'56 Century woes

[JohnD1956]

I remember precisely. It was rush hour, on a cool fall evening. It was nose in, in a parking spot. I started the car and was running it at a fast idle to warm it up when I saw an opening to back out. Without stepping down the idle I pulled the shift to reverse. There was a loud bang and reverse was toast!.  

[JohnD1956]

Since I have had my current 56 I will start the car and let it run about a minute to pull the choke off, then step down the fast idle untill it sounds like it is running around the 600 rpm I have it set for. Then I pull the selector into each position and before shifting from low to reverse I release the parking brake and as I pull it into reverse I let up some pressure on the brake pedal. In my car that stops the loud clunk and provides the smoothest transition to reverse.  I also make sure to tell the mechanics who do work on it about this because I plan to hold them responsible if they drop that strut. 

 

Supposedly, in some cases that strut can be replaced without dropping the transmission.  But I never tried to do that myself. 

[56Twotone]

Well thank you for telling me. That's one more entry on my list of paranoias. I knew the Dynaflows generally had a hard shift into reverse, evidenced by the sets of little tire marks in the garage. I've also heard some anecdote about Centuries having a more robust transmission variant than the Specials, don't know if that's true but I hope so, as I've heard a few horror stories. Thanks for the tip about shifting, I'll pick up that habit.

 

You say you step down the fast idle, how do you do that? My impression was that the automatic choke was the sole system that controls the fast idle cam.

 

Speaking of which, I'm just about to start the car up and verify that the vacuum choke is working as it should. Turns out that that stripped-out vacuum fitting wasn't actually threaded in tight. I Teflon taped the everliving crap out of it, so maybe now it works better and shuts that fast idle off. The choke definitely opened up last time I had it out, but maybe not enough to drag that cam back.. didn't think to visually check it, either. We will see.

[JohnD1956]

I can't explain how to adjust it, but mine seems to work as designed.  Cold it sets the choke which pulls the fast idle cam into place.  But when it first starts I have to keep pressure on the accelerator to prevent the initial "cold stall".  That may mean an idle speed around 1700 rpm for a half minute, then I can slowly let off the gas and it sounds like it runs around 1400 RPM.  After a minute I tap the gas pedal and it will drop.  If it's really cold out it may take an extra minute to finish stepping it down,  but I don't shift it into any gear till it's idling at the 600 RPM level. 

[JohnD1956]

2 hours ago, 56Twotone said:

I Teflon taped the everliving crap out of it,

I teflon taped one of those once. I leave the new one as it was built.

[56Twotone]

Idle is better! It turns out the idle stop screw was screwed all the way in to max idle, and even then it wasn't actually contacting the tongue on the throttle cam, because some screw on the throttle cam was incorrectly adjusted and butting up against the fast idle cam, keeping the valve open. It's hard to explain, but below is the picture of that screw, after adjustment. When I looked at it beforehand, it was catching on the leftward edge of the cam and holding the throttle open just a bit.

 

After that, I loosened the idle stop screw by ear until it sounded about right. It's probably idling a smidge high still, but this is where it's happy right now. Below is a video of a semi-cold start, and yes I do have to address the starter. You can hear towards the end that I'm still getting a little stumble on sharp acceleration off idle. I would have thought this to be the accelerator pump, but I pre-oiled the leather and it was building pressure quite well the last time I checked it. Before I thought the timing might have been too advanced, now I'm wondering if it being retarded could cause that issue... still no luck on finding a timing light to check. I am not a perfectionist with many things, but as long as this car doesn't run perfectly I won't be satisfied.

 

 

Of course, like a dolt I forgot to really snug down the carb bolts until a few minutes ago, so on new gaskets it's possible I wasn't 100% airtight between the air horn and manifold. I did also double check that the power piston and accel. pump were moving freely, which seems to be the case.

