Why can a marine carburetor not be used on a street application?

Discussion in 'Small Block Tech' started by Curmudgeon, Jun 16, 2013.

  1. gsjohnny1

    gsjohnny1 Well-Known Member

    being from the k-b era, some of his stuff was fluff.:eek2:
     
  2. sean Buick 76

    sean Buick 76 Buick Nut

    With a Holley type carb you really do need to stay on the mild size of the CFM ratings unless you are willing to spend the time and custom tune the carb to perfection, in which case you can get away with a higher CFM carb. :Smarty:

    The bottom line is that if a company recommends a carb they often tell you to get a 650 for a 350 engine because they know it will run fine right out of the box. Toss on a 850 Double pumper and you need to do a lot of trial and error to get the most out of the engine. And unless your heads are ported, and lots of $ into the engine the 850 will just use extra fuel and be harder to tune.

    Honestly, I would get a custom order 76 or newer 800 CFM 350 Buick Q jet with electric choke and TV cable setup for an overdrive trans down the road. The last Q jet I ordered from Everyday Performance was a 800 CFM Pontiac casting that helped make 585 foot pounds of torque with a mild 9:1 compression iron headed 500 CID Caddy engine. The carb was literally bolted on, hit the dyno and made within 3% of the final peak HP and TQ numbers as it did after the secondary's were fattened one step. It was about $400 with shipping and that was a custom spec carb with no core fee!

    I am sure that a Holley carb could make the same TQ and HP numbers, it comes down to personal preference and use of the car... Some guys like blonde ail and others like brunettes, each to their own. :TU:
     
  3. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    It's good to see so many educated and experienced posts in this thread now. Been an interesting read, for sure!

    Cheers all. :beers2:
     
  4. sean Buick 76

    sean Buick 76 Buick Nut



    The test car used was a 1971 GS stocker. Compression ratio was stock 8:1. The 68 4 bbl. versions had 10.25 ratios 2bbl engines all used 9:1 pistons. The car itself weighed in at 3550 lbs. The only options being radio and heater. The rear end was a 3.64, an ideal street/braket. A 3.9 or 4.1 is about maximum for street use while the lower 4.3 and 4.78 (Buick) or 4.36-4.88-5.12 (Chevy) should be used for racing only. 9 slicks were used for traction consistency.

    Test # MPH 1/4 mile Test Description
    1 83.1 15.76sec Test car as described
    2 83.6 15.70 KB350-2 shift improver kit
    3 84.0 15.65 KB55009 Stinger 1 Distributor Ignition or KB88114 Stinger Points Conversion Ignition. Use KB883904 1 HEI Conversion for 75 and later HEI Distributors or KB33117 HEI Spark intensifier kit if budget is limited. KB33101 or KB33102 Advance Curve Kit and KB/Stinger Ignition wire
    4 85.0 15.55 remove stock air cleaner
    5 85.1 15.53 KB46002 Hi Flow low profile air cleaner
    6 86.1 15.41 KB84001 Mufflers and 2 1/8 tail pipes and cross over pipe
    7 86.1 15.41 KB84001 Mufflers and 2 1/4 tail pipes and cross over pip
    8 87.6 15.25 KB81003 Headers
    9 89.2 15.09 Unplug headers (open exhaust)
    10 91.2 14.89 KB Mark 1H Cam Kit with KB17501 Double Roller Chain and KB11302 Valve Seals
    11 92.3 14.88 KB mark 2H Cam
    12 94.8 14.62 KB Mark C118 cam
    13 96.5 14.54 KB44200 manifold, KB88048 Intake manifold Bolts, KB4594 Electric Pump with Stock re-jetted carburetor (jetting instructions with carburetor)
    14 97.1 14.47 Carter 800 cfm Carburetor (jetting instructions included with the carburetor)
    15 97.1 14.47 Holley 850
    16 96.0 14.59 Holley 660
    17 95.2 14.68 Holley 600
    18 95.2 14.68 Carter 625
    19 94.0 14.81 Carter 500
    20 97.1 14.47 KB Carter 9810
    21 97.9 14.39 KB8002 Plenum
    22 99.0 14.28 KB19903 Deep oil pan with KB88004 Spinlock Oil pan bolts and KB42502 magnetic Drain Plug
    23 99.5 14.13 KB161B Converter
    24 100.0 13.93 KB149 Switch Pitch Converter and KB400SP Switch Pitch street/strip transmission
    25 101.0 13.84 Shut off switch pitch immediately after launch in low gear
    26 103.3 13.62 KB61004 10.2 Budget forged pistons with KB13006 rings
    27 105.4 13.39 Ed Mosler Big Valve ported heads
    28 105.6 13.37 KB Roller Rocker Arms, KB9405 Shafts and KB9508 Rocker Arm installation kit
    29 106.2 13.32 KB Aluminum crank, Water pump and alternator Pullies
    30 106.8 13.26 KB60004 Super-Lite Forged 12.5 Pistons and KB13106 1/16 Rings
    31 106.8 13.16 4.56 gears
    32 106.8 13.16 4.88 gears
    33 108.1 13.05 KB mark 3H cam Kit
    34 109.5 12.99 KB mark 5H Cam
    35 109.9 12.89 KB161ss 10 Trackmaster
    36 109.6 12.84 Bore engine .030 9355 cu)
    37 109.6 12.84 Alum rods
    39 109.6 12.84 Increase Rod and main bearing clearances to .003
    40 112.7 12.54 4 speed Muncie and KB Clutch, Pressure Plate and steel flywheel
    41 114.2 12.40 KB mark 5S Cam
     
