Hey Jim - it turns out the hat issue is a known thing, the machinist called Superflow and they were well aware of it, their fix was to use a 7 1/4 hat with an adapter they sell. I havent been able to go back yet, but it's still on the dyno waiting.. First off I need to check the coil and Pertronix module, I had this same type of problem on my 65 when my Pertronix coil went bad, and it went away when I swapped an MSD coil in. I did not lay eyes on the rev limiter setting, although it WAS at 5800 when the distributor came out 2 years ago. I hand checked each valve spring on a Rimac when the heads went together, they are TA 1125's with 300+ at 1.4. The cam is a Camcraft 218/230, 268/280, 110 LSA, 110 ICL .300/.323 lobe lift , degreed and verified, which doesnt strike me as a cam thats gonna overwhelm an exhaust manifold. We brought in timing two degrees at a time for 36 total, it dropped off at 38 The heads had bowl work when I got them that I cleaned up - no port work done that I could see but I blended the roof into the bowl with a bias toward the outer wall past the valve guide , did not remove a lot of material.. Carb is known good, was on a 12.7/106 car for years with no drivability issues This video is the pull we tried with no hat: The results are on Sheet #9 This video is where we reinstalled the hat - you can see the readout at the end, it peaked at 354 at 4200: You can hear it drop off at 4200-4300. This thing was well on its way to making 400+ if you look at the trajectory of the pull. with the hat, the CFM's are stable at 4800, the fuel rate is stable, if it was a mechanical thing I'd think one or both would drop off or fluctuate. Sheet #8 from an earlier pull with hat when webrought timing back to 36 from 38. You can see the the lbs/hr and scfm dont show anything funny (to me anyway)... I'm just scratching my head till we can rule out electrical, and see if headers change the 420o drop off...
I may be wrong, 50/50 chance, but the Pertronix 3 rev limiter resets to 5000 whenever its electrically disconnected.
You're on the wrong side of the 50/50. The Pertronix III has a factory default of 5500 RPM, can be adjusted anywhere from 5000 to 9000, and will hold the setting, once programmed, even with battery disconnected or the ignition turned off.
I fooled around with Mine and anytime I disconnect the battery it reset to factory, and I wasn’t t sure about the rpms but 5500 can easily be right. I was pretty sure I had to reset to my desired RPM each time., I wish I had my instructions handy to verify.
I’ve seen plenty of ignition issues with Pertronix distributors/conversions that show up on the dyno. Something you don’t always notice driving,but the dyno makes it obvious.
I've heard they can scatter spark, so I also have a fresh point dist (set up by my buddy at Everyday Perf) to try too. I wont be back there until week after next. RKammer - didnt know if that setting was held by capacitor, which after two years certainly could discharge and do whatever..
