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Old 12-31-2019, 09:00 AM   #1
Alley Rat
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Default Hesitation

First I apologize for possibly posting an issue/problem that may have been answered earlier.

I have a 1974 Scout II, Tara with a 304 engine, auto trans. It runs great at idle, and full speed... but when I try to accelerate or start off, the engine hesitates…. sometimes it backfires.
I had installed a new distributor with EI, spark plugs, new carburetor rebuild and a new fuel pump. My next guess would be the timing chain maybe off a click/link. Do you have an other possible cure? I would appreciate some guidance on this issue.
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Old 01-01-2020, 09:03 AM   #2
Robert Kenney
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Default Re: Hesitation

Hesitation and popping back through the carburetor upon acceleration is 99% of the time a lean condition, or retarded ignition timing.
No reason to think the cam timing is off. Also these engines use a gear driven cam and unless things are going seriously off the rails it is likely fine.

Back to the fix, some historical info. will help. Did it run like this before the carb rebuild and other work? Who did the rebuild?
The carb would have been a 2 barrel Holley I think, and they have a cam actuated accelerator pump system.

With the engine off, and the choke open, while looking down the carburetor with a flash light, advance the throttle off of the idle position and see if you get a good solid squirt from the accelerator nozzles. It should start squirting right as you begin the movement.
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Old 01-02-2020, 10:29 AM   #3
Alley Rat
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clip Re: Hesitation

Thank you Mr. Kenny,

I had hesitation problems before the new distributor, carb rebuild, coil and fuel pump. I thought all would end the hesitation problem.

I will check out accelerator pump as you have directed. I got the rebuilt carb from Auto Line products out of Canada. Where can I buy a better one?

I am scheduled to have the water pump replaced and I thought checking the timing chain for slack would be a good time while somewhat close to water pump. Is that a good idea?

Again, thank you sir,

Al
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Old 01-02-2020, 11:49 AM   #4
Hondo
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Default Re: Hesitation

As Robert said above, these engines use a gear drive for the cam, no timing chain to inspect/replace. I would use a can of carb cleaner at idle to spray around the intake manifold and vacuum ports to look for a vacuum leak. If idle changes while spraying the carb cleaner, you most likely have a vacuum leak.
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1975 Scout II healthy 258, Wide T19 , 4:1 D300 3:54s,
1972 Real clean stock Scout II P/S, P/B, 345, T18, 3:73s
1969 Mach I. Balanced ported 351W, 650 double pumper, Super T10, Detroit locker with 4.11s. Lowered with racing springs, bars, Konis etc.
(Don't worry about getting arrested when I drive the Scouts).
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Old 01-02-2020, 12:13 PM   #5
Alley Rat
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Default Re: Hesitation

Thank you Mr. Hondo,

I am at fault not understanding all about no timing chain. Mechanic suggested to do this and I did not question him then.

I will, within the hour, check carb and for vacuum leaks.

Thank you again Sir,
Al
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Old 01-03-2020, 11:27 AM   #6
Winchested
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Default Re: Hesitation

We have Csm gears direct driven from crank to camshaft no chain.
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Old 01-03-2020, 01:14 PM   #7
Alley Rat
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clip Re: Hesitation

Thank you Sir....

I have done some homework to see how the distributer works.

Obviously, I was gullible to my Mechanic's suggestion.

Thank you again,

Al
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Old 01-04-2020, 10:51 AM   #8
Winchested
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Default Re: Hesitation

Where are you in Canada? I'm in southern Ontario. Should have just installed a new Holley 2300 carb.

Have you gone through the carb tuning procedure as set out in the service manual?
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Old 01-07-2020, 07:19 AM   #9
Alley Rat
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Red face Re: Hesitation

I don't live in Canada....... I live in Colorado, USA.
I got the rebuilt carb from Canada.
My latest search for the hesitation problem is around high altitude adjustment. I live and travel 8,000-10,000 feet. I am installing smaller jets..... We will see....
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