Proper carb sizing

Discussion in 'Other' started by 6671, Jun 15, 2013.

  1. 6671

    6671 Well-Known Member

    Kenne-Bell used to recommend an 850CFM carb for the 401 and a 1000CFM for the 455. Considering a set of heads ported and a moderate size cam with all of the usaual mods like long tubes, ignition, fuel supply do you guys think Kenne-Bell was right? I have read that the 2 most popular siziong formula's are inadequate and undersize if used. Experienced opinions please?
     
  2. sailbrd

    sailbrd Well-Known Member

    Don't know about nailheads but it is well documented that 455's love big carbs. On the other hand mine ran equally well on a really really good circle track Holley 830 and a couple of different 950 Holley's (Biggs, QuickFuel, AED) I think for 455 a 950 is a small carb.
     
  3. Da Torquester.

    Da Torquester. Platinum Level Contributor

    I had the usual mods and headwork on my car. Was running a 3310 750 vac sec. Car ran a best of 13.06 et with that carb. Not very good. Finally switched to a Holley 950 hp. First run the car went 12.42 et. I was quite surprised and happy. Now I run a 1000 holley hp and with more work the car is in the 11s.
     
  4. 68TriShield

    68TriShield Have a Cigar!

    Call AED with your engine specs,they'll build on for you.
     
  5. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    The fact is that an engine with restrictive heads and intake needs a larger carb to run right vs an efficient engine. A 350 Buick needs a 750-850 CFM carb to make peak HP where as a chevy 350 with AFR heads only needs about 650 CFM to make peak power. For the longest time many Buick fans thought that larger carbs were needed on our engines because our engines need more fuel than other engines but the truth is that to cover up design flaws our engines need to be fed more fuel.
     
  6. DaWildcat

    DaWildcat Platinum Level Contributor

    Easy now, "design flaws"?

    I think you'd agree we're asking a lot more from these engines than what Buick Engineering was able to do. They did a great job of what was expected of them and the deliverables they were given, designing a production engine family that performed very well for production vehicles. We should be thankful that they and the marketing department were able to convince management to give the green light on the Stage 1 package for production, not to mention GSX.

    Devon
     
  7. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    I wouldn't exactly call the tall port intake runner design a 'flaw'. I realize this is a very old thread too, and new information has probably come to light after those comments.

    Here's my take on it: since the Buick intake design capitalize on velocity, the larger carbs are needed for more efficient plenum fill. Other designs seem to work opposite: more volume on intake design require smaller carbs for better velocity for fuel/air charge.

    This is of course speaking from a mild-moderate point of view--something stock to lightly modified.

    This is also why smaller carbs work fine on Buicks with forced induction--the plenum gets filled more efficiently.

    There are of course a myriad of variables in any equation, and no two are exactly alike. There are general 'rules of thumb' one can go by to be on a relatively 'safe side' but fine-tuning to the unique combination is key.
     
  8. 74regalnz

    74regalnz Well-Known Member

    350 2bbl to 4 bbl TA performance sell 600 CFM, Electric Choke Edelbrock Performer Carburetor with their intakes. But it everyone on here says you need 750cfm qjet. :confused: it will cost me over 2k to buy the TA kit with a 212 cam and ship it down here so i want to make sure that i get it right first time. Locally i have found zero info on buicks and if 1 more belly button fan says drop a chev in it i could get postal:blast:
     
  9. sailbrd

    sailbrd Well-Known Member

    A 600 cfm carb on a 455 Buick is a joke. I just finished running around in my car with a 650 Quickfuel while I was rebuilding the blower. Now I run a lot bigger cam than a 212 but it was no comparison to when I ran 950 Holley style carbs (that was NA.) There are basically two schools on all around carbs for a performance Buick, 800 Qjet or a 950 Holley. Not to say some others do not work but a whole bunch of people have good results with these carbs. If you are in the states you have quite a few good Qjet sources. Anywhere else in the world I would go Holley, Biggs, AED or QuickFuel.
     

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