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

Hey gang. Not really a major issue here, but would love to trouble shoot. The car is a 1950 Super Deluxe Eight, 327, Ultra, Carter 643s carb (rebuilt a couple years ago), mechanical pump pumping around 3.75 psi at idle, float height verified 3/16" per the Daytona instructions, distributor recently rebuilt...

Compression on this engine is lower - around 85 psi front to back. Head gasket replaced recently, valves lapped, lifters cleaned, but original valve guides and pistons/rings.

The car generally does everything it's supposed to it. It runs smoothly throughout the powerband, idles well, runs maybe slightly warmer than center on the gauge, 40 psi for oil at cruising speeds; around 10 at idle.

But, in the two years I've owned the car, I've never tried to wide open throttle the car from a dead stop. I've eased into it before, get sort of a running start, which has always yielded mixed results (although tonight it worked beautifully). Timing is around 10° (this was the advice from Advace Distributors, who rebuilt my IGP).

But from a dead stop, nothing to WOT, the car basically dies. No bogging, no delay, iust... total knock out. I take my foot off the pedal, it comes back, and I can continue. I typically ease into the accelerator and go about always down, which is about good to keep up with the traffic my neck of the woods.

I know she isn't a race car, and I most definitely don't want or need it to be. But I'm mainly curious here (because I was surlrised) - should it respond in some meaningful way from idle to WOT? Or is that just generally something you don't do with these cars. Like I said, it's 74 years old, but I figure it's better when all the systems in the car are working the way they're supposed (assuming this isn't normal). Thanks, all!

Come on Joe, do you think an owner showing off his new Packard to the neighbors would have accepted a car that could not take wide open throttle? The thing would have been back at the dealer with a loud complaint the next morning.

If it does it the instant you quickly give full gas, then likely the accelerator pump is not doing its job.

If it does it after a couple moments of full gas accel, then the fuel pump is not keeping up.

What happens if you give full gas at say 20 mph?

It sounds like your accelerator pump is not doing its job adequately. If your metering rods (if present) are adjusted a little too lean, it could contribute to the problem. A vacuum leak anywhere could also contribute to it, But the accelerator pump function and adjustment is the most likely problem. The engine should respond readily to the throttle.
Another possible contributor is a choke set too lean, or a stuck or missing manifold heat valve. Those 2 issues usually diminish when the engine is fully warmed up.

Hahaha, got a good chuckle on that, Ross...

Got it figured out (sort of). The pump adjustment was off, closer to 9/16" stroke; brought it down to 7/16". This almost immediately solved the issue of the stall at WOT, but still noticed it just being a little, I'm not sure... lazy I guess, so now I go back to timing (because what else could it be). I stuck the light on it and it showed the 10 degrees I would've expected. But just for fun, I brought the timing up until it the engine started to stumble, and backed it off. I tried to put my timing light on it, but even messing with the advance adjustment on the light, I couldn't determine to what extent it was now advanced, but certainly flashing inches away from the marks on the balancer. Either way, it seemed responded well to this adjustment without discernible "pinging." So I can only assume that the timing was retarded.

So while I got the result I was looking for, I'm also confused. The harmonic balancer was rebuilt maybe six months ago, and it has NOS timing gears and chain. I'm relatively certain the marks on the gears were aligned when I installed them, and they went back on their respective keyed shafts without much fuss. Possible that the balancer was rebuilt incorrectly, or are there other reasons the engine would seem to want so much advance? Thanks, guys!

Thankfully it sounds like a bit of adjustment was all that was needed. My 400 was the same way when I got it, though I suspect it was done to compensate for a sticking check inlet valve. After clearing the valve during my rebuild I tested the accelerator pump operation before I stuck it back on the car and it seemed fine. Though I’ve never driven it full throttle so I can’t say for certain

I doubt your timing chain is off. You can check the timing marks on the damper by putting # cylinder on TDC to see if the timing marks are correct. In some cases, the timing mark pointer may be different on some models than on others.

*sigh* I think it was largely my fault in not having the idle set correctly (again). I got it nice and hot, brought it down to 375(ish) in High, worked through the huffing and chuffing with the idle screws, and rechecked the timing. Everything was back on the spectrum. It wasn't THAT fast, maybe 475(ish), but seemed to be enough to bring the advances into play. Will get to road test tomorrow, but I think it's probably much closer to where it's supposed to be. Thanks, all!

Some engines require disconnecting and plugging the vacuum advance to check timing. I don't know if that applies to your car.

Overdrive kick-down switch? It kills the engine at full throttle but is supposed to so so only momentarily to allow the solenoid to release. A bad solenoid can cause it to kill nd stay off while holding down the throttle.