Packard Forum Index » Pre-War (1899-1942)

Hi all,
The old girl has developed a bit of a backfire and I would like to check the ignition timing.
I have read The Packard info sheet T&E -1522 and where it states Vibration dampener at front of engine marked D.C-1-8 at t.d.c.point for piston #1 etc I can't find any marks at all.
Is there an easy way of checking the timing that anybody knows about please
Thanks
T.C.

Backfiring isn't usually the result of ignition timing being off a few degrees - are you sure you have an ignition problem? If you still have the twin coil, dual point, double-ended rotor system, are you aware that you have to time each set of 4 cylinders (timing #1 and #6)independently? Or synchronize the two sets of points before reinstallating the distributor? Perhaps this is old info to you, but just in case I'll enclose a couple of articles previously published by PAC's local region which may help you; ignore the picture of the Delco distributor misidentified as a NorthEast unit.

As to timing marks on the damper, are you sure they're just not obscured by paint, or very faint? There should be two sets of marks, one for each set of cylinders that require timing. There are also timing marks on the flywheel that are useful for static timing, though you have to remove the starter motor to access.

Though it's complicated on the 33/34 cars with the dual ignition, one of the best ways to do ignition timing is the "by the ear" method, simply taking a series of test drives up a modest hill in high gear under acceleration, and progressively advancing the timing until you get just a faint hint of preignition.

I'm not familiar with T&E 1522 - can you give me a reference to where I can review it?

But again, ignition wouldn't be my first suspect with a backfiring problem - for example have you checked valve clearances?

Attach file:

---

  (387.13 KB)


  (227.50 KB)


  (178.40 KB)

Hi Dave,
I thought you would be the one to come up with the answer.
I'm not really certain which side of the car I should be looking at to find these marks and pointer but no doubt you can tell me.
I believe it's the timing because when I was checking the points I noticed the distributor move and I found the clamp bolts loose and just tightened them up where they were. Prior to that there was no backfiring.
Can you also tell me how I get the picture of the T&E drawing onto this site so that you can have a look at it.
Not being that good with "putors" it would help for the future
Thanks T.C.

OK, loose distributor, could be your problem.

Best to check your points and gap them first before proceeding.

Both sets of timing marks (#1 and #6) not all that easy to see, I understand why you might have missed them. Driver's side of the engine; the marks are on the outer face edge of the vibration damper, partially obscured by the front motor mount stamping. Pointer is also partially obscured by the lower radiator hose and is on the downside, low. You're really going to need a good light and some patience to find them! I recommend putting a dab of bright yellow or white paint on the tip of the pointer and on the degree line, it will be quite a challenge to get a small paint brush in there and hit the right spot, but ultimately makes life much easier.

If you're going to use a timing light, first do #1 cylinder in the usual manner, and lock the distributor down tight. Then switch your light to #6 and see where the second set of cylinders are firing. Kind of trial and error from that point, but WITHOUT moving the distributor, take off the cap, find the set of points mounted on a secondary, rotateable base plate, loosen the screw hold the points secure, and rotate the eccentric screw that rotates the secondary plate on which that set of points is located. This will change the timing of the 2nd 4 cylinders w/o changing the first. A couple of repititions and you should have it. I continue to use the factory timing, 6 degrees BTDC.

If you're going to do a static timing, take extra care to make sure all the backlash is out of the distributor drive. Sometimes I've removed the rotor, fastened a small C-clamp to the shaft top, and used a rubber band to hold the backlash.

Perhaps you can email me the image of the T&E, <dlczirr@optimum.net>.

Did you find the marks and pointer, or do you need a photograph? I'll be putting film in the camera for next week's PAC Covered Bridge Tour in NJ/PA and could take a photo or 2 from my spare engine where everything is quite visible.

Just a thought: Have you adjusted the carb-idle mixture screws lately? Backfire through the tailpipe (technically called an afterfire) when you're coasting can be caused by turning-in the idle adjustment too far, creating a lean mixture that doesn't ignite until it's in the tailpipe with hot exhaust.

If you get "pops" when you're off-throttle, try enriching your idle-mixture, and see if the backfire goes away.