Carb too small?
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Carb too small?

  1. #1
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    Default Carb too small?

    I called a place to ask about putting my engine on their dyno and they gave me the name and phone number of the guy who runs the dyno. I called that guy and he told me that my carb is too small for my engine and it will lean the engine out at upper RPM's. I am not looking for a recomended carb size.

    I'm looking for a confirmation or two that the scenerio of a lean out condition due to a too small of a carb is/is not possible? Thanks!
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    gn7
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    you really don't want to put your motor on a dyno with a dumb F'ck like that on the controls Carbs meter fuel based on the amount of fuel passing thru them. Any jackass worth a shit can make a 572 run dead rich with 600 cfm carb if so inclined. Find another dyno



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    Quote Originally Posted by gn7 View Post
    you really don't want to put your motor on a dyno with a dumb F'ck like that on the controls Carbs meter fuel based on the amount of fuel passing thru them. Any jackass worth a shit can make a 572 run dead rich with 600 cfm carb if so inclined. Find another dyno
    HEY GN7!! I am suposed to be the crusty one around here!! LMAO
    And your right.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster
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    That's what I thought. Thanks!
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    Are you running the engine NA (normally asperaited)? If there is no boosted air flow then the a properly functioning carb should be able to maintain the A/F ratio. It may run out of power due to lack of air and fuel but not go lean or rich as a result. I would agree with GN7. If that is the type of knowlege they are imparting before you pay them to dyno your engine, I would steer way clear of them. Perhaps he meant your carb doesn't flow enough air for the rpm/displacement you were talking about. But, if he can't articulate what he means, how can you trust his recomendations on tuning your engine.
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    gn7
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    Quote Originally Posted by 71hallett View Post
    HEY GN7!! I am suposed to be the crusty one around here!! LMAO
    And your right.
    you of all people should know I can get



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    Hey hot Rod, I personally would NOT dyno a motor with that small a carb on that big a motor. Yes it can work but tuning will be a bitch. I would be happy to let you go to the dyno with my 750 vac sec, It's on the boat as I type but can have it off before you get here. The numbers you will show will depress you and that is not worth the money you will spend. Beg borrow or whatever a 850 or 930 then go to the dyno. Both will bolt to your'e manifold and feed the motor even if the jetting is off a pinch. Alot has to to with feul, but alot also has to do with air mass flowing to the motor. If you get both on the right page the power will show. IMO M
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    Quote Originally Posted by ol guy View Post
    Hey hot Rod, I personally would NOT dyno a motor with that small a carb on that big a motor. Yes it can work but tuning will be a bitch. I would be happy to let you go to the dyno with my 750 vac sec, It's on the boat as I type but can have it off before you get here. The numbers you will show will depress you and that is not worth the money you will spend. Beg borrow or whatever a 850 or 930 then go to the dyno. Both will bolt to your'e manifold and feed the motor even if the jetting is off a pinch. Alot has to to with feul, but alot also has to do with air mass flowing to the motor. If you get both on the right page the power will show. IMO M
    I do hear what your sayin, Whats the point of dynoing what you are not gona use.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster
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    northern member Canuc's Avatar
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    Thumbs up base set-up

    dude , a 850 will fuel your 468 fine . i thought your cam might be a little to rad even with your compression . you do need a single plane for the r's your lookin for as many others have already said . i thought you had one with your orignal pile of parts you listed way back ??? any single plane would be better get some good gas from Busby jet it fat timing locked @ 36 and go from there
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    Quote Originally Posted by Canuc View Post
    dude , a 850 will fuel your 468 fine . i thought your cam might be a little to rad even with your compression . you do need a single plane for the r's your lookin for as many others have already said . i thought you had one with your orignal pile of parts you listed way back ??? any single plane would be better get some good gas from Busby jet it fat timing locked @ 36 and go from there
    After doing dyno time I will tell you that to prduce the numbers you hope to see the dyno guys WILL lean on the motor hard, run a very thin oil for fast and low friction flow. they Will kick the timing in the balls to achieve a good number. I have raced cars and boats in the 40 plus range but kick them right back down for the simpithy of the motor after the finals are over.IMO M
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    Hey ol guy, my carb is a 850 Holley DP w/mech secondaries. I don't need to borrow a carb, but thanks a lot for the offer!

    I'm thinking (hard to believe isn't it ) that I should have some more patience and just ditch the idea of using a carb to get on the water faster, keep making and saving my pennies to get my MFI flowed, run it on a dyno with the MFI, and call it done. That seems to make the most sense.

    I had a single plane intake but I sold it.
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    cfm
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    Quote Originally Posted by hotrod56cars View Post
    I called a place to ask about putting my engine on their dyno and they gave me the name and phone number of the guy who runs the dyno. I called that guy and he told me that my carb is too small for my engine and it will lean the engine out at upper RPM's. I am not looking for a recomended carb size.

    I'm looking for a confirmation or two that the scenerio of a lean out condition due to a too small of a carb is/is not possible? Thanks!
    Is it possible you heard/understood differently ?

    A restrictive carb to airflow will tend to richen up on the top end. And the opposite can be true also - too large a carb going lean.

    Each and every carb made is made specifically for a certain air volume going thru it. The more you go over or under of this value, the more issues you'll have in getting it tuned correctly through the whole rpm band.
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    An 850 on your 468 at 6,500 will be just fine. With that intake you are going to run I'm not sure it will make it to 6,500 and make power.

    The 565 was still making power at 7,000 with a 1,050 from the math it could use a 1,250 or larger.

    The operator is full of crap and I think I may know who he is.....check your p.m's

    But the dyno is still a good idea.... get on the water with it.. worry about your injection later. I was at Martinez this weekend, both days were great.

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    Quote Originally Posted by Sleeper CP View Post
    An 850 on your 468 at 6,500 will be just fine. With that intake you are going to run I'm not sure it will make it to 6,500 and make power.

    The 565 was still making power at 7,000 with a 1,050 from the math it could use a 1,250 or larger.

    The operator is full of crap and I think I may know who he is.....check your p.m's

    But the dyno is still a good idea.... get on the water with it.. worry about your injection later. I was at Martinez this weekend, both days were great.

    Sleeper CP
    Yea I don't know Jack Sh!t and that's why I start and read through these threads. But it didn't make any sense to me when I was told the 850 would lean the engine out in the upper RPM's.

    You do know who he is, I replied to your PM.

    Just keep rubbing it in (you were at Martinez - and I wasn't). J/K, It's my own fault it's taking me so long to get it on the water. I'll get there eventually and as long as it was worth the wait... then it was worth the wait. Biggest, most HP engine I've ever owned, by a long shot.
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