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Distributor

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purple72Gremlin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Jul/05/2019 at 2:02pm
Originally posted by V8Mart V8Mart wrote:

latest update....set initial timing back to 5, connected vac advance pipe to a spare port on the intake instead of carb, timing advanced to 20 at idle instantly , stumble reduced but not eliminated completely, stumbles when throttle is floored and sometimes results in a backfire through carb......too much advance perhaps?
If it backfired.....by by the power valve. But then it probably was gone anyway.  And sometimes you cant just buy the power valve alone for the motorcraft carburetor.....
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ChillyB View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChillyB Quote  Post ReplyReply Direct Link To This Post Posted: Jul/05/2019 at 5:45pm
Originally posted by purple72Gremlin purple72Gremlin wrote:

Originally posted by V8Mart V8Mart wrote:

latest update....set initial timing back to 5, connected vac advance pipe to a spare port on the intake instead of carb, timing advanced to 20 at idle instantly , stumble reduced but not eliminated completely, stumbles when throttle is floored and sometimes results in a backfire through carb......too much advance perhaps?
If it backfired.....by by the power valve. But then it probably was gone anyway.  And sometimes you cant just buy the power valve alone for the motorcraft carburetor.....

I'd think a stumble just as the throttle is applied is more likely acellerator pump than power valve?  But both are possible, and agree that a backfire can easily pop a MC2100 valve.  If carb hasnt been rebuilt in recent memory then do that.  Acellerator pump rubber gets stiff and develops pin holes.  Power valves are vulnerable to backfire.   
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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: Jul/06/2019 at 10:52am
I would like to remind all posters that my carb is virtually brand new...distributor looks very worn, cant find any suitable rebuild kits so will get a new or rebuilt distributor

that is all
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purple72Gremlin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Jul/06/2019 at 10:58am
Originally posted by V8Mart V8Mart wrote:

I would like to remind all posters that my carb is virtually brand new...distributor looks very worn, cant find any suitable rebuild kits so will get a new or rebuilt distributor

Virtually new doesnt mean much.  If it backfired, you blew the power valve. And IIRC you can adjust the acc pump. By the way, how long did the carburetor sit on the shelf?  As it sits.......rubber and paper gets hard. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote V8Mart Quote  Post ReplyReply Direct Link To This Post Posted: Jul/07/2019 at 1:25am
how do I know if power valve is bad, Had the carb apart to clean and all looks fine
that is all
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrblatzman Quote  Post ReplyReply Direct Link To This Post Posted: Jul/07/2019 at 7:54am
I have a good used distributor that I have had in storage for some time now...The number lists it as fitting a 1972 304 engine...Its dirty, complete with out cap, but should clean up and be fine...I ran across it while getting stuff ready for Saint Louis...I priced it at $35.00 if you or anyone else needs/can make use of it...I would install a new vacuum advance just as a routine thing...Bob in Fort Payne Alabama
Thankyou....Bob
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ChillyB View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChillyB Quote  Post ReplyReply Direct Link To This Post Posted: Jul/08/2019 at 5:46am
Originally posted by V8Mart V8Mart wrote:

how do I know if power valve is bad, Had the carb apart to clean and all looks fine

Blown power valves continuously pass fuel.  You may see it running in the vacuum passages.  It'll be wet under the PV's circular steel cover.  Seems like you have a lean stumble during acelleration so I'm still suspecting the acellerator pump.   Could be an adjustment, or a leaking diaphragm, or a leaking/missing red rubber check valve.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote V8Mart Quote  Post ReplyReply Direct Link To This Post Posted: Jul/11/2019 at 9:46am
took power valve cover off and it was full of fuel. Removed power valve and found gasket very soggy and split close to vac port. Valve seems to seat and unseat ok , put new gasket on...vast improvement but still not perfect, still stumbles when mashed very hard from idle but does not die, a gentler approach with the throttle works fine .All looks ok with the acc pump valve and diaphragm, squirts fine, no cracks or splits 



Edited by V8Mart - Jul/11/2019 at 9:48am
that is all
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Jul/11/2019 at 6:27pm
Holley carbs are fussy about the linkage adjustment for the accelerator pump.  You may already know the procedure, but if not familiar something you can check.  It kinda takes three hands to do it, but basically you hold the throttle wide open, then push on the pump arm (a small open end wrench is handy for this) to the max travel and then measure or set the clearance between the pump arm and the spring end of the arm that rides on the pump cam should be 0.015 inch.  When I read those instructions I admit it is confusing, and I have done it many times.  If the timing is advanced enough, and the pump linkage is set properly and you still have a stumble, you should try a larger shooter.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2019 at 3:29pm
Agree about the Holley Accelerator Pump and proper adjustment.
And if the Idle Speed screw is adjusted much, may have to readjust Accel Pump.
And watch out for the Accel Pump Arm that it DOES NOT ride on the
shaft mounted wound return spring instead of the plastic Accel Cam.
And the Metal Accel Pump Arms can get bent / tweaked out of original shape / contour.
Have also seen them "wore out" with a rough ditch worn into them on the cam end.
The black plastic Accel Pump Arms may seem kinda hoakey, but at least they can't get bent out of shape!
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