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

That's a very good question. I, for one, really don't know. I suspect that shaving or milling the combustion chambers might weaken the casting making it much more prone to cracking, especially with aluminum heads. I imagine those design engineers specified the casting thickness to be thick enough to withstand combustion pressures yet thin enough to permit adequate cooling. Changing their tolerances might not be a good idea. Thankfully I didn't encounter that problem with my convertible.

Hi Don:

I dealt with a pinging 359 that was always running above the middle of the temperature gauge. I installed a premium 160F thermostat with two 1/8 bleed holes to prevent water pump cavitation.

On that motor I would definitely consider milling the pistons to reduce compression. If the motor has been bored oversize the compression will be even higher.

For your car I would send the distributor to a rebuilder with a Sun Distributor Machine to assure the timing isn't floating around.

Another thing, those radiators are inadequate. Given the car doesn't ping in cold weather I would look into an oversized radiator core.

The timing marks are essential and unfortunately Packard did a lousy job stamping those dampers. I used to spend hours on some cars taking paint off and carefully highlighting the dampers to do the timing. The cars always ran better. Don't let anybody tell you they can time a car with their ear. That is baloney.

Finally who knows how far off those old carburetors are running. A five gas analysis might help isolate a lean condition especially if the car is put on a dyno. Using a scope of the dyno is even better because if the car is running lean it will show on the waveform. If only one or two cylinders are pinging that will show up as well. However, nobody uses scopes anymore except me and I'm in Detroit doing secret stuff.

Hope this helps.

I am thinking about crescent shaped cuts like are done on the tops of pistons for valve clearance in OHV engines. Probably would not take much to provide enough c;earamce so the valves would not contact the chamber.

(o{}o)

I have a couple questions and a couple possible answers. When you say 327 timing set I assume you are talking your timing gears and chain? In this engine you would ideally be somewhere in the area of 4 degrees advanced on the cam timing to be good (good performance that is) did you check the cam timing on the engine? It is possible you are one tooth off that would cause a backfire and/ or a miss.

With spark timing you can honestly make a timing pointer bring the engine to top dead center and make a tab that points to the 0 mark on the balancer or make one that points in a convenient location to check the timing and mark the balancer in that spot trust me it will work, race engines often have adjustable timing pointers.

When the head was repaired was it pressure tested? I have welded up then pressure tested many OHV aluminum racing heads only to find a pin hole or two that needed to be rewelded, that could cause a "miss" that feels similar to spark knock.

Have you run a compression test on the engine? This would tell you if you have a dead cylinder (blown head gasket or possible crack somewhere) and it will give you an idea if your compression is off the chart, 170ish PSI would be good anything over 200 PSI you probably have to much compression.

A bent valve will give you a miss and it it is slight it will still run slowly but when you put your foot into it it will get worse.

You don't want to modify the combustion chamber to much, the 54 head is the best designed chamber for the Packard line and one of the best combustion chambers in any flat head. You need some clearance over the valves to get good flow but the aluminum is not thick in that area.

A thick head gasket will reduce the quench on the engine and you will lose a lot of performance run stock thicknes. Flathead engines don't need a lot of spark lead so minimal if any spark advance.

You stated that the octane was around 109? This engine doesn't need anything that high. Remember higher the octane the more resistant the fuel is to igniting, that is why you can throw a lit match into a bucket of diesel and it will likely not ignite. I have friends with racing Ford flat heads that use 100 octane unleded aviation fuel, and that is with a 12V MSD ignition system with a lot of spark advance and compression.

Are you running a 6V ignition and points? There is a good chance that with the super high octane and a weak ignition system (say what you will but 6V ignitions are very weak) your flame is going out or firing inconsistently. Again good chance that this could cause your problem.

Did you use any sealer in the head gasket? With old aluminum and cast iron you get a lot of expansion rate difference and that puts a lot of strain on the head gasket their is this thick tar like sealer that is (was?) used in the aviation world, cant remember the name but might want to look into it.

The Hudson racers use to have head gasket problems with their aluminum heads back in the day and they would take a center punch and put a ridge around the combustion chamber, for them specifically around the valve area, it was like an early form of an O-ringed block/ head that you see today in race engines.

Quote:

Will a 359" pump 170#? More than 200# is OHV8 race car territory, can't be driven on today's pump gas.

jack vines

I would think that would be the upper limit. I have had 302 Ford street engines at around 9:1 CR in the 190 PSI range. These days a decently warmed over hot rod street engine runs about 200 PSI. You want to back off cranking compression on a heavier (over 3200ish LBS) car roughly 10-20 PSI and 10-15 if the engine is detonation sensitive which fatheads are, their are several more factors low octane gas, hot running ect but they don't really seem to be a factor in this case. So considering a 200PSI ideal and backing off 20 PSI for the cars weight and 15 PSI for detonation sensitivity you would be at 165 PSI and you would have some plus or minus wiggle room.

"I have had 302 Ford street engines at around 9:1 CR in the 190 PSI range."

With atmospheric pressure being about 14.7 PSI, wouldn't 190 PSI be considerably more than 9:1? The 359's are, I believe, over 9:1 CR, so can any 359 owner provide advice on what compression tests on a new or rebuilt engine show?

The cranking compression and the compression ratio are slightly independent of one another. Cam specs, rod stroke ratio, rod length, combustion chamber design, and probably some things I'm forgetting all play into cranking compression. You can have two 302 ford engines both with 9.1 static compression ratio and depending on the internals the cranking compression could be way off of one another as would their octane requirements.

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."

Have you reviewed this thread? You might want to make contact and get the details of how he solved the problem.

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