 

 

After that video, I wiped off the dust and took some photos. It cleaned up extremely well; the paint is excellent bar a few scratches, and the chrome + stainless has a couple dings but is overall very good. No dents or rust whatsoever in the body. According to an invoice I found, the black paint is original and the white on the outer body is a 1990 repaint with original pigments. The newer paint is far nicer than what remains from the factory. There are spots of bubbling and a couple other defects in the roof, not obnoxious but visible if you look. The '50s quality control adds authenticity. One of the whitewalls gave out after 35 years of service, so it got replaced with a used truck tire. The car definitely deserves new tires altogether, but I need to figure out what brand & thickness of whitewall I want. Maybe something a little healthier than what's on there, like 2.5-3".

 

As I was pulling into the garage I noticed that both headlights, one tail light, and one blinker had completely ceased to function. Hopefully these are just burned out bulbs, because I already dealt with that headlight switch once and I don't want to do it again. Honestly though, I am very happy with the results so far. I didn't expect my first time rebuilding a carburetor to be this successful, but a lot of credit is probably owed to the ultrasonic cleaner. It's cathartic to be able to get in and have it fire right off, even with the sketchy starter motor and modern gas (no ethanol.) I like the idea of keeping this thing as original as possible, so I don't want to throw in a modern unit. Hopefully the old one just needs lubrication, but I suspect getting to it will be a pain.

[rocketraider]

With an exhaust note like that, daresay you could make a Mustang think twice. I think it could be described as "sinister"😈. Not that the typical Mustang owner would even know what a Nailhead is...

 

Keep fine tuning. And don't forget the timing light next time you go on the Shore!😁

[KAD36]

Stock (worn) exhaust or something different?

 

 

Edited March 17 by KAD36 (see edit history)

[56Twotone]

Glass packs, I was told. As I look under there, the passenger's side is a bright blue and the driver's side is tan-ish and looks quite a bit older. I was wondering why the left exhaust sounded a little different than the right. I do like the sound though, and the Century does have some "sporty" pedigree so it doesn't feel entirely sacrilegious. I think it was the work of the previous owner in Colorado, or perhaps whoever owned it before they bought it in '81.

[56Twotone]

I think vapor lock might be part of the issue. Immediately after a cold start the car runs great with no stumble on acceleration. After a couple minutes the stumble makes an appearance under sharp throttle when stationary, or when put into gear. I just now had to let it cool down for 15 minutes before it would fire off. Other than that, though, it is running very smoothly.

 

 

 

I need to change the coolant and maybe try to get into the freeze plugs. I doubt that job has ever been done, and even with a rebuilt radiator + water pump and new coolant, it looks very brown under the rad cap. I believe the capacity is ~5 gallons and I have 3 handy, so that will be a job for next time. The engine stays pretty cool with a 160° thermostat, but hopefully a flush will end up meaning less heat inside the engine bay. I don't want to have to run a vapor-separating fuel filter or whatever other bullbird.

 

 

I leave tomorrow so I think I'm about done fiddling with the car, but it drives great and will start right up from the pedal so I am happy. Next time: a coolant flush, tuning, bulb replacement, and maybe tires so I can do a little cruising.. although I keep having to remind myself that that master cylinder is running with original 1956 leather cups and gaskets. Yikes.

[avgwarhawk]

Has the carb been rebuilt with new accelerator pump? 

[56Twotone]

Yes, that was just done a couple of days ago. I oiled the leather and let it swell inside the pump chamber; it built pressure very well when I put it together. The pump circuit seems to work fine after I start the car, but the engine bay gets real hot fast.

[Ben Bruce aka First Born]

6 hours ago, 56Twotone said:

Yes, that was just done a couple of days ago. I oiled the leather and let it swell inside the pump chamber; it built pressure very well when I put it together. The pump circuit seems to work fine after I start the car, but the engine bay gets real hot fast.

 Does it have the original exhaust manifolds or headers?   Headers, being thinner, release more heat .

  The engine will like a 180 thermostat better. 

 

  Ben

[56Twotone]

The manifolds certainly look to be original, but I will double check in a moment. Thanks for the info, next time I come down I'll bring a 180° and see what that does. I was told by the other guy who worked on the coolant system that it overheated with a 180°, but again that coolant doesn't look like it's performing as well as it could. And it still overheated with the 160° until I rebuilt the carb. How much of a pain is it to get to the freeze plugs with the engine in place?

