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Thread: Carb Question...

  1. #11
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    +2 for Patrick at Pro-Systems, just bought his 940cfm 4150, it was $970, tweaked and wet flowed.

  2. #12
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    The main problem with Holley four barrels is the needle and seat. They are at the top of the bowl and exposed to air. They will dry out after sitting the winter. The next spring they will not seal when the engine is started and the floats will overflow. New needle and seats every year.
    A Quadrajet carburetor has the needle and seat in the bottom of the bowl. It is covered with gasoline all winter and remains moist. If you use a fuel stabilizer the needle and seat works fine the next spring (and many springs after).
    Rebuilding a Holley is a crapshoot because the metering block can get plugged with debris or varnish and there is no way to clean it out unless you remove the welch plug.
    Plugged metering blocks are the main reason why there are so many used Holley carbs sitting in the junk pile!

    A Holley carburetor will shoot too much raw fuel into the engine every time the throttle is opened. This washes down the cylinders of oil, will cause premature wear to the rings and dilute the crankcase/oil with raw fuel. The diluted oil will wipe out the cam lobes on a flat lifter camshaft.
    A Quadrajet or Edelbrock carburetor has a cup style accelerator pump with a slot in the pump bore.
    Fuel will bleed off (back) into the float bowel when the throttle is opened slowly.
    Smaller pump shot.

    If the throttle is opened quickly less fuel will bleed off into the float bowel.
    Larger pump shot.

    Holleys have a positive displacement accelerator pump and once the pump shot volume and duration are adjusted (pump shooters and pump cam) the same amount of fuel is shot into the engine whether the throttle is opened slowly or quickly. This makes for a very rich air/fuel mixture when slowly maneuvering around the docks or at the launch ramp.

    The square bore Edelbrock has twin float bowls and twin needle and seats and is the same carburetor (Weber four barrel/Carter AFB) that Mercruiser used when they could no longer buy Quadrajets from GM. It is important to realize that Mercruiser chose the Weber Four Barrel over the Holley Four Barrel for installation on Mercruiser Sterndrive engines for reliability issues.
    Dennis Moore

  3. #13
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    Quote Originally Posted by WR-1 View Post
    I have no experience with Nickerson or Pro Systems but If your considering spending $800-$1000 I think you owe to yourself to do some research on Willy's carbs..they are very nice pieces IMO..you can change the jet size with the turn of a hex nut on the side of the metering block..he will build it and run it on a Dyno before he sends it..anyone else on here have any experience with them?
    Probably wouldn't be worth the money on a basically stock engine, but a Willy's carb will get you an extra 25-30 hp on a race engine. I have seen it in person. 430ci SBC 700hp engine, they added 20hp just by bolting on their carb, another 15 after some tuning. Very nice people and products.

  4. #14
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    Quote Originally Posted by Dennis Moore View Post
    The main problem with Holley four barrels is the needle and seat. They are at the top of the bowl and exposed to air. They will dry out after sitting the winter. The next spring they will not seal when the engine is started and the floats will overflow. New needle and seats every year.
    A Quadrajet carburetor has the needle and seat in the bottom of the bowl. It is covered with gasoline all winter and remains moist. If you use a fuel stabilizer the needle and seat works fine the next spring (and many springs after).
    Rebuilding a Holley is a crapshoot because the metering block can get plugged with debris or varnish and there is no way to clean it out unless you remove the welch plug.
    Plugged metering blocks are the main reason why there are so many used Holley carbs sitting in the junk pile!

    A Holley carburetor will shoot too much raw fuel into the engine every time the throttle is opened. This washes down the cylinders of oil, will cause premature wear to the rings and dilute the crankcase/oil with raw fuel. The diluted oil will wipe out the cam lobes on a flat lifter camshaft.
    A Quadrajet or Edelbrock carburetor has a cup style accelerator pump with a slot in the pump bore.
    Fuel will bleed off (back) into the float bowel when the throttle is opened slowly.
    Smaller pump shot.

    If the throttle is opened quickly less fuel will bleed off into the float bowel.
    Larger pump shot.

    Holleys have a positive displacement accelerator pump and once the pump shot volume and duration are adjusted (pump shooters and pump cam) the same amount of fuel is shot into the engine whether the throttle is opened slowly or quickly. This makes for a very rich air/fuel mixture when slowly maneuvering around the docks or at the launch ramp.

    The square bore Edelbrock has twin float bowls and twin needle and seats and is the same carburetor (Weber four barrel/Carter AFB) that Mercruiser used when they could no longer buy Quadrajets from GM. It is important to realize that Mercruiser chose the Weber Four Barrel over the Holley Four Barrel for installation on Mercruiser Sterndrive engines for reliability issues.
    Dennis Moore
    Interesting...however anytime I read something that seems as biased as your opinion against Holley's it makes me wonder what's the motive for the bias. If Quadrajet and Edelbrock carbs are so much better than Holley carbs...why do so many performance builders use Holleys? Is it because Holleys are tunable to specific apps and the others aren't? Just wondering.

