75 with a 250. I am getting black smoke coming from tail pipe. It's not like spueing but I can see the haze and build up on the exhaust tip. I checked the choke and checked the vacuum reading for maximum and it seems to be ok there. I do see that the ignition module is melted and running down where it's mounted. Could it be low kv? I am thinking it is running rich due to low kv.. Thoughts?.. suggestions?
yes you would have the same problem because you would have parted out the comet and put the motor in the mav
Do you have a carter rbs carb? If so the power valve diaphragm may be bad. If you haven't had the carb rebuilt recently,pick up a kit at your local auto parts store. Nowadays that's the only way to get a power valve. If the diaphragm goes bad,it lets the engine suck in raw fuel,idles rough and black smoke from the tailpipe! These carbs were made for emissions control,so they weren't the brightest candle on the cake,so to speak. I'd like to find a holley replacement for mine,but have had no luck in that as yet.
first sign of a...parts car...in the making... i think they smoke a little just before they make that transition...
That's what I was thinking but wanted to see what others thought.. I have not ever been inside a carb like this one but I am sure I could do a carb rebuild. I would like to check out a diagram first tho, I kinda wonder where the pv is in it.
One other note. I noticed that the air bleed (?) screw is barely cracked for maximum vacuum reading, maybe 1/4 turn. I am used to like 2 or 2 1/4 turns on other models. ..
I did snoop around for one and didn't find one. I'll recheck it tomorrow. Might even plug some off like the one for the ac controlls just to see what's up.
check to see if carb is loose by twisting it mine was doing simular things found one bolt gone and the other one loose
sure does sound like a vacuum leak Gene. in a worst case situation and you cant find a leak spray a little starting fluid around to see if the rpms pick up just be careful.maybe a hairline crack in a vacuum line.
Seriously,get a carb kit! The reason your mixture screw is in is that someone has tried to compensate for an over rich condition by turning it in! In reference to the ignition module,in my experience it either works or it doesn't. My original one had melted the,whatever it was sealed with,all down the fender skirt. The car still ran fine. I figured I'd better get a new one cause this obviously was my car giving me a heads up. Guess what? That module is still on there and the one I bought is still in the trunk! This is like a year later. In reference to you asking where the power valve is,in an rbs carb it is in the center of the float bowl. They're easy carbs to work on, just follow the instructions that come with the kit!
