We all have our favorite cars, and mine is my 1937 Packard Super 8 1500 Touring Sedan. With all of my cars, I add a Winter servicing non-ethanol gas with stabilizer (Bill Hirsch*), antifreeze, moth balls, cedar chips (on my wool interior cars), battery tenders, and set up a protectionbut not hibernation,so they can be started and driven if the weather is right. It makes it much easier to just get in and go in the Spring, too.
The '37, however, had not had its spark plugs cleaned or replaced in about 7-8 years, and had been started and stopped without much on-the-road driving. Of course, that fouls out plugs and gets unburned gas down into the oil. So knowing that, I changed the oil a few weeks ago. (The old '37 likes 30-weight Valvoline non-detergent. This is what it was born with and the non-detergent still has plenty of zinc.)
When servicing the spark plugs, I decided to buy a set of plugs exactly like the ones that were in it. They have been excellent and have lasted for years. They are Champion H10. Well, guess what? They don't make em any more! They have been replaced with H10C. What does the C stand for? There is not a clear explanation, but it might be the chromebase. I stopped researching after I read several reviews of disappointment from people using the new C's. The old H10 crosses over to an Autolite 216, which is a non-resistor plug which is what I want and I've always liked Autolite plugs, so I bought several sets of them. Remember always to check the REACH (depth of threads). Ours is 7/16" However, I wanted to see if I could bring the old H10's back to life, so I cleaned the porcelain and the top contact cap, and sand blasted the bottom end. I have had this plug blaster for years and it really does a good job of cleaning the electrodes and threads. I removed the seal washer, put the plug in the blaster, and rotated it 360 degrees and hit the blast button multiple times while rotating the plug. When the plug is removed from the blaster, the bottom end must be blown off with air to get rid of any remaining sand that might get down into the cylinder. After the threads and electrodes are blown off, I coat the threads with Anti-Seize for easy removal the next time. I dropped a little Marvel Mystery Oil down in each plug hole, getting some in the threads, then blew down into the cylinders with air. One note on this '37 319 CID Super is it has the same engine as Packard used in '36 as their Standard 8 and the '36 was to have 14mm plugs, while the 37 had 10 mm. Packard tests had shown the 10mm was more efficient with the Straight 8, allowing cooler heads, among other reasons, and they continued the 10mm through 1950, then in 1951 went back to the 14mm in their 327 CID Straight 8's (all series).
You might have noticed from the pictures our 37 has 14mm plugs and our '36 has 10 mm. Both have correct heads, but a reversal of the Packard manual specs. Our 37 had been owned in its later years by a man who worked in a Packard dealership, and it was common practice in those dealerships to drill out the heads and go to the 14mm. Right after I bought the '37, we did a valve job and re-surfaced the head, and saw no evidence of any work done on it to change to 14mm plugs. Comparing the '36 and '37, I dont notice any difference in plug foul. The '36 does run about 5 degrees warmer at 195 F in Summer. In my driving, I just dont see a lot of difference in the 14mm vs the 10mm, so I will make no change.
After the plug holes were blown out, I checked the plug wires for breaks or wear, then cleaned the ends with electrical cleaner spray (no flash or fire point) CRC, Part #02018.
When removing and installing plug number five, I found that I couldnt get the plug in or out with a spark plug socket or open-end wrench. The distributor bracket was in the way on the back side of the distributor. To remedy this, I took a cheap 13/16" spark plug socket and ground down the spark plug end on my belt sander until it would fit over the plug and beneath the distributor bracket, and then put a 3/4" open end wrench on the nut of the socket and the plug could be removed and installed with close, but enough, clearance.
The concern on spark plug work is not to under- or over-tighten. Over-tightening can damage the threads in the head and will distort the plugs inner gas seals, and under-torquing will not let the plug fully seal to the head and can cause pre-ignition and detonation. An over-tightened plug can also increase the plugs heat range, making it run hotter and possibly overheat the plug and engine. The above is for gasket typespark plugs as on our '37. The torque specs we use are for cast iron heads: 10mm = 7-11 ft/lbs, 14mm = 16-29 ft/lbs. The spark plug manufacturer recommends putting the plugs in dry, but we use thread seal and take our time to reach the above specs. The danger of the thread seal is the plug goes in easy and can easily be over-tightened. On a 10mm its finger tight plus ¼ turn more. On a 14mm, its finger tight plus ½ turn more. This is on cast iron heads and is just a general example. We always torque to factory specs and cast iron head plug torque is different from aluminum head plug torque. The '37 Super 8 manual calls for plugs to be gapped at .028. To install the plug, we always screw them in several threads with our fingers to feel that its not cross-threading, and then torque it down. With the plugs in and the wires back on, I got in, pumped the accelerator once to set the choke, and it started first turn and was smoothno misseswith a nice, smooth curb idle. Old plugs can many times be saved. Yes, it took me several hours, but I got to go through and check everything with a close inspection that I hadn't done in several years. I am glad that I took this extra time to go over everything so closely, because I did find something not related to the ignition system. It's being repaired now and it could happen to any car. Watch for the coverage of this in an upcoming issue.
There's nothing like fixing them yourself!
Keep 'em driving!
*Bill Hirsch Automotive Restoration Products, www.hirschauto.com, 800-828-2061