the DI, pointers, etc.
A long extension on the DI tip can reach the cam lobe, else insert a lifter, and use a pushrod, with the DI tip
placed into the top 'cup' end of the pushrod.
A standard metal degree wheel can be fitted to the nose of the cam.
(The internet printed degree wheels suffer from inaccuracy introduced by X-Y distortion and non linearity of home printers).

Unfortunately, the published cam specs for a given cam may differ from the actual as-manufactured measurements, and
camshaft lobe wear is to be expected on any used cam.

So don't expect an absolute match, be prepared to perform some 'interpolation' to identify the cams.

TheZster Avatar
TheZster Steven Z
SAINT LOUIS, MO, USA   USA
1978 Triumph 1500 "BLK-BRY"
Ain't worth the trouble.... use it as an anchor for the end of a trotline..... (don't know what a trotline is? - You're probably a yankee - or from California)…. New - specific grinds - or regrinds - are cheap - relatively speaking..... and usually warrantied to some degree..... Most cam grinders/manufacturers use a certain "lift" beyond TDC to determine duration.... (It's a marketing game - so they say)….

Buy a regrind from TSI - or whomever - send them the trot line anchor as a core.... and walk away knowing what you've got....

Z

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