I gotcha..makes total sense thanks!!

Also do yourself a favor, if you can run a vacuum guage to see where the power valves are opening is hugely helpful.

yea I've been planning to do that for awhile but now am having head/valve issues that I'm sorting out with the machine shop...I do have a vacuum/boost gauge but obviously its below the blower so won't tell me much...I plan to hook a portable gauge up to the vacuum port coming out of the bottom of the carbs or I have 2 vacuum ports on my carb adapter plate that I could use

From what I understand...PV should be sized half of what the vacuum is correct?? so if I'm pulling 10 lbs of vacuum at idle I need #5 PV's..is that correct??

That rule with pv's really doesnt apply with a roots blown non boost referenced carb setup. The 10.5's you have are fine.

As suggested, mark your dash where the secondaries open. Stay in the primaries and monitor your afrs. Adjust primary jet until you get desired afr. Then for high speed/wot, adjust your secondary jet until you get the desired wot afr.

I dont use those jet kits, as you said, they only have 2 of each jet size . Doesnt help when you need 8 of each on a twin engine twin carb setup.

I like to see the afrs start dipping into the low 12's early on , and into the mid to high 11's towards wot. I personally wouldnt bring all the timing in that early. That works great for NA engines, boosted engines not so much. Depending on how much boost youre running, 30* total may not be enough timing, and will be hard on your exhaust valves at wot.

I ran 88 primary, 96 secondaries, with pv in primary, on my blown 468s with holley 850s. That would prob be a good starting point for you to work off of.

I actually found an old post of yours MT to get where I'm at...kinda copied you exactly since ours motors at least at the time of that post were somewhat similar...

As far as timing...I just went with the threads I read as a starting point that 30-32 all in before boost builds is about where I'm probably gonna end up...to be honest with you this is my first crack at setting up and tuning a blown big block...I've done a blown small block in my dads street vehicle but it barely sees much over 3000 rpms so that was much easier lol...what should I look for as far as timing?? I assumed 30 was "safe" maybe not??

You mentioned the timing possibly being hard on exhaust valves...let me run this past you...I have at most 5 hours on this motor including literally 2 WOT runs that were at very most 1/4 mile long...seeing my WOT A/F and knowing where my timing is....do you think this would cause an exhaust valve to stick open in that short amount of time?? I'm asking this because it happened and I'm somewhat getting into a small battle with the engine builder over it....full disclosure with the heads...I bought them from a member here knowing that one had a sticky guide...I told them that and they charged me accordingly to "go through" the heads which on my itemized bill included cleaning, magnafluxing, valve grind, "checking/measuring guides, and assembly/setup for my cam using all new spring components....used the valves that came with the heads which are Inconel exhaust valves and they said the guides looked fine...I find it a little fishy that after 2 WOT runs it sticks a valve...thoughts??

Thanks

Stewart

Oh also as far as boost...it maxed out at 5 PSI on the gauge when I did those 2 pulls

Hard to say on the guide issue. Not enough timing, along with being lean, will certainly elevate the exhaust temperature.

the exhaust guides need to be on the loose side with forced induction. Also, i removed my exhaust valve seals tension springs to help get a little more oil to the guides. Some guys dont even run seals on the exhaust side for that reason.

I might have to agree with the builder. I had a problem when I changed from GM heads to Merlins, I was sticking exhaust valves also. I stuck #8-3 times and #6 once. My head guy kept going through them and everything was good. I would stick a valve within minutes after getting on plane. My Gen V engines were not getting water flow to the back of that head. Once I drilled out the back of my intakes and plumbed them to flow water it never happened again. All 4 corners run the same temp now. Before I would see 50°F differential.