Doubled keyed crank question

[blowbye]

I purchased a shortblock a few months ago with double keyed crank. I have an ati 15% lower that is double keyed. My question is, will I need to purchase a double keyed crank sprocket and trigger wheel or, do i just leave the second keyway out from the crank sprocket and trigger wheel and just cut the key down to fit under the crank pulley? What are my options here? Thanks

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[Catmonkey]

If the added key hole goes all the way under the crank gear, I'd be inclined to find a crank gear that's cut for it. But cutting the key down so it stops against the reluctor wheel doesn't seem like a bad idea either. You just don't want the key to move out of position when you're pushing the balancer in place. You might contact whoever assembled the short block and see what they recommend.

 

[blowbye]

The assembler said to cut down the key. I am just a little worried about having the open keyway under the timing gear. I've heard of the gears cracking. As far as sourcing a double keyed gear and trigger wheel im on my own. Perhaps the billet mmr gear would be the best choice.

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[Catmonkey]

At a minimum I'd use their billet gear. As far as I know they only sell the gear with a single key slot. If you intend to get the gear machined for the key, you might ask them what they do in their builds. Maybe they can cut the gear for you.

 

[blueovalkid]

Accufab sells a Billet crank trigger that is cut for a dual keyway
https://accufabracing.com/modular-crank-trigger

 

[Catmonkey]

Unless you're upgrading to the larger primary chain set (which is a can of worms), it's not going to work.

 

[blueovalkid]

Unless you're upgrading to the larger primary chain set (which is a can of worms), it's not going to work.

What is not going to work?

 

[Catmonkey]

Read Accufab's description: "These crank triggers will also fit on other model years 4.6L or 5.4L engines provided that the ’96-’98 chain sprocket is used."

Notice the difference in thickness with MMR's specific GT500 reluctor wheel.

 

[blowbye]

Talked with the shop today. Other then switching out the timing system and valve covers. It seems the best course of action will be to just cut the key down. Im going to order a billet lower gear and just double key the damper.

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[JimIII@jdm]

We typically do the 1/2 key on all street car applications running stock GT500 gears. With the larger primary gears we will double key the crank sprocket and use the double key billet trigger wheel from Accufab then run the full key.

Catmonkey is right on all accounts here. A good billet crank gear is all you need it's not going to slip on the key. I've seen balancers walk or slip on the key so that is the reasoning for double keying it in the first place.

JimIII