what rpm's am i wanting out of my sbc?
+ Reply to Thread
Results 1 to 11 of 11

Thread:
what rpm's am i wanting out of my sbc?

  1. #1
    Senior Member
    Join Date
    Apr 2010
    Posts
    173

    Default what rpm's am i wanting out of my sbc?

    Small block 383, world heads (looking for the papers on them), comp cam (also looking for the papers) 750 edlerbrock, air gap intake manifold, stock Volvo exhaust manifolds all mated to a 290 volvo out drive. What rpm do i want to stay under? I know i need the head and cam info to get an accurate red line number, but since I solved my timing issues, this motor seems to rev to the sky. I'm replacing my tach today so ill be able to get an accurate reading on my rpms. I definitely need to go up in pitch on my prop, that's for sure. I can feel it not biting very well. can I also get a few mph out of the right prop? I have some Volvo aluminum prop on there now. a little beat up.

  2. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  3. #2
    Senior Member TNYoungblood's Avatar
    Join Date
    Mar 2010
    Location
    Clarksville, TN
    Posts
    5,104

    Default

    Quote Originally Posted by jeffz0rz View Post
    Small block 383, world heads (looking for the papers on them), comp cam (also looking for the papers) 750 edlerbrock, air gap intake manifold, stock Volvo exhaust manifolds all mated to a 290 volvo out drive. What rpm do i want to stay under? I know i need the head and cam info to get an accurate red line number, but since I solved my timing issues, this motor seems to rev to the sky. I'm replacing my tach today so ill be able to get an accurate reading on my rpms. I definitely need to go up in pitch on my prop, that's for sure. I can feel it not biting very well. can I also get a few mph out of the right prop? I have some Volvo aluminum prop on there now. a little beat up.

    I've got a 350 mag (stock) with a Bravo 1 and i'm runnin about 4800 @ 62 mph in a 20.5 ft Rinker ... Now in my jet i had a 388 SBC that would spin 5700 .. I would talk with Volvo and see what it will handle vs. what the motor will handle ... You don't won't to blow up your out drive

  4. #3
    cfm
    cfm is offline
    Banned
    Join Date
    Jan 2008
    Posts
    1,263

    Default

    You have no info for us so how do we know how to give you a close answer ? Edit in: or any answer for that matter ?

  5. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  6. #4
    Senior Member
    Join Date
    Apr 2010
    Posts
    173

    Default

    heads specs are

    170cc head, 76cc chambers, 1.437" dual springs, Hydraulic Roller, Spring Specs:1.437": 125 lbs. @ 1.810", 340 lbs. @ 1.210", coil bind @ 1.160", max lift @ .560"

    cam specs are

    Duration 270/276, Lift .495/.503

    this help get a rough estimate of what rpm range i should be in?
    out drive is a 290 volvo with a 1.61:1 gear ratio.

  7. #5
    cfm
    cfm is offline
    Banned
    Join Date
    Jan 2008
    Posts
    1,263

    Default

    If that's a CompCams Extreme Marine cam, these in 383's will usually run fastest in an I/O at 4800rpm or so.

    I'd start with a 23" pitch stainless steel propellor and see what rpm you get at WOT. I would not prop over 5000 rpm with that combo.

    I don't know what props are available for that drive, so you need to do some searching around to see what others have found to be the best props (manufacturer and type) for that type boat with similar power.

    Aluminum props are typically a lot slower than the stainless ones.

    Propping can be everything. Not just size, but type.

  8. #6
    Lord of the Drinks Havasu Hangin's Avatar
    Join Date
    Dec 2007
    Location
    273.36 Miles from Havasu
    Posts
    2,352

    Default

    The right prop is key. Bronson Hill used to make me stainless props for the Volvos- they had a couple to choose from. You will pick up speed and bite with a stainless- they flex less.

    I'd keep it under 5,200- if you don't have one, I'd get get a rev limiter ASAP. If you hit something, the drive will come out of the water, and bad noises will come from the motor after zinging it without a limiter.

    What pitch is your current aluminum prop?
    "Warming the globe...16 cylinders at a time."

    Quote Originally Posted by Rexone View Post
    Perhaps I'm gay...

  9. #7
    Senior Member
    Join Date
    Apr 2010
    Posts
    173

    Default

    i have no ide what the pitch is on my current prop. its been dragged through the sand many times through its life im sure. any numbers on it have been rubbed away. might there be numbers inside the bevel that the prop cone sits on? a rev limiter will be my next install before a prop thats for sure. ill check bronson hill to see what they might reccomend for my particular set up. does gear ratio play a huge part in choosing a prop ?

  10. #8
    Lord of the Drinks Havasu Hangin's Avatar
    Join Date
    Dec 2007
    Location
    273.36 Miles from Havasu
    Posts
    2,352

    Default

    Quote Originally Posted by jeffz0rz View Post
    i have no ide what the pitch is on my current prop. its been dragged through the sand many times through its life im sure. any numbers on it have been rubbed away. might there be numbers inside the bevel that the prop cone sits on? a rev limiter will be my next install before a prop thats for sure. ill check bronson hill to see what they might reccomend for my particular set up. does gear ratio play a huge part in choosing a prop ?
    Yes...but any prop shop should be able to get you close. You want to prop your boat so that it's in the peak power band. Since we'll estimate 5,000RPMs is the peak with that cam and exhaust, that's where you wanna be.

    For example:

    22" pitch x 5,000RPMs x 1.5 ratio x 12% slip = 61MPH

    22" pitch x 5,000RPMs x 1.6 ratio x 12% slip = 57MPH
    23" pitch x 5,000RPMs x 1.6 ratio x 12% slip = 60MPH
    24" pitch x 5,000RPMs x 1.6 ratio x 12% slip = 62MPH

    You probably wanna put the biggest inch three blade on there your motor will pull to 5K. Usually, the only tradeoff to topend is the holeshot, but with a 22' boat and that much torque, I doubt it will have trouble popping out of the water rather quickly.

    I'd probably start with a 23" or 24" prop and go from there.
    Last edited by Havasu Hangin; 07-21-2010 at 07:10 AM.
    "Warming the globe...16 cylinders at a time."

    Quote Originally Posted by Rexone View Post
    Perhaps I'm gay...

  11. #9
    cfm
    cfm is offline
    Banned
    Join Date
    Jan 2008
    Posts
    1,263

    Default

    Quote Originally Posted by jeffz0rz View Post
    does gear ratio play a huge part in choosing a prop ?
    Yes, in pitch.

    A higher gear will require more pitch (than lower gears) for proper WOT rpm.

    Look at these links:

    http://go-fast.com/Prop_Slip_Calculator.htm

    http://go-fast.com/sterndrive_gear_ratios.htm

    http://go-fast.com/prop_slip.htm

  12. #10
    Senior Member
    Join Date
    Dec 2007
    Posts
    114

    Default

    Volvo drives tend to be bullet proof. Called V and told them I had the capability to turn 7k and whether the drive would hold up. Volvo gave me the ok. The weak link of the drive is the vertical shaft, which would snap in an instant if shifted at a hi idle (1000+).
    I see no problem spinning the 383 to 5800-6k. Od likes big eared props 16" dia. Try Solas or Michigan wheel for props. Use the alum. ones for anchors.

  13. #11
    Senior Member
    Join Date
    Apr 2010
    Posts
    173

    Default

    hopefully saturday il be able to get some wot passes after my new tach is hooked up so i can do some rpm/gps speed logging.

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Please select your insurance company (Optional)

Log-in

Digg This Thread

Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •  
 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95