Won’t keep running down street!

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Jim G
Posts: 41
Joined: Sun Jan 05, 2020 1:25 am

Won’t keep running down street!

Post by Jim G »

Well- TBird purchase all done. Still having problem with wanting to act like running out of gas while driving 2 to 4 miles and motor just coughs abit and dies. Have replaced old rusty gas tank and inline filter back by tank- flushed out lines and installed new fuel pump. Would get Air bubbles in glass fuel filter bowl in line between pump and carb. Replaced fuel filter and clamps inline back at new tank for better fit. Air bubbles mostly gone now- when quite- there is a 1/16-1/8 inch of airspace at top of glass bowl filter. Could gas tank old filler/vent cap be bad? Car had sit for a period of time between drives— think carb sticky things -floats- etc stopping fuel from filling bowls and going empty and stopping? After it sits for awhile and cranks abit car starts and will sometimes run on road for a mile or so then starts coughing and dies. Put in neutral coasting and sometimes restarts but only goes few more feet and dies.
Anybody suggest a good carb exchange TBird store? I have a few recent catalogs $$$$!
When starts it is never flooded like ignition problem. No gas smoke. Just like starves for gas!
Help!!! J G

T-Bird Bob
Posts: 32
Joined: Fri Aug 10, 2018 11:00 pm

Re: Won’t keep running down street!

Post by T-Bird Bob »

Hello Jim,
Sounds like a sticky needle valve to me, I had the same problem. Just replace that with a new one that is suitable for alcohol fuel (any new one is).
I got my carb parts here:

https://www.carburetor-parts.com/holley4000parts.html

If you look in the technical section, there is a great assembly video, that shows all the components of the carb:

https://www.carburetor-parts.com/Holley ... p_337.html

You can take the cover off the top of the carb when it is in the car. And the engine will run when the top is off! (not drive, but idle) You can watch the needle valve in operation. However mine looked fine when the carb was open, but the car was not driving...

You might still want to take the carb off and clean all passages.

YOU CANNOT REPLACE THE CARB! (Except with the same model)
The carburetor supplies the vacuum signal for the vacuum advance on the ignition - aftermarket carbs don't have that signal. Also: vacuum is the only advance mechanism in the stock distributor - without it the ignition timing will not change and that results in overheating and loss of power at high RPMs.

Good luck!

Bob

Daddio
Posts: 33
Joined: Mon Jul 01, 2019 12:51 pm

Re: Won’t keep running down street!

Post by Daddio »

After 4 miles, you should have used up all the fuel in the carb float bowl, so a sticky needle valve could be the problem.
A small air space at the top of the filter bowl is normal. However, bubbles in the filter bowl indicates restricted flow from the tank.
You have a new tank, OEM filter, non-OEM inline filter and fuel pump ... not much else left is there!! only the supply line. It could be pinched or corroded somewhere between the tank and pump. There have been instances where new parts are defective.
You could also run with the gas cap off to see if it is defective or an incorrect non-vented type.
Mike
1956 TBird
1959 Cadillac Biarritz
Massey Ferguson 165
2005 Lincoln LS
2014 GMC Yukon

CSavaglio
Posts: 267
Joined: Sat May 28, 2016 11:37 am

Re: Won’t keep running down street!

Post by CSavaglio »

To add to the other advice, another restriction to check is the section of soft line on the feed line to the fuel pump. They're notorious for swelling nearly closed inside from the modern fuels but looking fine on the outside.

If it hasn't been replaced yet, it's worth doing... Buy new, not nos since the modern rubbers deal with the alcohol better.

Switching to ethanol free gas solved literally all of my drivability issues in all three of my vintage cars, including when they sit for long periods, so that's a thought if it's available where you live.

Jim G
Posts: 41
Joined: Sun Jan 05, 2020 1:25 am

Re: Won’t keep running down street!

Post by Jim G »

Thanks for all suggestions. And I have checked most everything from gas cap to carb. Do you all think I should just go for and overhaul exchange and be done with it? It needs an Automatic Choke added to it as well. Previous overhaul years ago just stuck a manual pull cable into car dash bottom!
Also- anyone experience installing a new leather/ vynal cover on the dash of a ‘56? Previous owner 2 times ago removed this one and just painted the dash satin black.
Really needs covered for best look and I see I can order a cover in parts books for around +$50.00.?
Regards-
Jim G

Jim G
Posts: 41
Joined: Sun Jan 05, 2020 1:25 am

Re: Won’t keep running down street!

