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

What are the compresion readings on all of the cylinders????
What are u calling low compression?????
What is spec for optimal compression????

remove all sparking plugs. Knock guts out of 1 plug, thread for hose shank, install hose on shanke and install tool into offending spark plug hole. Bring offending cyl up on tdc and blow air/smoke thru hose to see/hear where it exits engine and reportback.

Did u inspect cam lobes to be sure they were not worn nearly round??????

U sais head was milled. WHY??? How much was it out???

Were the head bolt washers seats spot faced parallel to the new milled surface of the head. I'll go ahead and answer that question now: NOooo!

Do u ahve the OLD head gasket????? Inspect it closely.

FIRST, do the hose routine as outlined above. Watch for smoke and listen for air. Watch for smoke comming from other spark plug holes too. Report back.

Packard V8 asks the good fundamental questions for a good diagnosis.

Let me add one more. If the head was milled, did you check for sufficient valve clearance within the combustion chamber before you put the head back on? VERY important. If you didn't and the head was milled excessive, or more likely had already been milled once before and there isn't enough clearance, just a revolution or two of the motor will be enough to bend the valve heads by hitting the inside of the head, and also likely wear the heck out of the camshaft in fast order.

There are several ways to make the determination about sufficient clearance, if you think this is a possibility let us know and I'll give you the several methods I've used over the years. There are also several solutions to the problem.

Compression ratio on this engine is 7.00/1, so you should look for cold compression values in the range of 105 psi, done with all plugs removed, throttle and choke valves held open, and cranking each cylinder to at least 3 compression strokes.

The saga ends.

First, thanks to O_D and PackardV8 for your input. It is really appreciated and it's now in my notebook for use when I tackle the '41 without benefit of a mechanic.

The problem was partly mine in being "penny wise but pound foolish". I went into this with only the goal of fixing the dreaded super loud TICK TICK TICK noise. I was very hesitant to replace any parts that didn't 'need' replacing because of budgetary concerns. As a result, old valve springs were put on new valves. This was the cause of all the problems. Using the old springs on the new valves caused them to hang open. I feel kinda foolish admitting we did anything as dumb as re-using the old springs but if it prevents anybody else from attempting the same thing then feeling foolish is ok.

Today we replaced all remaining old valves with shiny new ones, re-checked to ensure that the clearance on all valves was exactly the same and measured with the pistons at TDC. Installed 16 new springs and valve keepers designed for use with the new valves. Disassembled and cleaned all the hydraulic lifters one at a time as described in the manual. Basically, we did what O_D recommended and did a complete, proper valve job.

After we put the head back on for the 4th time... I sent a small prayer heavenward and stepped on the gas. The engine caught after one rotation and after the lifters pumped up it ran as smoothly as whipped butter.

All's well that ends well.

Glad to hear your Packard is back on the road with a little "spring" in it's step!

JD,

I believe that "budgetary constraints" certainly are a consideration for most of us here. But in the end your Packard's back to running well, so congratulations. And as you've already experienced you wont be alone when you tackle the '41, with the resources of Packardinfo at your disposal.

Measure the SHORTEST of the old springs. I'd like to know what that measurement is.

Set all of the old springs on a smooth flat surface all bunched together in a tite group and visualy inspect them to see if there is wide variation in the height of the springs or just among a few of them and let us know.

Glad to hear your problem has been resolved and a tip of the hat for coming back and telling us that some of the problems was of your own making. It is easy to take bows when something goes right - more difficult to admit mistakes were made.

I second Randy comment on admitting to your mistakes> I know I have made more than I care to remember. As I was told when younger if you haven't made any mistakes you haven't done anything. Mistakes are part of learning. If you pass on your errors and post them here someone else can be saved the same or similar. Takes a big man to admit to small mistakes

Comparing the height of the valve springs to one another is a good idea. You may find one that has fatigued and collapsed somewhat. Who told you that you need new springs on new valves and that that was why the valves hung open? Your mechanic again I presume. Probably the reason the valves hung open was because the valve stem to valve guide clearance was not correct. Again your mechanic should have measured the clearance before he buttoned up the engine. I have had done and have done myself many valve jobs including ones where valves were replaced with new ones and have never replaced a perfectly good spring. Racing engines for sure but not a freeway car.

Valve spring failure, while not unknown, is pretty uncommon in these low-stressed engines. Anything is possible, but I wouldn't discard the old springs or even necessarily assume they were the problem; they are often not replaced even by top-notch engine rebuilders unless tested and found understrength. Over the years there have been occasional bouts of lousy quality replacement springs, I'm thinking back to some years to the double-helix springs for the prewar Eights and Super Eights,; for a period of time most everyone that replaced them had tne new ones break and then were ready to kill for the ones they had just discarded. Test them yourself, or have them tested and if OK, keep them.