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Thread: Blower Carb?

  1. #1
    paradigm shift
    What is the REAL difference between a N/A and Blower carb set up. I know they boost reference power valves but what else? Emulsion tubes - air bleeds get modified also? Looking for as detailed information as I can get. Not looking to try and modify myself but trying to justify cost of buying new or having my existing carbs set up by a known carb shop. I have a set of 850s that have had choke horns removed and boost referenced already.
    This is going in a 29' Vee hull and gets run at 3500 to 4500 rpm with a pretty heavy load for extended periods of time. Not in flat bottom that gets run either WOT or light loads when cruising if that makes a difference.
    Thanks.

  2. #2
    Warp Factor
    What is the REAL difference between a N/A and Blower carb set up.
    Price, as far as I can tell.
    I've run two sets of regular (rejetted) carbs on two different blower motors over a period of about 15 years, and everything was dandy.
    I'm not saying they don't make substantial changes to the carbs, I'm just not sure how much of it is necessary.

  3. #3
    ghittner
    Here we go..... I always get sh*t for this. I'm running two non boost referenced 750 DP's. The only thing you need to do here is make sure you are runing ZERO VACUUM @ WOT and you will be fine with no boost referencing. Mine idle perfectly no soot and no surge at all....Your's are boost referenced so no matter. Don't spend any more money on those carbs. as long as they are fresh, Run 'em.

  4. #4
    Unchained
    I ran two 850 DP on my 540 ci engine w/8-71 Hampton blower at 28% OD for three seasons. Stock #80 jets, No boost referencing, (waste of money) they ran fine. They came with power valves in the primary and secondary.

  5. #5
    flattie
    I had 2 holley 750 right off the shelf on my 468 for 4yrs stepped up last year and bought a set of 950 blower carbs that were built for my specific application. Started like a brand new vehicle but other than that maybe reved a touch quicker but no mph increase not worth the money listen to these guys

  6. #6
    paradigm shift
    Thanks guys I really appreciate your experiences.
    I really do not want this to turn in to a boost referenced or not thread. I probably should have left that part out. I understand you can go either way as long as your carbs are big enough and not pulling a vacuum at WOT.
    I'm really looking for information on part throttle information. Cruise is right up to the point secondary almost starts to open a lot of times and for long periods. If I run it in to the secondarys long the wife is not a happy camper. This is why I boost referenced these carbs. High load and high vacuum under the carbs at that throttle setting. WOT I understand.
    I came up through the flat bottom boats years prior. I never could run the flat bottom hard for as long as offshore style running I do now. Offshore is at higher loads for much longer periods of time. A 4000 rpm cruise in the flat bottom is just not practical for most for a very long and is not as much load on the motor.
    Thanks for your replies.

  7. #7
    Warp Factor
    I've always run 48-54 gears, so my motor was loaded pretty good, and have spent quite a bit of time at 4000 rpm, still on the primaries.
    The only difference I see with running longer is that it would be less forgiving of a lean condition. You might conceivably want to run as rich as 11.5 under heavy load for a little more intake air cooling (detonation resistance) when things get heat soaked.

  8. #8
    paradigm shift
    I've always run 48-54 gears, so my motor was loaded pretty good, and have spent quite a bit of time at 4000 rpm, still on the primaries.
    The only difference I see with running longer is that it would be less forgiving of a lean condition. You might conceivably want to run as rich as 11.5 under heavy load for a little more intake air cooling (detonation resistance) when things get heat soaked.
    Thanks and did not mean to say you guys do not run hard at all. I am just trying to compare apples to apples. Just seems to me the motor is under more strain now with the offshore then the old flat bottom. Fuel and oil temps seem to verify that also. I agree on the lean condition which is why I am looking for part throttle differences if any on a carb set up specific for a blower. Just trying to get information to justify cost. I will be using an O2 meter during set up to double check for any lean conditions at all throttle positions.
    48 gears thats got to be an E ticket ride.

  9. #9
    Heatseeker
    I ran two 850 DP on my 540 ci engine w/8-71 Hampton blower at 28% OD for three seasons. Stock #80 jets, No boost referencing, (waste of money) they ran fine. They came with power valves in the primary and secondary.
    Mark, what power valves were you running on this set-up? I'm still chasing a tune on my heap. I stepped up the blower this summer and almost fried the whole package. I'm running 850 center squirts with plugged power valves and 84's all the way around. It runs good(at 5 lbs. boost) but the mileage is terrible(about 1 mpg)!!!

  10. #10
    Dimarco21
    What is the REAL difference between a N/A and Blower carb set up. I know they boost reference power valves but what else? Emulsion tubes - air bleeds get modified also? Looking for as detailed information as I can get. Not looking to try and modify myself but trying to justify cost of buying new or having my existing carbs set up by a known carb shop. I have a set of 850s that have had choke horns removed and boost referenced already.
    This is going in a 29' Vee hull and gets run at 3500 to 4500 rpm with a pretty heavy load for extended periods of time. Not in flat bottom that gets run either WOT or light loads when cruising if that makes a difference.
    Thanks.
    540 c.i. 14-71 blower w/cooler 2% over drive, 6,000 R.P.M. 9.5 lbs boost @ 35 degs. timing in a 3,700 lbs boat. 2-850 cfm DP's w/ no choke horns, primary's :84 jets w/ 10.5 power valve (non referenced) secondary's :88 jets no pv.
    http://www.hotboatpics.com/pics/data/500/1949motor1.jpg

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