  5. #15
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    Most mechanics who work on customers boats are biased against Holleys. If you own "A" boat it is pretty easy to say that your Holley is a pretty good carb but when you work on 50-75 boats a year you soon develop a real disliking for Holley carbs.
    When I attended one of the Mercruiser service training schools in the mid 1980's (Mercruiser mechanics must attend a service school every two years to remain certified) we were asked our opinions on what carb should replace the Quadrajet (GM was discontinuing the Quadrajet). Overwhelmingly every mechanic said anything but the Holley.

    As a side note, everyone was asked about Ford marine engines and they got the same negative answer.

    The love of Holley carbs is generally only shared by people selling them and people that DO NOT repair customers boats for a living.

    Maybe there are some engineers working on engine projects in love with Holley carbs but anyone with practical experience, performing service and warranty work on a regular basis (for a living) is not very partial to them.

  6. #16
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    When I was building small block Chevy's, I loved the Q-Jet. Always ran great, easy to set up. It's hard to find a Q-Jet that will flow 940cfm though. If I wasn't looking at so much money I would have gone EFI. The cost of the EFI and new headers with O2 bungs put me over the top.

  7. #17
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    well i like all the carb . but when you make more power you need to use a a/f box to set the jets up . i had my motor dyno had more jet in it .put a a/f box on it i was in the 11. no good i am now at 12.7 at 3000rpm and 12.5 wot.your boat is the real dyno

  8. #18
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    Quote Originally Posted by Dennis Moore View Post
    Most mechanics who work on customers boats are biased against Holleys. If you own "A" boat it is pretty easy to say that your Holley is a pretty good carb but when you work on 50-75 boats a year you soon develop a real disliking for Holley carbs.
    When I attended one of the Mercruiser service training schools in the mid 1980's (Mercruiser mechanics must attend a service school every two years to remain certified) we were asked our opinions on what carb should replace the Quadrajet (GM was discontinuing the Quadrajet). Overwhelmingly every mechanic said anything but the Holley.

    As a side note, everyone was asked about Ford marine engines and they got the same negative answer.

    The love of Holley carbs is generally only shared by people selling them and people that DO NOT repair customers boats for a living.

    Maybe there are some engineers working on engine projects in love with Holley carbs but anyone with practical experience, performing service and warranty work on a regular basis (for a living) is not very partial to them.
    Dennis...I'm not pro-holley......actually, I don't know enough about carbs to be pro-any-carb...just wondering where you were coming from with the Edelbrock-vs-Holley thing. Except for a couple of AFB's in the 60's all my cars have had Q's on them. My one other I/O had EFI so this is my first boat with a Holley. It has a Holley 4150HP, 850cfm on my Gen VI 502 (mild-build). If I wanted to go to a Edelbrock for whatever reason...which do you think I should consider and would my intake have to be changed?
    Thanks

  9. #19
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    The Weber 4 barrel is sold by Edelbrock and is known as the Edelbrock Square Bore. You can use the existing intake manifold. For absolute reliability this is only second to the Quadrajet.

    The marine Edelbrock Square Bore carb has a max flow rating of 750 CFM and is excellent for boating.
    When the engines air intake volume is calculated in cubic feet per minute (that would be the maximum amount of air an engine can ingest in one minute with 100% efficiency) a 750 CFM carburetor calculates to the CFM rating needed for a 502 engine running at 5200 rpm. Engines never obtain 100% efficiency so 750 CFM is more than enough for your application. By NOT overcarbureting an engine, fuel mileage and low speed torque is maximized.
    Dennis Moore

  10. #20
    SB
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    Oh my gosh Dennis.

    Please put in your posts that it is of your opinion of Holleys vs Edelbrock and such.

    If the carburetor tuner does not feel comfortable tuning the carburetor at hand, that does not make the carburetor bad.
    I many times make the statement that the best carburetor for one to get is the carburetor one knows how to tune the best.

    I prefer Holley's for performance motors because I can tune them the best. For stock motors, the Eddie's are fine because they are very close out of the box.....if the customer so desires. Again, this is my opinion because of my personal skills/knowledge/ and etc.


    Anyhow,
    Many of us are here because of performance motors.

    How many Edelbrock's / Weber's are on the Blue Motors ? IE: The Mercury Racing High Performance motors ?

    Also in my opinion and experience the CFM mathmatics you are showing is old school Holley textbook. Things have changed with more modern cyl heads, camshafts, and of course carburetors themselves.

    As example: many times I'll and others will go 120VE% or more on that 'cfm carburetor math' on performance dual planes.

    As far as Prosystems, Willy's, and etc, if you call them on a near stock motor I guarantee that they'll tell you to run 'such and such' stock Holley. Guarantee ? Yup, I have personally and have had customers call on near stock and also mild performance engines and that's what they'll give you for an answer.

    Now, very high performance engines ? You bet ! There is more to changing fuel curves than jetting, PV's, step up springs, rods, and etc.

    Anyhow, I'm saying the above as we would be talking having a conversation.

    Just don't want this thread and info to be a one sided opinion.



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