Elevation Question?????
+ Reply to Thread
Results 1 to 7 of 7

Thread:
Elevation Question?????

  1. #1
    " Live Laterally " Dominator's Avatar
    Join Date
    Apr 2008
    Location
    Phoenix
    Posts
    4,536

    Default Elevation Question?????

    i just bought a boat from Cali and I am in CO. I am at 6500-8000 ft. I have a demon carb on a bbc and need to know if, how, where to change the jets so I can run it up here. Please let me know and thank you in advance.
    " NO MOTOR NO BOATER "

    " I'd rather be riding in my boat thinking about God, than in church thinking about my boat ".


  2. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  3. #2
    Senior Member Factory1's Avatar
    Join Date
    Oct 2008
    Posts
    1,134

    Default

    First off, If? Yes. You have less air up there and you are going to be noticably rich. How and where, jets, primary and secondary screwed into metering blocks found once you remove float bowls. Pull a bottom screw with a can under it to catch the fuel. Barry Grant makes a nice tool for this. Remove float bowls, you'll see the jets on the bottom of the metering blocks. They will be numbered 77, 84, something to that effect. You need to know what you have before you buy anything. I would start by dropping down 1 or 2 numbers at a time, primary and secondary evenly. Boat should start picking up performance and rpm as you close in on the optimum A/F ratio. You might ask this question in the on the dyno section, there are some very knowledgable people in there, and there is a formula for predicting jet changes based on elevation/ air density, I just don't know what it is. At minimum you need to know what jets are currently in your carb. Good luck, and don't tell anyone I was in here, the V-drive section got boring! F1~

  4. #3
    Gone
    Join Date
    Dec 2007
    Location
    Sparks, Nevada
    Posts
    1,824

    Default

    Very good.
    I wasn't here either.
    LOL

  5. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  6. #4
    " Live Laterally " Dominator's Avatar
    Join Date
    Apr 2008
    Location
    Phoenix
    Posts
    4,536

    Default

    Quote Originally Posted by Factory1 View Post
    First off, If? Yes. You have less air up there and you are going to be noticably rich. How and where, jets, primary and secondary screwed into metering blocks found once you remove float bowls. Pull a bottom screw with a can under it to catch the fuel. Barry Grant makes a nice tool for this. Remove float bowls, you'll see the jets on the bottom of the metering blocks. They will be numbered 77, 84, something to that effect. You need to know what you have before you buy anything. I would start by dropping down 1 or 2 numbers at a time, primary and secondary evenly. Boat should start picking up performance and rpm as you close in on the optimum A/F ratio. You might ask this question in the on the dyno section, there are some very knowledgable people in there, and there is a formula for predicting jet changes based on elevation/ air density, I just don't know what it is. At minimum you need to know what jets are currently in your carb. Good luck, and don't tell anyone I was in here, the V-drive section got boring! F1~
    THank I will do so.
    Quote Originally Posted by Fiat48 View Post
    Very good.
    I wasn't here either.
    LOL
    NICE!
    " NO MOTOR NO BOATER "

    " I'd rather be riding in my boat thinking about God, than in church thinking about my boat ".


  7. #5
    Senior Member Factory1's Avatar
    Join Date
    Oct 2008
    Posts
    1,134

    Default

    Well so much for the Dyno section guys helping you out. They can be a funny bunch to put it mildly. I think you might be scaring them with the "where to change jets" part. Here's what I want you to do. Get yourself a copy of Demons book on their carbs. It's out there, I've seen it. Read it cover to cover, and you'll know their carbs forward and backward. Pull your spark plugs out of your motor, buy new ones, put them in. Nothing fancy, same things you took out, or their equal in Autolite. Take it to your local lake and run it as is, do not change a thing at first. Who's to say it was ever jetted right in California. Maybe it was lean to begin with. Take it out and run it. If it's rich it's gonna tell you. Your gonna smell the excess gas, it might smoke a little, and your new plugs will turn black and wet. Then take my first advice. Do that and I'll try and check in on you once in a while for more help. Chow, F1~

  8. #6
    Senior Member speedealer's Avatar
    Join Date
    Dec 2008
    Location
    Albuquerque,N.M.
    Posts
    234

    Default

    I live in New Mexico and boat at 5000 ft. You can lean an out of box carb about 4 to 6 steps. I run a 482cid with solid roller with mid .650 lift and 245 duration, big port dart iron heads a Team G with an 850 holley. I run 82 jets squared without power valves. Also you can bump your timing to aronnd 38 to 40 degrees. Hope this might help. good luck.

  9. #7
    Senior Member Factory1's Avatar
    Join Date
    Oct 2008
    Posts
    1,134

    Default

    Every motor and application is different, and going lean out of the box will melt down some peoples engines. Example my combo with an out of the box Holley 1050 had to go up over 10 jet sizes to get to where it was happy. It was way lean as delivered for my application. Your motor will tell you what it wants, you need to learn how to speak it's language. F1~

+ 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