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1974 260z timing issue


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On 3/8/2021 at 1:17 PM, Dolfinz said:

I also checked the crankshaft pulley timing mark and found it to be at 10:00 and not near 3:00 as it would need to be to be at zero on the timing plate.

 

14 hours ago, Dolfinz said:

The lobes are flat and the crank is where the service manual timing mark shows it should be. 

Dolfin, you're contradicting what you wrote earlier.  You said the timing mark was in the wrong place.  How about a picture of your damper pulley and the timing plate?

Also not clear what you mean by "lobes are flat".  They should be sticking up like rabbit ears if you're on the compression stroke.

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In my prior statement I meant the timing mark on the pulley was at 10:00 and should be near 3 to line up with the 0 on the timing plate.  The timing mark on the crankshaft itself is at 3:00 as shown in the service manual.  I thought as long as the lobes were flat the valves were closed.  Do they need to be sticking up like you said?  I currently have the pulley and timing cover removed to verify the timing chain is correctly installed.  That's what I'm trying to determine.

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The lobes should look just like this.  I stole this picture from a Google search that linked to a CZCC thread but the picture wasn't in it when I opened it.  In case someone recognizes it.

It's starting to sound like you're on the exhaust stroke.

image.png

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I think that you just have an aftermarket timing chain sprocket (three holes instead of four) with no notch so no need for the holes at the top, and either a bad damper pully, or the damper pulley has been installed with no key in the keyway.  Might be that your guy pushed the key out of the slot when he installed the damper.

I'd pull that damper and check the key and keyway.

Your sprocket only has three holes, the factory sprocket has four.  Edit - I guess it might possible also to install the sprocket without the locating pin.  I see the 1, 2, and 3 on the sprocket so something is weird there.  So, I'd pull the sprocket also.  Use the tool so you don't drop the chain.

Overall, both your sprocket and your damper don't seem to match piston location.  Might be that your builder had the piston on the exhaust stroke when he installed the parts.  So, maybe you're right but he was wrong.  This is my new theory - your builder installed the sprocket on the exhaust stroke and maybe just eyeballed the damper pulley without the key in the keyway because it didn't line up.  Either way, since you know you're at TDC on the piston, you need to get the damper and sprocket to match.  Pull them off on and reinstall and hope no valves were damaged.

Short answer - something is not right so it's best to take it apart and start over.

image.png

Edited by Zed Head
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Forgot to ask - where is the damper pulley mark?  Can you post a picture of that?  Then you'll have TDC, cam lobe positions, and ignition timing marks.

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I can temporarily reinstall the pulley and post a picture but as I previously stated with it correctly installed and the keyway in place the timing mark on the pulley is at 10:00.  It should be on the zero on the timing plate correct?  That would need to be at about 3:00.  What confuses me is that's not 180 degrees out.  The pulley isn't the original but I still have the original and they are exactly the same.  Per the service manual everything appears to be correct except for the timing mark on the pulley.  I'm baffled.

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Did you ever confirm/know that the damper timing mark was correct before the engine was rebuilt?  You started your story in the middle.

I don't think that any of the timing mark plates available sit at 3 o'clock.  That would be horizontal with the damper center.  Maybe you have your timing plate in the wrong spot.  10 o'clock sounds right.

I can't find a Z picture (it's the one weird thing about all of the FSM and Owners Manuals - there are no good pictures of the ignition timing marks) but here's one for a Datsun 1200.  It's about the same.  Around 10 o' clock

image.png

4 minutes ago, Dolfinz said:

That would need to be at about 3:00. 

 

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Here's a grimey one.  It shows zero, but he has a later timing plate with an early damper.  A later damper would have just one notch, and sit at the zero at TDC.

https://www.zdriver.com/forums/280zx-s130-forums-77/can-i-get-crank-pulley-fit-34699/

image.png

Edited by Zed Head
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20 minutes ago, Dolfinz said:

I can temporarily reinstall the pulley and post a picture but as I previously stated with it correctly installed and the keyway in place the timing mark on the pulley is at 10:00.  It should be on the zero on the timing plate correct?  That would need to be at about 3:00.  What confuses me is that's not 180 degrees out.  

10 and 3 aren’t 180 degrees apart, more like 160/170.

It would be a good idea to start fresh. Set the engine at #1 top dead center. Then check the camshaft position to ensure it is in the correct position.

If it isn’t, reset the cam. A degree wheel is very helpful here, both for setting the initial timing up, and checking the opening and closing of the valves, camshaft lobe centers, etc.

If the cam timing is found to be correct, then there is some other issue.

 

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On 3/8/2021 at 1:17 PM, Dolfinz said:

I recently had my stock engine rebuilt.  When I got it back I put the remaining parts back on and I can't get it to start. 

I set the number 1 cylinder to TDC and pulled the distributor and found the shaft to be at factory spec with the small lobe forward and positioned at 11:25. 

I also checked the crankshaft pulley timing mark and found it to be at 10:00 and not near 3:00 as it would need to be to be at zero on the timing plate.

Just to reset things from the start.  It's not clear that you know much about the engine.  Can't tell if it came from a car or maybe you bought a box of engine parts.  All that's clear is that you had an engine "rebuilt".  And, "timing mark at 3" depends on if you're looking from the front or the back.  Could be on the passenger side or the driver side.

There is a variety of different ignition timing setups out there for the Z's and ZX's.  Some have the gradations on the pulley for use with a pointer, some on the timing plate for use with a single damper mark, and there are different timing mark plates for the Z and the ZX.  

Might help your cause if you started from the beginning, describing the engine and the car it came from and how long you've had them.  Good luck.

