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

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

  1. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The Q-jet that came on the 350 from the factory was capable of flowing up to 750 CFM. Like Madman stated, the Q-jet will only deliver what the engine demands. 750 is not too big for the 350. The link I posted is the carburetor I would use if I didn't have the good Q-jets I have. Look at my signature. That 470 demands a lot of air. I think the SA 870 would make a good street carburetor for my engine.
  2. Curmudgeon

    Curmudgeon Well-Known Member

    That is what I thought. Just not initially.:Dou:

    Yea you have one very strong build! I will admit it, I am jealous.
  3. 71skylark3504v

    71skylark3504v Goin' Fast In Luxury!

    I ran a 850 Holley DP on my bone stock 350 for a year and a half daily driven. It took some tuning but it ran great. And that's a FACT. Only reason I gave it up for a Q-Jet was to go for max MPG because I knew the engine was going to be stock for a long time. The mileage did not improve by much but the part throttle performance was improved slightly.
  4. Fox's Den

    Fox's Den 27 years of racing the same 355 Buick motor

    I think Larry's suggestion on the 870 vac sec avenger carb would work good on your application. I run the 750 DP Holley and in order to run the DP carb you do need more stall (I use 3000) and 373 gears. There can be some lag in the secondaries if the engine rpm is too low. But when I am at the track I am up to 2 grand to launch and when it hits the floor those secondaries rip the car right out of the hole.

    If you do use the larger car remember the the carb will be bigger and it may use a little more gas but hey I don't think we are worried about gas mileage here. I do think a 700 or a 670 will be too small for the 350. There are too many tests out there that had the larger carb making the car faster.

    I just can't see using the Q-Jet unless you want to stay original, there are just too many newer carbs out there that will work better and are now easier to tune.

    Too bad we don't have someone with several carbs of different kinds to use to test the performance and gas mileage to see which one is best.

    This thread has been interesting to read, lots of comments. Lots of opinions. :)

    Watch my video at the bottom of my sig, my car has no trouble coming off the line with a 750 DP carb.
  5. Jim Weise

    Jim Weise EFI/DIS 482

    Stay away from all Vacuum secondary series Holleys, the Avenger line in particular.

    All kinds of issues with them, of biggest concern is an issue with casting itself- it disintegrates over time.

    Holley long ago decided that everyone needs a 600 on the street, based on poor intake charge velocity motors like the Cleveland Fords and rectangle port Chev engines.. and the amount of small blocks running around at the time.. and as such, they calibrate the venturi vacuum required to open the secondaries in such a manner that on the bigger cfm vacuum secondary carbs, you would need a healthy 700 inch motor to have enough airflow to open the secondary. I made an 870 work years ago, with a fair amount of fooling around, and was sorry I ever bought that carb for a customer. In fact, I replaced it with a Q-jet, and was far happier with it's power and driveablity. I think I still have that 870 in a box around here somewhere. Considering what I found out about the casting issue later, I'm glad I yanked it off the customer's car.

    If your going Holley, go with a double pumper, 750 is a good all around carb. No smaller.

    The right choice for your build is a Q-jet. That is what I would run, for an all around carb, get a good used 850 or 950 Holley if your going to go to the track regularly. The 950 is big enough to "grow into" as often happens on engine builds over time.

  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Well, that's good to know. I have no experience with the SA Holley, and know of no one with one. Jerry, I think a Holley 750 DP or a good Q-jet built for your engine is your best bet.
  7. Fox's Den

    Fox's Den 27 years of racing the same 355 Buick motor

    I think these last two posts here sums it all up. Good remarks on this from everyone. It would be nice to get a good 800 Q-Jet that is rebuilt from one of our great Q-Jet mechanics here. Then you will not have to take it apart to tune it.
  8. Alssb

    Alssb Well-Known Member

    Car Craft $299 Shoot-out:

  9. Jim Weise

    Jim Weise EFI/DIS 482

    So I am reading thru the article, wondering how in the H they got a 750 Vacc secondary Holley to open on a 400HP 350 chev.

    Then I saw this picture..


    I busted out laughing..

    That is exactly how you get a VS Holley to open the secondaries. Zip tie the linkage.. been doing this for years.

    Too funny, the caption should read "So we could get the secondaries to open on these Holleys"-- " Variations".. ya right pal..

    And the "complex procedure to take of the top of the Q-jet" in the sidebar made me laugh.

    Real complex procedure. :rolleyes:.. takes me 5 minutes to pop the top off a Q-jet on the dyno for tuning. Not much longer than a Holley Jet change.

    On the latest Super Stage motor I dynoed, we bought a reman Q-jet to keep the budget in line. Picked it up on the way to the dyno shop from my jobber, so I had to tune it there.. took maybe 15 minutes, a screwdriver and a pair of pliers.. not complicated or difficult.
  10. Fox's Den

    Fox's Den 27 years of racing the same 355 Buick motor

    That is some funny stuff there Jim, If you have to zip tie the secondary throttles you might as well use a DP carb. It sounds like Jim has a quick way to get the carb apart to make changes. I only did one Q-Jet that I have on a 4 door Lark I have and it was some trouble for me to get apart.

    Maybe what we need here is a video or some pictures showing how easy this carb can be to work on if you do it right. The carb does seem like to be a good carb to use, I am just one of those people that never worked on it much.

    I would actually like to try it to see if I can get the car faster and get better gas mileage.

    Probably finding a 800 Q-Jet may be hard to find.

