Edelbrock carb vacuum?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jescates · 10-01-2003, 10:30 PM

I am swapping over from a points dizzy to an HEI. What runs best, running vacuum line to the ported side or the constant vacuum side? Any ideas? Thanks Jay

Bill72BB · 10-01-2003, 11:10 PM

I tried both ,and it runs ok both way but the ported side is the correct for the HEI , Check your advance curve at different RPM's the ported side should put you closer to the stock recomendations . Constant Vacuum will let it advance too quickly .
Here is a setup another member posted when we had this discussion awhile back.
GMC JIM posted this;
When I installed an H.E.I unit in my '71 GMC ( 402 engine) ; I had a distributor rebuild shop set the advance curves as per the GM factory manual. The specs are :- 0 degrees @ 930 RPM; 2 @ 1260 RPM; 16 @ 2400 RPM and 30 @ 4400 RPM. Vacuum advance specs are 0 degrees @ 8" hg and 20 degrees @ 17" h.g. Initial ignition timing is 8 degrees advance @ 600 RPM ( idle speed).
... Above specs are from GM 1971 Chevrolet Truck Service Manual.
... Another GM reference is the 'GM/AC/Delco Tune-up Specs Manual # SD-100. These specs call for a 10-13 degree centrifugal advance @ 2000 RPM and a total advance ( vacuum & centrifugal ) of 28 to 35 @ 2000 RPM...... When I installed my unit about 10 years ago; I used an adjustable timing lite and set the timing to 35 degrees @ 2000.........No problems and I am well satisfied with the engine performance............. Jim

jescates · 10-01-2003, 11:16 PM

Thanks Bill, will hook it up tomorrow and give it a go!. Jay

10-01-2003, 10:30 PM	#1
jescates Registered User Join Date: Aug 2001 Location: Mcloud, Oklahoma Posts: 656	Edelbrock carb vacuum?? I am swapping over from a points dizzy to an HEI. What runs best, running vacuum line to the ported side or the constant vacuum side? Any ideas? Thanks Jay __________________ 1970 C-10 LWB 1998 Jeep Wrangled TJ 2009 Honda VTX 1300 2013 Buick Enclave

10-01-2003, 11:10 PM	#2
Bill72BB Thats the Hillbilly way Join Date: Jul 2001 Location: Torrance,Ca Posts: 5,979	I tried both ,and it runs ok both way but the ported side is the correct for the HEI , Check your advance curve at different RPM's the ported side should put you closer to the stock recomendations . Constant Vacuum will let it advance too quickly . Here is a setup another member posted when we had this discussion awhile back. GMC JIM posted this; When I installed an H.E.I unit in my '71 GMC ( 402 engine) ; I had a distributor rebuild shop set the advance curves as per the GM factory manual. The specs are :- 0 degrees @ 930 RPM; 2 @ 1260 RPM; 16 @ 2400 RPM and 30 @ 4400 RPM. Vacuum advance specs are 0 degrees @ 8" hg and 20 degrees @ 17" h.g. Initial ignition timing is 8 degrees advance @ 600 RPM ( idle speed). ... Above specs are from GM 1971 Chevrolet Truck Service Manual. ... Another GM reference is the 'GM/AC/Delco Tune-up Specs Manual # SD-100. These specs call for a 10-13 degree centrifugal advance @ 2000 RPM and a total advance ( vacuum & centrifugal ) of 28 to 35 @ 2000 RPM...... When I installed my unit about 10 years ago; I used an adjustable timing lite and set the timing to 35 degrees @ 2000.........No problems and I am well satisfied with the engine performance............. Jim __________________ BILL Torrance Calif 90504 Member DUF Club Member Old Farts Club 72 3/4ton Custom Camper BB402/400 trans Dynomax Cerama-coat headers , Hei distributor ,Edelbrock 1411 air,ps,pb,leafsprings ,98 chevy 60/40 seat,S10 shoulder belts tilt,3.54 Dana 60 rear. 16" Eagle wheels with LT265/75 16 tires,Gaylord Lid,H4 headlights with 100W relay conversion. " If I knew I was going to live this long I would have taken better care of myself " Marriage changes passion...suddenly you're in bed with a relative. A GUY'S PRAYER.... Lord, I pray for a nympho with huge boobs who owns a liquor store and likes to fish and hunt and has a Harley .Amen ,

10-01-2003, 11:16 PM	#3
jescates Registered User Join Date: Aug 2001 Location: Mcloud, Oklahoma Posts: 656	Thanks Bill, will hook it up tomorrow and give it a go!. Jay __________________ 1970 C-10 LWB 1998 Jeep Wrangled TJ 2009 Honda VTX 1300 2013 Buick Enclave



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