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Old 07-02-2009, 10:01 PM
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427 bb miss break up while driving

My 57 Nomad with 427 bb 11:1 forged TRW pistons w/GM aluminum oval port heads. I guess they are same as Edelbrock with 2.25 intakes and 1.88 exhaust, Cam is Crane 228/236 degree 114 lobe separation .530/.551 lift. Stock '60s distributor (nice tight), now has Pertronix module added to it. Carb is 670 cfm Holley right out of the box. Weind intake. 4 speed tranny and 3.73 gears.

What plugs should I be running in it? At present I have Ford Racing plugs tried both AR3935 and AR3934 gap is .037". With both plugs engine has a bad miss, break up above idle when driving it. Engine is new and this combination is the only thing I've tried. I've changed the points over to pertronx and new 8 mm solid wire core wires and new cap. Also tried different coils. Results in no difference. Tried timing between 10 - 18 degrees initial, vacuum advance is working fine. Suggestions ?

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Old 07-02-2009, 10:07 PM
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Engine miss

If you've tried 2 different sets of plugs with the same results then your plugs are not the problem. What are you using for a coil and what voltage do you have going to it? Does it run good if the engine is reved while in park or does it break up as well doing that? This may be a starting point for your problem.
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Old 07-02-2009, 10:11 PM
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engine miss

I gues if I would have read the post a little closer than i would have seen the part about the coils...lol Check your voltage though. Do you a vaccum advance canister on the dist and does it have ported vaccum to it? Something else to consider.
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Old 07-02-2009, 10:35 PM
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Full intake vacuum to canister. The voltage is about 13+ volts to ballast resistor. It rev's good without the load of driving just standing still. Quick snappy throttle response. I guess I could try by passing the ballast resistor to see if any difference.
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Old 07-02-2009, 10:38 PM
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RSM has a point, "what voltage do you have going to it?" If you are using a internal resisted coil, the positive voltage wire to it needs to have battery voltage. (from your ignition switch) Information should be printed on the coil.

Your spark plug choice, and gap should work fine. I would double check the spark plug wire routing. 18436572 clockwise rotation. 5 and 7 are easy to get crossed up. 6 and 8 are less common, but still easy enough to cross.

Last edited by carsavvycook; 07-02-2009 at 10:40 PM. Reason: wrong word
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Old 07-02-2009, 10:53 PM
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I've rechecked wires 18436572 so many times...... But I have not checked voltage out of the ballast resistor to the coil. The coil in there now says to use an external resistor. It is 1.5 ohm resistance coil as required by the pertronx module.

Will running the coil without the ballast resistor burn up the coil?
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Old 07-02-2009, 11:08 PM
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Yes it will. Are you absolutely sure the air gap for the Pertronix is correct?

Also check the compression in the offending cylinder.
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Old 07-02-2009, 11:17 PM
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The only thing that I can recommend is to check and verify with Pertronix that you can use the solid core spark plug wires with their equipment.

I forget the manufacturer at the moment but their rule was "Do not use solid core wires with this unit". I remember this because I had just installed a hand made set of solid core wires the week before buying the electronic conversion. This may not apply to your situation but it is something to check.

Otherwise, all I can say is That is one terrific ride. Enjoy.
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Old 07-03-2009, 09:50 AM
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engine miss

First off, you should NOT have full vaccum to the distributor. You should have ported vaccum. You need to find a vaccum port that may have a small amount of vaccum at idle. As you increase engine rpm (hold your finger over the port)the vaccum increases accordingly.Disconnect the vaccum and set your timing,10 degrees should be good for a start. As the engine revs the vaccum increases which advances your timing. Sounds like your voltage to the coil is fine. Checking the airgap is a good idea on the Pertronics.
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Old 07-03-2009, 12:51 PM
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Prior to installing the Pertronx, I had regular points. The engine ran the same as it is now, bad. I installed the Pertronx to help the situation, but there was no change.

Pertronx gap is .009" minimum and even all the way around, distributor shaft is shimmed to .008" play up and down. The weights and springs are free and seem reasonable spring load.

I just added stainless braiding to each plug wire to shield it, but that was no help either. I don't think the solid wires are affecting the Pertronx since it was same issue with points. I will recheck literature it came with to see if I should have resistor wires.

I forgot to check voltage at coil coming out of ballast resistor. What should resistance be across ballast resistor? The coil says to use with external resistor.

I sure appreciate all you guys suggestions to my problem. I realize it hard to diagnose far away.
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Old 07-03-2009, 07:54 PM
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engine miss

Make sure you read my previous post. The vaccum advance must not have full vaccum to it.
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Old 07-03-2009, 09:17 PM
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Quote:
Originally Posted by RSM
Make sure you read my previous post. The vaccum advance must not have full vaccum to it.
The OP does not have a factory built 427. It has been modified.

With his compression ratio, and running pump gas, a manifold vacuum source to the advance will help to keep it from 'pinging', when getting on the throttle.

His complaint is a yellow spark at the plugs, and this could very well be retarded initial timing, combined with a ported vacuum source. The dwell comes to mind. It governs the 'on' firing time of the ignition coil, and a weaker spark could be produced.
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Old 07-04-2009, 01:16 AM
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I know you said that it was breaking up before you put the Petronix in it...but I think Seven up is right about not using the solid wires. So..while it's probably not your problem, it could cause one.

Your 670 is a street avenger right?

The reason I ask is I have seen a lot of complaints about the street avengers running poorly.

That being said...I have had a number of the street avengers, and even one of the off-road 670's that is supposed to be horrible. They all needed a little something...but they all ran perfect after a little tuning.

Even though I normally say that 90% of all "carburetor problems" turn out to be ignition...I am thinking this might be your 670 needing a little tuning.
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Old 07-04-2009, 12:29 PM
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I know the Holley is a 4150 but the numbers on top are ground out. Makes me assume it's a Holley remanufactured unit. Purchased as a 670 cfm. I don't think it's a street avenger as the diaphragm is not plastic.

The only way for me to know about jetting and power valve is to take it down. Will do that after the 4th.

The Pertronx literature says nothing about using solid plug wires. I prefer the solid wires for longevity. But It did say a low ohm coil (less than 1.5) could be used if there is an external ballast resistor. I have a higher output coil with only 0.4 ohm resistance that I can try.
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