New Blowers...........
 

Okay, here is a question for all of you OSO members out there who are more knowledgeable than myself when it comes to motors. I currently have stock 525sc's that use Wieland 177's and are attached to beefed up Bravo's. I am looking at moving up to a newer larger blower. The ones I'm looking at are the B&M 250's, B&M 420 mega, the 6:71, 8:71, and 10:71. I'm curious how much increase I will see with each and which one is the best choice for good performance upgrade with better reliability and won't destroy my Bravos every season. There are a few of each for sale on this board and I'm ready to go for it, I just need help deciding where to spend my money best.

All suggestions will be greatly appreciated!!!!!!!!!!!

Come on everyone, help a guy out.................lol

the 177's start beating themselves to death around 575 hp. Making more heat than boost.

the 250's are good to 700 horses.

420s are fine to anything you'd ever want to couple a Bravo to.

6-71 probably compares in size to the 250.
8-71 a little less than a 420.
10-71 a little more than a 420.

the -71 series of blowers are based on old GM diesel scavenging pumps. They are usually modified and fitted with rotor seals when converting them to a performance application - but in my opinion, the "made for performance" B&M pumps are a better match for you.

As far as "which one will make more power for you" the question requires more to answer properly.

Each larger blower has larger components, larger gears and bearings in its drive, and more swept area (assuming it uses teflon contact strips on the rotors). This means that for a given rpm, each larger blower requires more horsepower to turn which it removes from the net power available at the flywheel. This is further compounded by the blower belt situation. Each larger, meaner looking belt, requires more power in its operation.

Notice above that I specify that each larger blower requires more AT A GIVEN RPM. A given blower may deliver more volume at a lower rotational speed than a smaller one.

With that said, I hope that you can see that there is a good reason for so many different sizes of blowers.

You gotta figure out what your target horsepower is. Then, from the size and state of tune of your motor, one must determine the appropriate charge volume that must be delivered in order to reach that goal. The state of tune (heads, cam, etc) you are running will dictate the boost level and volume that will be necessary (a high flowing motor will require a given volume of charge for power but the volume will be delivered to it at a lesser boost than would be needed for a lower flowing motor). Once the volume/boost curve is approximated, it is easy to size the blower to the motor.

A "too small" blower will operate above its efficiency curve and not give good results. A "too large" blower will rob too much in the way of parasitic drive loss. It will also possibly fall below its efficient pumping range at lower engine speeds due to rotor seal leakage which will soften the engine's torque curve at low rpm which may or may not be desirable in its given application (rotor seal leakage does not affect output that much in the blower's normally efficient rotation speed range - only at low rpm and at high boost levels).

On your application, you may be able to add an intercooler and pulley your way to a safe 600hp without replacing your blowers, especially if you upsize your cam.

250's will allow you to do anything "within reason". especially when paired with intercoolers.

420's will be overkill, but they do look cool...

mcollinstn,

WOW! That was extremely helpful. I think my target horsepower is around 700-800 because I think anything over that is way too risky with my Bravos. I just put scoops on my hatches in preparation for these upgrades. Can I safely put 250's on w/o inner coolers and be safe? What would you do if this was your setup and you were upgrading?

a few years ago i had a 90 40 fountain with 454/365 mags in it and was looking at different blowers. B&M put out a pamplet on their different blowers and what they would do for the different motors with the 525 and the mega blower you could expect 750hp because the 525's had lower compression to begin with you could raise the boost, i have also read that the B&M blowers are not the best for making serious HP because of their rotor designs, hope it helps a little, this season we have to get to gether i know your at loto and so am i but were just on different parts of the lake im at the 6.5mm and your up around the 26mm if i remember correctlly , but hell lets make it a point.
later
Dave

Dave,

I totally agree we must make it a point to try to get together this summer!!

So am I reading that you'd suggest the 420's or the 250's?

The 420 B&M is claimed to be about a 6-71. Almost anybody's 8-71 will make more boost, more power. The B&M (now Holley) is pretty good for it's size, though.

blown1500,

Which would you choose?

Sheesh,

If I already had 177's and was gonna trash them, I'd dang sure skip straight to 420's. UNLESS you have a line on a raging deal on a pair of 250's.

Your target hp 700-800 will keep you happier longer if you bite the bullet and pop for intercoolers. 250's or 420's, I'd go with intercoolers.

On your 454's and stock heads you're gonna be staring at probably 12 pounds of boost to see 800hp. I can't IMAGINE NOT running an intercooler at those numbers...

You're gonna HAVE to do some work to your heads AND upsize the cam a LOT to see 800 hp inside of a reasonable boost range (less than 9 pounds).

Maybe I'm offbase here.
Somebody please give him better news than mine...

mcollinstn,
What do you expect I'd see with 250's and inner coolers?

Mine dynoed at 655 ft.lbs. of torque at 4600rpm and with 629HP at 5500 this past spring. 502 with 250.
HP is for bragging rights, torque is real world numbers.

