Packard Forum Index » Post-War (1946-54)

Don, a compression gauge can be had for around $20 at any auto parts store, they are a good tool to have on hand. It sounds like you are o the right track with fixing your problem. Just curious have you tried disconnecting the vacuum advance (make sure you block the vacuum line so you don't get a leak) and try driving it again. What was the reading on the vacuum gauge when you performed the vacuum test?

Thanks, OD for the link to that thread. Funny that didn't show up in my search before starting this topic; I guess I didn't word the search just right. Interesting fix, I'll have to take a look at my distributor to see what he's talking about. Can't help but wonder if they wouldn't have gotten the same result if they just retarded the timing a little bit.

Thanks, also, packard1984 for your suggestion to unhook the vacuum line and see how it is. I hadn't thought of that. I know to plug the vacuum line or the carb'll be running so lean that it'll most probably create a lean misfire.

I was given a compression gauge years ago by a retiring mechanic. It has to be held in place while the engine cranks. Since I don't have a remote starter and I'm a lone wolf, there's no way I can hold that and turn the ignition key at the same time. That's why I rely on the vacuum gauge readings so much. Now I was checking the vacuum back in '06, so I don't remember the reading exactly but I know it was 20 or 21 and rock steady. It went to near zero when the throttle was goosed and quickly returned to a steady 20 or 21 when the throttle snapped back to idle. I'll be using the gauge before, during and after retarding the spark.

Having 20 pounds (inches of mercury?) is extremely good. I know the type of compression gauge you have they are really good tools but like you said hard to use by your self. Seeing as how you have a 12V ignition on the car you could always get a starter button hold it in one hand and the compression gauge in the other.

http://www.summitracing.com/parts/anm-cp7853/overview/

Once again, thanks packard1984. I didn't realize how inexpensive those remote starter buttons are. Have to take a look at them.

Don, do yourself a favor and find someone with a screw-in compression gauge. I see them at garage/estate sales often for $5-10, as all the old DIYs are dying off.

jack vines

Thanks, Jack. I've got to start checking those garage sales!

Around here they can also be borrowed with a deposit from the major parts stores, like OReilly or Autozone (OReilly owns Checker too).

Depending on access, you can also jump the solenoid with a screwdriver on some cars, by laying a screwdriver from the big hot lug on the starter over to the smaller one on the solenoid, which will crank then engine from under the hood. I feel better using a starter button though, or borrowing a neighbor.

If you want to purchase a compression gauge but are having a hard time finding one locally you can go here:

http://www.summitracing.com/parts/sum-900009/overview/

I use Summit racing a lot the prices are usually better than anywhere else I have found you just have to wait a couple days to get the parts or tools after you order them. On a side note they sale the pakard dist brake conversions here as well.

Thanks, Richter12X2 and once again, packard1984 for the tips.I know my local Pep Boys did not have a compression gauge in their loaner tools when I was seeing just what they had to loan a while back (maybe someone had it out.) Considering the size of that store, they really didn't have a whole lot of tools to loan. I don't remember seeing one in Advance Auto either, but then again I was borrowing a spring compressor and may not have noticed the gauge. From what I've seen on this thread, it looks like Summit has just about everything.

I've decided to do the fix in the PAC forum thread that OD so kindly listed here. Seems simple enough and it worked for that owner during a coast to coast trip in the summer. So that'll be my next step in stopping the ping.

I found the modification mentioned in the PAC thread to be somewhat ambiguous, so I sent the author of that thread an e-mail. He replied very quickly and said that he didn't do the modification himself. It was done at Ross Miller's Speedwell Garage in Parkton, MD, and the author made notes as he was told what was done to the car. I called Ross and he told me what was done.

The purpose of the modification is to slow down or limit the amount of advance available through the vacuum advance system. By limiting the advance, pre-ignition from that source would be greatly reduced if not eliminated. Since there is no tampering with the basic timing, overall engine performance wouldn't be significantly affected. By putting two flat washers inside that long hex-shaped spring housing that mounts to the diaphragm housing, both the spring and the diaphragm's movement is limited as is the advance available to the breaker plate inside the distributor. It's really very simple yet ingenious when you think about it; I'll refer to this modification as the Miller Method since it's Ross' idea. Ross also said that it's very important to set the spark timing at zero, or TDC; these engines won't tolerate an advanced setting.

The thread author is a real gentleman, sharing his experience very freely. He reported that the modification hasn't stopped the pinging entirely. In his opinion, Packard simply pushed the engine past its limits and there is no real fix for it. He said you just have to live with it and back off the accelerator when it starts to ping. In view of his experience in driving his car from New York City to San Francisco, I'd say his counsel should be heeded. If you're going to "ask the man who owns one" about this problem, he's the one to ask. So unless someone here expresses a good reason not to do this, I'm going to employ the Miller Method on my car.