Here's the deal:

509ci NA 9.25:1 compression
AFR 315cc (305 cnc'd) Heads
Crane 741 (168741) Cam
Crane ignition Hi6M
Dart 6200 Intake (HP500)

I am changing out the stock Holley carbs and fuel system. -8 line all the way from the tank to the carbs, new fuel water separators (3/8” to -8 npt bigger openings), Keith Eickert Fuel Pump 120 GPH upgrade and Barry Grant Mighty Demon Marine 850 carbs.

I already know that this is adequate to feed the power.

Here are the questions:

1 – I need a baseline, or a place to start, for jetting. Do I stagger like I did on the Holley’s or do I just start with the standard 85p 93s and go from there?

2 – With so many people talking AFR’s. I purchased a FAST system and have had my tails bunged. Looks like the numbers should be:

Idle 13.4 to 14.1
Cruise / light load 13.6 to 14.1
WOT 12.2 to 13.5

Real life numbers would be great, no need to speculate here as I can do that all day long myself. If you’ve ran a similar set-up, great! That’s who I’d like to hear from. No blower comments, it’s Naturally Aspirated. Thanks in advance!

Dave

I will dig out my dyno sheets tonight I have a setup similar except for the heads. Got 565 on the dyno will be interested to see how much more the heads do over stock 500 hp heads ported

Anybody?

Dave

A Demon is a tricked out Holley ,,so i would say same as holley.

No it isn't. Los of differences in the way a demon works.

I for one really hate them.

Is anyone running Demons on a N/A boat? I'm really surprised. I know the 850's can flow up to 1000 cfm, just still wondering if I should stagger the jets.

Thanks,
Dave

I dont know of anyone using demon carb on a boat.
Merc uses holley on all perf products ???

Is it a merc manifold with the PCV valve in it?

To stagger question Merc sets them up safe and staggerd.
I am sure you know this = but 8 egt's on the dyno is the only way to tell for sure on each cylinder / stagger question.
Your one per side a/f ratio will keep you safe but not perfect.
Find a good dyno shop and spend the money on one at least one to know.
My 2 cents
Thumper

Demons in my experience work really great at WOT, but they suck everwhere else.

I concur Jeff
Me no like the Demon
Thumper

By u boy has one on his n/a BBC.