BTW, I just happened to notice that there is a smokin deal for a complete 250 package for sale in the OSO parts and classified ads sections. ;)

Hey 525 DON'T WASTE YOUR TIME GOING TO A 250 ,,,177 TO 250 IS JUST A WASTE ,THE INTERCOOLER WILL WORK ON LONG PULLS OR RUNS ONLY .
THE MEGA-BLOWER (420) IS A KILLER ONE TO CHANGE TO IT IS THE EXACT SIZE OF A 6-71 EXCEPT IT HAS A TWO LOBE ROTOR VERSES A THREE FOR 6,8,10-71,, IT MAKES TORQUE EARLIER AND IS ROCK SOLID ,YOU WOULD NOT NEED TO SPEND THE MONEY ON INTERCOOLER UNTI L ABOUT 12 LBS OF BOOST .THIS WOULD SAVE A TON :D :D :D

WE DID A 496 WITH A MEGA BLOWER AND HAD 913 FT POUNDS
SO IT WILL MAKE THE POWER !! I'VE USED TONS FOR 10 YEARS
WITH GREAT SUCESS !!
THEY ALL HAVE THERE PLACE BUT FOR YOU THE 420 IS KING :D :D :D

THERE ALOT OF 420'S AROUND ,,,I KNOW OF 5 ,AND BIGGER ONES

ALSO PLEASE THROW THE CAM AWAY ,ITS A GREAT MOTOR AFTER THAT :D :D

Just FYI, the 6-71 designation comes from the old GM diesel application where the engine had 6 cylinders @ 71 CID each. Or another way of designating it is to call it a 420 (6*71=426CID). Knowing this will make it easier for you to compare the different brands that use different ways of designating the size of the blower.
I would use a 6-71 or 420 size if you want my $.02

What are you doing with your old set up? If you are selling carb,blower,intake,pulleys etc. complete (so I could duplicate a 525 with my 454 mags) I may be interested.

Oh yeah, I would intercool it. Cheap insurance regardless of wether or not you gain hp.

The 420's would be the way to go...big enough to throw down a cooler charge and small enough to idle and dock well.
Not to mention last a lot longer than spinning a 250 twice as fast with an innercooler.

525, you keep coming back to the 250's. Does this mean you already bought some OR that you have a source for some really cheap?

How much? US1 is running 630hp. I'd say that is in the correct range. You might could coax 700 out of em with the right cam.

I still say that if you're gonna go to the trouble to turn bolts and flash cash, you'd be better off with 420s (and cam).

1500 has built more motors than any three guys combined on the board. If he says 420 @ 9 lbs and no cooler, then I ain't gonna argue with him. He knows how to make em live. I'd dang sure consult him and make sure you follow his recommendations to the tee (if you cut corners, then you're not following his advice and you're asking for trouble).

Stock 525's with Blower Shop 250's, carbs reworked by Nickerson to stage 5 mods, (1280cfm) v6 ignition modules, set timing to 32 deg. at full advance. I picked up 10mph in a 38 Cig. with 5#'s of boost.

Hey 525, when you doing this? I am usually at the 19mm and always there in the summer. We'll need to hook up this summer.

So I have a 38 KV w/ 468ci merlin blocks and heads. They are built for superchargers, but I don't know where to start. Sounds like the 420's are the way to go?

I already have the guages so I think I should get the huffers:) Let me know and if I should get the inner coolers aswell.

Thanks and see some of you in the summer!!!

HEY OBNOXUS21. WE NEED TO HOOK UP FOR A BEER OR 2 0R 3, SINCE WE LIVE IN THE SAME TOWN........525 RIGHT NOW I AM RUNNIG A 540 CU IN. WITH A B&M 250.IT IS A LITTLE ON THE SHORT SIDE FOR ME. AM GOING TO THE B&M MEGA IN THE NEAR FUTURE WITH AN INNER COOLER. ALSO TO BE ON THE SAFE SIDE I PUT IN TWO THERMAL COUPLERS, TO READ MY EXHAUST TEMPS. HTM SAID THAT THEY ARE DOING THAT TO ALL THEIR BLOWER MOTORS AND HAVING GREAT SUCCESS. HOPE THIS HELPS ....

PARTYHAWK.....yea I am usually having two or three or...........
Are you going to the MU game? I will be in the (Field) House:)
Is your HTM a 24 w/ some blue on it? It was either yours or KCHOTBOAT's I saw at Clinton a couple years ago. Where do you usually boat at?

BTW, my motors are rated at 500hp, I would get innercoolers regardless, but are the 420 Mega's the way or Procharger as few have suggested to me?

I had been throwing around the idead of blowers, since I got the boat and realized it was the cheapest way to get me in the 80mph range without new drives and N.A. motors. I have TRS and the guy before me had the same set-up.

I just don't want to sacrifice reliability, so how much boost would I want to run and would I have to do alot of "tinkering" having the blowers?

thanks for some input as I will be doing this before the upcoming season!

