ICDEDPPL

iTrader: (1)

The only reason not to go with a screw blower is price, roots vs screw = no contest. Screw blower is better in every way, intake temp, power, parasidic loss, idle quality, efficiency..etc.

Young Performance

For that power level, I would prefer a 4L. However, it's not available in a top mount. For a carb engine at 1000 hp or less, I would use a 3.3L. Anything more than that would require a 5L. Personally, I wouldn't go to the 8.3 until I was looking for well over 1300-1400. But, I wouldn't be doing it with a carb anyway. It would be EFI. We have made as much as almost 1300 with a 4L and over 1400 with a 5L, but they were EFI.
Eddie

HaxbySpeed

The 4.5L is badazz, and fills the gap nicely between the 4.0 and the 5 / 8.3L. The 4.0 is good too, they're both very efficient SC's. I wouldn't step up to the 5.0/8.3 unless you really need it.

HaxbySpeed

Looks like we were posting at the same time

MILD THUNDER

iTrader: (3)

Good info ! Is there a downside to running the 8.3 slower than say the 5 liter turning faster ? I'm used to roots stuff. I have noticed most screw blowers seem to be highly driven via the belt ratio

Young Performance

Yes,there is a huge downside.....distribution when in vacuum. They will pitch the air and fuel to one side. Now, I will say this. I don't really use the top entry blowers since we do such few carb setups. Maybe they are better than the axial blowers. I'm just not sure. In the axial blowers, air and fuel distribution is poor at idle and when in vacuum when the sc is spun slowly. For that reason, it is important to size the blower appropriately. I want to spin a Whipple at least 2:1. We have spun them as high as 3:1, but that's not ideal. You have to throw the Roots mentality out the window when dealing with a screw compressor.

I've seen them as bad as 3+ points of AFR difference from bank to bank when the blower is turned slowly. Once it gets out of vacuum, then it straightens out. We have gotten them better by using our DIS. The spark is hot enough to burn up most of that excess fuel, but's it's still not perfect. It tough to tune one when one bank is in the 14's and the other is in the 10's. Without having port injection, there is nothing that you can do other than spin it faster.

Whipple are absolutely wonderful pieces. And I totally agree with Haxby about the new 4.5L. It is an awesome piece. You just have to size them correctly. Bigger is not always better.
Eddie

KAAMA

iTrader: (1)

Okay, great info and responses guys, thanx! I did not know Whipple made a 4.5L too. Wow, I am have been really out of the loop for the last several years with all the marine performance upgrades stuff.and rarely on OSO much anymore with many changes in my life.

Anyway, so what do you guys think about the correct size of a carbed Whipple blower on a 582cid engine (4.3/8"stroke x 4.600" bore)....would the 4.5L be the right fit for my 582cid?....or.....would the 5.0L be the better choice?

Not trying to set any world records or anything. I think you guys know me by now---I just want excellent drivability, shifting, i.e. smooth idle quality, long 45-60 minute idling periods without loading up, etc, etc..

Not sure if this is relevant for for chosing the right size Whipple, but keep in mind, I will be running Big Tube Stellings w/5" collector/tailpipe dia. and want to turn the RPM's to about 6000-6200rpm @wot or so----1.5:1 gears on the #6 Merc drives----cruising speed/RPM @ about 3500-4500rpm or so. Inner coolers will begin to function once the boat is on plane---not during idle speeds. I think the inner coolers are the cupernickle (?) and came from The Blower Shop---so, they're not Whipple designed inner coolers (if that makes any difference or not---?).... and I will be doing most of my boating in fresh water here in the Great Lakes region. Also, will be using one of the top quality ignition boxes made by the guys who used to work for Crane----I cannot remember the brand name at the moment----anyway, it is somewhat based off the Crane Marine Ignition box.

Thanx again for all the input, friends

Young Performance

Kaama, the 4L and 4.5L are not available in a top entry (carb version) For a carbed setup, your only option is the 3.3L and 5L. To keep it simple, if you want under 1000 hp then go with the 3.3. If you want over 1000 hp, choose the 5L. This is all based on a carb version. If you go efi, use either the 4L or 4.5L.
Eddie

sutphen 30

give me a few details on this one,,what heads and ci?

HaxbySpeed

If you're stuck on going carbureted then the 5.0L is the clear choice. It will bolt up to everything you already have, and will feed those cubes at that RPM no problem. IMO, the 3.3 will run out of steam long before you get to 6000rpm with a healthy 582. The 4.5 would really be the perfect blower for your scenario, however.... I would price out the difference between the 5.0 and ignition box vs. a 4.0 with injection + selling off your existing carbs, linkage, flame arrestors, etc. The 4.0 will still get the job done and is cheaper then the 5 and 4.5
EFI is going to make achieving the rest of your performance goals much easier, and protect your investment.