Speedway Car that misfires at 5500 rpm

Back in my racing days,I used Jacobs Electronic high voltage spark electronic box.

Believe it of not the engineer is calling for COPPER plugs!

Everyone know Platinum will last but copper is still the best conductor.

Try a cheap set of Champion or Autolite and see what happen.

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Also check for

Intake gasket leak.

Fuel pressure

CFM requirement for the Holley carb.
Try a an without the air filter and see is it still choke at 5,500 rpm.

Good luck

might need rejetting as it may be laening out or starving at those revs
a larger fuel delivery line may help also
the valve springs may not be strong enough to cope at those revs!!!
you would need triple cut seats & stainless steel inserts are a good way to go
play with the timing or stick it on a DYNO
i bet you get more from timing & valves
let me know how it turns out or just ask questions im happy to help as i can no longer indulge myself [ broke my back]
CHEERS from DOWN UNDER
Rob.