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Distributor 1967 to 1974 Application Info |
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Couple of updates and thoughts:
My understanding of dual points agrees with BillD, in most cases. The two sets of points are both operating during each firing event, one to start the event and one to end it, allowing greater dwell time. However, the old Mallory "Double Life" that was the Group 19 distributor operates on a different principle. The two sets of points would each trigger 4 cylinders. This allowed for a higher dwell time and also it meant that each set of points was working at half speed. Point bounce was highly unlikely, since the points were effectively only seeing around 2500-3000 rpms. As for the pole pieces, I took a close look and checked my notes and here is an update: I have two of the 11106 units. The first was in my car when I got it and had pole piece 724 and a date coast of "6M15". The other was date coded "8E16" and had pole piece "732". I suspect that they were different model years, but the different pole pieces puzzles me. I would not be surprised if the "6M15" unit had been played with, I am pretty sure the "8E16" unit had not. Sorry for any confusion, PHAT! Thanks! Chris |
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DoughertyAMX
Supporter of TheAMCForum Joined: Sep/20/2016 Location: Washington, Ind Status: Offline Points: 519 |
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PHAT, I do not have the vacuum advance specs for my dual vacuum advance. Can I just convert to a single vacuum line advance like post Sept 69 and use the same distributor?
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401MATCOUPE
AMC Addicted Joined: May/20/2010 Location: Salisbury, MD Status: Offline Points: 5367 |
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You can put a single diaphragm vacuum advance on any dual diaphragm distributor.....but remember when they changed to the single diaphragm unit they also changed the camshaft as a set. Maybe little known fact...but the combination of two is what got them past emission requirements. The mechanical section of the 1111987 Type 1 (Dual Diaphragm) and 1111948 Type 2 (Single Diaphragm) are different.
The 1111987 Mechanical Advance Specs are at 900 Engine RPM = 0-4 degrees advance, 1500 Engine RPM = 12-16 degrees advance. The 1111948 Mechanical Advance Specs are at 800 Engine RPM = 0-2.5 degrees advance, 1600 Engine RPM = 17-21 degrees advance This tells me the main shaft cam and weights have different profiles. One additional note is a Type 1 set up the factory recommendations were 5 degrees +/- 1 BTDC (vacuum hose disconnected) and 34 degrees +/- 3.5 degrees Maximum Advance at 2000 RPM (vacuum hose connected). Type 2 set up the factory recommendations were TDC +/_1 degree (vacuum hose disconnected) and 45 degrees +/- 4 degrees Maximum Advance at 2000 RPM (Vacuum Hose Connected). That is a big difference, it is due to the combined additional mechanical advance and vacuum advance differences in each unit. You can get very close using your 1111987 distributor by using an adjustable vacuum advance that Mr Gasket Brand (Summit sells) and small changes to the weights/springs. Vacuum advance spec for Dual Diaphragm Unit is Max advance is 17-19 degrees, proper single diaphragm is 24 degrees.
