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We started the testing with a Holley 770 CFM Vacuum Secondary Carburetor. It is a GM Performance Parts unit calibrated for a 502. We added 5 quarts of 10W-30 to break in the engine. The numbers were strong right out of the box. If you notice we didn't have breathers in the valve covers. The grommets were too small for the breathers that we had. We were surprised that during all of the testing we didn't see any vapors or blow by from the open holes in the valve covers.