Thread: 350 SBC 6-71 Blower Carburetor Adjustments

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Hi Alex. Beautiful truck you've got there. You had limited experience with carbs so you jumped in with a supercharger and duels!! That is how you get'er done! LOL..

A couple questions for you. First you said, "I have an AFR gauge installed, and it was reading very rich (i.e.: saturated at 10.0) under load. I have adjusted the carburetor main and secondary jets from 68 / 76 to 64 / 72. For the most part, this looks to have leaned out the motor correctly. all eight carburetor idle mixture screws are set at 1 full turn out." What does "leaned the motor out correctly" mean? And at what rpm?
The mixture screws are for operation at idle. So we're talking about 2 different tasks. Also how is your AFR installed?
Has the blower maker offered any help or guidance? Or have you even asked them? And I'll end with this last question, at what elevation are we talking about? Sea Level?

Sorry for all the questions, but it's info we'll need to know.

Originally Posted by 34_40

Hi Alex. Beautiful truck you've got there. You had limited experience with carbs so you jumped in with a supercharger and duels!! That is how you get'er done! LOL..

A couple questions for you. First you said, "I have an AFR gauge installed, and it was reading very rich (i.e.: saturated at 10.0) under load. I have adjusted the carburetor main and secondary jets from 68 / 76 to 64 / 72. For the most part, this looks to have leaned out the motor correctly. all eight carburetor idle mixture screws are set at 1 full turn out." What does "leaned the motor out correctly" mean? And at what rpm?
The mixture screws are for operation at idle. So we're talking about 2 different tasks. Also how is your AFR installed?
Has the blower maker offered any help or guidance? Or have you even asked them? And I'll end with this last question, at what elevation are we talking about? Sea Level?

Sorry for all the questions, but it's info we'll need to know.

Thanks! I do love it, it's been a hobby now for a while. I had a single carburetor on it for a while with an Edelbrock RPM Air Gap intake, but she wasn't making enough power! This truck is a learning project, and let me tell you I've learned lots so far! I'm not new to motors (I have had different fuel injected V8's), but definitely new to carburetors. I was thinking about swapping to a Holley EFI setup, but it wouldn't be true to the era!

"how do you know the motor leaned out correctly".
After re-jetting the carburetors, under load the AFR is now around 12.5:1 (but I have not tested it at full throttle yet). As for RPM, the motor shifts at 5200; I have not seen that RPM yet, maybe 4000RPM or so (the trans shifts too low I know, but that's another thing to work out later).

"The mixture screws are for operation at idle. So we're talking about 2 different tasks. Also how is your AFR installed?
Yes I agree. The AFR is installed in the passenger side (I drilled out the wrong header) header, just past the collector in the 1 5/8" long tube header. See picture below (not allowed to make fun of the welds).

"Has the blower maker offered any help or guidance? Or have you even asked them?"
The blower is a Weiand 6-71; I have not yet asked them for any guidance.

"And I'll end with this last question, at what elevation are we talking about? Sea Level? "
Yep, sea level.