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I'm going to guess that he assumed that the timing plate mounted at 3 o 'clock.  3 o' clock is wrong from front or back.  Get the timing plate in the right place, at 10 o' clock, and all that's left is an aftermarket sprocket with no notch.  If the builder used the 42 links then it's right too.

Then, we're back where it should have been with "have you confirmed spark?".

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Found another good one that shows proper zero.  He has a degreed wheel but the pointer is right.  Also shows some nifty damper damage.

image.png

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To clarify a few things.  I have owned this car for 43 years.  It is the first car I ever bought.  The engine is original but has been rebuilt a couple of times.  The timing plate has always been located on the right side of the timing chain cover when facing the engine.  See the attached picture showing the mounting location.  The plate has 2 mounting holes and will only mount in this location.  The car had been sitting for about 5 years and I decided to get it running.  When I did I took it for a drive and somehow bent a valve on the number 5 cylinder so I took it to a former friend/mechanic with the new head I bought from z car source to rebuild.  He told me I probably had the mechanical timing off by a link or two and that was why I bent the valve.  He said he would make sure the timing was right this time.  He had a machine shop rebuild the lower end and then he put the rebuilt head on it a returned the motor to me to finish reassembling, intake, exhaust, carburetors and linkage, oil pump and distributor, alternator, starter, radiator and all fuel and coolant lines.  Once assembled we couldn't get it to even try to fire so we checked for fuel, spark and compression and we had all 3.  At this point I figured it had to be a timing issue and that's where we are.  I personally rebuilt this motor once but it was 35 years ago.  I know we are on the compression stroke at TDC because we verified it with a compression gauge in the spark plug hole prior to disassembly.  As I stated previously, according to the service manual everything looks right but the timing mark on the pulley location.  I assume this has to mean an issue with the timing chain but I wonder if I can't just remark the pulley at 0 on the timing plate and see if I can get it running.  Problem is I hate to try something that might not work and require tearing the thing apart again.  And the other thing that's baffling is it isn't 180 degrees off.  Hope this helps.

z3.jpeg

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1 minute ago, Dolfinz said:

The timing plate has always been located on the right side of the timing chain cover when facing the engine.  See the attached picture showing the mounting location.  The plate has 2 mounting holes and will only mount in this location. 

 everything looks right but the timing mark on the pulley location.  I assume this has to mean an issue with the timing chain but I wonder if I can't just remark the pulley at 0 on the timing plate and see if I can get it running. 

Thanks for the full story.

I've heard of the timing plate or pointer being on the other side, can't remember the reason, but I had assumed that would require a different damper.  

I don't know how you got in to this predicament but it seems like buying a new plate and putting it on the other side would work, since that's where your mark is.  The answer might be in this thread, below.  Don't overlook the standoff.

Any chance that your old damper has two marks on it?  One for each location?  You said that it matched the new one but maybe it has two notches.

 

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Found something in the 1974 FSM.  It's not 3 o' clock but it shows both sides.  Not sure what "cooler equipped " means.  You'd think that they'd just make a damper with two marks.

image.png

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  • 1 month later...

Well, one of you called it.  There was another timing mark on the crankshaft pulley that we found after disassembling the front of the motor.  We verified tdc and all mechanical timing marks where they should be, put it back together and the second timing mark was on 0 at TDC.  We put everything back together after I rebuilt the carbs again and she fired right up.  Problem is she won't idle on her own and after running for a bit she stalls and won't restart unless we hold the pistons in the carbs up.  They are SU carbs as I pulled the Hitachi's shortly after I bought it and replaced them with the SU's.  So, asking for more input.  I assume I will need to adjust the fuel dials underneath the carbs so should I take them downward to allow more fuel or tighten them to restrict the fuel?  Also, might I also need to make some adjustments on the linkage or tops of the carbs?

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These carbs (SUs and Hitachis) usually run well with the mixture (nozzle) screws down 2 1/2 - 3 turns down from the top. An easy way to check your fuel level in the float bowl is to remove the domes and pistons, turn your mixture (nozzle) screws down 9 1/2 turns from the top. Your fuel level should be at or near the top of the nozzles. 

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Found something in the 1974 FSM.  It's not 3 o' clock but it shows both sides.  Not sure what "cooler equipped " means.  You'd think that they'd just make a damper with two marks.
image.thumb.png.ebc3a6f7e1a261f0b133cc92aa9a7b23.png


On my L26 without aircon, the timing pointer was on the carb side of the engine where the aircon compressor would be fitted.

On my L28 it is on the spark plug side to allow space for aircon compressor.

I’m guessing cooler is a translation anomaly, meaning aircon.
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@Dolfinz When you checked the position of the tang on your distributor, are you sure you were on TDC Compression stroke? If your chain timing was off, I do believe you would probably have valve contact. IMO

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On 3/12/2021 at 3:52 PM, Zed Head said:

Found another good one that shows proper zero.  He has a degreed wheel but the pointer is right.  Also shows some nifty damper damage.

image.png

Wow Zed Head....I think that front cover has my name on it LOL

Edited by Diseazd
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On 3/12/2021 at 3:52 PM, Zed Head said:

Found another good one that shows proper zero.  He has a degreed wheel but the pointer is right.  Also shows some nifty damper damage.

image.png

Wow Zed Head, I believe that crank snout has Jeff G’s name on it 😬

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33 minutes ago, Diseazd said:

Wow Zed Head, I believe that crank snout has Jeff G’s name on it 😬

Sure does.  The end result was much better than it could have been.  A lot of filing, sanding, and polishing turned that mess into a usable snout.  Somehow I even got it round.  🙂

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