Need to cut keyway in crank gear....how?

fastsc92

fastsc92

Registered User
Ok i found out that my new cam has an intake center line of 105..and it needs to be 112, so it is advanced 7 degrees. I'm going to a machine shop to get a new keyway cut in the gear. My question is, how do i know where to put the new keyway? Also, which tooth do i use for the reference mark for lining up the two gears?
 
You have to degree cam...Which it seem syou did.However you didnt mark where to cut on gear....Redo it and mark..
 
how is that going to tell me where to place the keyway. It degrees in at 105 and should be 112. In that case i need a keyway cut 3 degrees from the top of the tooth that i'm using to index on the crank gear. Because its a 2:1 ratio, these 3 degrees will equal 6 degrees in camshalf rotation which will make a total of 111, which will make it almost perfect. Am i correct here? I just dont know how marking it with the degree wheel will help me.
 
it just misses with an offset key, that was the first thing i tried. I need about 4*. I figured it out and the keyway is going to be cut tommorrow. I just picked another tooth and used a pro-tractor and made a mark 4* off of the center of the tooth. We'll see how it comes out, if not, i can always buy another crank gear and try again. Hopefully this 3+ degrees difference will equal about 6 camshaft degrees.
 
You have to remove the cam sprocket and drill it to accept an offset bushing. The bushing fits in the degree hole in your cam which will rotate it enough that your timing marks will line up and give you 106* or whatever number your looking for.
 
that is very very incorrect. Offset bushings only work in SBC's, or similar cars. Our car does not have a dowel pin and the cam gear doesn;t bolt to the cam itself. The cam and crank gears on our car is held on by a keyway and one single retaining bolt that keeps the gears on the shaft. Therefor, there is no way of using offset bushings, and an offset key can only give about 1.5* of change.
 
no one makes an adjustable sprocket for the stock style timing set. Moranda makes a double roller that is adjustable, but it's over $300. I am having a key-way cut in the lower sprocket as we speak.
 
fastsc92
How much do you think,or how much would you pay for a adjustable sprocket ?
That would fit the stock style chain.If you had to go through this again.

Do you think that there would be a market for such a peice for the SCs?

Are you tring to adjust your cam for more horse or more bottom end torque,or just to a blue print mark?

Thanks randy
 
i'm adjusting it for what my regrind is suposed to be set at per the cam card..which will in turn produce the maxium hp, and usable rpm range. I would be interested, but in my case.....i will only have to do this once, and it was free for me to have a keyway cut. Just a bit of math to figure out where to place the new keyway.
 
So you don't beleive it would be worth it to make a adjustable sprocket
for other SCers.So they could blueprint there cam.

RANDY
 
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well if you're implying that I make the gear...then i cant do that. I think its a great idea, but i dont have the ability to make and machine gears for everyone. I dont mind helping and drawing the gear up on CAD, and indexing where a new keyway can be made, but i am not able to make them. But i do think it would be a great idea for the stock style timing set.
 
ok, here is the update. I had a hard time finding someone who will cut this keyway for me. I finally found two people who can and will cut it, but they both ran into a snag. The machine they use to cut the keyway, uses a center peice which fits in the center of whatever you are cutting. The catch is that with the inside diameter of the crank gear, the machine must use a 1/4" keyway. I need a 3/16" keyway. I hope everyone understands what the problem is. So here is my new question. Can i cut a keyway in the CAM gear instead? I think the cam gear has a smaller ID which will allow the machine to cut a 3/16" keyway, instead of a 1/4". Can i do this?
 
Yes it can be done on the inside of the sprocket.The machine process is called broaching.

You just need a broach with the width of 3/16.And the center with the same diameter as
the sprocket with a 3/16 grove cut in the center broach guide.Then you lay the gear in a
press ,with the broach guide in the center of the gear.Then place the broach cutter in
the center slot.Then press with a press to cut the broached keyway.After degree set up
of gear.

what you need.

1. A 3/16 broach & center 3/16 broach guide that has the diameter to fit the inside diameter of
gear.

2. A hydrolic press.

Randy
 
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that is what they were using, but with the ID of the crank gears...no one seems to have the right size peices to cut the 3/16" keyway. The center peice that fits this gear is where it jumps up to a 1/4" keyway. They would have to custom make the tool in order to cut it. This is why i asked if i could cut it in the cam gear...where the ID is much smaller, and they would be able to find a tool that will fit.
 
I suggest you talk to the machinist, those keys and keyways are METRIC not std. 3/16 and 1/4 DO NOT fit properly.
 
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