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Expert
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Location: Minor Hill, TN | When I drive my '61 fury the engine runs awesome but when I really step on the gas pedal its hesitant what causes this? I am not burning cheap gas ( no name brand)I am using a fuel with additive to clean the engine and fuel system . My dad is trying to figure out the problem . The timing has been set to were it belongs , The carborator has been cleaned and rebuilt I have been wondering if I should take it a shop were its hooked to a fuel system cleaning machine and also pour a fuel system cleaner in the tank and clean out the fuel system really good The car is tied up for the winter ( Hood is getting redone) |
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Expert 5K+
Posts: 9900
Location: Lower Mainland BC | .
Could still be the carb - or timing. I am suspecting that the accelerator pump isn't squirting fuel properly when you step on the throttle. This will mean the engine is lean at a time when it needs to be rich. Have you heard any back-fires during these episodes?
With the engine off, remove the air cleaner, pull open the choke and look down the venturis. Then quickly activate the throttle (at the side of the carb) while looking down the venturis. You should see two streams of gas being squirted down the throats (one stream per throat). If not = accelerator pump is toast (or not set correctly - they have different strokes).
https://www.carburetion.com/CarbNumber.asp?Number=3131S
Edited by 56D500boy 2023-01-12 11:53 AM
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Board Moderator & Exner Expert 10K+
Posts: 13049
Location: Southern Sweden - Sturkö island | Is there ethanol mixed into the fuel? The carburator kits with blue acceleration pump rubber plunger doesn't stand ethanol. I had to make a rubber plunger for a carburator I renovated, after not even a year. The blue rubber was turned to mush.
Also, bad earhting in the dizzy or defective vacuum pot on the dizzy |
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Expert
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Location: Connecticut | 1961plymouthfury - 2023-01-12 11:01 AM When I drive my '61 fury the engine runs awesome but when I really step on the gas pedal its hesitant what causes this? I am not burning cheap gas ( no name brand)I am using a fuel with additive to clean the engine and fuel system . My dad is trying to figure out the problem . The timing has been set to were it belongs , The carborator has been cleaned and rebuilt... ( Hood is getting redone) Stephannie - Don't worry about using 'cheap gas'. Any 87 octane will be fine. Not necessary to use fuel a additive. Just a waste of money. Your hesitation is likely caused by a misadjusted float or a bad accelerator pump. The float needs to be set with precision measurements, graduated in 1/16". Also, there are two different float settings (float level and float drop). Both of these need to be set correctly. When your carb was rebuilt, did they use modern ethanol-resistant gaskets and materials ? If they did, then there is no worry. Ron |
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Expert
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Location: Minor Hill, TN | I have used Shell Vpower but put ethanol treatment in the tank before I do . |
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Expert
Posts: 2633
Location: Minor Hill, TN | I learned at training school when I worked for Texaco if you use fuel with no or very little detergent additives you are decreasing the life of your engine . The closest non ethanol is phillips 66 and that is 90 octane but with a car like my '61 I would rather use a higher octane than 87 . |
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Expert
Posts: 2633
Location: Minor Hill, TN | Thank you for the suggestions my dad has a friend who is going to look at the car to see if he can solve the problem . I wont need the car again until car show and cruise in season that starts in March or April I have a feeling its either the timing is wrong or the acceleration pump . My dad is the 1 who steps on the gas pedal not me . |
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Expert
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Location: Connecticut | 1961plymouthfury - 2023-01-13 12:23 AM I learned at training school when I worked for Texaco if you use fuel with no or very little detergent additives you are decreasing the life of your engine . The closest non ethanol is phillips 66 and that is 90 octane but with a car like my '61 I would rather use a higher octane than 87 . That is likely pertaining to modern engines. As I said, you can run 87 forever on the low compression 60-year-old 318. That's what I've been doing on my three classics. No problems. The 350 in my 52-year-old Olds Cutlass has 213K on the original, unrebuilt engine. Ron |
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Veteran
Posts: 143
Location: Denver, Colorado, USA | 1961plymouthfury - 2023-01-12 10:30 PM Thank you for the suggestions my dad has a friend who is going to look at the car to see if he can solve the problem . I wont need the car again until car show and cruise in season that starts in March or April I have a feeling its either the timing is wrong or the acceleration pump . My dad is the 1 who steps on the gas pedal not me .
Hi 1961plymouthfury, from the information you've provided, there can be many causes of hesitation under acceleration. Without more information and careful diagnostics to remove variables, it will be easy for you to chase your tail. I would not add any fuel "cleaner" to the system since it will only add another variable into the diagnostics. Assuming the A318 has the factory compression of 9:1, 87 - 91 octane gasoline or gas-ethanol mix should not create hesitation in a properly tuned engine, assuming the carb's accelerator pump seal is made for ethanol mix. The only additive you should be running is a lead additive if the cylinder heads have not been upgraded to hardened exhaust seats since the 1956 - 1961 and 1962 - 1966 A-block heads dont' have high enough nickel content to run unleaded without hardened seats.
Exactly under what conditions is the hesitation occurring? Does it happen when the engine is cold? How about when it's at running temperature? Does it happen only after the engine has been idling for a long amount of time and then you get on the throttle hard? Does it happen when you mash the throttle wide open from a stand-still idle? Does it happen when you mash the throttle wide open when the car is rolling at about 40 MPH? Does it happen with the transmission in neutral and you quickly rev the engine up to 5,000 RPM from idle?
Where is initial timing set with the vacuum advance disconnected and plugged? What is the total advance at around 4,000 RPM with vacuum advance disconnected and plugged? What is total advance at 4,000 RPM with vacuum advance plugged in? Is the vacuum advance hooked to ported vacuum (correct) or manifold (incorrect) vacuum? If the distributor still has points, what is the dwell angle?
If one of the exhaust manifolds is equipped with a heat riser valve, does the valve stay open when the engine is at running temp, is it always stuck closed, or is it always stuck open?
While I've asked a lot of questions, knowing these details will help me provide more specific diagnostic advice.
I have some in-depth tech articles that may assist you and your father in diagnosing the issue:
Ignition timing and points adjustment: https://poly318.com/poly-la-ignition-timing-distributor-points/
Carburetor Tuning (doesn't cover two-barrels but much of the article applies to 2-barrels): https://poly318.com/poly-318-carburetor-selection-tuning/
Edited by PolyJ 2023-03-06 12:48 AM
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Hesitant poly 318
