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Old 08-07-2007, 08:04 AM
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Ignition breakdown

I'm having a problem with my ignition breaking down at around 6000 rpm. My ignition combo is on a 383 SB Chevy. I have a 5 year old MSD 6A box, a 2 year old MSD Billet distributor, with a new cap and rotor and a 2 year old MSD Blaster coil. I set total advance at 36 degrees BTDC. New Accel 8.8 wires and under 600 mile Autolite double platinum plugs. I average around 2000 miles a year. When the plugs are brand new I can shift at 6500 rpm with no problem. As the miles accumulate on the plugs the shift point drops lower and lower down to about 5800. It sounds like I have a rev limiter, but I don't. I put on the new cap and rotor because I noticed the center button was burned out of the cap. That told me that I had too much resistance in the secondary ignition so I replaced the 8 year old Accel wires and put in the new plugs. I"ve had the plugs read by a tuner that I and others have a lot of repect for. He thought the heat range and mixture looked very good. Other parts of my combo I should probably mention are Trick Flow 23 degree heads with 64cc chambers and dished pistons to give me a 10:1 compression ratio. Someone mentioned battery voltage and wiring to the MSD box. I''ve tested both and everything is good to go.
I'm thinking that maybe this is normal. Back in the day I had a 70 GTO I used to race and I had to put new plugs in it every Subday afternoon that I did. I thought with the newer ignition systems and better designed heads etc, plugs starting to break down after 500 miles or so wouldn't be an issue.
Any thoughts?

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Old 08-07-2007, 09:27 AM
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spark scatter

Could it be spark scatter. If it happens after you run for a while I would think that is it. Ions build up in the cap and cause spark scatter. You can vent the cap with two 1/8 holes below the rotor but I think the new msd caps have them. That or you have a wrong cap rotor combo with it grinding like that. I could be way off but just giving you ideas.
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Old 08-07-2007, 09:48 AM
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Ignition breakdown

Thanks for the input. The cap is vented and I used the cap and rotor that came with the distributor
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Old 08-07-2007, 10:38 AM
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Doc here,

The first step is to upgrade the Coil + wire to 10 gauge...the stock 14/12 gauge won't support a performance coil at all...

Everybody turns a "blind~Eye" to this until their $1000 Ignition system RUNS like crap in a can.and worse than The stocker that came out...THEN They contribute to the delinquency of the problem by throwing another $500 worth of modules, Mag or Fiber optic pickups, Caps, rotors, 6a Boxes, WIRES , WIZ~bang platinum plugs, indexing, and still get no better performance...

You tell a guy the wire supporting the coil is under~rated, and you get a laugh up the sleeve..."yeah..like right.." when the reality of the situation is, a stock coil pulls down about 15 to 20 amps under full load..a PERFORMANCE coil pulls down Right around 48 amps..you do the math..about half that currant is converted to USELESS heat in the wire robbing the coil of peak power...and it falls on it's face at the top end...

The cure is almost always, replace the wire from the coil + to the Ignition switch...If that can not be reasonably done...get a relay, use the existing coil + wire to power it, with the key, use the CW AND N.O. contacts to deliver power from the battery to the coil +..you need a 50 amp relay for this.,


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Old 08-07-2007, 11:53 AM
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Ignition breakdown

Thanks for the input, when my hand heals up I'll add a relay to the circuit.
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Old 08-07-2007, 12:32 PM
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Good info on the current draw on the ol MSD

I don't think you are supposed to use platinum plugs with the MSD.

try a set of champions...
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Old 08-07-2007, 12:41 PM
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Ignition breakdown

Thanks for the input. I've tried different brands of plugs including Champions. I like the idea of a bigger wire to the coil, after all it is a 67 with the original wiring harness. Besides that I didn't have any problem when I was running an MSD modified Summit rebuilt HEI ignition distributor.
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Old 08-07-2007, 12:58 PM
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Ignition breakdown

