need a recipe for 750-800hp blown bbc

[IMPATIENT 1]

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!

[BOOGEYMAN]

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.

[trbo355]

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!

[BOOGEYMAN]

Thanks Marty!!!! This is a great site with lots of cool info and some crazy boats, I think you will like it here!
Travis.

[IMPATIENT 1]

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!

[Wet Dream]

468, 8.5:1 slugs, 871 w/ 11lbs boost, dart 360 heads, 6000rpm

[SmokinLowriderSS]

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.

[IMPATIENT 1]

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.

[DMOORE]

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.

[FASTRAT]

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

[IMPATIENT 1]

thanks for the advise guys, all of it sounds good! i'll try and find a chiller over the winter but after the heads, carbs/fuel system, and pump overhaul, i'm gonna be broke! tonite i'm gonna spam some good stuff i've been holding onto to offset the cost.the airport is on my way to the lake and i always use avgas on the "big days" out on the lake, race fuel is 50 miles away.

[obnoxious001]

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.
That combination charts out to over 15-1 final compression ratio and is going to be hard on your wallet. I don't think that could possibly work for your intended usage and "mixed" fuel.

[trbo355]

I think everyone is on the right track about 10 to 1 being too high unless you use an intercooler. Even then there isnt much of a point to it unless you are stuck with those pistons. If you only ran 6 lbs it would be more feasible . What pistons are in it? How much dome? Most people think they have more compression than they really do when it comes to 454's. For example, a 119cc head and a flat top piston is only 8.0 to 1. Put on an old school head with the 100 cc chamber and you get a whopping 8.75 to 1 assuming a .020 deck height.

[IMPATIENT 1]

I think everyone is on the right track about 10 to 1 being too high unless you use an intercooler. Even then there isnt much of a point to it unless you are stuck with those pistons. If you only ran 6 lbs it would be more feasible . What pistons are in it? How much dome? Most people think they have more compression than they really do when it comes to 454's. For example, a 119cc head and a flat top piston is only 8.0 to 1. Put on an old school head with the 100 cc chamber and you get a whopping 8.75 to 1 assuming a .020 deck height.
haven't bought pistons yet, was gettin everyone's advise before i buy them so i could decide on heads and pistons.it kinda sounds like i need to go flat tops with 119cc heads,get a blower cam that'll match the flow of my heads, then get boost up near 8lbs., try to find a chiller ,and top it off with some 750 holley dp's. am i on the rite track here? i've been building bbf's to long, can't remember anything about bbc's anymore and i'm a gm master tech,lol.i've never built a blown bbc for a boat and don't have the cash to "hit or miss" with this mill, ya know what i mean.

[trbo355]

On carbs, it might be better the more i think about it to run vac. secondaries since the prop may load the motor at low rpm and 8 barrels wide open down low might not be the hot ticket. Im a holley fan but i gotta admit, the carter/edelbrock 750 with the air door secondaries sure work well on blowers. Maybe someone else can chime in on which carb handles the bouncing and sloshing better with the floats. That has GOT to be an issue in a fast boat.

[BOOGEYMAN]

No one thought you could get those carter/edelbrock cars to run so hard on a blower application........Then you did it, and Joe did it, and bill did it....and Noah did it.......haha and big numers from all set ups as well!!!!!
Travis.
There is so much hp i what most people would throw away it is a joke.....well good for the backyard hp guys I guess. Pretty awsome to take someones eles' "Junk" and beat them with it......And Marty you have done that more than once!!!!

[SmokinLowriderSS]

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.
The best thing I've managed to generate is 672HP / 588pounde Tq at 6,000RPM. I think the intercooler is a must for that small a blower . It's set here to run 1:1 drive. It's gonna put a lot of heat into the charge which is gonna fight you all the way along. Boost was limited to 10PSI
The cam I wound up with specd:
112.5* LSA
109.5* ICL
Overlap 29.5*
Lift:
Int .680"
Exh .700 "
Duration @ .050":
Int 251*
Exh 258*
IVO 16
IVC 55
EVO 64.5
EVC 13.5
The dyno run pulled as follows: HP/Tq
4,000 479/628
4,500 548/639
5,000 607/638
5,500 645/616
6,000 672/588
6,500 670/541
At that much RPM, and that much lift, the heads get to be a choke point as well. I think trying that 6,000 RPM a set of smaller rectangle port heads might be advisable. Sometyhing in the 310 to 320cc ports instead of the 295cc ports. Not so huge as to hurt ya badly down low, but to let it breathe more on top. Just a thought.

[IMPATIENT 1]

cool, thanks smokin!

[Havasu Carrera]

http://images6.theimagehosting.com/Blown Sleek (6).th.jpg (http://server6.theimagehosting.com/image.php?img=Blown Sleek (6).jpg)
I ran them and it sounded and ran really well!!
Blosdale said that is what burned all my pistons!!
Good luck!

[cstraub]

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 am assuming this is a pump gas engine. I don't think making 750 to 800 out of a 454 with a 6-71 as being feasable. I think a legit 625HP to maybe 670HP is doable but to get over 700HP with a peak of 6K would not happen.
Boost is a wonderful thing. I would shoot for a 7.5 to 1 compression and find some aluminum heads. The low compression and aluminum heads will be friendly to you and allow you to run a higher boost number on pump gas. Add a chiller as others have said and you would have a nice boost friendly engine.
Camshaft will be dependent on what heads you go with and what combination you end up with.
Is 750HP impossible, No but you are going to either have to add inches to the combination or turn up the RPMs.

