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Author Topic:   KP....we need help........ 1 1/2" carb
posted June 17, 2003 10:04 PM
We need some info on what GM carbs are best suited to being bored to 1 1/2". Any chance you could supply us with the numbers we are looking for? We have a #7030693 right this a good place to start or do we need to keep looking? And if we get this bored to 1 1/2" roughly what kind of flow we looking at?

Thanks, John

posted June 18, 2003 09:15 AM
At that venturi bore size, almost every casting will need to be epoxy'd as there won't be enough meat left at the narrowest point. We've done many to 1.450" but have started with the hard-to-find 1 3/8" venturi "school bus" carbs. Ones like the 7041118, for example, or almost any that end in 118, 136 (I think), or 137. I pay less attention to the actual #'s as there were actually many that had 1 3/8" venturi over many years.
Keep in mind, also, that just boring the venturi out is only the beginning. ALL fuel circuits, restrictions, emulsion tubes, power restrictions, air bleeds, etc will also need to be altered for the carb to work well.
Also, the flow will benefit from the baseplate being opened to 1.75", mill the shaft, and use Holley butterflies.
Our Outlaw style 2G's flow about 680cfm or a little more on a "good" day... :-)

Good luck and hope it goes well.


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