Jetting help
 

Ok so i have my boat ready to hit the lake (sunsation dominator). I need a baseline jetting number. Holley 4160 750 with metering block conversions done. Engine are 489 strokers with air gap intakes, l29 vortec heads, xm284hr cams, 9.4:1 compression, gil dry exhaust. Also do i need to stagger? I was looking at hp500 jetting as baseline but i know that is an 800 and from what i understand only staggered due to dart intake. Thanks in advance.

As far as jetting goes, it really isn't as simple as XX jets, for XX horsepower, or anything like that.

Slap a 1050 dominator on that engine, and you might need 96 jets to get to 12.5 AFR. Slap a 750 on there, and it might need 76 Jets.

What I would do , is put the jets in the carb, that came with it, for a starting point. A marine 750CFM, #9015-1 4160 carb, had 76 primary, and 34R9716-27 secondary metering plate, which would equal about a #79 jet.

I think your 750"s will work well. Like mild thunder said jets can be all over the board from carb to carb. Rule of thumb is if you need to go up or down more than 4 jet sizes - you have the wrong carb. The difference btwn 750 amd 800 is so minimal. I don't recall what the difference even is. You'll be fine though. It's not uncommon to tune your carb in reference to what cylinders are a little lean and ones that are rich. Anotherwords to have four different jet sizes is no big deal. Once again just try and stay within that 4+ or 4- from out of the box std jets.

Suprised no one has said it......Wideband 02.

I had 480 hp's with the 800 9022 carbs with dual plane intakes and still had staggered jetting. Start with your baseline and with patients and a little time you'll have it dialed in. just give it what it likes. I won't get into a debate how to read plugs but I personally look at the base ring consistency 360. I focus more on the strap to see the heat (color change) close to half way up. Most people's first glance at my plugs think I run to lean. But all there looking at is the porcelain. (White).

Also number your plugs or have a holder for them to keep them from getting mixed up. Keep a magnifying glass to help if you have bad eyes.

Alaways good to have also. I'm not 100% sold on them alone however good to have and are relatively inexpensive. Call me old fashion I guess. Pretty soon we'll be able to sit in a chair with a 12 pack and watch droids assemble our engines also. I'm gonna make sure and have my 12 pack in bottles so a can throw the empties at those stupid things. Lol.

How do i put a wideband o2 in with no bung. I have one but its not like i can just shove it up the tail pipe without it getting wet. When i say dry exhaust i mean thru transom. Water exits at the tips. If there is a way I am all ears because that would definitely make life easy

Btw. Took it out today. Got 45 minites into break in varying throttle nothing over 3500. Runs great. Was gonna make a hit at about the 2 hour mark but didnt quite make it. Got buzzer. Apparently I overlooked the drain plug on the back of the bottom rail on the exhaust manifold. It decided to pop out. Upon opening the hatch I had a good 1 1/2ft of water. Good times. Glad the buzzer worked otherwise it could have gotten real bad. Took 3 bilges 5 minutes to suck it dry. Lesson learned. Next time i buy used exhaust check the fittings. Lol

Secondary jetting also depends on if you're secondary powervalve or if its blocked.

My secondary pv will be blocked