    I know we are kind of pushing off the main subject some but this is always good info to learn on.
  11. Curmudgeon

    Curmudgeon Well-Known Member


    This is a boat load of information. I have to say I would not be very happy about a carb that the casting may disintegrate over time. It seems DPs are not very popular around here. It could just be my perception. I like the thought that I can open up the secondaries when I want. I have to admit I never gave any thought about growing into a carb but it makes sense. At least for now I am leaning toward a Holley DP 750 cfm to 950 cfm with an electric choke kit.

    ---------- Post added at 08:25 AM ---------- Previous post was at 07:54 AM ----------

    I don't think you are off topic. Even if you were, I will still take any opportunity to learn. Learn on!

    ---------- Post added at 08:28 AM ---------- Previous post was at 08:25 AM ----------

    Duck tape better watch out zip ties are on your heals.
  12. Fox's Den

    Fox's Den 27 years of racing the same 355 Buick motor

    I think you should get the 850 carb just a regular Holley DP of course if your mind is set on this style carb. One thing I would look for is getting one with a 4 corner metering adjustment. Then if you have a bigger cam in there you have the ability to open the secondary main idle adjustment some and this will help you bring down the main idle adjustment some on the primaries so the main idle transfer slots are not exposed too much.

    I had to very so slightly open the secondary throttle blades a very small bit to let me adjust the four corner idle adjustments a little better and I was able to bring down that main primary throttle blades. The secondary throttle adjustment screw is under the carb and you would normally not touch this if you do not have much of a cam in the car but can help with the idle system if and when you put in a larger cam. Like Jim said, in case of future changes with the engine

    Get the books that are out there for Holley carbs then you will have all the info you need on adjusting this carb to it's full potential, I like mine it works great and I use the 750. If I knew then what I know now I would have bought the 850.

    Also, if we get those aluminum heads in the future we will need that 850 for sure.
  13. Curmudgeon

    Curmudgeon Well-Known Member


    How difficult is it to run without a choke? I have never owned a naturally aspirated car without a choke. To be honest I have not given it much thought. I live in the middle of FL. We get a few really could days a year. But compared to some of you guys, I live in the tropics. Anyway how about it?

    ---------- Post added at 09:52 AM ---------- Previous post was at 09:43 AM ----------

    I have been looking at the Holley 0-4781S carburetor 850 cfm double pumper. It has that feature, as well as all the ports I would need.
  14. Fox's Den

    Fox's Den 27 years of racing the same 355 Buick motor

    Sounds like a winner to me, this one costs 613.55 from Holley and I see Summit has the best price. 589.00 The prices have really gone up since I bought mine in 1994 mine was 350.00

    One thing I forgot to tell you is Absolutely do not over tighten the carb as this will warp the base and screw this all up and will cause a vac leak. I like to use the two finger method of tightening and keep the fingers up near the head of the ratchet. Snug not tight works best you can always test the next day after the engine has cooled down.

    you might as well get a jet kit and an accelerator pump cam tuning kit and you will most likely have everything you need. Make sure you get the books on it this will be a big help too.
  15. Curmudgeon

    Curmudgeon Well-Known Member

    It is hard to beat first hand experience.

    ---------- Post added at 12:20 PM ---------- Previous post was at 11:54 AM ----------

    I agree. When Sean speaks (types actually) I listen (read actually).

    ---------- Post added at 02:08 PM ---------- Previous post was at 12:20 PM ----------

    It is a good idea to get kits, parts, books, ect. before you actually need them. Should sure help in fining tuning. Found this one, Holley 0-4781S 850 cfm double pumper carburetor. This S in the part number refers to the finish. The vibratory polished finish that is suppose to looks like chrome. for [​IMG] from Spider performance (http://www.spiderautomotive.com/holley04781.html). I will keep looking. I am a self admitted cheapskate.
  16. gsjohnny1

    gsjohnny1 Well-Known Member

    and i'll throw one in here just to confuse you more. I have a single plane intake on my 350 and I use a holley 600cfm. I have a bunch of carbs and tried the bigger ones. bigger is not always the answer. it depends on what you have done to your engine. :Smarty:
  17. Curmudgeon

    Curmudgeon Well-Known Member

    Confuse at will. You are correct bigger is not always better. However, when one compares the findings of Kenne Bell, specifically on the 350, and Jim Wise's years of building Buick's renders much wisdom. I know I bring Kenne Bell into the thread often. However. if someone else had done as much research as Bell did I would be using his/her findings as well. Regardless if those findings were in opposition or in support, so long as it was comprehensive and detailed. I prefer data driven findings, as well as real world experience. I guess you could say, I am a victim of my education.
  18. sailbrd

    sailbrd Well-Known Member

    Jerry, I live in Michigan and don't need a choke. If it is going to snow I get out the skis not the Buick. :grin: Without a choke you have to spend one minute warming the car up. Even my blower setup does not take all that long to warm. You just work the accelerator pump a little.

    Even though I put this together for blow through this is how I tuned my QuickFuel 650

    I cruise at 70 mph with 15:1 AFR

    You use a much smaller carb when you are doing a blow through supercharger.

    Another good trick with a Holley style carb is to get one with annular boosters. It will act a little smaller than it's rating. To tell you the truth we may all worry too much about size. It is really about tuning. I could put a 950 on your car and make it work very well. I know because I put my 950 Biggs on my sisters 302 Mustang. Did not have any major problems. I was just trying to find out how crappy her Edelbrock was. It was too big but with the progressive linkage it drove well.
  19. Curmudgeon

    Curmudgeon Well-Known Member


    Now that I think of it, every Harley performance part I bought was stamped "For off road use only." A kind of proactive litigious immunity. Although, I thought it funny picturing me on either my Fat Boy or Deluxe tearing up the trails. Not that I could not mind you: just expensive dirt bikes. Oh those were the days. No biking for me.
  20. sean Buick 76

    sean Buick 76 Buick Nut

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