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Discussion Starter #1
ok
I'm building a 572 bbc 8 to 1 pistons
solid roller 758 lift 114 lobe separation.
I want to buy a set of heads but before I do I thought
I would get some opinions . I called brodix and ask what
their thoughts were. they said to use bb3 xtras.
I know there are alot of knowledge on this forum .
any help out there
this motor is going in my hydro
thanks
 

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ok
I'm building a 572 bbc 8 to 1 pistons
solid roller 758 lift 114 lobe separation.
I want to buy a set of heads but before I do I thought
I would get some opinions . I called brodix and ask what
their thoughts were. they said to use bb3 xtras.
I know there are alot of knowledge on this forum .
any help out there
this motor is going in my hydro
thanks
Is this a N/A motor, If so why the low CR? You could go 10.5:1 cr on pump gas, also you need your heads flow #'s before you pick a cam, you'll get better results that way. If you give alot more info about your motor, boat and intended use that would help alot.:)
 

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My 621 BBC is getting Brodix BB4 Xtras. Trick Flow 360's are pretty darn nice too!
 

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Discussion Starter #6
heads

somehow I left out the blower bds 871
the cam is a lunati solid roller
758 lift
264 in
280 ex
114 lobe sep
 

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I'm so lost I don't know where to begin. How do you know what your compression ration is if you don't know what CC your chambers are.

Do you know what you want your compression to be. Do you know the dish size of the pistons you have and the distance in or out of the hole?
Have you bought any of this stuff, or is the stuff you want to buy.
X2 He's brought up all excellent point of info any good builder would ask :)

I always like to know the application it will be used in

What type of boat, size, drive, gears,exhaust and intake, prop and weight

After picking the right comb parts. Just like buying a good suit

the final fitting starts :)hand
 

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Bb3 xtra

ok
I'm building a 572 bbc 8 to 1 pistons
solid roller 758 lift 114 lobe separation.
I want to buy a set of heads but before I do I thought
I would get some opinions . I called brodix and ask what
their thoughts were. they said to use bb3 xtras.
I know there are alot of knowledge on this forum .
any help out there
this motor is going in my hydro
thanks
I ran a set of cnc bb3 xtras on my 572 last summer. They were 355/119s. Compression was 10.4, cam was .714I, .690E. Any way the motor made 837 at 6300 without a perfect tune. I know this may not have much to do with your blower motor but they made good power on my 572. Brodix also stated that they were borderline of being too big for my 572 at 6300.
 

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I ran a set of cnc bb3 xtras on my 572 last summer. They were 355/119s. Compression was 10.4, cam was .714I, .690E. Any way the motor made 837 at 6300 without a perfect tune. I know this may not have much to do with your blower motor but they made good power on my 572. Brodix also stated that they were borderline of being too big for my 572 at 6300.
This why I hate Brodix heads. Everything I look at says the 3xtra cnc is a 366 cc intake. What can be really confusing is when the CCs are less on the cnc heads than the as casts. Like the 2xtra as cast is 365, but the cnc is 355:)sphss
Not counting the fact that each series head requires its own dedictaed shaft rocker stands.

Jungledave, are you sure yours are 3s or that the CCs are 355?



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The first flag is the 8-71 on 572 inches. Going to take some decent over drive with a real good set of heads and a cam of that size. Did a dumb test one time and found it took about 3.0 lbs to break even on a 9.1 555 incher with a 10-71. Sounds like this will be pump gas. Its probably going to need 9-11lbs of shitty air with the 8-71 to make 950 hp. That spinnin the 8 pretty hard
 

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This why I hate Brodix heads. Everything I look at says the 3xtra cnc is a 366 cc intake. What can be really confusing is when the CCs are less on the cnc heads than the as casts. Like the 2xtra as cast is 365, but the cnc is 355:)sphss
Not counting the fact that each series head requires its own dedictaed shaft rocker stands.

Jungledave, are you sure yours are 3s or that the CCs are 355?
This is why you can't really judge a head by it's advertised volume unless you know something about the port. They're all differenet ports, even though the volumes are similar, or even the same.
 

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The first flag is the 8-71 on 572 inches. Going to take some decent over drive with a real good set of heads and a cam of that size. Did a dumb test one time and found it took about 3.0 lbs to break even on a 9.1 555 incher with a 10-71. Sounds like this will be pump gas. Its probably going to need 9-11lbs of shitty air with the 8-71 to make 950 hp. That spinnin the 8 pretty hard
machineHead, I completely agree he is has to spin the hell out of that 8 to cover the heads and cam. But oon this "dumb" test you did. Did you obtain the 3psi with the throttle, or with pulleys at wot.
I'm not sure I understand what you guys are saying. If I read it right, you're saying an 8 is to small to build boost on a 572 with good heads/cam? Or that it took 3 lbs boost to cover the losses from the blower? Or something else entirely.... Care to elaborate?
 

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David, it is going to be hard to built enough boost with a 8-71 on that motor to justify the cam shaft. If you match the cam to a set of heads, it should have more boost than he can easily make with the 8. If from the beginning you knew you were going to run a 8-71, you would choose a smaller cam and there fore a smaller set of heads. Basically, the blower will have a hard time delievering enough air for that cam along with the heads that cam wants.

I not really sure what Machinehead was trying convey with the 3lb thing, or how he even limited the boost to 3lbs. With the throttle? or with pulleys?



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I'm not sure I understand what you guys are saying. If I read it right, you're saying an 8 is to small to build boost on a 572 with good heads/cam? Yes. Or that it took 3 lbs boost to cover the losses from the blower? guessing Yes. Or something else entirely.... Care to elaborate?
I know on Nelson's 509, his (fresh) 1071 was working to make 15# @ 6000rpm. I can't imagine what the air temps will be with an 871 trying to make 10# on a 572, especially if you put stoopid big heads on it like some mentioned above.
 

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David, it is going to be hard to built enough boost with a 8-71 on that motor to justify the cam shaft. If you match the cam to a set of heads, it should have more boost than he can easily make with the 8. If from the beginning you knew you were going to run a 8-71, you would choose a smaller cam and there fore a smaller set of heads. Basically, the blower will have a hard time delievering enough air for that cam along with the heads that cam wants.

I not really sure what Machinehead was trying convey with the 3lb thing, or how he even limited the boost to 3lbs. With the throttle? or with pulleys?
I know on Nelson's 509, his (fresh) 1071 was working to make 15# @ 6000rpm. I can't imagine what the air temps will be with an 871 trying to make 10# on a 572, especially if you put stoopid big heads on it like some mentioned above.
I certainly don't claim to be a blower expert but based on what you guys say, I'm guessing a gas blower must be a lot looser than one for alcohol. On my 565, I run a similar cam (a bit less lift), 10.5:1 CR, a decent set of heads (probably "stoopid big" by some estimations;)) and can build over 5 lbs boost at 4% under. The same basic motor/blower combo as mine made 12-14 lbs at around 25% over. Don't remember exactly as they were on the dyno just after me and I didn't keep track of all the changes they made.
 
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