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Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar) 68X,GoPac,390,4sp,52A 69X,GoPac,390,4sp,64A 70X,GoPac,390,4sp,87A,8 70X,GoPac,390,4sp,BBO,8 70 Jav SST,390,AT,BSO 74MatX,401,AT,Prototype 74MatX,401,AT |
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919 |
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Yes, agree, there's a big difference between the 2 Distributors. Looks like a "B19" Vacuum Advance Canister is relatively close to the specs of the original #1115362 Single Vac Can. "B19" = 24 Engine Deg Max Adv, 7" Start Adv, 16" Max Adv. #VC1760 = Napa Echlin Part # for "B19" stamped Vac Adv Can. ( 1973421 = GM Part #, used on 1969-70 Chev Cars & Trucks ) BUT.... you may/should also Re-Curve the Mechanical Curve also. ----- -> Single Diaphragm 1970 390 CID-4V Effective with/after Engine Code 209X26 #1111948 SINGLE DIAPHRAGM Type 2 Distributor #1115362 SINGLE DIAPHRAGM Vacuum Advance Canister Last 3 digits of Part No. are stamped on Canister #1111948 Centfigugal Mechanical Advance, Engine Degrees & RPM: 0-2 Deg Mech Adv at 800 Engine RPM 17-21 Deg Mech Adv at 1600 Engine RPM 28-32 Deg Mech Adv at 4400 Engine RPM #1115362 Vacuum Advance, Engine Degrees: 24 Degrees Max Vacuum Advance Adv Start at 4"-6" Mercury Full Adv at 18.5" Mercury ----- -> Dual Diaphragm 1970 390 CID-4V Prior to Engine Code 209X26 #1111987 DUAL DIAPHRAGM Type 1 Distributor and #1973426 DUAL DIAPHRAGM Vacuum Advance Canister Last 3 digits of Part No. are stamped on Canister #1111987 Centfigugal Mechanical Advance, Engine Degrees & RPM: 0-4 Deg Mech Adv at 900 Engine RPM 12-16 Deg Mech Adv at 1500 Engine RPM 22-26 Deg Mech Adv at 4000 Engine RPM #1973426 Vacuum Advance and Retard, Engine Degrees: 17-19 Degrees Max Vacuum Advance Adv Start at 5"-7" Mercury Full Adv at 14.5" Mercury 9-11 Degrees Max Vacuum Retard Retard Start at 5" Mercury Full Retard at 14" Mercury ----- This charts shows DISTRIBUTOR DEGREES, not CRANK DEGREES for a number of "available" Vac Adv Cans for Delco Distributors: Edited by PHAT69AMX - Apr/07/2018 at 10:19am |
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toolmanxiii
AMC Addicted Joined: Oct/16/2010 Location: Moncton Canada Status: Offline Points: 1384 |
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I'm confused now ..my dual vacuum advance dizzy has no mechanical advance . but uses manifold and ported vacuum to advance timing .
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71 360 Hornet sst 83 2wd 360/727 Eagle wagon (crashed)
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919 |
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toolmanxiii, is it a Delco Type Dizzy or a PrestoLite ? (plastic) Type ?
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401MATCOUPE
AMC Addicted Joined: May/20/2010 Location: Salisbury, MD Status: Offline Points: 5367 |
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All Delco Distributors in AMC had Mechanical Advance, if it doesn't act like it then it maybe frozen or previous owner locked it down. That would be highly unusual, most performance distributors (pick your poison on brand) are Mechanical only since a lot of High Performance Engines don't have much vacuum to make the Vacuum Advance effective. The main thing the vacuum advance does in my mind is adds in economy at part throttle conditions............just disconnect yours and on a road trip your mileage will plummet.
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Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar) 68X,GoPac,390,4sp,52A 69X,GoPac,390,4sp,64A 70X,GoPac,390,4sp,87A,8 70X,GoPac,390,4sp,BBO,8 70 Jav SST,390,AT,BSO 74MatX,401,AT,Prototype 74MatX,401,AT |
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toolmanxiii
AMC Addicted Joined: Oct/16/2010 Location: Moncton Canada Status: Offline Points: 1384 |
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Prestolite . and did a test . the line on front advances timing rear line retards timing . front line uses manifold vacuum rear line uses ported vacuum . I got it back in the late 70's when i built a 232 to race spec's.
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71 360 Hornet sst 83 2wd 360/727 Eagle wagon (crashed)
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919 |
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I tend to agree with 401MatCoupe, your PrestoLite Dizzy also has Mechanical Advance weights and Springs, they are just hidden buried down deeper in the distributor housing in those kind than they are in the Delco type distributors that have the mechanical advance right there on top right under the rotor button.
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67 Marlin
AMC Addicted Joined: Feb/21/2015 Location: Minnesota Status: Offline Points: 877 |
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Phat - Here's an update for your chart at the top of the thread. 1111191 Delco distributor (1967 343) has 728 on it for the mechanical advance. This jives with the TSM, which says 13 to 15 (26 to 30) degrees, albeit by 4400 RPM. So, right in the middle.
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