Heres a chart to figure out what CFM you'll require. I figured your 468, turning 6000RPM, 6lbs of boost, you'd need 1137CFM. With 30% larger carb, your at 1478CFM.

From what I've learned, it is very hard to overcarb a roots setup. Its not like a N/A setup, where the engine can become lazy. The Roots compressors dont like any restriction on top of them when they need to draw some air. The single dominator works well I'd say up to about 700HP. And I think you're gonna be well above that level. Have you thought about converting to a SSM setup???? Now that would be wicked!!!

Right now I am running twin 850 marine carbs on mine. No boost reference. I have 8.5PV's in the primarys. On a highly modified 468, I'd really lean towards a twin 750 or larger setup. I think you'll find the engines will idle better, have better distribution, and make more power. With a agressive cam and the blower, the engines like to be fat at idle (why you hear blower surge). With my single dominator, I had to back the idle mix screws so far out, they almost fell out the carb, just to get it not to stall when around the dock. I coulda changed air bleeds and did some mods, but never did. With the 850's, I can shift in and out of gear all day and not puke a motor. One thing against me though is the large ssm props, they bite hard when put in gear, so you might be ok.



The size of carb(s) or CFM required for a given application can be calculated by the following formula A: {(CID x RPM) ÷ 3456} x {Boost ÷ 14.7) + 1} = CFM required. The amount of CFM required will determine carburetor size and quantity. If you try to use a carb with less CFM than required, performance and economy may be greatly reduced. Bigger is not always better when selecting carbs that are 30% over what is required, you may encounter problems in fuel distribution.

How about my friend Brians Scarab redo?? I think you'll like this one Rookie. Was a 1979 Hull. Totally redone. Stringers, new deck molded for it, new transom, etc. Had 700HP 540's, with TRS. Did 92mph. Then, totally redone, and SSM IV drives and boxes installed. Still need to dial it in, but I think once its all done it should run upper 90's with the same motors.

Mild, that's a great looking old Scarab! Before I bought my Panther I was looking at a totally redone 1976 Scarab with twin small blocks. Great looking boat but I am glad I ended up with the resin bucket that I did. SSM drives would be nice I know I'll end up with different drives in the future once the blowers are added. I probably will need to replace transom eventually....it is a 80's Wellcraft. I will visit drives then.

Thanks for the links and the carb information. I have a few carb setups to try.

Changing from stock twin all in one shifters to Zero Efforts.
I bought new 4 new 33c cables. Had a friend machine new cable end J-Hooks for the Zero Efforts. When I bought the shifter I didn't realize that the J-Hooks did not come with them.

Last weekend I finished up adding a little Garming GPS, drive and trim indicators. I ran out of dash room so I bent up some Acrylic and mounted them under the fairing. I will redo this over the winter and I will probably end up removing the compass.

Awesome job, keep diggin'!

Love it man!

My compass went this summer when I needed a place to mount my custom heads up indicators! I like them but already working on small LCD that will display the indicators instead!

You got to love all the little projects we can do to these boats to improve fit, form and function!!

http://i69.photobucket.com/albums/i4...b/6a88170b.jpg

Out enjoying some fruits of my Labor..........Day!
Running back to Grand Haven with JimV (Valako) on little Lake Michigan.
GoPro is the next purchase. Camera phones just don't cut it.

Click on Video
http://i43.photobucket.com/albums/e3..._VIDEO0010.jpg

mild thunder, how did that scarab run w/ the inner strakes all the way to the transom ?

rookie were did you end your inners ? hows it runnin ?

thanks

Good catch on the inners!

I haven't added them yet. After removing the hook, filling in the bottom and sharpening the strakes I just put it in the water. I wanted to see the comparison with only doing one thing at a time. I then got lazy.

The bottom changed the attitude of the boat. It is much smoother in rough water with less trim. Actually the boat feels softer now and the bow kinda floats. Before the end of the season I will add the 6' strakes I already have and also have another set of strakes made to go to the end of the transom.

I actually haven't ran it out this year with my fastest props. I did 78.7mph @ 5800 with 4 people and under 1/2 tank of fuel. 6250RPM is where they peak.
After the bottom work with my cruising everyday props I went from 46mph to 51mph @ ~3600RPM (right before secondaries open) and 75.1mph @ 5200.

All I have been doing this summer is putting a lot of Gas in the boat. This winter the first thing I am going to do is pull the engines and put new cams in. The cams I have in now I believe I am just blowing gas out the exhaust!