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Discussion Starter #1
Guys,

The drive pin in the camshaft seems to have become a real issue with our trucks. I thought I would post some photos of a simple set up fixture that you or your machine shop can build that will make the seemingly daunting task of installing a 5mm drive in place of the pin quite simple.

Square up an 8" x 8" piece of 1/2" aluminium.

Bore a 1.101 hole and then machine a 5mm groove on center.

Slide the fixture over the nose of the cam and pin (I used a gauge pin so my slot is longer) and then indicate the top of the fixture parallel to the bed of the mill.

Indicate the center of the pin hole and machine the slot for a 5mm drive key.

As set of V-blocks is nice but not necessary.

Hope this helps, feel free to call with any questions. :D
 

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Bac To The Future
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Pretty darn cool, Guy. I have a really (and I mean REALLY....) stupid question, though, as I am not a machinist.....

How do you machine the keyway when the fixture is in the way?
 

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What do you have to do to the gear?
 

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Discussion Starter #4
TheBac;1569977; said:
Pretty darn cool, Guy. I have a really (and I mean REALLY....) stupid question, though, as I am not a machinist.....

How do you machine the keyway when the fixture is in the way?
Actually a very good question, not all readers here are machinists.

The fixture is only for setup. It allows you to properly orient and postion the cam for drive key machining. You remove the fixture after set up.

Ben46a;1569994; said:
What do you have to do to the gear?
No change to the gear is necessary, it already has a slot in it. The cam normally has a 5mm pin that is installed perpendicular to the rotational axis of the cam. The drive gear will shear this pin under certain circumstances. Installing a drive key will spread the load out over a much greater surface area.

There are other threads with pictures of this type of failure.

Thanks to Eric Merchant for bringing this to our attention and conception of this fix last year.

I had heard of how difficult that some considered this type of machining to be after the cam was ground.

I thought I would pass along one possible setup and machining solution to help people out that already had cams without the key installed.

Using an 8" square piece of stock makes repeatability excellent as far as indexing the cam goes with relation to the crank as we have extended the setup fixture well past the diameter of the cam gear.
 

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Thanks Guy!, also if you dont mind...... what type of key do you use, i can see a woodruff key, but if you just use 5 mm keystock how do you secure it from walking out and causing catastrophic failure.
 

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Discussion Starter #6
Ben46a;1570072; said:
Thanks Guy!, also if you dont mind...... what type of key do you use, i can see a woodruff key, but if you just use 5 mm keystock how do you secure it from walking out and causing catastrophic failure.
I use 1/4" hardened key stock and then surface grind the width down to 5mm.
 

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Thanks for the explanation Guy. Makes perfect sense now.
 

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Just put bearing retainer or red loctite on the keystock?
 

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Discussion Starter #9
I use a 3/16 EM and then machine for a .001 press fit. Whatever you do, don't use a 5mm EM.
 

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nice fixture Guy.... Looks easier then our method of doing it with a dial indicator....

You have my UPS acct number and address...... (informally ordering this now)
 

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Is that my cam? :D
 

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This looks as though it carries over the poor factory tolerances on the pin location. Is there a way we can degree in the cam during installation to make sure its where we want it? Are there offset keys available? If so are they strong enough?
 

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On the opposite end of the shaft are two index/drive holes. They should align with the pin/keyway on the stock cam. The pin is vertical when the piston is at TDC.

Ultimately however, you need to dial in the cam on the engine. To do it right, you need an adjustable cam gear and the cam timing spec.

Guy and I talked about this briefly just the other day. :)
 

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Discussion Starter #15
RickDLance;1570904; said:
This looks as though it carries over the poor factory tolerances on the pin location. Is there a way we can degree in the cam during installation to make sure its where we want it? Are there offset keys available? If so are they strong enough?
Rick,
Poor factory tolerances? It is actually a stacked tolerance between the crank pin, crank gear, cam gear, and cam pin. The same cam installed in 5 different engines could index in 5 different places with regard to crank angle.

Offset keys could be made but I think I have a better idea. ;)
 

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The alignment on the crank is the one that I worry about. It sets the timing for the reluctor wheel. At least that key is easy to index correctly. Like guy said, the cam has stack up issues to overcome.
 

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Why not line up the v - blocks, indicate the cam journal for C/L then sweep in the pin hole. Or perhaps line up the v - blocks, indicate the cam journal for C/L then sweep a cam lobe that would be at the 12 Oclock position (prep to the table) to make sure the pin hole or slot would be in relation to the lobes? Same with the crank.
 

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When the pins starts to shear, does it usually mess up the hole on the cam? If so your method wouldn't work correct? Are the stock cams just case hardened, or are they heat-treated through?
 
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