F54/P79 Swap Project

[240260280]

Nope. Even though the chain is quantized, the sprocket tooth change increases the amount of tension on one side of the chain therefore the amount of slack must also increase on the other side. It is a very small amount to measure and will be challenging unless done precisely and accurately.  The crank and cam basically must be pinned to do the measurement. The fact they both rotate when moving the sprocket causes the inaccuracy of the measurement. The fact the sprocket has many teeth sharing the pulling makes it further more difficult for some to comprehend. The fact the chain has two parallel runs, also spreads the tension and causes torque. The fact the stretch of the chain may not be uniform is yet another variable. The fact the cam teeth may not all be worn the same amount also complicates things. And of course the group of valve springs loading and unloading the cam as it rotates makes for tension fluctuations as the cam is rotated to take up the slack.

If you reduce the complexity to the fundamental, it is clear that moving the sprocket to remove the slack on one side causes more slack on the other. The challenge to measure it empirically requires addressing all of the items in the paragraph above.

 

 

[LeonV]

This is not complicated, Captain Obvious is correct. The sprocket connects to the cam and the cam is free to spin. The sprocket's clocking doesn't change chain tension, outside of the fact that the valve springs can statically load the sprocket to favor a direction. When the sprocket is removed and set to various positions, it can feel as if it's altering chain tension. With the engine running, chain tension is the unchanged although cam timing would be different.

[240260280]

Done

 

[Captain Obvious]

So my ZX motor came out of a car with an auto trans, and I've got a couple questions about that...

First, I've noticed that the thin steel plate that goes between the block and the transmission is different. The manual version is one piece, but the auto version uses a two piece version with a separate small piece that bolts into place on the bottom. They did that so you could access the bolts that attach the torque convertor to the flex plate.

Question is... Can I use the auto version with a manual transmission, or do I need to source one of those plates?

Second, Are flywheel bolts the same as flex plate bolts? I'm guessing that the flywheel is probably thicker than the flex plate and used longer bolts, but I'm sure someone here has been through all of this before and knows off the top of their head.

[siteunseen]

I bought a Zx motor too a few years ago.  My '77 flex plate had a bigger sort of rounded looking triangle opening for the crank and the starter hole.  It has a locating dowel pin thing that holds it on but I'm almost positive the bellhousing bolts and starter bolts are what holds it on.  It's sandwiched in between the block and the bellhousing so I don't see how it has any protruding bolt heads.  The ZX flex plate has a smaller hole just big enough for the crank's rear to fit through.

ZX dust cover...

 

[siteunseen]

'77 plate...

There is two short bolts with nuts on the bottom but they go through the bell housing too.

Edited September 19, 2019 by siteunseen

[Captain Obvious]

Well I don't know if all the auto's looked like this, but this is the trans plate I've got from my 83 auto. Two pieces:

And there were some sort of brackets at the bottom of the bell housing. Probably some sort of stiffener members to account for the huge torque increase from the later year motors    . Two aluminum brackety things :

The look like this when installed:

 

[siteunseen]

And that light weight flywheel. You got your money's worth.

[Zed Head]

My 81 engine had steel gusset brackets.  I've read that they were for NVH reduction.  If you look at the engine-transmission assembly from the side you can see that there's some leverage there.  There's a lot of weight hanging under the last bolts in the engine, without those brackets.

[Diseazd]

17 hours ago, Captain Obvious said:

So my ZX motor came out of a car with an auto trans, and I've got a couple questions about that...

First, I've noticed that the thin steel plate that goes between the block and the transmission is different. The manual version is one piece, but the auto version uses a two piece version with a separate small piece that bolts into place on the bottom. They did that so you could access the bolts that attach the torque convertor to the flex plate.

Question is... Can I use the auto version with a manual transmission, or do I need to source one of those plates?

Second, Are flywheel bolts the same as flex plate bolts? I'm guessing that the flywheel is probably thicker than the flex plate and used longer bolts, but I'm sure someone here has been through all of this before and knows off the top of their head.

Not sure about these two questions Capt, but would assume you need longer bolts for the flywheel versus the flex plate. I am sure that you need to install the brass bushing in the rear of the crankshaft though.........the autos didn’t have that bushing installed.

[Zed Head]

21 and 26 here show a difference.  Nissan calls both "flywheel"s and considers them part of the crankshaft.

http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-280z/piston-crankshaft

[Captain Obvious]

Thanks Diseazd. It's my assumption as well. That the manual trans flywheel bolts are longer. And I've got a pilot bushing on my parts list of thing I'll need.

And Zed Head, thanks for posting the pic in the parts breakdown.. It pointed out #22 PILOT-CONVERTER -  12330-E3000. I had not noticed that on there before. I would have figured it out as soon as I tried to get the rear main seal off the crank, but it's better to discover that now rather than be surprised by it later.

Here's #22 sandwiched between the flex plate and the rear face of the crank. Give it a twist (as can be seen by the holes that don't line up anymore):

and a pull, and it comes off the back of the crank. They only use this on the auto versions: