What is the length on the LT1 crank key?

1.) 1 3/8" (Long)

2.) 3/4" (Short)

Thanks!

 

Not sure where you got those choices, but the LT1 uses a special cut-back key. It's not the same as a normal SBC key.

 

Man this is getting confusing. Shoebox, it all started with degreeing my cam. The cam needs to be installed on a 106, but after checking the degree, it keeps comming in at a 108. I need to advance it two degrees. First, I cant find a machine shop in my area capable of machining the cam sprocket to allow for a cam bushing. Two, I cant run an adjustable timing chain, because I am running a non vented opti setup. I contacted my cam grinder, and they said that I need to run an offset (2°) crank key, but I am unsure which of those keys I need.. Please help, im going nuts!

 

I measured an old key and it is 3/4" not taking into account the cut-back portion. You could always customize the non cut-back key or run a keyed hub.

If you alter the phasing of cam to crank, you will have to make up for that in programming in the computer. The opti is used to determine crank position, if you alter the relationship, the programming should be altered by the same amount.

 

Rob, I have never seen a crank key on an lt1, so I am a bit unsure on what you mean by "cut-back" portion. Can I alter my "new" key to be "cut-back"? So if I alter the crank position, by advancing 2°, would I have to add 2° from the current file in the pcm? Thanks for your time and patience..

 

also Rob, where does the Opti actually pick up is "sense" or "trigger" from? is it the camshaft dowl pin?

 

You can see the cut-back keys in this diagram.

As you know, the opti is driven by the cam. It can only use that as a reference for cam and crank position. It derives the crank position from a set of openings on the shutter wheel. It's knowledge of crank position depends on the mechanical phasing of the cam to the crank by the timing set. If you alter that phasing, you alter what the opti thinks is the normal position.

I would rely on a knowledgable programmer that has dealt with this before to guide you.

 

What complicates me is this:

1. If you enlarge the dowel pin hole on the camshaft sprocket, you are moving the position of the camshaft.= altering the cam/crank position Throwing the opti off.

2. If you use a offset crank key, you are moving the position of the crank,altering the cam/crank position =throwing the opti off.

3. If you use an adjustable timing chain, your moving the position of the dowel pin, = altering the cam/crank position= throwing the opti off.

So it seems to me that no matter what you move in order to degree it, your throwing the opti off. And the cars with adjustable timing chains seem to be running ok? Im sooo lost as what to do now

 

Any neighbor or friend with a small drill press? Even one made primarily for wood would work for this. As you stated, it's not rocket science.Call your cam grinder back, and ask for someone knowledgeable.