hello, I have a 1967 camaro with a 350 bored .40 over, double hump 350 hp heads with new roller rockers. mild cam (228/232 with 480), edelbrock coolrise intake and a holley 750 carb. headers and new exhaust. engine is a fairly fresh rebuild and I have set the timing at 36 degrees BTDC. and seems to be running very good, BUT, the exhaust I very rich smelling. I have replaced the plugs, wires and cap. set the mixture screws at about 1 1/2 to 1 1/4 screwed out. again, it seeems to be running fine, but the exhaust is EXTREMELY STRONG. it actually sticks to you if you get in it, and you smell it all day. WHAT CAN I CHECK/CHANGE OUT/REPLACE/READJUST? its giving me a headache! thanks for your help friends... tim


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Setting idle screws like that is just a starting point. Before you get started, double check your float settings and make sure that the fuel level is just at the bottom of the openings, but not coming out. You get it warmed up then with an accurate tach to look at, turn them in a little at a time equally until you see the rpm start to drop. You can then either set them at the point at which they drop the rpm 50 where it will be slightly lean or leave them at the point just before it drops where it will be a little richer but will idle a little smoother. Your throttle setting should be closed enough so that it is not into the off idle slot, because that is transient fueling for going from closed to opened throttle. Aside from that, you might adjust timing a bit, but make sure it will restart hot without cranking too hard. You might look into an ignition amp that has msd, that might clean it up a little. If you still don't like the smell, you can always put a high performance cat on it, that will do the job.

 

Thanks Kevin, I have set the floats to what I think is right, but might not be. I moved the screws inward until the engine started losing rpms, then opened them until it ran smooth, but is still very strong smelling. would the fuel filter or the erg valave have anything to do with it?


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Not the fuel filter or EGR, but maybe the air filter if it isn't free flowing enough. Especially if the carb was adjusted then you put the filter on and it was a little restrictive, that could mess you up. On the other hand, old pre-cat cars obviously had more emissions than newer cars, so maybe you just aren't used to that being the case. You could check your plugs and see how they look. If they are all sooty looking, then maybe it is a little rich, if not then it is probably normal. From your description, it doesn't really sound like anything is majorly wrong with the carb...