Trying to pick the right blower
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Trying to pick the right blower

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    SLOW MEMBER slowboy's Avatar
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    Default Trying to pick the right blower

    I am getting ready to pull the trigger on a used blower to run on my Cp tunnel this year. It currently has a very well prepped 6-71 which cavitates badly and just cannot supply enough air for my 400ci SBC. I was thinking of getting a 8-71 hi-helix with the delta opening on the bottom. Enough blower? Dont ask, you will laugh when I tell you how much power I want to make. It will be running on corn and the long block can pretty much withstand anything I can throw at it.

    Thanks
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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by slowboy View Post
    6-71 which cavitates badly
    I'm curious what you mean by this.

    cav·i·ta·tion
    n.
    1. The sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces, such as those resulting from rotation of a marine propeller.

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    Senior Member Smallblocksperry's Avatar
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    Quote Originally Posted by slowboy View Post
    I am getting ready to pull the trigger on a used blower to run on my Cp tunnel this year. It currently has a very well prepped 6-71 which cavitates badly and just cannot supply enough air for my 400ci SBC. I was thinking of getting a 8-71 hi-helix with the delta opening on the bottom. Enough blower? Dont ask, you will laugh when I tell you how much power I want to make. It will be running on corn and the long block can pretty much withstand anything I can throw at it.

    Thanks


    id like to know some details on this "unbreakable longblock"

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    SLOW MEMBER slowboy's Avatar
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    Quote Originally Posted by Budweiser View Post
    I'm curious what you mean by this.

    cav·i·ta·tion
    n.
    1. The sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces, such as those resulting from rotation of a marine propeller.
    Ok.. Cavitation was not the best term. How about "the fricken blower cannot pump enough air."
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    SLOW MEMBER slowboy's Avatar
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    Quote Originally Posted by Smallblocksperry View Post
    id like to know some details on this "unbreakable longblock"
    Nothing is unbreakable buddy.

    If you dont have any information for me, move along.
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    gn7
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    Define "enough air"

    A 6-71 is capable of 30psi on a 400. Unless you have some serious heads on the thing, a bigger blower on a small block is going to move the air the blower can push. 50psi in the manifold doesn't mean shit if its stuck in the manifold.



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    SLOW MEMBER slowboy's Avatar
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    At 33 percent over we saw a loss of over 200 hp at 5700 rpm vs a tune with 27 percent over. Boost levels were at or around 14-15 psi at 33 over and 10-12 at 27 over. I would not consider the heads to be all that great, but they are darts and have had quite a bit of work done to them. They are 23 degree heads. The blower was fresh last spring and was stripped. It is currently sitting on an intercooler which I am not going to use this upcoming season.

    All of this information is off the top of my head, I will have to try and find my dyno sheets to confirm everything.
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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by slowboy View Post
    Ok.. Cavitation was not the best term. How about "the fricken blower cannot pump enough air."
    Okay, cavitation is just an embellishment term. I do that from time to time too.

    Just so we're all on the same page....

    What's the current OD ratio/%?
    What psi are you seeing?
    What psi would you like to see?
    What is the set up in your boat/car?
    What results are you seeing?
    What results would you like to see?

    Or is this a dream engine that hasn't seen a wrench yet?

    I'm all good with talking "what if's"... so long as I know they're what if's.

    So far this all screams of a pimple face dream scenario... Just sayin.

    Been there too.

    EDIT:
    Quote Originally Posted by slowboy View Post
    At 33 percent over we saw a loss of over 200 hp at 5700 rpm vs a tune with 27 percent over. Boost levels were at or around 14-15 psi at 33 over and 10-12 at 27 over. I would not consider the heads to be all that great, but they are darts and have had quite a bit of work done to them. They are 23 degree heads. The blower was fresh last spring and was stripped. It is currently sitting on an intercooler which I am not going to use this upcoming season.

    All of this information is off the top of my head, I will have to try and find my dyno sheets to confirm everything.
    Now we're talking real info. NICE!
    Last edited by Budweiser; 01-02-2013 at 05:13 PM.

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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by gn7 View Post
    Define "enough air"

    A 6-71 is capable of 30psi on a 400. Unless you have some serious heads on the thing, a bigger blower on a small block is going to move the air the blower can push. 50psi in the manifold doesn't mean shit if its stuck in the manifold.
    Sounds like you're on the right track. If he's seeing a loss with more boost, makes sense the added boost is costing more than it's making. In other words, it's not making it's way into the cylinders.

    Good call. You amaze me with your forethought sometimes.

    BTW, happy new year.

  13. #11
    gn7
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    Quote Originally Posted by slowboy View Post
    At 33 percent over we saw a loss of over 200 hp at 5700 rpm vs a tune with 27 percent over. Boost levels were at or around 14-15 psi at 33 over and 10-12 at 27 over. .
    This tells you everything you need to know that there is a cork in the engine. Take you choice, heads aren't up to the flow requirements, the cam is short, the exhaust sucks.

    I'll bet the blower is looser than hell and you leaking either past the rotors and case, or between the rotors up the center. It isn't pumping for shit.