  5. gsjohnny1

    gsjohnny1 Well-Known Member

    again, k-b has a lot of bs back then. lot of stuff worked, a lot didn't. don't you remember those days..........
     
  6. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    What works for one setup may not do so well on another. Combination is everything. If someone tries to put something together listed in some step by step guide or just slap it on and expect it to tune itself and then it doesn't work like they want it to, the first thing to do is usually blame the parts or guide, not thinking that just maybe the problem exists between the ears. :p

    Then there's the advertising aspect. A manufacturer or purveyor of parts may 'fluff' up or round up some numbers to make something look good for the sake of sales. So there's some discernment involved as to what a reasonable expectation should be.
     
  7. WV-MADMAN

    WV-MADMAN Well-Known Member

    Exactly!

    With a Holley, your best bet is to use the smallest carb you can get away with.

    You can tune an 850cfm to run pretty good on a bone stock 350.

    But if all you need is 600cfm, youre not gaining anything with the extra 250cfm.

    Infact, you can start losing low-end and mid-range power due to hurting port velocity.
     
  8. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Use a spread-bore carb and your port velocity issues will be resolved, with the added bonus of getting to use the proper CFM the engine needs, compliments of the adjustable massive secondaries...plus the extra gas mileage.:bglasses:
     
  9. Jim Weise

    Jim Weise EFI/DIS 482

    I didn't even notice we were in the Small block forum..

    Only thing that really changes here with that realization is forget about a 950...

    750 is plenty big for anything you can do with a NA 350. Still a good choice.

    Q-jet still the best choice, in my opinion.

    JW
     
  10. Fox's Den

    Fox's Den 355Xrs

    I have that 1985 KB parts book with all that in it. You have to wonder how accurate it really is. No one at that time was racing a Buick 350, at that time it was all geared towards the 455. I was 26 yrs old then, the beginning of wanting a fast car.(Well really 10 years before that), Stuck in that 268 Comp Cam in, stock stall, Holley spread bore carb a 650cfm. The KB car used in the tests was a Apollo not a Skylark. It is a lot lighter. Apollo, Nova both the same.

    Maybe I should do some testing myself, I still have the 650 spread bore and a 750 Carter AFB and I even have a Thermoquad that is apart now in a box. I used the Carter when I first dynoed my motor and I was only able to get to 365 Hp. Slapped on the 750 DP Holley and managed to get to 395 Hp. BSFC was better with the Holley too.

    I liked the Thermoquad it was kind of a Q-Jet replacement as the Spread bore Holley. When I had the old stock motor with the 268 cam The Thermo made it run faster in the 1/4, but it was flooding after having it on the floor and that one ended the motor at the time.

    ---------- Post added at 10:02 AM ---------- Previous post was at 09:54 AM ----------

    You are probably right about this especially using a DP Holley. Right in their own instructions it is recommended to use a lighter car or more gear and stall with this type of carb.