Post by Jim G »

Bob- this 56 only has a single vacuum diaphragm Distributor as I see other 56 with a dual vacuum diaphragm distributor.
Could this change over that someone did cause this TBird to run hot in idling Parades?
Motor seems to run real smooth when it is running and temp stays at mid point normal city driving..?
Thanks again-/ Jim G

T-Bird Bob
Posts: 32
Joined: Fri Aug 10, 2018 11:00 pm

Re: Won’t keep running down street!

Post by T-Bird Bob »

Hello Jim,
As long as you have the original tea-pot (Holley 4000) you should be fine. I just said you cannot use a modern Edelbrock or Holley aftermarket carb with the original ignition distributor.
When you said that someone replaced the auto choke with a manual one, I think you might already have a newer carb and your ignition timing doesn't work properly.

Here is how it was intended in 1954 to 1956 (1957 Y-block has newer style centrifugal plus vacuum, but 1960 six cylinder engines still used load-o-matic):

1) The carb would supply vacuum to the ignition advance diaphragm as the only means of advance.
2) The carb switches between manifold vacuum or venturi vacuum by means of a spark control valve and supply whichever is greater.
3) The manifold vacuum is ported right above the throttle plate and shut-off when throttle is closed.

So your ignition vacuum can have 3 stages:
1) At idle or whenever the throttle is closed, no vacuum is supplied to the ignition and the timing will remain at initial timing (6°BTDC for auto, 3°BTDC on manual transmission).
2) When you accelerate lightly or cruise, the throttle plate is opened and the port is accessing manifold vacuum. That same manifold vacuum holds the spark-control valve closed which makes this signal go to the distributor.
3) When you floor it, manifold vacuum will collapse, because the throttle is fully open. Now there is no vacuum signal to the spark control valve and it will open. That allows venturi vacuum be supplied to the distributor. (You remember high-school physics: a medium flowing through a restriction, pressure will drop in that point - same effect sucks in fuel in the carb.) This pressure is dependent on engine RPM and therefore provides a signal related to RPM.

So every bodies problem on here is that there is no aftermarket carb that does supply this kind of functionality. Usually those carbs have only ported manifold vacuum. If you go aftermarket carb, you also need an aftermarket distributor. None is available with tach drive so your tachometer goes out the window...
(I always propose getting everything as close to stock because any change will open a can of worms...)

The problem with this load-o-matic set-up is that the values for manifold vacuum and venturi vacuum are so largely different! The 1955 distributor is set up to have maximum advance (everything, because there is no other mechanism) at ~2" Hg. That is because venturi vacuum at high RPM is likely only around 2"Hg. Now you know that a healthy engine at part load cruise will easily exceed 20"Hg. So you are driving around in cruise mode with your ignition always at max advance, which is about 30° on my 55.

However, this could save you, if you don't ever go drive high load high RPM:
Attach a vacuum gauge to your manifold and drive around as aggressive as you would ever do in a T-bird (usually limited by brakes and handling). Try the highest speeds uphill you would go! If your vacuum never drops below 5-6"Hg, you are probably fine with your aftermarket carb and stock distributor.
(I just realize that I have to do this....)

Something else: as described above, almost all carbs supply no vacuum to the ignition at idle (as in parades) and it will idle at the static setting (6°BTDC for auto and 3°BTDC for manuals). The only thing that prevents a stock T-bird from overheating in parades is an electric fan. Or some fancy radiator, pump and distance piece changes.
I had my `55 also run at mid point in the city as long as outside temp are below 85° (29.5°C), at 100° in Arizona I could no longer idle longer that 30seconds and needed to keep moving. Temp needle was at the P.
Can you put in some photos of the carb and distributor?
For re-covering the dash, the dash has to come out - not difficult, but a huge amount of work, especially wiring. The cover itself is not expensive, because it is only a flap piece of vinyl with two seems at each end (where the windshield corners are).

Good luck and I hope it helped somewhat...
Have fun!

Bob

Jim G
Posts: 41
Joined: Sun Jan 05, 2020 1:25 am

Re: Won’t keep running down street!

Post by Jim G »

Yep— Thanks again. I will send a picture soon— JG

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paul2748
Posts: 1322
Joined: Sun Mar 15, 2009 12:23 am
Location: Northeastern New Jersey

Re: Won’t keep running down street!

Post by paul2748 »

To determine what distributor you have (single vacuum chamber), remove the cap. If you can see small springs on the points plate, it is a 56 and earlier. If you cannot see springs on the points plate, it is a 57 and later distributor
1956 Fiesta Red 312
1954 Ford Victoria 312
1948 Ford Convertible Street Rod 302

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