Originally Posted by Scottem
Part # 1803 500cfm 4bbl
Symptom: Exhaust stings my eyes and really stinks badly.
I assume the carb is running rich and after adjusting the air/fuel screws on the front of the carb, confirming there are not gasket leaks, timing is good as is the vac gauge reading (18lbs). Adjusted the auto choke and its good. Condition persists..
Edelbrock says the primary jets on this carb (primary carb on a dual carb set up) are
Metering Jets: .086
Metering rods: .065 x 0.57
I have a tuning kit from Edelbrock.
Question: What size jet and rods should I run to make the rich condition go away?
You want to go leaner! That's the quick answer. Sounds a little "smart a...", I know, but this retort is as broad an answer as your question.
Having extensively tuned a 1405 (specifically), both on the road and chassis dyno,
I start out tuning carbs with:
1. attach a vac gauge, (manifold vac) to insure no leaks most street engines will be between 15-20 hg
2. insure your timing is within parameters most rigs run 12-14 deg.
3. attach a vac gauge ( manifold vac) with your idle at or near 750-900 (?) adjust each mix screw for the highest vac reading, all the while maintaining your desired idle setting.
4. Also, know there are two vac ports on that carb, OK 3, if you count the PCV port. One is full manifold and the other is timed" or "ported". As every engine is different, the choosing of which will depend on how your engine responds to the input. This is a whole other can of worms.
If you bought this carb new, you would have gotten a setup/install guide. In the back of the guide is a graph chart for tuning the carb's AFR. To go lean you select "X" metering rods and springs, to go richer, you selct these etc. If you don't have a guide, it is available on their site as a download in the technical section.
"No one" on this site can recommend specific rods and jets. I will go out on a limb and state that one would usually start by changing the metering rods. It's a case of knowing where the AFR goes "fat" (rich).
Each engine is different in too many ways for any of us to answer " What size jet and rods should I run to make the rich condition go away" again, the simple answer to your quest may be "go leaner".
Outside of many hours of road testing, a chassis dyno is your next best way to learn what your AFR is doing over a broad RPM range. Otherwise, buy an AFR meter on your own and have at it.