Ignition break up at 4000+ rpm

[Ziegelsteinfaust]

I have a mid 90's Corvette LT1 engine in my C10 with a gmpp 4 barrel intake, Q-jet, and pertronix equipped distributor. The engine was rebuilt with 10-1 compression, and not the factory 10.5-1. The heads are gasket matched to the intake, slight porting, and back cut valves.

The truck pulls hard to 4000/4500 rpm where it just rolls over, and you can hear then engine kind of make a bum bum bum sound.

Right now I am convinced it's ignition break up because a bad module.

All plugs check out fine, and the timing light works on all cylinders.

The truck drives great under normal circumstances, and mpg is right where it roughly should be. I have no issues hauling heavy weight either.

Any ideas on something else to check?

Or at the next oil change. I am going to just put the distributorless ignition back in.

[Willshook]

Making sure the Pertronix has 12V would be my first check.

I wouldn't go back to the OptiSpark for anything...

[Dead Parrot]

Did it always do this or is it a recent development?

Possible the cam is RPM limited.

I would change the plugs first. Possible you got a bad set or they somehow went bad after installation.

[Ziegelsteinfaust]

Originally Posted by Dead Parrot

Did it always do this or is it a recent development?

Possible the cam is RPM limited.

I would change the plugs first. Possible you got a bad set or they somehow went bad after installation.

I belive it to be recent. I rarely take it above 3000 rpm to do anything.

The cam is rmp limited, but that should start to happen around 5500 rpm. Not 3500/4000.

[MySons68C20]

Go ahead and put a new module in and see if that works.If not it never hurts to have an extra.


"Yes, a bad ignition module can definitely limit the RPMs of an engine, as it controls the spark timing and intensity, which directly affects how well the engine can combust fuel at higher RPMs, potentially causing the engine to lose power and struggle to reach higher revolutions per minute when faulty.
Key points about ignition modules and RPM limitations:

Spark generation:
The ignition module is responsible for triggering the ignition coils to create the spark that ignites the air-fuel mixture in the engine cylinders.

Weak spark at high RPM:
When an ignition module is failing, it might not be able to produce a strong enough spark at higher RPMs, leading to incomplete combustion and reduced power.
Symptoms of a failing ignition module:
Besides limited RPM, other symptoms include rough idling, engine misfires, difficulty starting, and a check engine light."

[Ziegelsteinfaust]

Originally Posted by MySons68C20

Go ahead and put a new module in and see if that works.If not it never hurts to have an extra.


"Yes, a bad ignition module can definitely limit the RPMs of an engine, as it controls the spark timing and intensity, which directly affects how well the engine can combust fuel at higher RPMs, potentially causing the engine to lose power and struggle to reach higher revolutions per minute when faulty.
Key points about ignition modules and RPM limitations:

Spark generation:
The ignition module is responsible for triggering the ignition coils to create the spark that ignites the air-fuel mixture in the engine cylinders.

Weak spark at high RPM:
When an ignition module is failing, it might not be able to produce a strong enough spark at higher RPMs, leading to incomplete combustion and reduced power.
Symptoms of a failing ignition module:
Besides limited RPM, other symptoms include rough idling, engine misfires, difficulty starting, and a check engine light."

I don't have another module, and the HEI i have is not compatible with my engine. Wrong distributor gear material. Nor do I own wires for it.

[MySons68C20]

Originally Posted by Ziegelsteinfaust

I don't have another module, and the HEI i have is not compatible with my engine. Wrong distributor gear material. Nor do I own wires for it.

$50.00 buys a module for the Pertronix....