525....

a buddy of mine is selling a used twin 420 b&m setup. i'll find out what he wants for it and the details of what is included.

OBNOXUS21 .. HAVE HAD A PROCHARGER ON MY MARIAH. IT WAS OK. HAD A LITTLE LAG WHEN YOU KICKED IT IN THE ASS BUT NEVER HAD ANY TROUBLE WITH IT. BUT LOOKS AND PERFORMANCE I LIKE THE ROOTS TYPE BLOWER SYSTEMS NO MATTER WHAT BRAND YOU DECIDE TO GO WITH. WORK PARTTIME AT THE MARINA AT CLINTON IN THE SUMMER TIME. USUALLY HAVE A COVERED SLIP. MAKES IT REAL EASY TO GO TO THE LAKE THAT WAY. MY HTM HAS BRANDYWINE FLAMES TIPPED IN GOLD. CAN ALWAYS FIND ME AT THE CLINTON OR PERRY ON THE WEEKENDS. ONCE A MONTH AT LOTO IN THE SUMMER. HAVE A CONTACT HERE IN HAWKVILLE REAL GOOD ON BLOWER KNOWLEDGE. LETS HAVE A BREW OR TWO, CAN ALWAYS FIND TIME TO TALK BOATS. WILL WATCH THE GAME ON TV. WORKING MIDNITES RIHGT NOW SO WOULDN'T HAVE TIME TO GO AND GET TO WORK.

Nice clean looking set up

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hey the 420 is fast ,BUT ITS LIKE ALL OTHER ROOTS BLOWERS THEIR 65 TO 70% EFF. AND A PROCHARGER IS 80+ THE ROOTS WOULD NOT NO WERE THE WHIPPLE, PROCHARGER,OR VORTEC
WENT ,PERIOD ,BUT THE 420 IS A GREAT KILLER CHOICE ,NOT THE 250 ITS TO SMALL FOR YOU :D :D :D
BLOWN 1500 AND I WORK TOGATHER SO LET US KNOW WHAT YOU NEED ;)

BOBBY DANIELS------------------------------------------------------

I am a little confused, but are you say to go w/ the Pro Charger/Vortec type charger? I am a little confused with what you said, sorry. The procharger is 80% efficient? A couple other people suggested the procharger.

Thanks.

P.S. Looks like 525sc and I will have to have a little "fun" run at LOTO this summer:);)

SORRY FOR THE CONFUSION THE PROCHARGER///// VORTEC AND WHIPPLE WILL ALL OUT RUN THE ROOTS TYPE BLOWERS AND ARE ALOT MORE EFFICENT !!!THE ROOTS ARE LIKE 420,,,250,,,8-71-ECT
YOU CAN GET A GREAT DEAL ON THE ROOTS TYPE ,THE OTHERS COST MORE BUT WILL FLY !!!!!!:D :D :D :D

Centrifugal blowers out flow roots at high RPM's, roots far outflows at low RPM's. Depends how strong a holeshot you need.
I think centrifugal is easier on the drive, but roots looks much cooler!

Hello, Guys!
The blower you need is contingent on many factors. I don't know enough of them yet.
The Bravo outdrives have started having problems for me with about 750 ft lbs. Some can take more with the right modifications. That is not my area of expertise, though I have seen a few.....
The most efficient blower known to man is a turbocharger. They are big bucks and must be right on to work.
Next in line are the screw chargers(Whipples) and the centrifugal (Pro Charger, Vortech, etc.). Of the roots type, if the B&M is the correct size for what you need, they usually win. All the other roots types are less efecient. I have had the best luck on roots other than B&M with Littlefields. Most of the others are good, and not too far behind. " Your results may vary". Teflon strips and other things help determine which is best as do tolerances-a few are pretty bad, but most are fine.
Between the Whipples and Pro Chargers, they both make about the same maximum power on the same engine, same boost, etc. The Whipple makes a lot more boost and power at a lower rpm. The Whipple will make boost as soon as you hit the throtle no matter how low you go and run from there. The centrifugals can make good power from a low rpm, but their boost is very rpm dependent. If you can take the low speed torque hit, the Whipple will win. If you need a gentler low end, the centrifugal will make a gradual increase untill at the top end, they will run with the Whipple.
The carburetion is very important also. I have worked on 250 B&M's with Dominators, but the 850 #4781 with boost reference or the new Holley blower ready carbs seem to do better. Two very small 4v carbs are even better. If you have to have the "look" of the roots, in the case that started this thread, I would look for a 420 B&M. Cam, heads, and exhaust are critical to max out the system, but just the blower will make for a big improvement!!
There are so many factors, heads, displacement, stroke(not the same effect as displacement) CAM, HEADS, exhaust, many more.
Your best bet is to figure out the torque you need in any circumstance and make an engine to do that. If anyone wants more than this, pm and I'll gladly find a way to communicate with you:D :D

if your interested in 2 complete new 420 mega set ups, i have them for sale, i need to have $6500.00 for them. you can e-mail me @ [email protected]