Thread: 305 running rich

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i have an '83 305 sbc, edelbrock intake, headers and 550 cfm edelbrock carb. from cold start to hot engine, it is running rich with the smell of gas coming out of the exhaust w/ dark smoke. there is no return gas line from the carb.

i have adjusted the choke (electric) so that i know for sure that it is in the open position when the engine is hot, also i fiddeled around with the two idling screws on the carb, but they dont seem to take a big difference.

would the problem be that the 550 cfm carb is just too much for the little 305? i beleive that it has the stock cylinder heads/valvetrain and cam, would it be too much for this setup?

thanks

Need to change the jets and or metering rods...Edelbrock has a chart on their site that shows what you need to change to, they also sell a tune kit for the carb.

how big of cam how much? how much vacuum ? there are two caps on top of your carb held in by two screws take the screws and turn them till loose. turn the top caps till the power pistons can be seen they are spring loaded so they can pop up. now turn in the screws so caps will not move when engine is runing now you can seen if the power pistons are all the way down at idle. if not it will run rich . with up the power rods will be at the thin part of the rod it will run rich . the set up springs will need to be lighter to pull the power piston down in the well so they are at the thick part of power rods less fuel .if that is rigth move on to power rods and you may need jets. the power valves can get sticky is well and can stick up

Possible excessive fuel pressure. No modern 4-bbl needs more than 5 psi at the carb inlet. MORE PRESSURE WILL NOT MAKE MORE HP.

Sniper – The Edelbrock carbs tend to run a bit rich out of the box. Great for turbo motors and some combinations of aftermarket cams and heads, but with your basically stock (low compression) 305, some tuning is required.

What you probably have is an Edelbrock 1403 carb, which is actually a 500 cfm electric choke model. Interestingly enough, they have been sold as 550 cfm as well. If it is in fact a 1403, you can use the drawing below to diagnose your condition and remedy with a jet and probably a metering rod change. Verify the number as it is important. The next step up is a 1406, 600 cfm that uses larger main jet.

I would suggest that you change the metering rod to#1463 (.067 x .052) as this can be accomplished in five minutes without opening up the top of the carb. If you’re still rich, I would go to a #1422 Main Jet (.083) and this will almost certainly address problem. If you change the jet, remember to buy a new gasket – even if the carb is new – as it can stick and tear when the top of the carb is removed and will leak. Nothing worse than having to go back to the store for a gasket!

Before you start, down load the manual here:

http://www.edelbrock.com/automotive_...ers_manual.pdf

For the first time reader, it’s a bit confusing but pour a cup of coffee and study it before you start. Pages 20 and 21 are critical for you to understand if you have not taken these carbs apart before.

Good Luck!
Glenn