Edited March 18 by 56Twotone (see edit history)

[EmTee]

18 minutes ago, 56Twotone said:

And it still overheated with the 160° until I rebuilt the carb.

Sounds like it was running too lean; probably due to all of the accumulated crud...

[Ben Bruce aka First Born]

Remember!!   The thermostat ONLY controls the minimum temperature, not the maximum.

 What is overheating, the engine or the coolant?  If you are saying the coolant is heating above 220 or so going down the road  AND WILL NOT COME DOWN,  you have radiator [ the coolant cooler ] problems.  If coolant  stays cool at road speed, but overheats in town low speed driving, you have air flow [ fan? ] problems.

 

  Ben

[old-tank]

1 hour ago, 56Twotone said:

How much of a pain is it to get to the freeze plugs with the engine in place?

HUGE!...even with a proper tool.  Unless the plugs are leaking you will not fix the problem with all that work and aggravation.

[KAD36]

1 hour ago, EmTee said:

Sounds like it was running too lean; probably due to all of the accumulated crud...

^ that plus check for timing retarded (I.e. late timing) when you get your timing light…a couple degrees of advance usually helps with cooler running.

 

I had a shop instructor once tell me that he could hold onto the #1 wire and when the coil fired he would blink his eyes to time an engine.  He is probably not teaching any more.  Just goes to show you there is no place for not listening to your own common sense.  I remember my friends saying “ I’m not gonna try it, you try it”.  🤣

[56Twotone]

Nothing actually overheated after the carb was rebuilt, the temp gauge stayed in the green and only ever slightly rose towards "H" after lots of idling.  My concern is that the engine bay itself might be getting too hot for modern gas and causing vapor issues. I did save the old carb gaskets in case double-layering them between the air horn and intake manifold would help, but I'm not sure if that's just an urban legend.

 

The coolant that's currently in there is relatively new, but quite dirty, so in all likelihood it is not functioning as well as it could. The water pump is new and the radiator was shipped off to be rebuilt. Whatever crap that's floating around now came out of the block. I'll change the coolant and take it to a shop for a real flush when it's back on the road, just so I know nothing's going to dislodge and clog the rad.

 

Of course, my theories are all just guesswork, since I wasn't able to verify dwell, vacuum, or timing.. Next visit I'll bring my bucket of harbor freight diagnostic tools and really get it nailed down.

[old-tank]

10 minutes ago, 56Twotone said:

My concern is that the engine bay itself might be getting too hot for modern gas and causing vapor issues.

Not vapor lock since that only occurs on the suction side of the fuel pump.  Maybe carb boiling over or percolating and there is no cure other than fuel injection.

[56Twotone]

3 minutes ago, KAD36 said:

when the coil fired he would blink his eyes to time an engine.

Holy schiz, that must have looked like wizardry. I am having a lot of fun figuring things out. With the modern vehicles I usually work on, you just sort of toss parts at the issue and hope the error codes clear. The Buick certainly requires a different mindset and a lot more ingenuity.

[56Twotone]

3 minutes ago, old-tank said:

Not vapor lock since that only occurs on the suction side of the fuel pump.  Maybe carb boiling over or percolating and there is no cure other than fuel injection.

Ok - still learning all the terms. I'll make sure the timing and carb adjustment is right before I worry about that. Whatever the case, I think I'd just live with it before fuel injecting such an original car.

[carbking]

41 minutes ago, 56Twotone said:

 I did save the old carb gaskets in case double-layering them between the air horn and intake manifold would help, but I'm not sure if that's just an urban legend.

 

 

Not only is using thicker gaskets than recommended by the manufacturer to do some good being an urban legend; IT CAN CAUSE ACCELERATED WARPAGE OF THE CASTINGS!

DON'T DO IT!