    You know at least using the Q-Jet or the Thermoquad The back two barrels do open up when floored you just have to wait for the flap on top to feed the engine as it is needed where as the Holley vac secondary carb does not open the back two and has to wait for the spring to open it up. Guess that is why it was wire tied in previous video Jim put in.

    ---------- Post added at 10:20 AM ---------- Previous post was at 10:02 AM ----------

    I think you are right there I don't think the 950 is going to help much and will probably hurt the gas mileage. A 750 is in my opinion the largest carb you should use for the 350 unless you have a heck of a lot of modifications done to justify using a bigger carb.

    The Q-Jet will have smaller primary bores than the 750 Holley so there again the the gas mileage will most likely be better with this carb.

    The best Q-Jet would could be the 800 if you can find one then you get the most cfm out of the carb and still have those small primaries for gas mileage. Actually the velocity should be higher since the front two act like a 2bbl and then the back are kicking in when the car gets moving. It will probably 60 ft better with this carb because of that higher velocity when first romped to the floor.

    Anyone have a number for that carb and which vehicles it came from.
     
  11. sean Buick 76

    sean Buick 76 Buick Nut

    The easiest way to find one of these 800 CFM Q jets that are for 350 Buicks is to find a 76 or 77 Buick Century or Regal. Basically any car that is newer than 75, has a Buick 350, and a 4 barrell will have the prefered 800 CFM Q jet that has the Adjustable Part Throttle (APT) feature.

    One important thing that I noticed using both the 750 and 800 CFM Q jets is this:

    On the street the 800 is much better! This is because the primaries are larger and you do not have to get into the secondaries as often.

    I ended up with better fuel mileage with the 800 vs the 750 because I got into the secondaries less. This is with spirited but not flat out driving... I just found the car kind of gutless with the primaries of the 750 carb when going up hills. With the 800 the car went up almost any hill and got up to any speed I wanted and as long as I did not get too heavy on the gas pedal it would never use the secondaries.

    The full throttle power is about the same between the 750 and 800 CFM carb due to the fact that most 350s do not need much more than 750 CFM like others are saying

    I was selling off some of these 76-80 Q jets but I am down to about a dozen so I am keeping them for spares.

    The most common 800 CFM Buick carb is the 71-74 455 carb however they require extensive modifations to work well on the 350 due to idle air passages being different ETC, and these do not have the APT feature.

    Some info on the ID of the Q jets.

    http://www.cliffshighperformance.com/tech_carb_ID_2.html
     
  12. WV-MADMAN

    WV-MADMAN Well-Known Member

    Bigger primaries got better MPG:eek2:

    Why that's impossible!!!

    :laugh:

    Just mess'n with you Sean, you know I respect your opinions.

    I just don't understand how Q-jet people cant get this simple concept.

    If an engine requires X amount of air/fuel to do Y amount of work...

    Smaller primaries will require more throttle to reach X.

    Anyone that has ever switched back and forth between Holleys and Q-jets will tell you that a Holley needs far less throttle to do the same driving as a Q-jet.

    There are plenty of reasons a Q-jet should get better MPGs than a Holley, but smaller primaries aren't one of them.
     
  13. Curmudgeon

    Curmudgeon Well-Known Member

    Sean,

    Thanks, I asked for it. This is detailed and comprehensive. It will take a little time for me to go through. But a cursory review does tend to confirm Bell's finding that the little 350 likes a bigger carb. Who did the research? Any word on when your book will be available?
     
  14. sean Buick 76

    sean Buick 76 Buick Nut


    I am working away on the book however things are going slowly because I got a promotion at work and I have a TON of responsibility... I am now the head Environmental Health and Safety Advisor for a large construction company so even days off may be interupted with issues.

    Here is the testing, I just typed it up to make it easier to read:

    http://www.v8buick.com/showthread.php?120004-Kenne-Bell-350-testing-from-1984


    The two reasons why Q jets typically get better fuel mileage than a Holley are:

    1. The Q jet is a more sophisticated carb, if working correctly it has many advantages over a Holley carb on the street.

    2. When using a stock engine the Q jet is properly calibrated from factory, where as bolting on an aftermarket carb and not customizing it is normally worse on fuel.

