How are the 420 mega-blowers?

[blownbbf]

A friend of mine was going to buy a b&m 420 mega blower for his boat and I was wondering if you guys have any bad experiances with them?
Are they as good or better then a roots style 6 or 8-71?
Please respond quickly,hes going to buy it soon
Thanks
Rick

[DEL51]

I don't think they are as good. The rotors are a 2 lobe design and they mount to the manifold differently than the roots.The price is close to the same as an 8-71.They are not bad blowers,I just think a quality 8-71 from BDS,Littlelfield,Kuhl,etc is superior.

[paradigm shift]

Not sure on new 420 but they used to be 2 rotor and straight. I would go with 8-71 and a manifold that has a peaked floor like BDS. Much better fuel distribution. Whipple makes a nice set up but for looks nothing beats a BIG roots. I know old school but I know what I like. All depends on what your friend has in mind to build and of course $$$ amount budgeted for project. Just my .02. I would not get in a hurry also.

[Craig]

I've been running one on my 509 for 13 months now. 878 horsepower, no problems that were blower related.

[Jbb]

I ran one on my jet for about 30 hrs without any problems at all Two lobe rotor design does give good fuel distribution.I have since upgraded to a Blower Shop 8-71 and their delta shaped intake evens up the fuel dist Pretty well. The difference is,as I see it the The Blower Shop one has billet end plates and bearing retainers and appears to be a much stronger unit.Something else ,since Holley bought out B&M's blower division there have been some parts availability issues!
The Mega blower is also a pain in the ass to keep polished with the close together ribs on it !

[blownbbf]

Craig what kind of heads did you use with your 509 and how much boost did you run. Thats a ton of power
Thanks guys for the replys,any more info with the 420 mega?
[ September 27, 2002, 06:14 PM: Message edited by: blownbbf ]

[Infomaniac]

If I remember correctly, the carb mounting is cast into the top of the blower. No provision to change carb type, location or injection later on. Even if you only intend to run plain Holleys, when it comes time to sell it, the buyer needs to be OK with that also.

[Clown]

Infomaniac:
If I remember correctly, the carb mounting is cast into the top of the blower. No provision to change carb type, location or injection later on. Even if you only intend to run plain Holleys, when it comes time to sell it, the buyer needs to be OK with that also.I have made some adapters that allows you to run whatever kind of carbs needed , Also made angle adapters so I could mount them inline,Less linkage problems!!!

[Craig]

blownbbf:
Craig what kind of heads did you use with your 509 and how much boost did you run. Thats a ton of power
Thanks guys for the replys,any more info with the 420 mega?GM steel square ports. Some port work done to them. The real secrets in the cam, unfortunately I lost the spec card on mine Its a good size Crane hydraulic roller. When they dyno'd the motor they said the thing holding me back at that point was the carbs, two 750's. I figured hell,this is more than enough to break a drive!!
Craig

[blownbbf]

Craig:
blownbbf:
Craig what kind of heads did you use with your 509 and how much boost did you run. Thats a ton of power
Thanks guys for the replys,any more info with the 420 mega?GM steel square ports. Some port work done to them. The real secrets in the cam, unfortunately I lost the spec card on mine Its a good size Crane hydraulic roller. When they dyno'd the motor they said the thing holding me back at that point was the carbs, two 750's. I figured hell,this is more than enough to break a drive!!
CraigWhat is a good size roller to you? .700 lift ....bigger??? what is your guess on the camshaft duration. I think you owe it to "hotroders" to know your specs on your camshaft And that was with no intercooler either? Dam..