SBC banging @ 3200 RPM

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Blue man

Blue man

Blue Dart
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Jun 12, 2016
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Crosby, Txeas
I have 30 over 340 with eddy aluminum heads, 3310 Holley vacuum secondary, mild purple shaft cam good to maybe 5000 rpm, a built 727 tranny with 2500 stall, MSD mechcanical dist, E3 plugs, MSD 8 mm wires. It idles fine. At 3200 rpm the engine as developed a bang or mist fire. Oh, I did change recently to a new style coil it’s blue and squared shaped mounted on the passenger wheel well that MSD says works with the MSD 6AL ing box. It’s an older box mounted in the car to heater box. This is not a fresh engine build it driven only on weekends an older restoration,

Thinking a new cap and rotor, suggestings welcome...
 
You got a rev limiter in that SBM?
Either as part of the MSD, or perhaps in the tach
That sounds like an E-core coil. They seem to work well with CDI.
I had trouble with that fancy stuff and went back to inductive; with a big fat square-top Accell SuperCoil. No more trouble since 2002.

Cap, rotor and wires are not likely involved.

If it continues to bang after 3200 well then I guess it's not a rev-limiter,lol. In this case I would suspect rotor phasing. But first disconnect the vacuum advance can and try again.
 
Last edited:
AJ/FormS said:
You got a rev limiter in that SBM?
Either as part of the MSD, or perhaps in the tach
That sounds like an E-core coil. They seem to work well with CDI.
I had trouble with that fancy stuff and went back to inductive with a big fat square-top Accell SuperCoil. No more trouble since 2002.

Cap, rotor and wires are not likely involved.

If it continues to bang after 3200 well then I guess it's not a rev-limiter,lol. In this case I wouls suspect rotor phasing.
Click to expand...
It had a old Mallory coil in the car when I bought years ago. You might be on to something. I have the factory rallye dash and tach. I did update tach for the MSD system, again years ago...
 
AJ/FormS said:
  • Just started? Right after an oil change?
  • That happened to me when they took the ZDDP out of the oil and my cam started puking lobes almost right away.
Click to expand...
This is a car I drive every weekend and put gas in. It was bound to start giving me a few headaches. It stater with a new coil upgrade. I’m thinking it is distributor related...
 
AJ/FormS said:
You got a rev limiter in that SBM?
Either as part of the MSD, or perhaps in the tach
That sounds like an E-core coil. They seem to work well with CDI.
I had trouble with that fancy stuff and went back to inductive; with a big fat square-top Accell SuperCoil. No more trouble since 2002.
Hey AJ,
The question you ask over the weekend was do you have a rev limiter. The answer would be yes there was a 6200 rpm chip in the MSD BOX. I called the the distributor selller and he told me to pull the chip out and it worked. That little 340 will hunt now...

My apologies for your comment on don you have rev limiter I am a 60 year old dumb a$$....

Thanks

Blue Man

Cap, rotor and wires are not likely involved.

If it continues to bang after 3200 well then I guess it's not a rev-limiter,lol. In this case I would suspect rotor phasing. But first disconnect the vacuum advance can and try again.
Click to expand...
 
Blue man said:
I have 30 over 340 with eddy aluminum heads, 3310 Holley vacuum secondary, mild purple shaft cam good to maybe 5000 rpm, a built 727 tranny with 2500 stall, MSD mechcanical dist, E3 plugs, MSD 8 mm wires. It idles fine. At 3200 rpm the engine as developed a bang or mist fire. Oh, I did change recently to a new style coil it’s blue and squared shaped mounted on the passenger wheel well that MSD says works with the MSD 6AL ing box. It’s an older box mounted in the car to heater box. This is not a fresh engine build it driven only on weekends an older restoration,

Thinking a new cap and rotor, suggestings welcome...
Click to expand...
It's probably the damn MSD box. Half the new ones now days are Chinese knock off's and you never know.I don't think I have ever been to the drag strip but they didn't announce that someone needed a box of some number or the other. And By the way, SBC is Small Block Chevy. We call our engines by the numbers.
 
toolmanmike said:
It's probably the damn MSD box. Half the new ones now days are Chinese knock off's and you never know.I don't think I have ever been to the drag strip but they didn't announce that someone needed a box of some number or the other. And By the way, SBC is Small Block Chevy. We call our engines by the numbers.
Click to expand...
It was the rev limiter chip yeal your right Mopar or no Car. I have old habits. 340 340 340 or 440 440 440 I have both in 70 Darts

Thanks,
TMM
 
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