    The other factor is that as you say it takes X amount of air and fuel to do X amount of work. When cruising on the highway at low load the Q jet has the potential to be better on fuel that a Holley due to higher velocity of the air and fuel with the smaller primaries. When beating on the car the difference between any two carbs will be less.

    A perfect example of what I am talking about is the 2 GC (stock 2 Barrel 350 carb) vs a Q jet. When driving easy the Q jet is better on fuel, but when beating on it the 2 barrel is better.
     
    Last edited: Jun 24, 2013
  15. Fox's Den

    Fox's Den 355Xrs

    I would say that this makes logical sense. So my primary 750 Holley should be closed some as compared to the 750 Q-Jet that has smaller primaries since the primaries on the Holley will be larger. lets say to run the same amount of rpm. I think we can all say that this is why fuel injection coupled with the computer works so well. All these opinions really make you think here lets keep on rolling.
     
  16. Gary Farmer

    Gary Farmer "The Paradigm Shifter"




    I could have swore I said pretty much that same thing 2 pages ago...
     
  17. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Sean was comparing Q-jet to Q-jet primary size, and the ball was taken and ran with on primary size generalized for all carbs apparently.

    Reading comprehension is your friend.

    To heck with all the bickering. If one is hell-bent on Holley I'd recommend a 650 CFM DP with a 1" 4 hole spacer if the 350 is relatively mild-moderate. Tune it to run great and live with the mileage, which won't realistically be more than a couple MPG difference anyway.

    Have fun and enjoy life. Peace everyone.
     
  18. WV-MADMAN

    WV-MADMAN Well-Known Member

    Agreed...

    To a fault at times.


    That's why I have never once suggested just ''bolting on'' a Holley.

    Their strongest point is the ability to tune them to work right.

    Just bolt it on and go misses the point and will lead to bad MPG.

    This is exactly why Im against running to much carb!

    Of course a ''properly tuned'' Q-jet is better than running the wrong size Holley.

    My contention isn't that you can just toss a Holley on and beat a Q-jet...

    Its that the proper sized and tuned Holley beats the Q-jet.

    Why do Q-jet people always assume that people who buy the most tunable carb there is never tune them:Do No:

    Do you run out-of-the-box parts store reman Q-jets?


    As an example from personal experience...

    Not a 30 year old story or something I read on the internet...

    My '69 1-ton dually came with a 2bl-307 and 513 gears.
    I swapped the rear to 373s and put a '68 327 Q-jet and a performer intake on the 307.
    Mpg wasn't bad for a 7,000lb truck at 13mpg.
    But the truck was nutless powerwise:shock:
    I then swapped in a tall-deck 427 and tuned a 600cfm V-S Holley.
    The truck is now a beast, and Ive grossed it out at the scales at 17,000lb before:shock:

    Its current MPGs..........13.
     
  19. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Run what you want. Whatever tickles your pickle.

    Gas mileage won't be day and night difference between two properly functioning and tuned carbs with similar applications, but the spread bore certainly has the advantage here.

    You have to admit though, there is a reason for spread bore design, just as there is a reason for square bore design.

    Q-jets won't have as much get up and go with partial throttle as a Holley, but the difference in mileage will be seen during cruising without going up too many steep hills. There's less transitional CFM when opening it up to full throttle with a square bore, so it'll have a smoother power transition compared to the heavy kick the Q-jet gives. Whatever you prefer.

    Personally I wouldn't go Holley if i were to go square bore, I'd go Edelbrock performer, which I had considered for a long time. Heard good and bad about them, but such is the case with any carb. Now there's a carb that wins the 'easy to tune' competition. Inexpensive too.

    Peace
     
  20. Curmudgeon

    Curmudgeon Well-Known Member

    WV-MADMAN

    I'm actually looking forward to working on whichever Holley I select. I can still lift these parts.:TU: I also realize that a car is a system. By tweaking and tuning I have gotten about all I can get out of my current set up. I like tweaking and tuning. I am only running a 600 Eldebrock now. So I believe I am leaving some on the table. Plus I am looking down the road because of items I have and just need to install. And those parts I am about to buy: Like the carb and torque converter. I am 90% sure of the carb. The more I read about torque converters the more I have realized the more I need to read.

    Thank you for your input.
     

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