Re: Ping In 359 Engine

Posted by Don Shields On 2014/4/27 17:51:35

Responding to the most recent posts, I think the spark timing is set for the 327 engine, 6 degrees BTDC. The 359 spec. is 0 degrees, or TDC. With it advanced that much, with heated fuel and the centrifugal and vacuum advances working, it's advanced too far and results in pinging. Back when the head was welded and ground, I put a vacuum gauge on it and the needle was nice and steady. I don't have a reliable way of performing a compression test, but the vacuum gauge showed that there were no problems with cam timing, casting cracks or porosity, bent or sticking valves, low cylinder compression etc. The prior owner had the electrical system converted to 12 volt, negative ground, point-type ignition, so the spark is nice and strong. There is no backfiring, coolant usage, steam, or burnt coolant odor in the exhaust, so a headgasket problem is ruled out. The problem is an intermittent ping when accelerating under load, not a miss. The noise is a rattling sound similar to dice in a dice shaker.

The carburetor was overhauled three years ago by a rebuilder recommended to me by the local Corvette Club and I can't detect any problems with the carb's performance. The radiator had a half-dozen seepage leaks when I bought it. I took it to a trusted local radiator shop ant they fixed it and flow-tested it. The engine was running hot, I finally traced that to a too-low pressure radiator cap (6#). This cap was venting too soon and too often, dropping the coolant level too low to adequately cool the engine. The parts list shows a 6# cap is OK (not to my experience), but they also list a 12# cap. Couldn't find that, but I did get a 14# cap. That keeps the coolant level up, and now the temperature gauge needle doesn't go anywhere near hot. I installed a 160 degree thermostat when diagnosing this problem.

My repair stategy is this: First I'm going to retard the timing slightly as OD recommends. If that's successful, I'll cut out the octane booster and maybe the premium gas. If needed, then I'll look into the more drastic steps like sending the distributor out and milling piston heads. With this engine running as well as it is, and the booster mitigating the ping as much as it has, I just can't justify the more drastic steps at this time. Since the car travels less than 500 miles per year on average, it'll be some time before I'll know if the first step works or not; I usually only fill the tank twice or so a year. I do use Stabil Marine Stabilizer in the fuel.

I hope I've addressed all the questions; if not please let me know. Many thanks to Owen_Dyneto, RichK, JW, Tim Cole, Jack Vines, Ozstatman and packard1984 for sharing your knowledge and wisdom so willingly. I've learned so much and I'm ever so grateful to have information of this quality, breadth and depth virtually at my fingertips. It just goes to show you, even after more than a century, it's still wisest to "Ask the man who owns one."