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Distributor

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V8Mart View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote V8Mart Quote  Post ReplyReply Direct Link To This Post Topic: Distributor
    Posted: Jun/25/2019 at 1:57pm
I am new to the world of AMC and would appreciate some advice on the distributor on my 73, 304 Hornet. When I take off the cap and rotate the shaft by hand it seems to ride up as if trying to unmesh the gears, this does not seem normal to me, am I right?I see no evidence of it riding up when engine running as rotor and cap show no damage . I also believe I may have a problem with the vac advance unit, possibly leaking diaphragm or seized mechanism since the car has been stood for many years...in order to compensate in some way, I notice the previous owner set the timing to around 15 degrees....when I set back to 5, the engine  stumbles on initial throttle opening but runs ok otherwise. Am I looking at getting a new distributor or is it possible to repair what I have?...it looks like the advance unit is not easily detachable from the distributor body. Also, is there a way of adjusting the acc pump mechanism on the 2bbl carb...just in case this is causing my problem.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2019 at 2:20pm
Normal to run poorly at factory setting of 5 deg.  this was done for emissions, NOT driveability.  The other part of the equation is the mechanical advance should have been limited to get the right total advance at rpm.  for example, 36 to 38 degrees is probably where you would want it to be.  With 5 initial and another 15 distributor = 30 engine degrees you would be at a nice safe total of 35.  Advancing the idle to 15, the distributor should be limited to 10 distributor = 20 engine degrees to get the same 35 total.  In my experience you will find 20 initial and 40 total to give the best performance.  Text book performance advance curve would be 12 initial and 36 total.  The advance in the distributor is limited by a pin in a slot.  You can modify the slot or put a bushing over the pin to limit travel.  don't be afraid to experiment.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2019 at 3:53pm
There is Endplay in the Distributor as stock and it is ok for stock, maybe as much as 0.150". 
The helical cut of the drive gears pulls the Distributor Shaft down under load
and also pushes the camshaft into the bloc, along with other things...
Is it an AMC Delco Points Type Distributor?  What are the stamped numbers on it?
If so the Vacuum Advance Canister is held in place by 2 Screws
and suitable replacement Vacuum Advance Canisters are still available.
Would think your existing Distributor is entirely and somewhat easily serviceable.
Unsure about the 2-Barrel Accel Pump adjustment, what Model Carb ?  Pictures help.
Link to an existing thread here containing considerable AMC Delco Distributor information.
It used to be a "sticky" here, but fell from grace...

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ccowx View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2019 at 5:09pm
What you need is a B-1 type vac advance diaphragm for a Delco Remy distributor. It is the same distributor as in just about any GM V8 from the mid 60's to the early 70's, at least. The vac canister is available from Amark or American parts depot etc. You can likely get it cheaper from Amazon or Jegs or similar. As for your timing, try around 7-10 btdc and see where it starts to detonate, then back off about 2 degrees. The advance curve is fairly slow and conservative, so it may pick up off the line without going too far advanced. If not, shorten the curve as mentioned above.

All easy cheap fixes!

Chris
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V8Mart View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote V8Mart Quote  Post ReplyReply Direct Link To This Post Posted: Jun/26/2019 at 11:49am
Ill make a start by advancing the timing back up and see how it goes. From what I recall the shaft lifts way more than 0.1" when I twist it. I noticed the mech advance springs looked a little loose/worn  too...its all a bit tired I think. Not sure what type of dist, though it uses points,cant find any screws to retain vac advance unit.....will have to look closer  ,  and the carb was a new replacement by PO, looks a bit like a motorcraft 2bbl but no obvious markings on it

Edited by V8Mart - Jun/26/2019 at 11:56am
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ccowx View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Jun/26/2019 at 12:56pm
The two screws that hold in the vac advance are under the cap. End play on the distributor is important, but only so much. As mentioned, the rotation and gears will suck it down to being seated on the oil pump shaft anyway. Shims are easy to buy to tighten that up. Otherwise the unit is fairly bulletproof. The advance springs are no big deal because you will likely replace them anyway, as part of tuning the distributor. Mr. Gasket, Accel and others all make advance tuning kits for that distributor, which include springs and weights and in some cases bushings for the advance.

Overall, the Delco distributor is pretty solid and easy to fix. I can not think of any other points type unit that it could be, so likely it is still the stock Delco one.

Chris

PS: It sounds like you have a timing light, so you can get a rough idea of how the advance is working by revving it up and watching the timing advance. Unless it is reaching full advance before 3000 rpms or so, the springs in the dissy are within usable range.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jun/26/2019 at 7:18pm
Quite a bit of AMC Delco Points Type Distributor info and pictures here in this thread:
( edit: doh!  sorry, failed to realize the below link had already been posted )



Edited by PHAT69AMX - Jun/28/2019 at 10:54am
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V8Mart View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote V8Mart Quote  Post ReplyReply Direct Link To This Post Posted: Jun/27/2019 at 6:34am
thanks guys, plenty to keep me busy once I finish repairing the body
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Jun/28/2019 at 4:02am
It should idle smooth and respond cleanly to throttle opening with a 5 degree initial timing setting. Advancing the timing beyond that often covers up some other problem in the engine tune, usually faulty carburetion. I prefer fixing the actual problem to slapping a band-aid over it.

1972 AMC timing specs were actually pretty close to ideal.

My 1972 360 idles very smooth and responds instantly to the throttle from idle with enough torque to break both tires on a 4000 pound Wagoneer. It's timing is set to OE spec. I found that worked best after ten years of experimenting with other settings. Turns out AMC knew what they were doing.
'66 Marlin: 327/T10/3.54 Twin Grip
'72 Wagoneer: 360/TH400/3.31
'73 Ambassador: 360/TF727/3.15
'77 Hornet: 232/TF904/2.73
'84 Eagle: 258/TF998/2.35
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V8Mart View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote V8Mart Quote  Post ReplyReply Direct Link To This Post Posted: Jun/28/2019 at 5:11am
I dont seem to be getting any initial advance when throttle opened from idle . I removed the vac unit,sucked on it (??)  seems to work ok all seems free, from what I can tell, I am not getting much vacuum from the take off on the carb,(tried both take offs by the mixture screws, no difference)  feels weak when I put a strip of paper against it and work throttle...certainly not enough to activate the unit, I get advance once the mech adv kicks in....I will check around for any vac leaks, the blanked off take offs are a little suspect, I would expect it to idle badly with a vac leak but its fine, when I disconnect the vac advance pie there is no difference in idle.
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