Chrankshaft Water Pump/Balance Shaft Sprocket. Why 2 pc and adjustable? - Cobalt SS Network



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Old 10-12-2017, 08:26 AM   #1
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Chrankshaft Water Pump/Balance Shaft Sprocket. Why 2 pc and adjustable?

I am doing a build and purchased a short block with new liners, new forged pistons and new forged rods.

My plan is a balance shaft delete, TVS blower, larger injectors, LS1 throttle body and MEFI4B to control the unit. This is going into a 1986 Lotus Esprit.

I took the short block apart to clean and paint the block. When I did this, I noticed that the crankshaft sprocket the turns the water pump and balance shafts had a crack at the key. I also saw that this was a two piece unit that looked to be adjustable (GM 55557168). I looked on line and these go for >$100.

I had pieces from another LSJ engine and went into that pile to find a replacement sprocket. All I found was a one piece sprocket GM 90537301. This obviously was not adjustable and it had a smaller hub thickness (.413" vs the .741" thickness on the GM 55557168 sprocket). This made me think that maybe the GM 90537391 was from the parts pin of a 2.2 L I had and that it got mixed into the parts bin of the LSJ.

A couple of questions:

1) why the 2 pcs design of the GM 55557168? It looks like it can advance and retard about 5 degrees. Why would they need this for just the water pump and balance shafts?

2) Since I am doing the balance shaft delete, my thought is to use the GM 90537391 and just make a spacer hub to shim out the sprocket and accommodate the different overall thickness between the GM 90537391 and GM 55557168). This would be simple to make as it would be .328 thick with a key slot (.741- .431).

here is a pic of the two sprockets
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Old 10-12-2017, 08:51 AM   #2
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In for answer on adjustable WP/BS sprocket. This is the first I have seen these and I have no idea what the adjustment would be needed for. You are deleting your BS so timing won't matter at all. I would just use a standard fixed sprocket. Where did you get your short block from? If the timing chain and BS chain/components are used I would replace those with the OEM Cloyes timing chain kit from Crate Engine Dept. with the upgaded ARP bolts for the guides.
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Old 10-12-2017, 08:55 AM   #3
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I already have new chains and guides, as well as the ARP upgraded bolts. Just did not mention it in the listing.
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Old 10-12-2017, 09:19 AM   #4
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Quote:
Originally Posted by Medida View Post
I already have new chains and guides, as well as the ARP upgraded bolts. Just did not mention it in the listing.
10-4, well I wouldn't mess with that adjustable gear at all especially with BS delete. As it is cracked and due to it's construction it looks like a liability.
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Old 10-12-2017, 09:55 AM   #5
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No, I will not use the adjustable one because it is cracked

I cannot understand why the GM 55557168 is adjustable. What was it intended to do?

On the other hand, I do not know if the GM 55557168 is standard with the LSJ. Do you know what is?
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Old 10-12-2017, 10:01 AM   #6
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Quote:
Originally Posted by Medida View Post
No, I will not use the adjustable one because it is cracked

I cannot understand why the GM 55557168 is adjustable. What was it intended to do?

On the other hand, I do not know if the GM 55557168 is standard with the LSJ. Do you know what is?
I know that on CED they list the timing chain kit as L61/LSJ which I bought for my L61. I know for a fact that the WB/BS sprocket is fixed std. sprocket and not adjustable. I'm curious as to the reason for the adjustable sprocket as well. Hopefully someone here knows and will chime in.
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Old 10-12-2017, 10:25 AM   #7
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I called the local chevy parts department. They show that the current number for the crankshaft waterpump/balance shaft sprocket is 12642713. The old number was the 55557168. So for some reason they made this sprocket adjustable for the lsj

A new one is $145...yikes

Since I am deleting the balance shafts, why not take the 90537301 and make a hub shim to get it to the same thickness (note: I would only need to do this shim on the crank side to get the same plane in the engine as the GM 55557168)? It would be no cost to do.
thoughts?
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Old 10-12-2017, 04:19 PM   #8
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actually the accessory gear is spring loaded and I would assume its to absorb the shock load of going wot just replace the gear with a new unit of the same yours is the only one I have ever heard of or seen cracking some advice for ya you should extend the crank keyway also the stock key bends rather easy

only the lsj and the lnf use that gear
the only difference from the l61/lsj timing set is the accessory gear
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Old 10-12-2017, 07:22 PM   #9
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Mr Belvedere

thanks, that makes sense on why it is adjustable.

I already had the crank milled to take a full key
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Old 10-12-2017, 09:05 PM   #10
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its not an adjustable gear
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