Flywheel timing mark wrong on HUP

[Malcolm Towrie]

I just worked on a HUP. It ran ok, but I decided to check ignition timing. I got #1 on compression stroke and then rotated the flywheel until the ball bearing insert in the flywheel lined up with the indicator pointer. Then I rotated distributor to match the rotor to the wire to #1 plug. It wouldn’t start. Nothing, except the starter would occasionally stall on the compression stroke, indicating timing was way too far advanced.

So I went back to basics and found TDC on #1 firing with a leak-down gauge, which is pretty accurate. I marked the flywheel with the real #1 TDC with yellow paint, and set up the dizzy for that. It then started and ran fine.
The true #1 TDC firing was about 90 crank degrees off from the ball bearing mark.
Just wondering why the flywheel was so far off? According to the manual, the flywheel locates on 3 dowels and 6 bolts. There’s no mention of indexing the flywheel to the crank to ensure the TDC mark is correct.
Are the dowels offset to ensure correct indexing? Or the bolts? I guess not.
Did the flywheel on later engines fit, but with different indexing?
Malcolm

[Lynn Eades]

Usually the manufacturer makes the fasteners off set. 90 degrees seems odd for a 6 cyl???

[Phil Waterman]

Hi Malcolm

I will assume that the engine was running fine, and nothing had been disassembled prior to using the timing light. Now possible cause:

1. Firing order and spark plug leads, the engine really doesn't care which hole on the distributor cap, as long as they are in the correct order.

2. The gear on the end of the distributor shaft has shifted. I had this happen on the road in my C60S pin broke then jammed at a different point. Hole in the shaft was elongated from wear, have found several distributor that had loose gears.

3. Which timing hole are you looking through? Assume the one on top of the starter and not the one one manifold side of the engine.

Just some thoughts, because the timing mark is so hard to see, I've added timing mark to pressure plate so I can time the engine through inspection plate. When I have engine apart I mark the drive shaft with the three TDC with white paint saves time adjusting the values.

Cheers Phil

[Lynn Eades]

Aha! Phil, that will explain the 90 degrees. I was only thinking of the hole down the side of the bell housing, not one on top.
Malcolm is there a ball bearing pressed into the front of the flywheel, which should time through the lower hole? That's how a British GM was timed.

[Malcolm Towrie]

Originally Posted by Phil Waterman

Hi Malcolm

I will assume that the engine was running fine, and nothing had been disassembled prior to using the timing light. Now possible cause:

1. Firing order and spark plug leads, the engine really doesn't care which hole on the distributor cap, as long as they are in the correct order.

2. The gear on the end of the distributor shaft has shifted. I had this happen on the road in my C60S pin broke then jammed at a different point. Hole in the shaft was elongated from wear, have found several distributor that had loose gears.

3. Which timing hole are you looking through? Assume the one on top of the starter and not the one one manifold side of the engine.

Just some thoughts, because the timing mark is so hard to see, I've added timing mark to pressure plate so I can time the engine through inspection plate. When I have engine apart I mark the drive shaft with the three TDC with white paint saves time adjusting the values.

Cheers Phil

Hi,Phil,I don’t think firing order and dizzy gear location are relevant to this problem. The problem I see is when I get the number 1 piston at TDC firing, the pressed-in ball bearing and the UIC mark on the flywheel are approx 90 crank degrees away from the pointer, when they should be right at the pointer.
I’m using the peek hole on the right hand side of the bell housing, the one that faces forward. It’s just below the drivers seat. Is this the right one? I ask because I think I saw a peek hole on the passengers side of the bell housing as well. If I should be using that one, that would explain the 90 deg error.
Malcolm

[Jordan Baker]

The doesn’t specifically address your questions but maybe it does. Regardless this is an excellent reference website dedicated to the Chevy inline 6 engines.

This article is about timing
http://devestechnet.com/Home/StoveboltTiming


This one is about flywheels.
http://devestechnet.com/Home/Flywheel

When I setup my engine I referred to these and it started fine on the first try.

[maple_leaf_eh]

Malcolm, would you like one of us to speak to Jeremy. He's had you performing miracles on the Centurion alot, asking really detailed questions about the twin diesel Sherman lately, and now fussing with a HUP. Surely you're not the only smart wrench at the Museum?

[Malcolm Towrie]

Thats some good info, Jordan!
Especially the pic of the flywheel:



I zoomed in and took some measurements. Looks to me like the bolt/dowel cluster spacing is not symmetric, which is what I would expect to ensure flywheel can only be mounted to crank one way.

The info also confirmed I used the right peep hole for the timing. So I suspect a mistake was made during flywheel manufacture. Anyway, it is what it is and engine runs fine.
Malcolm

[Malcolm Towrie]

Originally Posted by maple_leaf_eh

Malcolm, would you like one of us to speak to Jeremy. He's had you performing miracles on the Centurion alot, asking really detailed questions about the twin diesel Sherman lately, and now fussing with a HUP. Surely you're not the only smart wrench at the Museum?

Terry, no, I'm not the only wrench at the museum, BUT I'm retired, I live on my own (so come and go as I please), and I LOVE working on this stuff. So I can spend a LOT of time there!

Malcolm

PS: the only time I use the stove is to boil oil and brake fluid out of brake shoes and pads at 450 deg. F. I have to stash the smoke detectors in the fridge. See the advantage I have?

[maple_leaf_eh]

Glad to hear the Museum work is a still challenge and lots of fun. Keep smiling and doing what you like best.