Hey Doc what do CW and N.O. stand for? I thought I'd just run my hot wire to the relay from the Ford starter solinoid I have under my hood. I'll wire in a 50 amp fusible link to protect the circuit.
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Old 08-07-2007, 03:31 PM
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Quote:
Originally Posted by ernkazern
Hey Doc what do CW and N.O. stand for? I thought I'd just run my hot wire to the relay from the Ford starter solinoid I have under my hood. I'll wire in a 50 amp fusible link to protect the circuit.
Doc here,

Ford solenoid will NOT work..they are not made nor are they rated for continuous duty, and will overheat and fail within the first 60 minutes...(if not start a fire to the surrounding area..)

C.W = Center Wiper or movable Contact

N.O. = Normally Open (coil De~Energized) Contact.

You CAN NOT just toss a 50 amp fuse link in there and call it good...especially if the wire is only rated good for 30 amps on an AWG chart for the gauge and length of the run..guess which one is going to burst into flames first??? Ain't gonna Be the link..



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Old 08-07-2007, 04:38 PM
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Ignition breakdown

You misunderstood what I meant. I'm talking about connecting the wire to the battery side of the relay. The side where you would normally connect fusible links etc. to.
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Old 08-07-2007, 06:08 PM
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ignition

Earlier you said I would have to use a 10 gauge wire and the relay may flow up to 50 amps. Are you telling me now that the 10 gauge wire won't handle 50 amps? If not what size wire would I have to run from battery power? I should explain I already have a Ford solinoid under my hood. I use it to operate the Chevy starter. I would be installing the fusible link at the battery side of the relay then connecting a 10 gauge wire from the other side of the fusible link to the relay.
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Old 08-07-2007, 08:42 PM
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Quote:
Originally Posted by ernkazern
You misunderstood what I meant. I'm talking about connecting the wire to the battery side of the relay. The side where you would normally connect fusible links etc. to.
Doc here,



Then your Solenoid / Relay would be "On" 24/7/365, and you'd have dead battery's every morning..IF YOUR TALKING ABOUT COIL ENERGIZE......


UNLESS you were referring to the contact TERMINAL #87 of the relay, that brings power to the Relay, FOR THE CENTER WIPER, (#30 Contact) when energized by the switched, Fused ignition control wire..Then that would be fine...

(STANDARD BOSCH RELAYS..GET THEM ANYWHERE, $3.99 A POP, NUMBERS ARE CONSISTENT STANDARDS)





(DIAGRAM FOR THE RELAY)



  • COIL # 85 = 14 GAUGE Power From the "now Ignition" Coil + wire from the Ignition switch (on/off)

  • COIL # 86 = 14 GAUGE properly bonded ground.

  • CONTACT TERMINAL # 30 CENTER WIPER= 10 Gauge wire to the coil + wire.

  • CONTACT TERMINAL # 87 NORMALLY OPEN DE~ENERGIZED = 10 GAUGE WIRE From The fuse link and battery.

  • 87a is not used in this application.

Simple and Cheap as pie..

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Old 08-07-2007, 09:04 PM
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Quote:
Originally Posted by ernkazern
Earlier you said I would have to use a 10 gauge wire and the relay may flow up to 50 amps. Are you telling me now that the 10 gauge wire won't handle 50 amps? If not what size wire would I have to run from battery power? I should explain I already have a Ford solinoid under my hood. I use it to operate the Chevy starter. I would be installing the fusible link at the battery side of the relay then connecting a 10 gauge wire from the other side of the fusible link to the relay.
Doc here,

Not unless your planning to wrap the 10 gauge wire a couple of times around the car first..

For your purposes (at least, but, more exist)..the two parameters dictate the gauge of the wire for automotive..maximum ampacity of the wire by gauge (AWG Charts) , and length of the run (AWG Charts..or experience)..

You more or less won't be concerned with the rest..like composition of the wire, velocity factor, resistance per foot, type insulation, number of strands per circular mills..Skin effect, For Bare Bones Automotive wiring..

