14 minutes ago, Mark Maras said:

When it doesn't want to rev past 4000 rpms, is that under a load? Will it rev past 4000 rpms with the trans in neutral or with the clutch disengaged?

It’s only under load, I didn’t rev super high but I didn’t notice anything odd over 4k in neutral

Check the grounding of the distributor. Or fix it if the ground test results are poor. The module's main ground is through the mounting points, which require a good grounding of the distributor body. The instructions don't really make that clear. Run a separate ground wire if yours is missing. You need that current flow to create a strong spark.

https://images.carid.com/pertronix/products/pdf/1183-installation-instructions.pdf

On 12/29/2025 at 10:25 AM, lm71z said:

It’s only under load, I didn’t rev super high but I didn’t notice anything odd over 4k in neutral

The reason I asked is that I had a similar problem many years ago. The difference is I was in a stock 71 Z on the freeway when the car slowed and wouldn't go above 3000 rpms under load. It would free rev to 6000 rpms with no hesitation. My Dad knew instantly what was wrong. I blew out the fuel filter under the hood, and it ran great again. It does seem odd that a poor fuel supply would occur when you're working on the electrical system, but I'd give the fuel system a quick pressure and volume test to rule it out. You also mentioned that there was a slight problem above 4000 rpms in the past. Maybe it was caused by a lack of fuel, and just got worse.

2 hours ago, Mark Maras said:

The reason I asked is that I had a similar problem many years ago. The difference is I was in a stock 71 Z on the freeway when the car slowed and wouldn't go above 3000 rpms under load. It would free rev to 6000 rpms with no hesitation. My Dad knew instantly what was wrong. I blew out the fuel filter under the hood, and it ran great again. It does seem odd that a poor fuel supply would occur when you're working on the electrical system, but I'd give the fuel system a quick pressure and volume test to rule it out. You also mentioned that there was a slight problem above 4000 rpms in the past. Maybe it was caused by a lack of fuel, and just got worse.

Typically...

Dies fast = electrical

Dies slow = fuel