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Timing marks and an advanced timing gun- dumb question I'm sure.


7502
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I know this is probably one of the dumbest questions to come up in awhile but I'm throwing it out there. I was having a real bad time verifying TDC - comparing the various marks on the flywheel, timing chain sprocket, and pulley for my 75 with a 123 distributor.  I eventually found a shop that was willing to take a look at it. He confirmed that the flywheel had been installed incorrectly explaining why the various marks were not indexed properly. He marked the flywheel and lower pulley for TDC w/ green paint and set the timing. I was actually relieved that there was a good explanation for the problem I was experiencing.

 

So this morning I decided to break out my timing gun to see what he actually set it to and to see if I could see his new marks. This is where it gets weird. With my timing light, no matter what advance I choose the pulley marks are always in the same place. In other words I can't dial in the timing gun to tell me what the timing is.  At idle,  I can see his timing marks on the pulley and I can watch it advance as I rev the engine but changing the advance on the gun does nothing to pull the paint mark to the pointer on the case. At idle it's near the pointer so I can see his marks just fine. I can't see the marks at all on the flywheel. I even drove over to a friends house and tried his gun. We both have the Innova 3588 advanced timing guns and both guns behaved the same.

 

What could be going on here? Car runs well, but I'm missing something very basic on this issue.

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If you are watching the timing advance with engine speed but you can't move the timing mark by adjusting the dial on your timing light there is something wrong with your timing light (and your friend's too)  The system is very simple, it looks at the amount of time between the spark impulses and it knows that the crankshaft has turned 720 degrees between them, the dial is just a "time offset" based on that calculation.  If by moving the dial it does not change the position of the timing mark in relation to the pointer the timing light is not working properly. 

 

My biggest worry is that the "flywheel had been installed incorrectly". The only way this could happen is if the dowel locating the flywheel had been left out.  If this is the case there is a chance the flywheel will MOVE ON THE END OF THE CRANKSHAFT and damage both the crank and flywheel (it could shear off all the bolts and the damage could be catastrophic!!!)  Where did you take the car?  Go see Ron Ager @ NW European Autoworks  he is an old 2002 guy and he can check it out for you.

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Thanks Preyupy, this has been a real head scratcher for me.  My friend assures me his timing gun works properly on his MGB.  Maybe his gun is kaput at well.  I'll reach out and see if I know anybody else w/ a timing gun but no one is coming to mind.  I know Ron A, and have used his shop in the past. They did my 5 speed swap. Actually, the guy I took it to I shares his building and also their credit/debit system but maybe charges less.  The mechanic told me the locating dowel on the flywheel may have been moved for some reason.

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You can't "move" the dowel, there is one spot on the crankshaft and one large hole in the flywheel.  To move it would require some rather difficult machining. My guess is they just left it out, the bolt pattern on the flywheel/crank is symmetrical so without the dowel they can be bolted together in any one of 8 positions.  My worry is the bolts are designed to hold the flywheel to the crank in tension and the dowel is there to make sure they don't move in shear,  the bolts will not survive very long if the flywheel starts moving on the end of the crank. 

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I am all over this topic, since after a multi-year rebuild I am off to my brothers Monday where the car is to fill the brakes with fluid and do final tuning. I bought a new Innova 5568 and have the "book learning" from the manual and some great FAQ members who have helped me understand the proper steps for checking timing. But no real experience yet.

 

When I recently rebuilt my motor, my flywheel did have the alignment dowel and when we set TDC and attached the cam sprocket and installed the distributor, I felt good because:

 

- The cam mark was lined up

- The rotor pointed to the mark on the dist body

- The flywheel slit line was in the housing window

- The pulley mark aligned with the pointer

 

She fired up and ran fairly well first key turn. But as I said, next few days will be dialing in with the new Innova.

 

But one thought, and not sure this has any bearing or even applies to your timing gun. Mine has a 4 and 8 cylinder setting. Is there any chance yours does and is not set for 4? I am sure this is an important setting, but not sure how it would affect readings using 8 on a 4 banger.

 

And I assume your friends MGB is a 4 cylinder, so incorrectly set lights in two cases is very unlikely.

 

OK - there's my completely useless post :) But I can't wait for the final update explaining yet another 2002 mystery!!

 

Randy 

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I too have the 5568 and I believe the only time the number of cylinders matters is when you are using the dwell setting.

 

In the initial post of this thread, he said he bought the 3588, but I assume he meant 3568... since I cannot find that other model.

 

The 3568 does not have the dwell function, so the # of cylinders setting will not apply.

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The mystery of the wonky Innova 3568 timing light has been solved. A friendly car repair shop down the road let me try his Snap On timing light and it works as expected on my car. I asked him how much it costs and he said $450 because it has Snap On written on the side. Still not sure why my timing light works fine on my Karmann Ghia but refuses to work properly on the BMW but that's one of life's little mysteries I guess.   Did I mention I'm using the 123 Switch Distributor, although I doubt that has anything to do with it.

 

So now I need recommendations for a new timing light that's better suited for my car than the Innova 3568 but don't want to spend $450 for the Snap On model.  Don't really want to just buy another 3568 since my friends 3568 also doesn't work on my car.

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That's a weird one. No need to go the full Snap-On here. OTC is a good brand. Have a look in tool catalogs at 'middle range' type brands and then look at the no-name brands on eBay that they have been badge engineered from. Lots of manufacturers get their parts from the same factories now with the only difference being the logo on the side and the price. 

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