    When B&M first released the 144 blower they did some tests on a stone stock small block Ford. They found out real quick the the HP went straight in the shitter when the heads/cam hit their limit. They could continue to increase boost and the power kept dropping. Its wasn't the size of the blower, or that it no longer moved air. It HAD to be moving more air, the increase in boost is a result if added air over what the engine consumes.

    You are simply wasting HP making boost, but not adding one drop more air flow into the engine. You could install a tight 8-71 and make the same boost you are at 30 over, and still not make any more power.

    IF YOU WHAT THE TO MAKE BIG POWER WITH A BLOWER, FIRST YOU NEED TO MAKE BIG POWER WITHOUT ONE!!!!!!!

    Trying to make some huge amount of HP with nothing more than boost is a total waste of time!!
    We have had this same discussion on these boards before that power is just a couple more psi away, and that is total bullshit.

    shitty ass heads and a tiny ass cam will get is ass wiped by a properly built blower motor using less boost.


    You don't need a 8-71 hi helix and a delta until you have an engine that can move the air that blower can move. It can't make one single addition HP stuck in the manifold. Stop trying to make 50 psi and start trying to MOVE AIR!



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    SLOW MEMBER slowboy's Avatar
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    This is no dream engine, and is currently sitting between the stringers of my CP tunnel which I am about to tear apart and paint, but that is another story.

    Here is the deal. When I built this engine (actually my machinist Lance Line built it, you might have heard of his brother Jason) the goal was to make 1k hp with a SBC on e-85. We made just shy of that. Prior to the long block being finished I had sent my blower to BDS out in Cali. I talked to one of the tech guys when the blower arrived there, he asked me what my goals were, I explained everything and told him the power I was HOPING to make. I was assured no problem, just needs to have all this work done, at the tune of around 2k. Bingo, get the blower, put in on the engine, slap it on the dyno and the results were good until around 25 percent over at 10-12 psi. Any pulley combo over that created a sharp drop in both torque and HP.

    We thought at first that the valves were being held open, Comp cams thought the pushrods were flexing, Everybody had a different idea. Then I called BDS. I was THEN informed that the blower I sent them was a "small bore 6-71" and that there was no way that blower would support the kind of air flow needed to support 400 plus CI. Lance made some calls and confirmed what I was told by BDS. That would have been great information before I spent 2k with them.....

    I ran the boat on a mellow tune this summer as I had just started getting into actually racing and wanted to learn the ropes with out having something completely wild. I ran it most the summer at around 15-20 percent over making 8-9 psi of pressure on E-85. I am going to run E-98 next year as I am tired of the inconsistency of the E-85 around here.

    That leaves me where I am at now. I am going to sell the 6-71, intercooler, and carbs. I want to replace it with something that will move enough air that I dont need to run it 40 or 50 over, the ethanol will help keep the air cool to some extent.

    That is why the question, 8-71, hi-helix, delta, 10-71, 14-71 and spin real slow? I really like the PSI stuff, but cannot spend that kind of $$ right now.

    BTW, turbos are real cool, I will be running them on my "street car" hopefully, but want to stick with a blower for the boat.
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    Quote Originally Posted by gn7 View Post
    This tells you everything you need to know that there is a cork in the engine. Take you choice, heads aren't up to the flow requirements, the cam is short, the exhaust sucks.

    I'll bet the blower is looser than hell and you leaking either past the rotors and case, or between the rotors up the center. It isn't pumping for shit.

    When B&M first released the 144 blower they did some tests on a stone stock small block Ford. They found out real quick the the HP went straight in the shitter when the heads/cam hit their limit. They could continue to increase boost and the power kept dropping. Its wasn't the size of the blower, or that it no longer moved air. It HAD to be moving more air, the increase in boost is a result if added air over what the engine consumes.

    You are simply wasting HP making boost, but not adding one drop more air flow into the engine. You could install a tight 8-71 and make the same boost you are at 30 over, and still not make any more power.

    IF YOU WHAT THE TO MAKE BIG POWER WITH A BLOWER, FIRST YOU NEED TO MAKE BIG POWER WITHOUT ONE!!!!!!!

    Trying to make some huge amount of HP with nothing more than boost is a total waste of time!!
    We have had this same discussion on these boards before that power is just a couple more psi away, and that is total bullshit.

    shitty ass heads and a tiny ass cam will get is ass wiped by a properly built blower motor using less boost.


    You don't need a 8-71 hi helix and a delta until you have an engine that can move the air that blower can move. It can't make one single addition HP stuck in the manifold. Stop trying to make 50 psi and start trying to MOVE AIR!
    I totally agree with everything you stated. I dont think that any of the above are my problem. I can assure the blower was tight. As far as camshaft, it is a billet 50mm core custom cam that Comp made specifically for the boat. Comp assured Lance and I that the camshaft was not the problem. The headers we used on the dyno were similar to the ones on my boat (but flipped of course) Im not trying to make 50 psi, but when the power drops off at 12 psi something is wrong. All the "experts" tell me its the blower.
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    SLOW MEMBER slowboy's Avatar
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    I want to add, I really appreciate the insight..
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