WHY are you using TWO solenoids (unless you have a heat soak problem?) , on a Truck with a standard battery Location? a Genuine GM DELCO starter and solenoid should operate the engine just fine on it's own..with stock headers and stock battery location.

It sounds like the PROBLEMS you are having (So Many Different, and all at once in Electrical, in ALL the forums..and I read them all....) you may be at the end of your Skill level, and tool compatibility..It looks as if it may be time to seek the help of a good auto electric shop in your area..to correct all the problems..

You could also start anew with a brand new kit..and remove all the OLD hacked harness..and install it all back in brand new..with instructions and phone support.

Our Rates are $125.00 an hour plus material per problem..area wide (SF bay area..) yours may be somewhere close.

I think I'd go one of those routes were I you..


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Old 08-07-2007, 09:15 PM
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Quote:
Originally Posted by ernkazern
You misunderstood what I meant. I'm talking about connecting the wire to the battery side of the relay. The side where you would normally connect fusible links etc. to.
hi ernk and doc. thats the way i read i read your earlier post, ernk mentioned he had a 6A box, i have that box on 2 different cars and as i remember the big fat red power wire is hooked to 12+ hot all the time, the ign switch is attached to another wire which activates the box with ign on. one of my cars has the ford soleniod and i hooked that big red power wire to the bat+ of the solinoid. good tip about the relays doc, i use those lots to offload current draw through switches on high draw elect. accesories. doc, the other day i answered the post about fuel sending units in gas tanks and mentioned i just did one in a C4 and the reostat was indeed in the tank halfway down right at the float pivot. you thought it was a jeep as in CJ4, it was a corvette. C4= corvette 4 gen. no offense intended ive read enough of your electrical posts to have great respect for your elect. knowledge.
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Old 08-07-2007, 09:48 PM
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Quote:
Originally Posted by techron
hi ernk and doc. thats the way i read i read your earlier post, ernk mentioned he had a 6A box, i have that box on 2 different cars and as i remember the big fat red power wire is hooked to 12+ hot all the time, the ign switch is attached to another wire which activates the box with ign on. one of my cars has the ford soleniod and i hooked that big red power wire to the bat+ of the solinoid. good tip about the relays doc, i use those lots to offload current draw through switches on high draw elect. accesories. doc, the other day i answered the post about fuel sending units in gas tanks and mentioned i just did one in a C4 and the reostat was indeed in the tank halfway down right at the float pivot. you thought it was a jeep as in CJ4, it was a corvette. C4= corvette 4 gen. no offense intended ive read enough of your electrical posts to have great respect for your elect. knowledge.
Doc here,

YES when you are using a Ford type of solenoid, the battery Side "ONLY" is a good positive binding post for good mechanical connections...NO different than the Solenoid "B" terminal (big top post) on a GM DELCO .. THAT is why they use it..

For Me it's Easy enough to confuse a C4 with a CJ4 when dealing with postings..when you consider between EMAIL, PM, POSTS, and folks walking in asking.."How Do I do this" and Telephone, FAX and INVOICE..I answer at least 150 questions in an 5 to 8 hour period..from a hospital bed....

AND most of what I deal with , Corvette wise..ENDS at the C3 Generation..getting too expensive to care for the new electronic nightmares anymore..at least here in California..

The one in the Avatar, is my DD..Rescued off the back of a truck on it's way to the crusher on the highway, for $800 and a running Ford probe..Since then it has been restored twice (5 years) and runs like a watch..and will hold it's own down the two lane..all numbers match..and it's #43 of 50 that EVER came to California that year..(not smog viable that year..) Last appraised (last year, at $31,000 by my insurance company)..the only other thing that would make it more rare, is a factory 4 speed..BTW this was the only year Corvette put in a L/S DANA Posi rear end STOCK..







When I rescued this car, it had no interior..No paint (to speak of..) , would barely pull itself on a trailer..and everything rubber..wasn't..


This is about 3 months after..Helps to have shelfs full of parts..


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