supercharged SBC's
 

Blew a motor this weekend and I am going to repower with blower small blocks.I am considering 383's.Does anybody have any experience in this setup.I plan on using 871 blowers.
Fishead

why did you want to use an 8-71?
Thats alot of blower for a "small" engine.

DAVE

FORGETABOUTIT

Vortec is now making a killer blow-thru carb setup that would be sweet on a 383 (in fact, either Hot Rod or Car Craft had a buildup or two within the last month). The carb is also completely sealed by the new blower box which will make life really easy.

You also don't have to worry about what to do with those blowers in terms of height.

Hot Rod magazine has a similar article on the Vortech carb blower.
Looks like the perfect set-up.
They tested it on a GM HT383 crate motor that was modified with a Edelbrock RPM Air Gap, 750 Speed Demon carb, Comp Cams XE282HR cam, 1.6:1 rockers, 9.1:1 compression, Vortech heads (I think). Without the blower this combination made 476HP@5500 and 505 lb-ft@4400.
First run with the blower had a 6" crank pully and a 3.47" blower pully pumped out 3lbs of boost for an almost 100HP gain.
Swapped the blower pully for a 3.125" and got 7lbs boost and 643HP@6000 with 600lb-ft from 3500 to 5500 and max was 606lb-ft@4900.
Swapped blower pully again to a 2.95", got 8lbs boost and 677HP and 627lb-ft@5000.

:D :D :D :D

Dave F,
The reason for the 871 is that it will turn slower and not make as much heat as a smaller one that would need to turn faster.
Dixie Doug,
Why do you say forget about it?
Fishead

What drives are you running? If they're alphas, FORGETABOUTIT.
A mildly warmed up 330 would probably go faster for a lot less money. But if you want that blower look a 177 or 256 would be more than adequate to feed a SBC at around 5psi without turning too fast.
my $0.02
Gary

I am running KAAMA drives so HP and TQ is not a concern.This boat was made for small blocks only Big Blocks will not fit.

I guess that answered my questions.
You might just consder a well built 350 with blower pistons. It's easier/cheaper to put together than a 383 and a little extra boost will make up for the torque. If you could use many of your current parts, you could do it very economically. If you have to replace the existing crank, rods, & pistons, then you'll only need a new flywheel, so a 383 might not be a bad idea.
A cast crank, good rods/bolts, blower pistons (8:1?), heavy duty valves, and a 177 (same blower used on BBC 525SC) at 5-7 lbs might make a reliable engine.
My $0.02,
Note, I've had a couple 525SCs but never put together a SBC blower motor, so my input may not be worth $0.02.
BTW are you running Twin Disc 502 trannys with the Kaamas?
Gary

Sorry, that was supposed to be FORGED crank.
Gary

I have 2 in depth posts about roots blowers you may find informative.
The post entitled "engine builders check in Supercharging 454".

Unless you plan on putting around 15# of boost in, an 8-71 is way too big. You'll spend more hp just turning it then you'll be getting back.
Just to give you an idea; an 8-71 will put 10# of boost in a 350 at 20% underdrive. On a 400, 10#=10% underdrive.

Just as a comparison; a 177 Wieand (for example) is able to put UP TO 16# of boost in a 350.

A 6-71 is able to boost a 350 to 7# at 10% under drive and a 400 to 7# at a 1:1 drive.

Just giving you some food for thought.

One thing you can trust me on is an 8-71 is too big for a marine SBC unless you're in competition.

DAVE

Supercharged SBC
 

Fishead,
I am running a littlefield 6-71 on a SBC. Been a long road getting it dialed in but I think I have finally got it. If I had it to do over again I would have built a BBC. But I am finnaly happy with what I have (for now:D ) What are your spacific questions? Drop me an E-mail and I will send you some pics. -------------- T

The 350's that I have are all forged 4 bolt mains,and Aluminum heads.The only thing that I would have to change is the pistons and the cam,so I think this is the way I am going to go.What kind of number could I expect (HP and TQ) with a blown SBC running about 5lbs of boost.

gary,
I am running Twin Disc 502's

fishead


Get in touch with Marv Hineman at The Blower Shop (661) 299-5483 www.theblowershop.com he'll be able to point you in the right direction.


Doug

fish,
If you need help feel free to email or pm.
DAVE

fishead
I'm lookig at setting up a cat with the Twin Disc trannys and swapping out the blown Kaama drives for a couple inline ASD 6s that I can get cheap. Do you have a manual or any practical info on the trannys?
How reliable are they?
Gary

I've never been much of a fan of AL heads on boats. Blow an impeller and you've warped it. But with the good internals,around 8:1 CR, the AL heads, and a good cam I would think you could easily push 5-7lbs of boost with a 177 blower on 92 octane.
You might want to contact one of the Blower specialists (back of Powerboat mag) for everything. They could probably give you exact hp numbers. My guess would be a little over 400hp.
BTW, dont forget a new ignition that will run 10 degrees initial and around 28 total.
Gary

I think I would try and duplicate what Hotrod magazine did as far as parts, and build a similar basket of parts. Seven pounds of boost and 600 ft/lbs. of torque with the weight advantage of a small block would make that an impressive combination. I have run aluminum heads on marine applications for better than 10 years and never had a problem. Mercruiser certainly seems comfortable with it. I think secondly the modern designs for better airflow in heads are done in aluminum so they get better return on RandD costs.

Fish, my buddy has a pair in his garage. He doesn't use them since his new boat has BIGGER power. I don't remember the details, he ran them in a 32 Skater. I think they were built by Troy Dennis. Let me know if you are interested.

Shawn

Gary,
I run a Blue Lightning Marine 434ci SBC, Procharged 3.8 lbs boost 738hp. hooked up to an ASD6 in a 18 Donzi.

http://www.offshoreonly.com/gallery/...enginepro2.jpg

http://www.offshoreonly.com/gallery/...=1505&size=big

GEOO;)

Hey Fishead
 

Did you get my E-mail?

Tee,
Got your email and motor looks great.I will be calling youprobably tonight.
Fishead

P29Scarab on this board Procharged his two 383's with great success. You may want to check with him.