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Thread: 6.2L Bravo One compatibility with SBC???

  1. #1
    hkunz
    My new Cheetah has a 6.2 Bravo One, which for old motorheads is a stock bore 350 Chevy with a 400 crank which yeilds 377 cubic inches. It looks like a SBC, other than some Mercury Marine stuff on it. The question is, what version of the SBC is it? Can I get some Harland Sharp roller rockers and throw on it like every other SBC, or is there some special high-zoot rocker that's required? Will aluminum rockers hold up over time in the marine "always on" environment? Or, should I step up to the investrment cast steel rockers from Competition Cams? Will I see any results from a change like this?
    Thanks!
    Mike

  2. #2
    HP350SC
    My new Cheetah has a 6.2 Bravo One, which for old motorheads is a stock bore 350 Chevy with a 400 crank which yeilds 377 cubic inches. It looks like a SBC, other than some Mercury Marine stuff on it. The question is, what version of the SBC is it? Can I get some Harland Sharp roller rockers and throw on it like every other SBC, or is there some special high-zoot rocker that's required? Will aluminum rockers hold up over time in the marine "always on" environment? Or, should I step up to the investrment cast steel rockers from Competition Cams? Will I see any results from a change like this?
    Thanks!
    Mike
    You will need self aligning rocker arms. Crane gold, in the ratio of your choice are a good buy. Not sure if the Harland Sharp is available w/self aligning. Also the reinforcement web for the center bolt valve covers is a little tight. I had to tap cover past rockers and then it was fine. H.S. rockers are even wider so?
    Rockers will hold up fine. As far as performance increase, I have done a couple sbc's (w/144 blowers) and it was zero speed increase from just the rockers.

  3. #3
    hkunz
    Thanks for the answer.
    If there is no change in power, why do it? When you made that modification, did you use rockers of the same stock ratio, or did you change the ratio as well? Would a ratio change help, (such as from 1.52 to 1.55 or 1.6) or would it mess up the computer?
    How tight are the clearances in these motors? What are the chances of contacting the intake valve against the piston with a ratio change, everything else remaining stock?
    Mike

  4. #4
    HP350SC
    Went to 1.6 on the 350 mag. with no change in power, no clearance issues on my motor.
    If it were me, I'd leave your motor alone and go big block when you can afford it. A good stainless prop is money well spent.

  5. #5
    CBLavey
    My new Cheetah has a 6.2 Bravo One, which for old motorheads is a stock bore 350 Chevy with a 400 crank which yeilds 377 cubic inches. It looks like a SBC, other than some Mercury Marine stuff on it. The question is, what version of the SBC is it? Can I get some Harland Sharp roller rockers and throw on it like every other SBC, or is there some special high-zoot rocker that's required? Will aluminum rockers hold up over time in the marine "always on" environment? Or, should I step up to the investrment cast steel rockers from Competition Cams? Will I see any results from a change like this?
    Thanks!
    Mike
    Save your money, I have the same engine set-up in my Lavey. After extensive research I was told that the investment in rockers, even 1.6's would not yield any significant increases.
    On the other hand, a good exhaust system will. I installed a set of EMI manifolds which made a big difference. I went from spinning a 22" bravo 4 - blade at 5200rpm lightly loaded to spinning a reworked 24" bravo, (now 24 1/2") at 5200rpm with a full load.
    The install was done by Rob at Quality Performance Marine, who I believe has done a few of these for Cheetah. It's a good investment if you plan on keeping your boat for a while.

  6. #6
    69 Elim
    What type of heads are on the 6.2? any other specs that you know of? I went on mercury's website, but didn't tell much.

  7. #7
    LaveyJet
    My new Cheetah has a 6.2 Bravo One, which for old motorheads is a stock bore 350 Chevy with a 400 crank which yeilds 377 cubic inches. It looks like a SBC, other than some Mercury Marine stuff on it. The question is, what version of the SBC is it? Can I get some Harland Sharp roller rockers and throw on it like every other SBC, or is there some special high-zoot rocker that's required? Will aluminum rockers hold up over time in the marine "always on" environment? Or, should I step up to the investrment cast steel rockers from Competition Cams? Will I see any results from a change like this?
    Thanks!
    Mike
    I thought a 400 crank in a 350 made a 383 stroker motor?
    Not nit pickin, just want to know.

  8. #8
    HP350SC
    Save your money, I have the same engine set-up in my Lavey. After extensive research I was told that the investment in rockers, even 1.6's would not yield any significant increases.
    On the other hand, a good exhaust system will. I installed a set of EMI manifolds which made a big difference. I went from spinning a 22" bravo 4 - blade at 5200rpm lightly loaded to spinning a reworked 24" bravo, (now 24 1/2") at 5200rpm with a full load.
    The install was done by Rob at Quality Performance Marine, who I believe has done a few of these for Cheetah. It's a good investment if you plan on keeping your boat for a while.
    I agree. I also like the Stainless Marine kit. Nice quality, complete kit, 5year warranty and good gains. We got ours at http://www.cpperformance.com/product...ne-exhaust.htm

  9. #9
    SmokinLowriderSS
    Personally, if you want long-term reliability, stay away from aluminum rockers, in ANY form. Aluminum has a fatigue life that steel does not have. Eventually, aluminum rockers break. In order to be strong enough to survive very long, they have 2 other things steel ones do not have. They are BIGGER, and actually are heavier than steel ones of comparable strength. If you want to take the motor open every few months to check the rockers, sure, go AL. If you wantr to leave them alone for decades, go steel.
    That said, here's the 2 SBChevy combinations via MorTec.com:
    Two common, non-factory smallblock combinations:
    377 = 4.155" x 3.48" (5.7" or 6.00" rod)
    400 block and a 350 crank with "spacer" main bearings
    383 = 4.030" x 3.76" (5.565" or 5.7" or 6.0" rod)
    350 block and a 400 crank, main bearing crank journals
    cut to 350 size
    Also, yes, a good intake and exhause system are worth far more than a changed rocker ratio are when looking for HP.
    I'd also save up for a Big Block if you want SERIOUS propeller-turning muscle, no other good way.

  10. #10
    HP350SC
    Personally, if you want long-term reliability, stay away from aluminum rockers, in ANY form. Aluminum has a fatigue life that steel does not have. Eventually, aluminum rockers break. In order to be strong enough to survive very long, they have 2 other things steel ones do not have. They are BIGGER, and actually are heavier than steel ones of comparable strength. If you want to take the motor open every few months to check the rockers, sure, go AL. If you wantr to leave them alone for decades, go steel.
    Oh c'mon man. What kind of rockers are you buying? lol Every few months they could fail on a stock motor? We better let Teague and Mercury racing know

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