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Tuning question I can’t figure out. HELP

Posted By Melly 4 Years Ago
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312YBlock
Posted 4 Years Ago
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If you are running with a stock single point distributor the problem could be point float at 3500 RPM. I run a 55 T-Bird w/312 and a new Mallory Dual point tech drive distributor. The dual points cut the individual point open/close rate in half. If you are 12 volts and running a point distributor without a ballast resistor the points will burn out. Modern resistors made in Asia are just plain junk and will fail at some point, this happened to me, symptoms include momentary hesitation at steady speed and eventually severe backfiring. If you want to sleep nights and remain with tech drive I highly, highly recommend the Mallory Dual point distributor with an MSD 6A or 6AL ignition box. This little beauty will put only 3 volts to the points which it uses solely for timing (points will last forever just set gap and forget dwell), and it eliminates the need for a resistor as well as the condenser which is also complete junk, and give you a boost in performance that will light your fire. I put mine through an 85,000 volt epoxy filled coil with amazing results. You’ll love it!

PS a failing condenser will give same symptoms as above for the resistor.

1955 312 T-Bird Warwick, NY
312YBlock
Posted 4 Years Ago
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I should have looked up “dizzy” ignition before I posted as most of what I put there doesn’t apply to your situation.

1955 312 T-Bird Warwick, NY
Ted
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The grounds both within and outside the distributor need to be rechecked.  Unhooking the tachometer temporarily is a good suggestion.  If that doesn’t make a difference, then this sounds like a points or condenser issue.  As mentioned, point bounce could be the problem but also insure that the point gap is set to spec.  The point gap being on the big side can create issues.  A condenser not being tightened properly can also do the symptoms you mention.

Lorena, Texas (South of Waco)


Florida_Phil
Posted 4 Years Ago
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Why run points at all?  I have a 1957 distributor in my 292 with a Pertronix unit, no ballast resistor and a 1.5 ohm Pertronix coil.  It's cheap enough and works perfectly.   I went to this setup when I couldn't find a points and condenser set that would work more than a few days.  Most auto store YBlock parts are junk.   


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DryLakesRacer
Posted 4 Years Ago
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I agree Phil. I went thru 2 condensers before I woke up and went to the Pertronix Unit with their coil and I kept the stock ballast. They are also available for the 6 volt systems too.

56 Vic, B'Ville 200 MPH Club Member, So Cal.
Joe-JDC
Posted 4 Years Ago
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Point bounce is why I asked if the engine pulled past 3500 rpm.  Remove the points, bend the spring backwards a small amount, reinstall, set gap, and go for a test drive and see if the stumble goes away, or moves up the rpm scale.  If it changes, a performance set of points should solve the issue.  Joe-JDC

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Melly
Posted 4 Years Ago
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Going to try some of these suggestions hopefully this weekend. Have checking into tune up information and read so information on mechanical timing, vacuum timing, total timing. Found it to be interesting. Also found out something I did not know. That you can adjust the vacuum canister with Allen wrench through the hose port. Am I getting into this more then needed.? Any input on this subject.
Joe-JDC
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Not all vacuum advance cannisters can be adjusted.  Joe-JDC

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Florida_Phil
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Posted 4 Years Ago
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I see your car has O/D.  There should be an extra wire leading from the kickdown switch to the distributor. The purpose of this wire is to momentarily ground the distributor so the transmission O/D can down shift.  The kickdown switch is open to the elements and can be troublesome.  Temporarily remove this wire to see if it may be affecting your problem.  I had all kinds of intermittent ignition trouble with mine, so I disconnected it.   I have been told leaving this wire connected will blow a Pertronics unit.


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Melly
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first put in a pertronx igniter ll with a flame thrower ll  coil.  Seem to have great improve things. Tach issuse seem gone, pulls through rpms steady and power good.  Only issuse is when putting pedal to floor at cursing speed pulls strong but this  full throttle then cause a slight floating as it pulls rpm.  I am thinking it might be a timing issue or carb. issuse.  My timing is at about 10 degrees, vac.  at 17.  I have a 57 312ci  B intake  Holley street avenger 570 cmf ( do not know what jets size inside or power valve ) , 57 distributor.
At present to lead for the kick down is not connected.  Have not heard the idea that connecting this lead will cause a problem.  Any thoughts on this kickdown lead so I don't make a mistake connecting it? 


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