Timing plates issue

[AZDatsun]

I have the 280zx f54 block but a front cover from a 280z with the 280z timing plate on it and never really thought about it but do the numbers line up to the same? Or should I get a 280zx plate? I have the p79 head also if that matters
 
I can’t tell but it looks like the 0 would be on different spots
 
280z timing plate
 

 
280zx timing plate
 
 


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[Zed Head]

I'd get the ZX plate just because it goes to 30.  It's handy for checking that your advance mechanisms work correctly.

I've not got in to this issue but the damper pully probably plays in to it also.  And it looks like the mounting holes are different but that would mean the timing covers are different.  

Always something new cropping up.  

[AZDatsun]

Ok I just bought the zx plate and I will line them up to see if there is a difference at 0. I will report findings back on all this ones it arrives from zcar depot


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[Racer X]

4 hours ago, AZDatsun said:

I have the 280zx f54 block but a front cover from a 280z with the 280z timing plate on it and never really thought about it but do the numbers line up to the same? Or should I get a 280zx plate? I have the p79 head also if that matters
 
I can’t tell but it looks like the 0 would be on different spots
 
280z timing plate
 

 
280zx timing plate
 
 


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Given the one that goes to 30 has a greater distance from zero to 20 than the one that only goes zero to 20, it would appear that each is made for a different diameter damper pulley.

If you have a 280ZX damper, the scale for that setup should be the one to use. If you have a 280Z damper, use the scale for that setup. At different pulley diameters, the length of the arc as the crank rotates changes, i.e. a smaller pulley swings a shorter arc than a larger one for a given amount of rotation. So a larger diameter pulley will require a longer scale to measure degrees of crankshaft rotation.

 

You are only checking crankshaft position with this, so the cylinder head isn't a consideration. Set the crankshaft at #1 top dead center, mount the pointer so the 0 lines up with the mark on the damper, and lock it down.

I have never given any consideration to front cover production changes, if any, that may have occurred over the life of the L series engines. So I can't say there would or would't be a difference from the 280Z to the 280ZX. The brackets both look like they have mounting holes at the same distance, and the upper hole is smaller than the lower hole on each one, and both mount under the bolt heads on the lower right two cover bolts, the bottom one being larger diameter than the one above it.

 

 

 

[AZDatsun]

Great now I need to figure out where my damper pulley is from. I just measured it and based on what I read I must have a 280z pulley because it’s about 5.5” and it looks like the later 280zx were 7” in diameter


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[Zed Head]

I had a Z and a ZX engine in the garage at the same time for along time but never really looked at the dampers or timing plates.

Big picture, your Z damper is older and probably close to failure.  But the ZX damper is pretty old too.  The ZX damper is probably an improvement over the Z damper, if it's changed.  No reason to add mass or size without purpose.  I'd get a ZX damper and use that.

Just thoughts..

p.s. there are dampers for sale out there that are advertised as 71 - 83.  I wonder if people run in to size problems, with the timing plates.

Edited January 30, 2021 by Zed Head

[AZDatsun]

I guess if both plates align at 0 that’s good enough because you can use a timing light with the dial adjuster but good point about after market pulleys


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[AZDatsun]

So I learned something. The 280zx timing plate does not fit on the 280z front cover it’s too long. So yeah who knew there was a different front for later engines. I guess the moral of the story is if you have the smaller damper you need to use the small timing plate along with an earlier year front cover.






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[Captain Obvious]

Huh. Well whadda you know?

A local Z buddy of mine is (I think) planning to use his Z front cover on his ZX motor. Why? I believe the answer was "Because it's cleaner."  Haha! I'm going to have to mention this to him...

[AZDatsun]

I found the answer the 280zx timing plate just goes onto a different hole and used some sort of metal stand off tube with a longer bolt as seen here you can see that hole in my pictures to the top left of my timing plate



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[Captain Obvious]

Oh. Well nevermind then. All the timing covers are the same.

I've got all the hardware for the ZX timing plates, so we're all set. It's all in the box:

[AZDatsun]

That was some good sluething


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