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#10492 03/11/2004 9:10 PM | Joined: Mar 2002 Posts: 31 Junior Member | | Junior Member Joined: Mar 2002 Posts: 31 | How do you know when you have the thermostatically control choke set right for leanest burn?
I have a Rochester BC carb on my 54 Chevy sedan. I rotated the coil spring setting on the front of the carb a few notches for lean burn. Car seemed to burn nice and lean on the flat runs(clean exhaust - no black soot at idle anymore), but when the lady and I went for a road trip into Virginia, we lost all kinds of power climbing the hills north of Sparta, NC. A number of times I had to drop down into first gear and we're talking foothills folks, not the Cascade Mountain Range.
Anyway, can anyone share some lean burn setting hints for the 235 L6 Blue Flame?
Cheers from NASCAR country
Spito, spitero, huchtooey splateus!
1958 GMC Series 100 stepside
1954 Chevrolet Bel Air 4-DR sedan
1966 Chrysler Newport 2-DR hardtop
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#10493 03/11/2004 11:47 PM | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | The choke thermostat should not affect the warm mixture at all. The position is mainly to time when the choke gets fully opened. Once the water temperature gets up to about 150 the choke should be fully opened. The BC I have on my 261 works the best when the choke is set to one notch lean. It depends on the condition of the thermostat stove though. There is a piece of tubing that drops down to the exhaust manifold to provide heat for the choke. If it is gone the choke will never open.
If you want to tune the Rochester you have to change the jet. You also may need to mess with the power valve spring and oriface size. Most of the time problems arise it is with the power valve sticking open. The power valve is the little ball in the riser that the jet is in. There is a piston above it that forces it off its seat to open it.
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#10494 03/16/2004 6:23 PM | Joined: Mar 2002 Posts: 31 Junior Member | | Junior Member Joined: Mar 2002 Posts: 31 | Thanks Josiah!
I will take that BC off and check out the quality of my rebuild (done more'n three years ago in Seattle before moving out here).
Meantime, I have a new reman BC from the Vintage Auto Parts folks (vapinc.com now in Denver). Because this new reman carb has an additional vacuum nib at its throat (for the automatic tranny I s'pose) I'm gonna run a small line from the nob to a PCV valve which I'm gonna put where my crankcase vent tube is now.
I'm hoping this will get the motor running really sharp.
Cheers from NC
Spito, spitero, huchtooey splateus!
1958 GMC Series 100 stepside
1954 Chevrolet Bel Air 4-DR sedan
1966 Chrysler Newport 2-DR hardtop
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