Engine: stumbling on initial throttle application

[gerry r]

Having just acquired a 1959 Lark V8 Hardtop automatic I am having trouble when applying throttle even when nearly warmed up with it wanting to die. Since I am far from being much of a mechanic the only thing I could think of was a bad accelerator pump. The person that sold me the car is my neighbor and he told me the carburetor was rebuilt not that long ago and he has always been a straight shooter as far as being truthful so I accepted that at face value. It is worse when cold but still does it when warm so I really have to feather the gas peddle when taking off and cannot trust it in traffic. The engine was totally rebuild less than 5000 miles back and really seems to run nice otherwise, even starting easily when cold and idling fine. Any thoughts out there? Thanks in advance.

[64V-K7]

Vacuum advance work?

[jclary]

Vacuum advance work?

I believe you two have nailed the two most likely causes.

[1oldtimer]

Vacuum advance or acc pump. With the air cleaner off (and the car off) look down the throat of the carb, push the acc linkage slowly and evenly down to full throttle. There should be a nice even stream of fuel coming out both squirters. The vacuum advance check is to take off the dist cap, unhook the metal line from the carb, hook a rubber hose to the metal line and suck on the hose as you watch to see if the breaker plate moves. Lots of reading to do if you need to replace the vacuum advance (easy to replace), as they don't really make a direct replacement.

[TWChamp]

What kind of gas was used in the car?
That ethanol corn crap goes bad quickly, so I pay extra to buy the good gas without corn in it.

[gerry r]

What kind of gas was used in the car?
That ethanol corn crap goes bad quickly, so I pay extra to buy the good gas without corn in it.

I'm not sure what was used in it before I got it but I put 4 gallons of non ethanol premium in a basically empty tank before starting. Thanks for the vacuum advance idea will check tomorrow. Anybody else wants to chime in please do and thank you all.

[StudeRich]

The above suggestions are probably what is wrong, plus your guess of the accelerator pump, however also check that the Automatic Choke is set cold, with the butterfly closed lightly, adjust as required. The idle speed should be close to 650-675 RPM in Park.

[Mike Van Veghten]

In order -

1. Accelerator pump bad/misadjusted/dirty passages inside the carburetor/leaking body gasket.
2. Idle mixture screws misadjusted, (yes, this could be a cause). Open them about 1/2 turn, see what happens.
3. Low "initial" ignition timing. (not the vacuum advance). Raise the timing, the book ignition timing is low for best drivability, milage.
4. Could also be a small vacuum leak in the intake system. The accelerator system can't keep up.
5. Power valve not working correctly (inside the carburetor).

There's a coupla things to look at, good luck.

Mike

[Hawkowner]

You do not say what the carb is if it is a Carter A F B or Eadlebrock copy check the checkvalve for the accelerator pump.
.Check the voltage to the coil to make certain the resistor is in the circuit .voltage should be B+ cranking and approx 8 volts running there have been untold carbs overhauled for points problems.
Hawkowner

[karterfred88]

I think more basic info is needed. Carb type, 2 or 4 barrel, OEM or replacement. Sounds like the accelerator pump is most likely, as "feathering" will work it past the hesitation, but other circuits in the carb could have a "clog" during transition from low to high circuit. Also, vacuum advance from the wrong carb source, ported verses direct, can also contribute, but usually not allow "feathering" to work past it, just a "bog". The points and condenser can also cause this effect, especially condensers, which are very questionable on quality lately, look closely at the point contacts for signs of arcing. Better yet, just change them, put them in a tool box as spares if it doesn't help.

[Studebakercenteroforegon]

We have a local experienced Studebaker mechanic who could check your car out.
My first thought was already mentioned above - 4 or 5 degrees more of initial timing.
Have you joined the Northwest Chapter yet?

[T.J lavallee]

It's possible you have a Stromberg carb. If so, check for a vacuum leak after confirming your accelerator pump (plunger) is providing two good streams of fuel.(see post #4) Some of these carbs were set up for California specs. Look at the back side just below the top edge of the carb horn for a vacuum pipe. Some were blocked off with a rubber type sleeve. Check to see if the rubber is cracked. If so it will suck in too much air causing the very problem you describe. You'll then have to re-adjust your idle screws, of course. Good luck with your 59' H/T.

[wdills]

I had the exact same situation with my Hawk. Rebuilt engine, rebuilt carb, new distributor and it would not accelerate off idle. Bumped the initial advance from 4 deg's up to 10 degrees, problem solved.

[gerry r]

I think more basic info is needed. Carb type, 2 or 4 barrel, OEM or replacement. Sounds like the accelerator pump is most likely, as "feathering" will work it past the hesitation, but other circuits in the carb could have a "clog" during transition from low to high circuit. Also, vacuum advance from the wrong carb source, ported verses direct, can also contribute, but usually not allow "feathering" to work past it, just a "bog". The points and condenser can also cause this effect, especially condensers, which are very questionable on quality lately, look closely at the point contacts for signs of arcing. Better yet, just change them, put them in a tool box as spares if it doesn't help.

Sorry to take so long getting back but I haven't got the car home yet to check myself but I did find out from the previous owner it has a Stromberg 2 barrel carb.