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Edelbrock 750 dying at idle when hot.

Started by Plum70Dodge, October 03, 2024, 08:11:35 AM

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Plum70Dodge

440,  Auto, 2400stall convertor, 3.23 rears.  Comp Cam specs 274/488 int 286/491 exh.  Through hipo exh manifolds.
Mopar Dual plane intake. Stock heads.  Running 19 inches of vacuum.
Timing 12* initial  34* at 2800 rpm.(no vac).   With the vacuum hooked up its idling about about 25* @950 rpm in park.
This was a edlebrock 750 manual choke that I added an electric to. 
 
This car runs down the road perfectly. Sometime I get a small amount of pinging if I dont use octane boost.
The carb is about a year old and Ive never been able to get this right.
Once it warms up fully, (10 mile drive or more) the carb loads up and the engine dies when at idle for a long time.
Think long red light, or trying to idle through the grass at a car show. it idles fine in gear when cold.
Running a standard Carter mechanical pump with a 3 nipple fuel filter sending excess fuel back to the tank. (calif spec car)
I just replaced the fuel pump (again) and measured the pump rod. Still looks new 3.22"
Any thoughts guys?

Bullitt-

#1
Over exposed idle transfer slots will cause one to stumble or die under load .
  about half way down in this article
http://www.superchevy.com/how-to/45638/

.                                               [glow=black,42,300]Doin It Southern Syle[/glow]       

DeathProofCuda

Quote from: Plum70Dodge on October 03, 2024, 08:11:35 AMThe carb is about a year old and Ive never been able to get this right.
Once it warms up fully, (10 mile drive or more) the carb loads up and the engine dies when at idle for a long time.
Think long red light, or trying to idle through the grass at a car show. it idles fine in gear when cold.


What have you done to try and get the carb dialed in?  What do the plugs look like?

Off the shelf carbs will generally be set up to run on the rich side, because an overly rich mixture is safer (engine-wise) than a lean one.

You can certainly tune a carb the old school way, but adding using a wide-band air-fuel meter makes it a lot simpler to dial in each of the carb's fuel delivery circuits (meaning just because it sits and idles beautifully doesn't mean it is going to run worth a $hit at cruise or wide open throttle). :alan2cents:

Is your dizzy hooked to ported or manifold vacuum?  If ported, and you are getting that much vacuum advance from the distributor, then your idle transfer slots are definitely over exposed, as suggested by @Bullitt-.



Plum70Dodge

Thanks. Thats great info. As a side note I have had occasional trouble with the throttle not fully closing sometimes. As if it were stuck on a high idle. This would surely be exposing the transfer slot. Man if a stronger throttle spring fixes this I'll be amazed. 

MoparLeo

25° at idle is way too much.
Check out the Edelbrock tuning manual attached.
moparleo@hotmail.com  For professionally rebuilt door hinges...