Something still doesn’t seem right. I have never seen a big cube big block want an air bleed over .070 with a small idle jet like a .035Freddie wrote: ↑Tue Jun 02, 2020 3:10 amHarry, thanks for the reply. This is idle only so haven't even got into the main circuit yet. That 5 mins run time was strictly idle.enigma57 wrote: ↑Tue Jun 02, 2020 2:07 am Freddie, I have been following with interest. Lost track of your current jetting, though. Holley lists 92 mains for these carbs if running power valve and 96 mains if power valve is blanked off. Now that you are getting closer with air bleed sizes, you may want to try the larger main jets Holley specs and see how they work with your new air bleed sizes. I'm thinking 75 idle air bleeds and 45 high speed air bleeds as a starting point? FWIW, out of box Holley installs 0.35 primary and 0.37 secondary pump nozzle size. Out of box jetting should give you a starting point or base line to work from.
Sounds as if your initial timing is good. Double check timing to make sure total advance is limited to 36 degrees, give or take 2 degrees either way when all in, though.
Do you have a good (known) carb to try in order to tell whether everything else is OK?
Regarding your priour carb running rich as well...... Is there any indication of ring seal issues resulting from fuel wash down of cylinder walls over time?
Just a thought,
I have 84 secondary jets with a 25 PV.
Yeah the engine is a brand new rebuild for the exact reason you mentioned, fuel wash. In fact builder said he'd never seen a cleaner intake and bores as it run so rich for 5000 miles. So trying to avoid the same.
I do not have another 4500 carb (a few 4150 style but no other 4500s)
Going to try an 85 IAB tomorrow (75 right now). Clearly still need to lean it out.
Have not checked total timing yet, will do that
Also going to check coil and spark voltage and make sure that's good
In dominators a .037-.038 jet and .066-.070 bleed work good on most engines