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It looks like I may have spoke too soon about my success with the valves on my '51 200 Deluxe. Not that the valves aren't still quiet but another that I think must have been caused somehow by my work on the valves.

Wednesday I took it out for it's first drive. Before it was just sitting in the carport and idling for 10 minutes or so.

The car starts up fine and the only noise I hear sounds like someone holding several lengths of chain together and shaking them. As I drove away Wednesday, and as the engine got warmer, the idle speed increased until it was really racing if I put the transmission in Park or Neutral. By the time I got home the engine was trying to race so hard that I didn't dare to try to put it in the garage and just parked in the driveway and shut the engine off while the transmission was still in gear. After a few hours I figured the engine was cold enough that I could at least get it under the carport and did so but not before noticing that the earlier situation was beginning to repeat it's self. I've checked the linkage for binding and it's fine. The automatic choke assembly was a little loose so I tightened that up but it made no difference. I figure it has to be something that happened to the carb during the valve work but don't know what it could be. During that, I didn't attempt to lift the head off the engine but sort of set it on it's side on top of the exhaust manifold. I checked the linkage with the parts car and it looks the same to me - no bends or anything. I checked the wiper vacuum system and it's all intact and plumbed correctly. Before the valve work it did seem like the auto choke was hanging up a bit but nothing like this. It almost seems like a vacuum leak but I don't know where it could be and I've never had anything like a manifold vacuum leak make an engine race so fast. The fact that the RPMS increase as the engine warms up has me stumped. In fact, the whole thing has me stumped.

I need all the help I can get on this one, please.

Hard to understand how an engine can gain that rpm unless the throttle plate is opened and additional fuel is being fed.

Sounds classic bass ackward. You got something on up side down that's supposed to lower the idle as it warms. Like the thermostatic spring. Retrace your steps of what you did and recheck it against the manual or diagrams. Otherwise, it's a fuel leak or float dumping fuel in uncontrolled. You'd get a black sooty tail pipe is that's going on.

It seems like a fuel delivery issue. Has the carburetor been rebuilt lately? I'm just questioning the float, jets, float needles and seats, or metering needle/rod. There were several times in the past when I had removed an intake and the carb sat empty of fuel for a couple of days. I'd end up pulling the float and needle, then backing out the metering needles a bit before resetting them. Everything would be fine as long as gasoline remained in the carb to keep the seats and seals moist.

Is the throttle return spring worn or weak?

Ross has mentioned rubber bushings or washers on the upper firewall accelerator linkage mount that have frequently self destructed and caused issues. Any chance something there could be binding and not letting the linkage return to fully close the throttle.

Get the motor in the racing condition, shut the key off, and look at the carburetor linkage. Maybe the choke is together backwards and going on fast idle as the motor warms up.

Just a thought:

When you set the head up on the exhaust manifold, it might have leaned up against the side of the carb linkage, If so, this could've bent the linkage around the idle speed set screw. Bending can crank up the engine speed and not show much skew at all in the linkage. If the pressure against the linkage at that point was great enough, it could also have bent the throttle shaft. That condition may only affect it when the throttle plate warms up or the shaft twists a bit while your driving, as you describe. (More on that below.)

If it was me, that's where I'd start looking, right around the area where the linkage meets with the throttle shaft. It might be something pretty simple.

Rather than driving the car, just let it run with the hood up and air cleaner removed, then blip the throttle until it sticks, and have a look. I don't know what your definition of "runaway" is, but if it's too extreme, you can ask a friend to work the accelerator for you. Or, you could just move the linkage yourself and have a friend ready to shut off the key if things get too hairy.

Good luck.

Owen,Fish n' Jim, Howard, Tim, '55 Packard Guy, Packard Illiterati - I'm sorry for having apparently tossed this out and left everyone hanging. Not to mention not acknowledging the help that was offered by you all. In my defense, we had a pretty good blow in Portland Saturday afternoon - even a tornado touching down in the area. While keeping the lights on, I lost my Comcast line thus ending my TV, Phone AND Internet Service. Comcast "forgot" one appointment but finally got out here today - service restored just 15 minutes ago.

Having no TV, phone or Internet meant that I had a lot of time on my hands uninterrupted. Except for being cut off from this website after asking a question, it was kind of nice.

But, back to the Packard. The only thing that was disturbed during the valve job was the head and valve train. Didn't open or fiddle with anything else. During reassembly I did notice that the left side accelerator linkage bracket was loosed at it's joint so I did switch the bracket from the parts car so Howard's suggestion of a linkage problem could be part of it, I found that I could, with a little effort move the carb linkage forward over a little "hump" to a more fully closed position thus bringing down the RPMs close to normal. The thing is that the car ran very well - noisy, but well before my "Valve Experience". When I disconnect the linkage from the carb, the linkage moves freely with no binding anywhere so I don't think the linkage is a problem and I was careful to note which part of the linkage on the passenger side went where when I was taking it apart Plus I had the parts car to guide me - at least in the beginning.

There was a moment after I had balanced the head on the exhaust manifold when I thought the head was getting away from me and so I grabbed it with little thought of doing possible damage. This is a long way of saying that I think that '55 Packard Guy may have something when he talks about bending things that shouldn't be bent - more or less supported by my finding that the throttle was binding just a little.

I think my next step will be to take off the carb and see what the throttle shaft looks like compared to the one in my parts carb. I probably won't get to that until the weekend but I may be able to grab a few minutes as I know it won't take long.

Once again, my very belated thanks to Owen, Fish n' Jim, Packard Illiterati, Tim, Howard and '55 Packard Guy for helping me figure this one out. I was really disappointed when, thinking I had the car pretty much sorted only to find a brand new problem - but I guess
that's the Hobby!

As soon as I have the carb off and sorted, I'll let everyone know.

One interesting thing is they list different versions of the linkage. Probably something to do with the transmissions but there are several combinations so unless the parts car is identical maybe something to look into.

Perhaps someone can explain the difference in the long and short rod versions and save the trouble but if not, and it was a rod that you changed it might be worth a careful comparison of what is there now with the item removed to see if there are any length differences. Could be a different version piece won't let the throttle close properly.

I've had the throttle cross shaft that runs over the engine break on me.
Also, I've had the accelerator pedal stick on the floor board when the floor was rotten.

I would disconnect the throttle linkage at the carb and work the throttle by hand and see if the runway problem persist when the holding the throttle on carb is on it's stop. If it does, then it's a carb issue. If it doesnt, then its a linkage bindage issue/alignment/adjustment issue.

Simple test and it will at least let you know where to be looking.