 

Jon

[56Twotone]

Thanks for telling me, I'm glad I didn't try it. Is the same true for carb spacers? I look at Corvette boards for info on the WCFB, and I'm seeing that many owners cut spacers from cork, metal or phenolic board to keep heat off of the air horn. I will try to bring a laser thermometer next time too, to see what temperature the bowls are actually reaching.

[carbking]

42 minutes ago, old-tank said:

Not vapor lock since that only occurs on the suction side of the fuel pump.  Maybe carb boiling over or percolating and there is no cure other than fuel injection.

While not guaranteed as a cure, there is something that may be tried:

 

In the 1930's, Packard fabricated a sheet metal shield insulating the carburetor bowl from the exhaust manifolds. As I recall, there was maybe a 1/4 inch insulating air gap between the sheet metal and the bowl. I don't think I still have one, but maybe one of the Packard folks would post a picture.

 

Jon

Edited March 18 by carbking (see edit history)

[rmartens]

Does it sound like there's a slight exhaust leak under the hood?  At the start of the video it sounds like my '56 Century does, and I know my exhaust crossover on the bottom side of the intake manifold needs addressing.  Otherwise, even the exhaust note sounds similar to my Flowmasters.

[carbking]

6 hours ago, 56Twotone said:

Thanks for telling me, I'm glad I didn't try it. Is the same true for carb spacers? I look at Corvette boards for info on the WCFB, and I'm seeing that many owners cut spacers from cork, metal or phenolic board to keep heat off of the air horn. I will try to bring a laser thermometer next time too, to see what temperature the bowls are actually reaching.

A phenolic spacer would tend to reduce heat to the throttle body, not the airhorn. As the throttle body is directly connected to the bowl; there generally is some reduction of heat to the bowl.

 

Metal would not reduce the temperature, but acts like an increase in volume of the intake plenum. This MAY add a minute amount of power at wide open throttle. Spacers in general, especially those over 1 inch, can worsen idle characteristics.

 

I would not think cork would be of sufficient physical make-up to be used for a spacer. Hard wood is often used.

 

Jon

[KAD36]

7 hours ago, 56Twotone said:

Holy schiz, that must have looked like wizardry.

Yeah that was the second or third word that came to mind LOL. Power Technology 102.  
 

In his defense he did teach us to use a matchbook cover to set points when in a jam, so not all screws were loose.

[56Twotone]

Hah. I guess it's only wizardry if it works. Otherwise you're just a crackpot.

 

I have no shortage of hardwood and wood tools, so next time I can make a spacer if need be. I doubt they sell WCFB-specific patterns.

[56Twotone]

9 hours ago, rmartens said:

Does it sound like there's a slight exhaust leak under the hood?  At the start of the video it sounds like my '56 Century does, and I know my exhaust crossover on the bottom side of the intake manifold needs addressing.  Otherwise, even the exhaust note sounds similar to my Flowmasters.

You know, I was thinking I heard a little more raspiness under the hood than would be considered normal, even with the air cleaner on. I didn't think to look into it since I was preoccupied with the carb. My daily driver Subaru has a rotted out flange before the muffler, so admittedly I'm a little numb to loud exhaust. That boxer 4 banger is not nearly as pleasant to listen to as the 322, if you can imagine.

[EmTee]

On 3/18/2023 at 11:37 AM, 56Twotone said:

Whatever crap that's floating around now came out of the block. I'll change the coolant and take it to a shop for a real flush when it's back on the road, just so I know nothing's going to dislodge and clog the rad.

Install a knee-high nylon stocking in the upper radiator hose.  Poke it into the tank, slip the open end over the hose nipple and clamp it under the upper hose.  It will catch any flakes that are exiting the engine before they can plug up your radiator core.  Check the stocking after a few hundred miles to see how much crud is being shed by the block.  Once the stocking stays clean you can remove it, although leaving in is cheap insurance...

 

 

14 hours ago, 56Twotone said:

You know, I was thinking I heard a little more raspiness under the hood than would be considered normal, even with the air cleaner on.

I believe there's a core plug on the bottom of the intake manifold that can rust-through and let exhaust leak from the crossover used to warm the carburetor.