Where to start?

[Wedgexx]

My 416 has a small miss at constant rpm. Especially noticeable between 2500-3000 rpms. It has msd billet dist that's locked out. Msd blaster 6 al and wires. Ngk racing prov 7 plugs,and Quick Fuel 850 carb. It doesn't stumble on acceleration.
I recently changed power valve to 4.5 due to running really rich. I noticed it more after swapping power valve.
I'm not sure if I have fuel or firing issue. 150# compression on all cylinders,valve lash good. Custom grind comp cam 245/251 556/573 110 lsa. I'm running it at 24* timing due to street driving almost totally.
Swap carb first? Already swapped cap and rotary.

 

[fishy68]

How do the plugs look? Sounds like possibly a lean misfire. Maybe just me but it seems to me that race plugs tend to foul easier. Strokers generally like 30-32* of timing, why do you have yours set so low? I run mine at 28 initial with 6 degrees of centrifugal advance in by 2000 and drive it on the street a lot. Not enough timing can help foul plugs quicker.

Instead of being a parts changer why not diagnose the problem. If it were mine I'd install a wide band 02 gauge so I could see just what the fuel mix is really doing. I installed one on mine and was astounded at how far the carb was off even though the plugs didn't look too bad

 

[gtsdude]

With distributor locked out and you have only 24 degrees of timing you may be getting spark jumping between terminals in the cap when you start to rev it up, especially if the rotor is not phased correctly. Bump up the timing like noted above and see if that helps. I had a similar issue when I broke a new cam in, just set dizzy to where it would run to break it in and forgot to set it with a light on first test drive, would start missing at 5k, bumped it to 34 total and no more missing.

 

[Wedgexx]

Thanks for the replys. I'm going to go up on the timing and see how that works. The miss was more noticeable when I went from 6.5 to a 4.5 power valve. That's why I think it's possibly a lean misfire also. The plugs are a little black and smutty which looks rich.
This is my first stroker, been out of playing with cars for 25 years. Things have changed a lot from my Mallory dual point and mild 340's.