V.I. Outlaw

Vacuume ports under the carb have been plugged with brass plugs so unless i drill them out boost ref is all I have if I want the power valves to actually work. I need to get the boat in the water and test. C&J built the carb for blower application. I will call them and see what they say.

supermx96

11.5 is the max i want to see on boosted emgine , i have melt a piston last summer at 12.5 afr

MILD THUNDER

iTrader: (3)

Marine is a little different when it comes to carbs, especially with a blower. For the most part, the PV's are open when on plane. There aren't many scenerios where you're cruising pulling manifold vacuum with a blower.

For example, lets say your running 3500RPM, chances are you may be seeing 0'' on the boost/vacuum gauge. At that point, the valve is open, whether its a 2.5, 4.5, 6.5, etc. Vacuum keeps the valve closed, no vacuum, its open. Now, in a car, you can cruise on the freeway pulling vacuum, keeping the valve closed for good economy. Then when the throttle is opened, vacuum drops, pv opens, and provides the extra fuel you need to accelerate. Boats for the most part rarely see this light part throttle cruise scenario.

Running a single carb, making almost 800HP, you need some fuel flowing thru that carb. From what I've seen with that single dominator setup, you'll want PV's front and rear, along with BIG jets. Not a fan of the 3 circuit carb myself.

If it were me, I'd probably install 4.5PV's, hook up the reference line, install #100 or #102 jets, and start making some passes, checking plugs at cruise, and WOT. Start fat and work your way down. With that blower setup, watch the #1,2, 3, 4 cylinders. The Fronts will run leaner than the rears.

jamontes

iTrader: (2)

Great Post - Thanks for the insight Mild Thunder... V.I. - I am about a week or so away from installing this exact set up in my Baja. Keeps us posted on your results. I have Nickerson Dominators on mine, but did make a mild cam change thaks to RM Builder.

benjen

You have 3 circuit carbs...............I would think you need to play with each air bleed as well!

articfriends

iTrader: (1)

Regardless of your how your power valves are referenced or how your carb is set-up, ALOT of guys have turned pistons into ashtrays guessing at jetting, the ONLY right way to do it and know your good is to install a O2 bung and buy a afr meter. they are not much these days and then you can dial this right in without guess work. If not, VERIFY wot fuel press then put a set of #100 or 102 main jets in secondarys and work your way down until plugs look decent after wot, a hard feat too do these days wiith unleaded, 10% eth gas, (pugs don't color that good) Smitty

MILD THUNDER

iTrader: (3)

I concur smitty. Big fan of the 02 bungs myself.

V.I. Outlaw

Thanks guys!! I have installed 97s in the secondarys and will test it this weekend. The previous owner ran it with the 94 jets front and rear with the power valves open all the time. It was really rich at idle but seemed fine at wot. He ran several poker runs and claims to have gotten 87mph out of it. I just had motor freshened up and the only thing my builder had any concern over was the exhaust valves looked like they had seen some heat so we replaced them with new inconnel valves. might have been caused by the intercooler being non functional at the time. (pick up wasent low enough). That has now been fixed and the power valves being open at idle has been fixed. I pulled the plugs at end of last season and they looked good,no signs of detonation or excessive heat. Can a AFR bung be installed in CMI elbow top headers? There is a blocked bung where the pipes merge into the collector. does this just go into the water jacket or all the way into the exhaust gases? Where is the best place to mount an AFR bung with my setup?

V.I. Outlaw

There is a picture of my setup in the Baja section under "25 outlaws with big power" I think thats what The OP called it, page 2 I think.

MILD THUNDER

iTrader: (3)

I saw in your Baja post, that your making 7.5psi of boost. This concerns me a little. With a 540CI, that little blower, you must be driving the heck out of that blower, or have a really small cam and peanut port heads (which I doubt).

Id be very careful with that setup, especially without a intercooler. How much are you overdriving it now? Do you have a intercooler? Alum or iron heads?