[BOOGEYMAN]

http://images6.theimagehosting.com/Blown Sleek (6).th.jpg (http://server6.theimagehosting.com/image.php?img=Blown Sleek (6).jpg)
I ran them and it sounded and ran really well!!
Blosdale said that is what burned all my pistons!!
Good luck!
why was it those carbs that burnt pistons???? bad tune ups hurt engines.

[BOOGEYMAN]

Is 750HP impossible, No but you are going to either have to add inches to the combination or turn up the RPMs.
trbo355 is getting 800 out of a iron headed, cast piston, small block 355 in a turbo application all under 5,000 rpm.

[Blown 472]

trbo355 is getting 800 out of a iron headed, cast piston, small block 355 in a turbo application all under 5,000 rpm.
uh huh :rollside:

[Wet Dream]

trbo355 is getting 800 out of a iron headed, cast piston, small block 355 in a turbo application all under 5,000 rpm.
Yeah, at what cost?

[trbo355]

Yeah, at what cost?
Not much. It's actually a 150K stock block 355 SBC with twin turbo's and a 75 shot and some of the worst SBC heads on the planet! Way too much story there to get into but i do have a megablower 420 (same as a 6-71) on a SBC 355 with ported iron stock heads, 1 5/8 primary pipes and 12 psi on pump gas that makes a dead even 600 HP at the crank with twin 625 carters. He can get the HP he is after. BBC is so superior to SBC in terms of airflow even with mild heads. The reason Havasu Carerra probably melted down is cuz the carter/edelbrock carbs on a roots blower need a TON more jet in the secondaries to get the A/F in line. I actually ran a sec.jet size intended for the 750 cfm carb and the .120 needles and seats to get a nice 11.8-1 A/F ratio. I think the jet was stepped up 15 jet sizes over stock! The rotor pulses mess with the booster signal compared to a N/A setup Twin 625's would pull 3 in.HG at 6600 rpm WOT between the carb and blower, hence the need for 750's on a BBC. Throw on some fatty header pipes, twin 750's and 8.5 to1 and spin 10 psi and it WILL make easy 700 plus. Hell, HOT ROD magazine put an 8-71 on a nothing crate 454 with rec. ports and got 850!

[BOOGEYMAN]

Its all right here........Take a few minutes and read the first few pages, you can make a ton of reliable hp with a very small budget if you know what you are doing.
http://www.turbomustangs.com/smf/index.php?topic=61219.0
Its not always money that buys hp!!!!!

[cstraub]

Its all right here smart guys........
http://www.turbomustangs.com/smf/index.php?topic=61219.0
Its not always money that buys hp!!!!!
. . .money or no money it's combination that makes power.

[BOOGEYMAN]

. . .money or no money it's combination that makes power.
You are exactly right!!! Just seems like I see a lot of people on hot boat that just have more money than brains and spend tons of cash to achieve a hp goal that could have been done with about 1/4 of the money they spent.

[cstraub]

You are exactly right!!! Just seems like I see a lot of people on hot boat that just have more money than brains and spend tons of cash to achieve a hp goal that could have been done with about 1/4 of the money they spent.
On mnay forum I read about guys that have tried 3 and 4 camshafts in their engines. They don't want to spend $450 for a custom cam and $75 for flow numbers but they will spend $269 x 4 = $1076 trying roller cams to see if they work.

[IMPATIENT 1]

excactly, i'm one of those guys who can't afford a "hit or miss" kinda attitude, that's why i ask ALOT of questions before trying anything myself. its so much easier(and cheaper!) to ask someone that's been there,done that and has the knowledge to steer me into the rite direction.its all about the combo , not the dollas spent!!! that's a dragboat fact!

[BOOGEYMAN]

[QUOTE=cstraub69] They don't want to spend $450 for a custom cam and $75 for flow numbers QUOTE
You must be talking some real big hp numbers for cam like that. You can make 1200 hp on cheap summit brand hydraulic flat tappet cam, and you get the cam and lifters for $75! :D
Travis.

[jets4me]

i have a 468 with a 10.71 blower shop blower and i have 2 1050 dominators and a superchiller that makes 15psi at full throttle and makes 10 pounds boost can i run pump gas or not i have cast iron heads that have not been touched fare as port work thank you

[Havasu Carrera]

Not much. It's actually a 150K stock block 355 SBC with twin turbo's and a 75 shot and some of the worst SBC heads on the planet! Way too much story there to get into but i do have a megablower 420 (same as a 6-71) on a SBC 355 with ported iron stock heads, 1 5/8 primary pipes and 12 psi on pump gas that makes a dead even 600 HP at the crank with twin 625 carters. He can get the HP he is after. BBC is so superior to SBC in terms of airflow even with mild heads. The reason Havasu Carerra probably melted down is cuz the carter/edelbrock carbs on a roots blower need a TON more jet in the secondaries to get the A/F in line. I actually ran a sec.jet size intended for the 750 cfm carb and the .120 needles and seats to get a nice 11.8-1 A/F ratio. I think the jet was stepped up 15 jet sizes over stock! The rotor pulses mess with the booster signal compared to a N/A setup Twin 625's would pull 3 in.HG at 6600 rpm WOT between the carb and blower, hence the need for 750's on a BBC. Throw on some fatty header pipes, twin 750's and 8.5 to1 and spin 10 psi and it WILL make easy 700 plus. Hell, HOT ROD magazine put an 8-71 on a nothing crate 454 with rec. ports and got 850!
Yes probibly was the tune up. To much timing or to little fuel. But Blosdale said I washed out the rings and that caused the blow by. Hmm I will never know. lol

[LynnsJet]

There is no bling witha turbo.
I would never give up my roots for a turbo in an open boat.
Closed engine is another story