240Z, 260Z, 280Z Performance / Technical Discussions related to performance motor enhancements, upgrades.

Crankshaft pulley 280Z (1978)

Old 08-18-2015, 12:01 PM
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Crankshaft pulley 280Z (1978)

Hi - new here (question below) - did a search on our wonky, free spinning inner crankshaft pulley and found the following thread :

https://www.zdriver.com/forums/240z-...n-13079/page2/

There, Zbuild of Brisbane, OZ in a 2005 thread helps explain the broken pulley I am trying to diagnose for my cousin...

Just as a bit of an explanation. . . the damper or harmonic balancer is the pulley at the front and bottom of the motor. . you'll see a belt that runs round you alternator, water pump and to a big pulley near the bottom of your block.
This pulley is attached to the end of the crank and is made of 2 pieces, an inner section and an outer section. The 2 sections have a rubber section in between, and can move independently of each other (only a very small amount) this helps "dampen" vibrations created in the engine. When you get your engine balanced, they normally balance the crank and the damper as one piece (or at least they did with mine).
When they get old, the outer section can sometimes move a little on the inner section which can give you inaccurate timing due to the fact that you use a notch on the outer ring to time your engine.
Cheers - Simon

found a bit more about dampers: on "Inner Autoparts"

" The harmonic balancer, or vibration damper, is a device connected to the crankshaft to lessen the torsional vibration. When the cylinders fire, power gets transmitted through the crankshaft. The front of the crankshaft takes the brunt of this power, so it often moves before the rear of the crankshaft. This causes a twisting motion. Then, when the power is removed from the front, the halfway twisted shaft unwinds and snaps back in the opposite direction. Although this unwinding process is quite small, it causes "torsional vibration." To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft that's causing all the trouble. The balancer is made of two pieces connected by rubber plugs, spring loaded friction discs, or both. When the power from the cylinder hits the front of the crankshaft, it tries to twist the heavy part of the damper, but ends up twisting the rubber or discs connecting the two parts of the damper. The front of the crank can't speed up as much with the damper attached; the force is used to twist the rubber and speed up the damper wheel. This keeps the crankshaft operation calm."


The rubber isn't in between the block and the pully, its actually part of the pulley.
cheers - Simonl
I still don't completely understand the mechanism (nor have I attempted to take the pulley off with a 27mm impact wrench). It apparently broke when the accelerator jammed due to an stuck interior carpet, over revving the engine, and snapping the belt. There is currently a belt making the Alternator work, but the AC Belt is disconnected.

Can someone please help / suggest a solution ? Running, the car sounds like a can (or tin) of bolts rattling around! Otherwise car is in good running shape.

THANK YOU
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Old 08-18-2015, 12:11 PM
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Welcome to ZDriver!

Originally Posted by geopanoramic View Post
I still don't completely understand the mechanism (nor have I attempted to take the pulley off with a 27mm impact wrench).
It's a weighted pulley. That's it. Using an impact gun is the complicated route requiring radiator removal, and moving the a/c condenser out of the way. The easy way is to use a 2ft breaker bar against the ground and quickly tapping the key to start the engine (coil disconnected obviously).

Originally Posted by geopanoramic View Post
Can someone please help / suggest a solution ? Running, the car sounds like a can (or tin) of bolts rattling around! Otherwise car is in good running shape.
Solution: replace crank pulley.
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Old 08-18-2015, 01:49 PM
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Awesome suggestion. 3/4 drive breaker probably better than 1/2 drive....once i get it off. Do we fix existing or need new version.
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Old 08-19-2015, 06:56 AM
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Originally Posted by geopanoramic View Post
Do we fix existing or need new version.
Bolded and underlined for clarification...

Originally Posted by NismoPick View Post
Solution: replace crank pulley.
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Old 08-19-2015, 07:47 AM
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Originally Posted by NismoPick View Post
Bolded and underlined for clarification...
Ha! I have BEHELD ! thank you, I suspected so and really did believe you the first time.

I am going this Z fix for, no WITH my younger cousin.
I usually work on VWs, subarus, other rigs, etc.

MUCH THANKS. SO we are definitely in the market for a crank pulley...

Last question - don't we need to get the radiator etc. out of the way to get the harmonic puller on there? I assume woodruff key etc, is all good and tight, and this pulley isnt just going to fall off once the bolt is loose.
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Old 08-19-2015, 04:17 PM
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hi, the cousin here.

we got the nut off no problem. That technique worked the nuts.
Banged on the pulley, but do not know how to proceed without a puller.

Pull radiator etc and use a harmonic puller?

Is there any way to do it without the puller?

Dad here: when the over-rev happened, the AC compressor bearings and shaft froze, causing that belt to snap. The associated forward pulley is ok but the rear puller is loose with an 1/8 to a 1/4 of space around it. I'd say the damp part is toast. We took a photo from the front (can't get in there with the fan and radiator) and cannot see the wood ruf key in the slot....)

We really need a crank shaft pulley. Suggestions?

Last edited by geopanoramic; 08-19-2015 at 08:02 PM.
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Old 08-19-2015, 08:25 PM
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Originally Posted by geopanoramic View Post
hi, the cousin here.

we got the nut off no problem. That technique worked the nuts.
Banged on the pulley, but do not know how to proceed without a puller.

Pull radiator etc and use a harmonic puller?

Is there any way to do it without the puller?

Dad here: when the over-rev happened, the AC compressor bearings and shaft froze, causing that belt to snap. The associated forward pulley is ok but the rear puller is loose with an 1/8 to a 1/4 of space around it. I'd say the damp part is toast. We took a photo from the front (can't get in there with the fan and radiator) and cannot see the wood ruf key in the slot....)

We really need a crank shaft pulley. Suggestions?
With the fan removed you will have room without removing the radiator. You need a puller you can borrow from most Oreilly stores. They have several types. Make sure you get one with a live center so you don't damage the threads in the crank.
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Old 08-19-2015, 11:45 PM
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Awesome. Thanks !
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Old 08-26-2015, 11:34 AM
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THANKS - we got it off barely. Pushed against the bolt head, then pushed against some sockets on the inside of the crank. It was a baby three arm puller from autozone. What we really needed was an old school puller that was bigger and better suited for tight spots.

So we have forward movement.... The "damp" rubber part of the inside pulley is history. Now its a question of finding the right replacement, etc.
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Old 08-27-2015, 07:19 AM
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If you are on Facebook, check out the group "Datsun Parts and Needs". About 10k members and I'm sure someone can get you a pulley pretty quick.
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