Crazyhorse

I'm the guy KAAMA was referring to as the friend that called the two big-name blower shops in January 2004 for quotes on a B&M 250 rebuild. I can assure you that the quotes from both shops was indeed what KAAMA said and that's why I elected to have Holley do the rebuild.
I've always heard good things about both TBS and BDS and have no doubt that had I picked either of these shops I would have gotten top-shelf work. I was not, however, willing to drop that kind of money on an open-end quote for my B&M 250.
Just to make sure there's no misunderstanding here, I would highly recommend either TBS or BDS to anyone looking for quality workmanship.
Dave Ritter

plums

bbq70 can your billet 250 blower make more power than the stock merc 575 weiand blower?

BBQ70

Dave,

I only commented because as i read KAAMA said it was for tear down and evaluation only. As quoted by KAAMA

"He called a few well known supercharger manufacture'rs out in California and if I remember correctly they both told him they wanted about $1000 just to tear them down and give you a recommendation. That's A LOT of SMACK to be laying down for a tear down---especially before parts and labor"

That makes it sound to me like we charge a lot for the tear down. I was only trying to clarify that it was a quote for the repair not a charge for tear down and evaluation only. You call it a quote but KAAMA did not, there is a big difference. If my comment came across wrong, then please forgive me. Like I said i was only trying to clarify that it was a quote. Anyways, I am glad Holley was able to take care of you on the rebuild, and it looks like it was a good price as well.

zahndok

I have been wondering whether with the blower shop 250 replacement you would expect an increase or decrease in performance . I have always understood the 575 blower to be a 256. Don't know if "6" is insignificant.

BBQ70

Plums,

Our blower is not really going to make much of a power difference over the stock Merc 575. We have had some of our customers report about .5 to 1 pound of boost increase at the same drive ratio, while other say that the boost is the same. Our blower is going to be more durrable then the stock blower. It will allow you to spin the blower faster without having some of the problems we have seen with the stock blower. Our blower uses a double row bearing in the front and a roller bearing in the rear. We also use heat treated rotor shafts and heat treated and ground gears.

Ron

Steve Zuckerman

Ron,
Chime in here, because this is an observation and question that I have regarding the Weiand 256. In general I have found it to be a more durable blower than the B&M/Holley 250. Is that because the 256 has a rear oil reservoir? Is it because it has 8 mounting points VS 4 for the Holley, for less case distortion? There are several diffeneces between the 2, another being.
The 256 has "machine fit" rotors. The Holley has teflon tipped rotors. Wouldn't anyone's teflon tipped rotor supercharger seal better, and therefore be more efficient (deliver more boost per RPM)? However, the teflon tipped superchargers that I have run, lost power as the teflon seals began to wear, and seemed to need re-tefloning every season.
Conversely, the machine fit rotors of the 256 should continue to deliver the same amount of boost, because there are no teflon seals to wear out, even though it would seem to be less efficient from the start. I figured that was one of the reasons Mercury chose this supercharger for this waranteed motor.
One less headache (re-tefloning).
I asked you guys what else we could do to improve my 256 while you were freshing it up, and I believe one of your options was to teflon seal my rotors, which I passed on for the above reason. By the way, the blower seems to be performing very well.
Regards,
Steve

BBQ70

Steve,

The Weiand mounting flang (8 bolts on the side of the case) vs. the B&M bolting through the bearing plates is much stronger and does not allow the blower to flex as much. This was the good design, however the Weiand only uses single row bearing in the front and rear, which is not as good as the B&M blowers that use a double row bearing in the front and roller bearings in the rear.

As far as the teflon OD strip. Normal wear on the teflon strips is .003"-.004" on the rotor to case clearance. This should not wear any more unless you have twist in the case or back fire the supercharger. The bottom clearance on a non teflon OD blower should be between .007"-.009". So the teflon stripped blower should be a little better then the non teflon blower. The problem comes in when the non teflon blower is larger then the .009" number. This is where we would recommend putting a teflon strip in to tighten up the clearance. So to try and answer your question, yes the teflon blower will "wear out" the strip and you will see a slight performance drop, but this is usually minimal. And the teflon strip will be tighter under normal wear then the non teflon blower. The non teflon blower like the Weiand 256 should in therory not lose performance unless you have a failure inside the supercharger. There are pros and cons both ways and it was more of the manufactures preference. All Weiand blowers were non teflon blowers and all of B&M blowers were teflon stripped. They both used them as selling points, but it all came down to how they wanted to build their units.

I personally do not think most people will see the differnce between .004" clearance of the teflon to the .007 clearance of the non teflon blower. When most of the performance loss is noticed is when the blower was back fired hard enough to open the bottom clearance around .010 or more. We have installed teflon in the Weiand blowers when the bottom was at .007 to start with the customer found no real increase. However, when we have installed teflon in blowers where the bottom clearance started at .012 or more, they did see a boost increase. So as long as the clearances are within spec to start with, it will be good either way.

Hope this helps
Ron

BBQ70

zahndok,

The rotor diameter and lenght are the same in all three blowers. Well acually the weiand rotor is around .025" smaller then the B&M. The 256 is just the name/number that Weiand gave it's supercharger to be different then the B&M blower. If you notice all their blowers have differnt names like the Weiand 142 vs. the B&M 144 or the Weiand 177 vs. the B&M 174 blower. Basically they are the same displacement, at least so close that their would be no performance difference due to displacement. Any performance differences are in the rotor profile not displacement.

Ron

zahndok

Thanks BBQ70.
One last question, Sorry for being dense.
So were all the 575 blowers Wieand 256 style or were some of the late model 575 blowers really B&M 250 style. Mine is an 02 after Holley owned everything and I believe says Holley on the blower case. Just trying to determine if mine might be more like the B & M style inside as far as bearings and stripping.

I think I'm going to go ahead and remove the front cover and mod it for a drain plug this weekend. Might as well if I remove the cover to change the oil. Would at least give me a better place to suck the oil from next time.

BBQ70

The 575 blowers went from the Weiand style to the new Holley style. They still use the same single row bearing in the front but went to a sealed single row bearing in the rear. The sealed rear design does not have an oil reservor. They used the bearing plate castings from the B&M line. On the new style, Holley does heat treat the seal surface which is a good thing.

Ron