Enigne hesitating at mid throttle

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Alexis Collaud
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Enigne hesitating at mid throttle

#1 Post by Alexis Collaud »

Hello,
I'm running my freshly rebuilt engine (616/12 1600S 75cv 1962) full original except the C&P (AA Big Bore)
Ignition is a 123ignition, curves are loaded (Bluetooth version)
The car is running well except that when I'm acelerating "mid throttle" the engine is 'hesitating", seems a bit "muffled", or as if not all the cylinders are running. If I go full throttle then it is OK and the acceleration and sound is clear

When I test the engine without running (car is parked) everything is OK, it is just when it is loaded
I've already removed and cleaned the Zenith 32, full control also done :
- Float level OK
- Fuel pump injection Ok (approx 0,3 cc)
- Jets as per the manual (0130, 220, 50, 140, 40)
Zenith 32.jpg
I've synchronized the carbs.

Any idea where / what I should check ? What coule explain the engine is "not well" mid throttle but OK when full ?

thx a lot

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John Clarke
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Re: Enigne hesitating at mid throttle

#2 Post by John Clarke »

Salut Alexis
You say You are running with AA 86mm Barrels / Pistons but you have stock Jets as per manual. Could a change of jet / jets make a difference. I don't use the NDIX on our 86mm engine so I can't suggest a fix , Others may disagree, but would start with carbs.
Regards Jay
 

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Wes Bender
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Re: Enigne hesitating at mid throttle

#3 Post by Wes Bender »

The standard Zenith jets will work just fine with the 86mm PCs. Since I don't speak "123" I can't comment on that. I would review your timing curve settings on it though and then check to see if your idle mixture screws get a good response when adjusting them.
Some days it's just not worth chewing through the restraints.....

Dave Erickson
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Re: Enigne hesitating at mid throttle

#4 Post by Dave Erickson »

The first thing to do is run a leak-down or compression test. Since the engine is new you should verify that the heads are working correctly and you don’t have a soft cylinder due to a leaking valve or head to cylinder joint.

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Martin Benade
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Re: Enigne hesitating at mid throttle

#5 Post by Martin Benade »

Also make sure the carbs are synchronized at part throttle. Search for the procedure.
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