Reply With QuoteI sent this to my buddy Marty that builds a lot of hp with mostly stock bbc parts and blowers, hopefully he will chime in later this afternoon.
Travis.
i bought a 6-17 blower for a bbc, and i'm tryin to build a parts list for this winter build up. the blower was puttin out 7psi of boost on a stroked 525 bbc and i got the whole blower kit reaaaallllllllyyyy cheap and have decided to blow my tx-19 instead of using nitrous on it. i've got a nice forged 454 crank and some standard length h-beam rods for it. i don't have alot to spend on the heads.what kinda compression does it take to develop 700+hp in a 7psi blown bbc? i don't wanna stroke it.would like to build all my power at 6krpm's or slightly above it.am i dreaming or can i do this without dropping a shiat load into it?cam suggestions? already have a all roller set-up but gonna run a blower cam.any input would be appreciated and used, thanks guys!
I sent this to my buddy Marty that builds a lot of hp with mostly stock bbc parts and blowers, hopefully he will chime in later this afternoon.
Travis.
Ok, need more info. Is it gonna be a 454 or bigger? What heads do you have to use? What RPM does it need to turn to match your prop? I assume it's fresh water cooling so water temp and detonation shouldn't be much of a problem.I race stuff with 4 wheels so i gotta convert the brain over to boats here! LOL Did you get any extra pulleys with the setup? If it is a 454, you should be able to get a decent 10-12 lbs. out of a 6-71 blower. Is it teflon stripped? I think a comp. ratio of 9 to 1 would be a good compromise between power and the ability to run 92 pump swill without detonation on long WOT pulls. Gotta love low cyl. head temps with all that lake water keeping things in check. With a decent set of lightly ported stock oval port castings and 10-12 lbs. boost, i think 750 HP should be attainable without sacrificing reliability. If you keep RPM below 6300 rpm, it should live a long time. Big blocks have one hell of a heavy crank and aren't too fond of spinning much more than that for extended periods (like in a boat). Duration places power peak so i would look for a cam that has around 235 duration at .050 intake and 240-250ish. dur. exh. at .050. Much more than that starts to hurt low end response. Shoot for a L/C of 114 to minimize overlap and cyl. blowdown on a boosted motor. If you run a roller cam, run as much lift as that duration will allow. I would think on a BBC. you can get around.600 lift figures with out pushing the cam profile too hard. Besides, who wants valvetrain problems spinning the hell out of it for 5 min. WOT? Did you get carbs with the setup too? Twin 750 cfm's would be great for this combo!
Thanks Marty!!!! This is a great site with lots of cool info and some crazy boats, I think you will like it here!
Travis.
Ok, need more info. Is it gonna be a 454 or bigger? What heads do you have to use? What RPM does it need to turn to match your prop? I assume it's fresh water cooling so water temp and detonation shouldn't be much of a problem.I race stuff with 4 wheels so i gotta convert the brain over to boats here! LOL Did you get any extra pulleys with the setup? If it is a 454, you should be able to get a decent 10-12 lbs. out of a 6-71 blower. Is it teflon stripped? I think a comp. ratio of 9 to 1 would be a good compromise between power and the ability to run 92 pump swill without detonation on long WOT pulls. Gotta love low cyl. head temps with all that lake water keeping things in check. With a decent set of lightly ported stock oval port castings and 10-12 lbs. boost, i think 750 HP should be attainable without sacrificing reliability. If you keep RPM below 6300 rpm, it should live a long time. Big blocks have one hell of a heavy crank and aren't too fond of spinning much more than that for extended periods (like in a boat). Duration places power peak so i would look for a cam that has around 235 duration at .050 intake and 240-250ish. dur. exh. at .050. Much more than that starts to hurt low end response. Shoot for a L/C of 114 to minimize overlap and cyl. blowdown on a boosted motor. If you run a roller cam, run as much lift as that duration will allow. I would think on a BBC. you can get around.600 lift figures with out pushing the cam profile too hard. Besides, who wants valvetrain problems spinning the hell out of it for 5 min. WOT? Did you get carbs with the setup too? Twin 750 cfm's would be great for this combo!
haven't gotten any heads yet, would like to stay cheap with either 990's or some edel rpm's. gonna stay 454, no stroking it.the blower has a couple of extra pulley's and my unk told me that on a 454 it should put out at least 8-9lbs. of boost, but its not tefloned yet.will have to wait to have the rotors tefloned, maybe winter 07.i can get some reman. holley 4150 750 dp real cheap at a local carb shop we have(@400.00 for a nice set) . would 10 to 1 compression be to much to blow on pump gas? i have 2 tanks and would like to burn super in 1 and race fuel in the other, burn off the super cruzin and switch to the passenger tank while racin for balance.i would like to build all my power in the 5700-6200 range, spin a b-cut dominator.thanks for the info!
468, 8.5:1 slugs, 871 w/ 11lbs boost, dart 360 heads, 6000rpm
I have one built on Desktop Dyno, will report when the cam iteration calculations are done. 4-million to run tho, pretty wide cam parameters. Prob be late tonight .... I'll report progress.
Based on 454, Performer RPM heads (stock), 8.5:1 CR, 2ea 600CFM carbs (1200CFM induction), BDS 6-71 no intercooler. Aprox 250* duration (.050") on the roller cam sat the HP peak at 6,000, working from .650" lift and up.
468, 8.5:1 slugs, 871 w/ 11lbs boost, dart 360 heads, 6000rpm
what would the same set-up do at 10 to 1 with 8lbs of boost?am i lookin for detonation trouble?i've always ran nitrous and the blower set-up is alot different.
Impatient,
the only thing I would say is spend the money up front for an intercooler. It makes such a huge difference in the ability for the motor to make power AND run on pump gas. My motors are making 800 on 91 octane with only 7.5-1 compression and will run for hundreds of hours. Even if you have to be glued to E-bay it's worth it. If you are planning on running AV gas or race fuel, it might not matter for ya, but if you are like me, and like pulling up to the fuel dock, I would really look into it.
Darrell.
Impatient,
the only thing I would say is spend the money up front for an intercooler. It makes such a huge difference in the ability for the motor to make power AND run on pump gas. My motors are making 800 on 91 octane with only 7.5-1 compression and will run for hundreds of hours. Even if you have to be glued to E-bay it's worth it. If you are planning on running AV gas or race fuel, it might not matter for ya, but if you are like me, and like pulling up to the fuel dock, I would really look into it.
Darrell.
i totally agree...an intercooler is a must...it helps with detonation & keeping the fuel cooler into the motor, thereby makeing more power...i have read where u can make as much as 100+ HP from running one...u can find them sometimes on EBay...u just gotta be patient...also...u can find 750cfm carbs on there for cheap!...ck with Chris (cstraub) for a cam recommendation...he's sharp...just my .02 cents
fastrat
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