Carb Adjustment Help

[jonathan-m]

Hello Everyone,
I decided my weekend project would be to disassemble and clean out my Carb (an Edelbrock 4-Barrel on a 350 Small block crate engine). Its never ran exactly well, so I thought this would be a good learning project. I don't really know how old the thing is, so I figured once I cracked it open I would know if I needed to do an actual rebuild or just a good cleaning.

Anyways, I opened it up, and didn't think the gaskets looked bad, so I opted for a real good cleaning with carb cleaner. I soaked all the parts, scrubbed out the bowl, and cleaned the jets really well. When I started reassembling, I adjusted the floats a little bit ( I followed the directions on the edelbrock site, hopefully I did it right). And finally after I got everything put back together properly, I ran a new choke cable to the engine bay and connected it to the choke lever (The PO never bothered to put a choke cable on when they put this engine in, so I've driven around for 2 years without one).

Here's where I'm having a bit of trouble. I lightly seated the adjustment screws, then backed them both out 2 full turns. I adjusted each one a quarter of a turn at a time until the engine sounded smooth at Idle, and then a drove it out the road and back to test it on slow speed, acceleration and higher speed. I did this several times, and basically, no matter how I adjusted the mixture screws, it would always start "choking" big time when I accelerated unless I engaged the choke, in which case it ran fine at higher speed. I noticed that the idle sounds kind of fast too and I can't get it to sound slower with any mixture screw adjustments. I only have one other vehicle with a manual choke to compare this too, and that is a motorcycle. Whenever I pull the choke on the bike, the idle speed goes way up. When I pull the choke on the truck, the idle speed doesn't seem to change.
I'm still not exactly sure how all of these adjustments are supposed to work together, so I'm kind of making blind adjustments without knowing exactly what I'm changing. I know that the choke increases the richness of the air/fuel mixture by restricting air supply, and the mixture screws do the same thing, but I'm not sure why I can't find a "sweet spot" with my mixture screw adjustments without having to pull the choke whenever I'm accelerating or at high speed. I can get it to sound good at idle, but not at speed, which is really confusing me. Is there something else that can be adjusted?

Can anyone please elaborate on this for me so I can understand better?

Sorry for the noob questions, but I'm still a novice when it comes to these kind of things. I don't have anyone close to me that I can learn these things from, so I've been lurking here a lot,learning from build threads and trying to teach myself things as I go along.
Thanks for the help!

Jon

[hotrodhomi]

Here are the tuning vids.
How much hp is the engine supposed to have? is your carb a 1405? you might need a calibration kit to change out the jets and metering needles.

[jonathan-m]

oh cool beans, thanks for that link. Mine is a 1406 I believe, and I have no idea what the horsepower should be for this engine.

[hotrodhomi]

Originally Posted by jonathan-m

oh cool beans, thanks for that link. Mine is a 1406 I believe, and I have no idea what the horsepower should be for this engine.

The reason why I ask is that 1405s (man choke) and 1406 (elec. choke) are not big carbs (600cfm). They work great for stock or mid builds, but are too small when you start making good hp.

[hotrodhomi]

Just remember, before tuning a carb you need to make sure that everything else is in tip top shape. Good plugs, wires, timing etc..

[protrash64]

In my limited experience and knowledge ()......I have learned that when pressing the accelerator the airflow increases so therefore the engine needs more fuel to take atvantage. It sounds like you are describing a 'bog'. You need to adjust the linkage on the front drivers side of the carb to apply the accelerator pump sooner. There are 3 holes, choose a lower hole.

The mixture screws only work at idle. To adjust the idle speed you need to adjust the screw that holds the linkage in place; again on the drivers side of the carb. If you run the engine and then play with linkage you should see where it stops. You will also see the linkage on the front drivers side corner pushing down on the acc pump assembly.

If its running and driving you're 1/2 way there. I suck at this stuff , but what Ive mentioned so far I do understand.

[jonathan-m]

Alright, I'll give this another go in the morning, I think now I understand what I'm doing a bit better

Thanks guys