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Old 02-14-2007, 09:45 AM
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building a blower motor

Hi Guys:

I am so glad that I joined this forum. The knowledge of the members is very helpful. I need some help with suggestions for the selection of a blower. My brother is building the motor and neither of us have ever built a blower motor.

Motor is 406 ci small block chevy.
8.5 compression ratio
Heads 72cc, 2.08 intake, 1.6 exhaust
Isky R_359 roller cam for blower engines

Which blower would be best for mostly street and occasional trip down the drag strip. Motor is going in a 1995 Monte Carlo SS.

Thanks for the suggestions and let me know of any questions that you might have.

Sincerely,
jeff taylor
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Old 02-14-2007, 10:15 AM
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I just bought a Wieand blower kit for a small block. I have not got it running yet. It too was my first blower motor. All the instruction were clear and all of it went together very nice. There is a lot of info on the web about blower motors. One thing I found out is to use a double key crank and get rid of the balancer and use a billet blower drive hub on the crank. I got mine from BDS.
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Old 02-14-2007, 10:43 AM
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Blower motors not only require special pistons, but special rings and cylinder wall finishes, too. Also consider your valve type and materials.
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Old 02-14-2007, 10:59 AM
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We are using the special pistons. They were a little expensive, but it was a necessity.

XNtrick:
What do you mean when you refer to a special hone or finish on the cylinder walls???
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Old 02-14-2007, 11:17 AM
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Quote:
Originally Posted by 468ci1956
We are using the special pistons. They were a little expensive, but it was a necessity.

XNtrick:
What do you mean when you refer to a special hone or finish on the cylinder walls???
The texture and angle of the scratches in the walls is dictated by the ring material.

http://www.aa1car.com/library/2003/eb90329.htm

You are probably looking at a couple hundred dollars for rings,
or you can rebuild the engine in 8-10,000 miles.
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Old 02-14-2007, 11:53 AM
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Quote:
Originally Posted by xntrik
Blower motors not only require special pistons, but special rings and cylinder wall finishes, too. Also consider your valve type and materials.
that really depends on the amount of boost. a good stock 8.5:1 motor could withstand 5-7 PSI easilly. the pistions are not real important, a good forged pistion would do the same. a blower pistion has a little more surface left on the top, that's the only real diffrence from a regular forged pistion
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Old 02-14-2007, 01:18 PM
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4-71,6-71,8-71???

come on guys i need your advice.
jt
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Old 02-14-2007, 01:32 PM
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Quote:
Originally Posted by 468ci1956
4-71,6-71,8-71???

come on guys i need your advice.
jt

OK, IMO

The screw type Whipple-charger internal compressor from Kenne-Bell is the hands down winner.

The twisted rotor Magnuson is second.
The B&M 144 is a goodie.
I like the belt driven centifugals, depending on the engine and useage.

I don't like junk sticking out of the hood.
It's illegal, draws cops and negative attention, looks ancient.

Ancient roots blowers are sucking up the rear.
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Old 02-14-2007, 01:35 PM
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Quote:
Originally Posted by matt167
that really depends on the amount of boost. a good stock 8.5:1 motor could withstand 5-7 PSI easilly. the pistions are not real important, a good forged pistion would do the same. a blower pistion has a little more surface left on the top, that's the only real diffrence from a regular forged pistion

Matt, I did NOT say that it couldn't withstand it.

I said it won't last very long. The results speak for themselves.

Heat destroys rings.
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Old 02-14-2007, 01:38 PM
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I think which blower you go with is as much a matter of your personal taste as anything else. Your motor will handle any of the popular blowers if you don't go crazy on the boost. I personally chose a 6-71 for my mildly built 350 sbc mostly for the classic looks. I'm running 7# of boost and am very pleased with the performance of the motor. I don't race it... the blower is for the cool factor more than performance.

One technical aspect that may influence your choice is blower displacement vs. blower rpm vs. added heat. For a given boost level you will have to spin the smaller blowers, like the Weiands, at a higher rpm. Higher rpm in the blower means more heat added to the charge. More heat means less detonation margin. I spin my 6-71 at 1:1 which gives me 7# at 5,000 rpm. An 8-71 spun 1:1 at 5,000 rpm puts out 14# (more air displaced per revolution). To get the 8-71 down to 7# you would have to underdrive it 15%. This would also lower the temperature of the charge to some degree.

Take a look at the chart on BDS's web site.
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Old 02-14-2007, 02:12 PM
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Boost is a measurement of backpressure.

Bigger cubes or better flowing top-ends make less boost with the same driven volume.

Roots blowers are far less efficient than most all the newer types, especially the Whipple compressor. The Whipple actually compresses the air inside itself before dumping into the intake manifold, and is far more heat efficient, as well as producing smooth intake flow, which roots types do not.

The Magnuson helical rotor has proven to be more temperature efficient than the roots by a good margin also.

Bigger blowers also make undesireable pulsations in the intake tract.

Let the old myths die.
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Old 02-14-2007, 03:08 PM
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You would have a very hard time beating the performance you would get from a Vortech or Paxton belt driven supercharger kit. We have done dyno work on some pretty mild small block builds that made 600 HP on the engine dyno with the V-1 Vortech. On the wild side we have done Ford Mod Motors that have wheel HP'ed 600 and are street driven.

This would be the route I'd take for a charged application.
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Old 02-14-2007, 03:12 PM
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I think that xntrik has made some valid points, but all of the points he has made are definitely more suited for a race motor running 15+ lbs of boost, high RPM, and looking for that "nth" degree of maximum performance.

I run a Weiand 142 roots blower on an extremely mild 355. It has *gasp* hyper eutectic pistons; *ghasp* stock valves; and *ghasp* regular moly rings. It's been together for three years, I take it to 6 grand all the time and it pushes mid 12's in a 3200lb S10 in full street trim...

Bottom line, you have to build for what your intended performance levels are going to be. Don't worry about your exhaust valve metallurgy, specialized ring configurations on a custom built piston, or ultimate blower effeciency if you just want to push 6psi in a street car.

Last edited by jameskirk1; 02-14-2007 at 03:22 PM.
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Old 02-14-2007, 05:24 PM
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Why are blowers through the hood illegal?????is this a 50 state thing....does this also include tunnelrams? what if you dont have a hood on say a t bucket can you run a blower on a non emissions vehicle through the hood.(West Virginia at least in my neck of the woods is very very lax on emissions regs)

Shane
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Old 02-14-2007, 05:40 PM
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They are'nt illegal......in the state of California anyway, except on an emission controlled veh. obviously. Theres plenty of big jimmy's sticking out of hoods all over the place, same with tunnel rams.
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