ROCHESTER CARBURETORS

Bulletin 9C-331 15 December 1957

	BULLETIN 9C-331 PAGE 4 OF 4
	MODEL 4G 1957-58 CHEVROLET TRUCK — VACUUM ADJUSTMENTS AND SPECIFICATIONS
	1957 1958 APPLICATION 283 CU. IN. 322 CU. IN. 283 CU. IN. 348 CU. IN. CARBURETOR No. 7009661 7011161 7009662 7011162 7012303 7011487 7012145 PRIMARY SECONDARY PRIMARY SECONDARY PRIMARY SECONDARY PRIMARY SECONDARY Bore 1-5/16" 1-5/16" 1-7/16" 1-7/16" 1-5/16" 1-5/16" 1-7/16" 1-7/16" Small Venturi 1/4" 1/4" 1/8" 1/4" 1/4" 1/4" 1/4" 1/4" Large Venturi 1" 1-1/16" 1-3/16" 1-1/4" 1" 1-1/16" 1-1/8" 1-1/4" Main Metering Jets .047 .048 .056 .078 .048 .047 .054 .067 Idle Needle Holes .046 — .046 — .046 — .046 — Sec. Lower .030 — .029 — .030 — .031 — Discharge Middle — — .027 — — — .027 — Holes Upper — — .027 — — — .027 — Supplementary Idle Ports — .025 — .025 — .025 — .025 Lower Idle Bleed .067 — .036 .036 .067 .036 .045 .098 Pump Jets .024 — .024 — .026 — .026 — Power Restrictions .034 — .043 — .034 — .058 — Idle Tube Restrictions .038 — .026 — .030 .026 .029 .040 ADJUSTMENTS DIMENSIONS DIMENSIONS DIMENSIONS DIMENSIONS PRIMARY SECONDARY PRIMARY SECONDARY Float Dimension 1-5/8" 1-35/64" 1-5/8" 1-11/16" 1-11/16" Level Gauge BT-89 BT-117 BT-89 BT-143 BT-89 BT-143 Float Dimension 2-1/4" 2-1/4" 2-1/4" 2-1/4" Drop Gauge BT-93 or Scale BT-93 or Scale BT-93 or Scale BT-93 or Scale Pump Dimension 1-1/16" 1-1/16" 1-1/16" 1-1/16" Rod Gauge Scale Scale BT-145 BT-145 Idle Dimension — — 31/32" 31/32" Vent Gauge — — BT-145 BT-145 TUNE-UP 1957 1958 Spark Plug Gap .033 - .038 .035 Breaker Point Gap .016 .016 Cam Dwell 28°-32° 28°-32° Ignition Timing 5° B.T.D.C. 4° B.T.D.C. Idle R.P.M. 475 Neutral 475 Neutral
	CARBURETOR TOOLS AND GAUGES AS LISTED ARE AVAILABLE THROUGH UMS DISTRIBUTORS
		Rochester Carburetor A GENERAL MOTORS PRODUCT — A UNITED MOTORS LINE
	FORM NO. 1259 I.P.S.	PRINTED IN U.S.A.

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