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Crankshaft pulley nut size?


argniest

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Hello

does anyone happen to know what the size of the Crankshaft pulley nut is, on a 1978 280z?

I need to get a socket/wrench on it, before I begin doing my cylinder leak down tests. So far I havent found out what size it is listed as, in the FSM. I need to go buy it tomorrow, because I am sure I dont have anything that big. I have been able to partially view it when looking from the side of the car, laying on my back. And its looks pretty big. But it is really difficult to get at. I think I will remove the 4 bolts on the fan and at least push the fan back up close to the radiator. Then I should be able to get the wrench on it....

To actually take the fan out, and get it completely out of my way, it seems like I might have to take a whole bunch of other things out first. And I would prefer to avoid that. Since my only main goal is to just be able to get a huge wrench on the Crankshaft pulley nut, and hold while I do leak tests.

thanks

Thanks!

Edited by argniest
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ALso one other question, how in the heck can I remove the plastic engine fan? I noticed two sets of four bolts. Found 4 bolts on back of fan, that didnt seem to help at all, and then 4 bolts on a metal bracket that the fan propeller shaft runs into. But some other force seems to be holding it onto its bracket???? It doesnt seem to want to budge. I just wanted to get it out of the way so I can get a big wrench on the crankshaft pulley nut.

I saw your message about taking a fan belt off, but I have never removed any belts and I think I might not want to attempt that right now....I got enough other things I am already into right now.....

thanks

PS PLease look at pictures you will see what I am talking about in a little better detail.

post-23329-14150813650764_thumb.jpg

post-23329-14150813651492_thumb.jpg

Edited by argniest
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The bolt is 16 mm x 1.5 (pitch). You also need to make sure the length is correct and that is 32 mm if I remember correctly.

This is going to be a really dumb question...but what does the pitch mean? I havent seen/heard of that before. Remember I am a noob working on my 1978 Z car, which is my first car to really work on.

And when you said the bolt is 16mm are you talking about the crankshaft pully nut, because someone else said it was 27mm. Just wondering....

Edited by argniest
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The 4 bolts that you point to in your picture hold both the fan, and the fan pulley to the water pump. This is the "standard" arrangement in most RWD cars by the way. You should at least loosen the fan belt before removing these bolts.

The reference to the crankshaft bolt being a 16mm bolt refers to the bolt diameter, not the head. The head requires a 27mm socket, but 1 1/6 works just as well, being 26.9875mm. The trick is that on the older engines at least, you need a 6 point socket. And the wall thickness of an impact socket will prevent it from reaching the bolt head. Since it is very difficult to find a 6 point 27mm non-impact socket in the U.S. the 1 1/6 socket is and easy substitute.

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Yeah mate, the 27mm or 1 1/16th measurements refer to the bolt head diameter.

The 16mm reference is how thick the bilt shank is.

The pitch is how coarse the thread is, usually expressed as how many turns per mm. 1.5 mm is a coarse metric thread. 1.25 is fine and 1 is very fine.

Google it mate...seems you have access to a computer! :stupid:

So in bolt speak you have a crank pulley bolt "M16X1.5" (M is for metric). Head sizes can vary. Take a look at the camshaft bolt!! Same M16X1.5 as the crankshaft bolt in all other respects except the head.

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Yeah mate, the 27mm or 1 1/16th measurements refer to the bolt head diameter..

Yeah I figured that :) And yes, I did find 27mm sockets...wasnt easy but I found a short one and a deep one, at two different hardware stores locally. And I was able to at least turn the crankshaft pulley nut from under the car (dont worry all power was disconnected, and car was in nuetral with blocks, so I am not gonna run myself over)

I believe I can do the leak down tests by wrenching on the crankshaft pulley nut from below car. It isnt easy but I was able to do it. I just need a helper to control the air compressor for me. I also was able to control and see the leak down tester from under the car...so if needed I can do that too. But of course I need someone to listen to the sounds of leaking air, and I would rather do that myself. I need to clone myself I guess for this job.

The 16mm reference is how thick the bilt shank is.

Makes sense too.

The pitch is how coarse the thread is, usually expressed as how many turns per mm. 1.5 mm is a coarse metric thread. 1.25 is fine and 1 is very fine.

That was the only thing I wasnt aware of. Thanks for explaining it.

Google it mate...seems you have access to a computer!
And yeah, I am ALWAYS googling all kinds of things :) I just didnt google that. Was hoping someone here would jsut give a quick explanation. YOU JUST DID! THANKS!!!
So in bolt speak you have a crank pulley bolt "M16X1.5" (M is for metric). Head sizes can vary. Take a look at the camshaft bolt!! Same M16X1.5 as the crankshaft bolt in all other respects except the head.

Thank you.

Edited by argniest
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For metric fasteners, the 1.5 is the distance per thread in millimeters. If you measure from one thread peak to the next peak of an M16x1.5 bolt, it will be 1.5mm across. Because the distance is small, it's easiest to measure 10 threads and divide. 10 threads = 15mm = 1.5 pitch.

SAE threads are measured differently. The pitch is threads per inch. A 1/4-20 bolt will have 20 threads in one inch.

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Lead and pitch are closely related concepts. They can be confused because they are the same for most screws. Lead is the distance along the screw's axis that is covered by one complete rotation of the screw (360°). Pitch is the distance from the crest of one thread to the next

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Well I cant believe how much I just learned about nuts and botls :) in this single thread. I mean more than I never knew before. And it will help me look at them differently from now on.

The good thing is over the past few months of winter, I have learned so much about the car. I love it!!!! And this forum has taught me so much too!!! And a few of my freinds, neighbors, and 2 relatives nearby are also getting in on this project in one way or the other.

This is just awesome! I just cannot wait to get the car running better and be zooming down the road ....

Edited by argniest
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