Rochester 1 barrel too rich

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53 stickfigure

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Joined
Aug 27, 2016
Messages
437
Location
Ohio
Ive got everything running pretty good but im not sure how to lean out an old rochester carburetor. It idles fine, accelerates great but the fumes are so strong i smell like raw gas in minutes. There's no black smoke at all but she has a small popping miss at idle. I have 6 gallons of 110 octane mixed with 4 gallons of 93 octane in the tank now. I'm happy with the way it runs but the fumes are killing me.
 
What's the compression ratio?
That's too high of octane unless you have 11.5 to 1 or higher.
Too high of octane won't burn completely in the cylinder and will finish burning in the exhaust without the high compression to burn it. It will will actually reduce the HP and performance of the engine.
I've got a 621 Horse big block in my 65 Goat, that is 10.2 to 1 and I run 91 in it. I run 110 on the 450 Horse nitrous side [ddd
 
Doesn't help that you are running race gas in what is essentially a tractor engine. Put some regular fuel in in with a little two stroke oil. If it doesn't improve then rebuild the carburetor, it could probably use it regardless. Doesn't get much simpler than those...
 
I was running regular fuel, just tried the high octane to see if it would help. Everything in the carb is new. Drove her a couple miles today and ran great. I heard or read somewhere that the float adjustment controls the mixture, lean or rich, but that dont sound right to me. You can smell the exhaust 20 feet away but no smoke at all and plugs are clean. I even tried a hotter plug, new points, new air filter and plug wires. Everything is new except the coil.
 
It has a jet that can be changed. Jets typically have the size stamped on the side. I'd have a new gasket before I tore into it though!

BoB
 
Doesn't make sense. If it was really running that rich you would have black smoke out the exhaust, the plugs wouldn't be grey, it would stumble off idle, something. If it's just exhaust odor and nothing more I am still inclined to think you have a fuel issue because of the high octane OR if there was some old stale gas in the tank still. You can jet it down some, the Rochester B uses the same jets as the 2G series. Wouldn't hurt to throw a coil on it too, but again if it's strictly odor with no other symptoms it's gotta be fuel related...
 
I`ve had a 440 bring tears to my eyes without black smoke. went down a few sizes on the primaries and bumped the timing a tad... made us both a lot happier
 
I played around with the timing today but ran best where it was. I'm going to jet it down this weekend. Chopping onions aint got nothing on bringing tears to my eyes like my exhaust fumes.
 
I'd make sure the choke wasn't sticking closed at idle. Going down the road it could suck it open and run fine, at idle, not enough vacuum to open it.
 
I assume you have the original 235 and three speed manual. What's your idle speed? (Should be down around 500 RPM.) If the throttle is open too much at idle, you'll draw fuel at "cruising" volume...

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I dont have a tachometer but I'd guess I'm idling between 500 and 600 rpm. I need a 6 volt to 12 volt converter and a big tach. My eyes aren't what they used to be.
 
I assume you have the original 235 and three speed manual. What's your idle speed? (Should be down around 500 RPM.) If the throttle is open too much at idle, you'll draw fuel at "cruising" volume...

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If it's a '53 3 speed with the original engine that would still be a babbit 216. '53 was the conversion year, with only PowerGlide equipped vehicles getting the full pressure 235. They went across the board in '54.
 
Thanks for enlightening me, BED.

53, I think a tach is a required tool. Set your idle mixture for highest RPM (or highest vacuum reading) then back your idle speed/throttle screw down... repeat as necessary...

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If it's a '53 3 speed with the original engine that would still be a babbit 216. '53 was the conversion year, with only PowerGlide equipped vehicles getting the full pressure 235. They went across the board in '54.
Thats what i thought too but 53s, both 3 speed and powerglide are 235s. Powerglides had a few more horsepower than the 3 speed cars. The old chevy shop manual doesnt even list a 216 in a 53 car. I ran my engine numbers and its a low pressure 235. Also you can identify a 216 and a 235 by the lifter gallery cover.
 

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