Man messing with carbs to get a good AFR results,4 carbs to tune , I don`t miss those days ... have a truck full of bleeds and jets etc . If I added up all the fuel I used tuning I`d probably could have gotten EFI 5 years ago.
Not sure what you got going on there , seems strange to have it so lean with such large jets.

simple jet plate mods though brought jets into range , post is just to share what I found and what I did plus to help understand they are rolling the dice if they bolt stuff together and NEVER at least look at the afrs. A little rich, waste gas, alot rich, well can wash the rings, alot LEAN, game over! A local guy put roots blown 509s in his 38 or 42 fountain (never saw the boat), wanted me to help check "tune" on the water. Dual 4bbls, 8-71s. I told him my hourly rate and that he would need to get some 02 bungs put in SOMEWHERE so I could get some readings. Said he'd just do it himself and look at plugs (I did NOT have anything to do with building his motors or picking his combo). Called me up this fall, said he took it out and everything was "fine", put it in boost for about 15 minutes around 4200 to 4500 and for some reason motors started breaking up. Opened hatch and there was oil blowing out his breathers. I just shook my head. I told him he probably hurt the motors, he wanted to argue with me. So after it kinda sank in that they MIGHT be hurt he asked IF I could fix/ tunes his motors at my shop, dyno them, etc if they were hurt. THEN informed me hed like to come "hang around" anytime I was working on them (he's retired}. I said your welcome to come see them apart, see them run on dyno but I cant have you standing here all day every day. I decided I was kinda "booked" up at that point, not worth the aggravation!! second or 3rd time he's hurt these motors from what I heard!

Wonder if that's the same guy I sold my 8-71's to? Almost sounds like same GUY... ahhhh

You spent 3 days of people time making the tune right. If you know better, he would definitely be money ahead starting with the best carb possible for the app.

Point is the carb theoretically should have been right for the build but didn't but articfriends was kind enough to share info with us and got to the bottom of the issue and shared. There's got to be a ton of 850's on top of 600 hp engines without issues. I've been running carb performance engines for years and never ran into what he did.

should have put a Dom. on it.

True but keeping under 600 hp. My next builds in the works as I gotta get this 12 meter out of the shop and on the water. will interesting and will post dyno. 496 or 540 with 4150 970 cfm pro systems and holley 2 circuit 1150. Who knows we'll see. Just depends what heads I strap on. Any info is good info. Will have both with adequate ported intakes. Wished I had my NOS bow tie blocks but is what it is. Good bad indifferent will post. Would like to go the 548 route but will see what future brings. Regardless will be dyno' with both. Fk. I just wanna get on the water. Lol.

my guess would be the 496 like the 4150 pro systems 970 and the 548 be liking the 1150.

Any Mark 4 bow tie blocks around pm me.

John