Packard Forum Index » V-8 (1955-56)

Thanks Jack ya know we live blocks away and I would love ya to hear my 400 and give me your thoughts.

The diameter of the spring affects the frequency. Larger diameter lower the frequency. That is why high performance motors have a smaller inner spring. By definition valve float is the pistons hitting the valves. It's not called valve smash because the contact forces are very small. The valves aren't getting out of the way fast enough and so the redline is set before the point of valve float. Exceeding the redline risks valves hitting the pistons. My guess it that Packard used the larger springs because they are quieter. When those motors are good they are very quiet.

Given that a Nissan Six can be hot rodded to 1000 horsepower or a Honda Del Sol four to over 600 I don't understand beating the daylights out of the Packard V-8. It's not a deep block so it has a lot of flex, the rockers need to be replaced with stamped steel, the lifters need to go out the window, the oil feed to number eight rod bearing is bad, and the carburetors and ignition need to be replaced with computer controlled fuel injection. Given the situation, my favorite Packard V-8 was always the 2bbl Clipper because those were the ones I saw coming in that were still original owner cars. Although up in the barn Charlie Clancy's 55 Patrician was sitting idle with 99,000 on the odometer.

By definition valve float is the pistons hitting the valves.

Tim, not that I'm well-read on the topic, but is that really the definition? After all, you can get valve float in a flathead engine where the valves can't hit the pistons. I would think a more correct definition of valve float is when the valves fail to follow the action of the camshaft profile on valve closure due to inertia of the moving mass.

Owen_Dyneto Quote:

Dave, that is a correct definition, particularly if you add that the failure to follow the cam profile is due to insufficient spring pressure above a certain RPM, a broken spring or some problem with the cam lobe. Also, on an OHV design engine it is ALWAYS the exhaust valve float that causes a problem because the piston is coming up in the bore just as the exhaust valve is returning to its seat. If there is valve float, the exhaust valve is "hanging out there" where it can be hit by the piston. This usually, but not always, bends the face of the exhaust valve, although sometimes it will also crack the piston top...both being a bad situation.

Tim Cole Quote:

The first part of your statement is true, but it is not why high performance engines have a smaller inner spring that is an interference fit with the ID of the larger outer spring. It's the interference which reduces or eliminates the harmonics of the spring pair through friction. A single spring (large or small) will have its own harmonic which at the right open/close frequency can cause some of the coils to contact each other. Ignoring coil bind at max lift (which would break one or more springs immediately upon initial startup), harmonic caused coil bind does not happen with interference fit spring pairs (or triples for that matter).

Craig

While we're this deep into the discussion of valve springs, I'd like to find out something I've wondered about for a while. According to my 1956 Motor's Repair Manual, the valve springs on all 1955 engines had 66 lbs tension and the 1956 all had 92 lbs tension. Is this correct? If so, one of my theories as to more "lifter noise/problems" on 1956 engines *could* be caused by the increased pressure, no?

WC, the Motor's Manual #s are rather incomplete, here's the ful data from the factory specs (both intake and exhaust springs are the same).

1955
78-86 lbs @ 1-3/4 (valve closed)
158-172 lbs @ 1-3/8 (valve open)

1956
87-97 lbs @ 1-3/4 (valve closed)
173-187 lbs @ 1/3/8 (valve open)

I can't address your question with any certainty but my own observation is that the 1955 engines were more prone to lifter/valve noise than 1956, but there are others who have far more experience with both year's engines and far better qualified to comment.

Here is what my handbook says: "Multiple valve springs are used where large lifts are required and a single spring does not have enough strength to control the valve." Call it what you want, but a single spring has one frequency and a second spring has another.

Suppose an engine is turning 5000 rpm. Each valve is then closing 2500 times per minute or 41.66666 hertz. Next suppose the degrees of rotation for closure is 30 then the closing time is 2 milli seconds. Suppose the spring can close no faster than 3 milli seconds, then the valve remains motionless for 1 milli second. In the time the valve is motionless the piston has moved approximately 1/4 inch. In an interference engine this is huge because the piston is moving toward a fully extended valve. A spring that requires less than 2 mill seconds to close is thus higher frequency because it can cycle more times per second. The old BSA motorcycles would rev high enough for valve smash with commensurate problems.

I think if the motor was converted to computer control it could be adjusted to produce around 500 horsepower (600 with nitrous). A modern Ford will tolerate that, but a lesser motor will explode. So that would be a good test of the unit.

Attached is a cutaway of a modern oil system. The old practices have been discarded. These old motors aren't engineered for those kind of results.

I like the engine for normal service. Once the basic problems are sorted out they drive very well. Even with the Ultramatic. I wouldn't be caught dead in a 50's Cadillac, superior engine and transmission notwithstanding.

But gee willikers, my cheap modern car will cruise comfortably at 100 mph, although if a deer jumped in front of me I would be a dead duck, so I don't that. I have a crack in my right front parking light from swerving to avoid a turkey buzzard at less than 55mph.

Attach file:

---

  (40.83 KB)