750 carb in a 350

[Posted]

Guys, my truck struggles when at idle at stop signs. I am running a an edlebrock 750 in my 350 with dart heads, and aftermarket cam. Seems to run super rich and just does not adjust. Should I go to a 650 size?

[geezer#99]

No!!
You should put a fuel regulator on it set at 5 psi and maximize your initial timing.

[Posted]

okay. is that something I just buy at NAPA or so? What does mazimize my timing mean? thanks for the reply. I am no tuning guy. I may have to reach out to someone to help me.

[geezer#99]

Best to get a holley fuel regulator.
Here's an example.
Napa or your local speed emporium might have them.
http://www.summitracing.com/int/parts/hly-12-803

Maximize your initial timing means putting as much initial timing into your motor so that it doesn't ping or is hard to start when hot.
Better heads and more cam need it.
If your initial is too low you need to turn up your idle to get it to idle right and then you're likely idling on the power circuit. The rich smell and no adjustment says you're idling on the power circuit.
Depending on the elevation where you live, your initial should be at least 12 degrees or even up to 18 degrees.
When you crank in more initial, your motor speeds up, you turn the idle down and then your mixture screws should work.
Try timing first and regulator later.

[Posted]

okay. So I place this regulator in-line with the fuel line? Set at 5 psi? I think my timing is right around 13, but I will have to confirm. You nailed exaclty what I smell and is happening. Smells rich, and no real response when using mixing screws. I can adjust idle only.

[geezer#99]

Yes, that's how you install the regulator but don't rush out and get one quite yet.
Do your timing first.
Check your initial timing. Make sure you plug the vac line to the distributor when you do that.
You might need to confirm your timing marks too.
Look here for info on that.
http://www.crankshaftcoalition.com/w...op_dead_center

[Posted]

thanks for the help!!!

[WyoCustomC10]

Sounds like the same problem I had with my Edelbrock 1406. Make sure the vacuum lines are hooked up to the carb correctly. I switched the distributor vacuum line to the correct port and it ideals fine now (non-emissions).

[piecesparts]

How much cam do you have and are you running an automatic tranny? If you have a cam profile (which creates the lope in your engine idle) that is large enough that you have to adjust the idle stop up to keep the engine running, then you should be looking at possibly changing out your torque converter to a higher stall number. That way you can idle that engine back down and set your carb, where it is not trying to idle in the transition area of the venturis. I had to take my 84 stroker engine to a 2300 stall on my 700 R4 tranny and after that my whole issue straightened out. I can now idle my engine at a normal idle speed and the truck does not stall or falter, when I try to pull away from a stop.

I did find that a 750 CFM carb is somewhat a little too large for a heavier vehicle, like a truck, when used as a daily driver. (I know there will be some argument on that statement), but Holley, Edelbrock, and Carter all agreed on that thought process. A 750 will work great on a lighter vehicle (Camaro or Malibu0, but will be ineffeicent when trying to move a 4000 lb truck. That is what I experienced with my try at a 750 CFM. The carb comes into it's self when above 1500 RPM, but at lower RPMs it just slobbered like a dirty old cow. This will just help to put additives from your fuel on the backs of your valves if you continue to use it.

I went to the Edelbrock AVS carb (650 CFM) and found a reasonable middle of the road process. This all works off of the amount of air passing through the ventruis and how that air signal works to move fuel and mix properly in the cylinders. This is alos supported by the carb manufacturers and any one of their techs will help you with that information. A lot of people do not like the Edelbrock mechanical carb line, but it is an old design and it works well, if you spend some time adjusting jets, springs, and rods to get the right mixes. I see the best alignment for my setup as going to a fuel injection setupp to get a larger fuel/airflow capacity as the best trasition from what I presently have. To go to a quadrajet carb, would require a different intake manifold, and I am not on board with that much work.