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GMC Jim · 12-23-2002, 05:27 AM

I purchased my H.E.I. unit from a firm that specializes in distributors, re-building ; including H.E.I. I was told they would calibrate the unit to factory specs or what I might desire...
I furnished the specs as outlined in the GM Service Manual for a 402 engine. Centrifugal advance - - [ degrees] ( 0 @ 930 RPM )
(2 @ 1260 RPM ) (16 @ 2400 RPM ) 30 @ 4400 RPM). GM also specifies ( 0 degrees vacuum advance @ 8" Hg ) ( 20 degrees vacuum @ 17" hg ). Purchased a new vac advance as old one was not in calibration.
I installed the distributor on the engine and set it up per previous stated specs. I also have another reference which, I believe is a great cross check and is not difficult to accomplish!...
This manual "1971-80 Tune-Up Specifications" published by GM-AC-Delco ( Man # SD-100 ) This reference states that centrigal spark advance @ 2000 RPM should be 10-13 & total advance ( incl. vacuum) should be 28-35.
So, I dialed in the timing lite 32 degrees; set engine speed at 2000 read on the "0" mark on the c/shaft damper timing indicator.....

12-23-2002, 05:27 AM	#5
GMC Jim Senior Member Join Date: Dec 2002 Location: Portland, Oregon Posts: 901	HEI-- Cent & Vac advance I purchased my H.E.I. unit from a firm that specializes in distributors, re-building ; including H.E.I. I was told they would calibrate the unit to factory specs or what I might desire... I furnished the specs as outlined in the GM Service Manual for a 402 engine. Centrifugal advance - - [ degrees] ( 0 @ 930 RPM ) (2 @ 1260 RPM ) (16 @ 2400 RPM ) 30 @ 4400 RPM). GM also specifies ( 0 degrees vacuum advance @ 8" Hg ) ( 20 degrees vacuum @ 17" hg ). Purchased a new vac advance as old one was not in calibration. I installed the distributor on the engine and set it up per previous stated specs. I also have another reference which, I believe is a great cross check and is not difficult to accomplish!... This manual "1971-80 Tune-Up Specifications" published by GM-AC-Delco ( Man # SD-100 ) This reference states that centrigal spark advance @ 2000 RPM should be 10-13 & total advance ( incl. vacuum) should be 28-35. So, I dialed in the timing lite 32 degrees; set engine speed at 2000 read on the "0" mark on the c/shaft damper timing indicator..... __________________ '71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal).