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Hot Rods Intake suggestions for SBC

Discussion in 'The Hokey Ass Message Board' started by sedantudor, Feb 7, 2016.

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  1. sedantudor
    Joined: Jan 28, 2012
    Posts: 129

    sedantudor
    Member

    I am looking at upgrading the 47 this year. Currently I am running a SBC 355 cubic inch with about 11.5:1 compression. The intake is a dual plane with a 650 carb and an HEI ignition. I am looking at couple of options each of them being multiple carb set ups. The ideas are:

    1. Tunnel Ram - The problem here is the operating RPM range may be too high for a street car. From my research the RPM range for a tunnel ram is about 2,800 to 8,000 RPM. I have a 2,200 stall speed converter in the turbo currently.

    2. Dual Quad - I was looking at a dual quad set up with two 500 cfm carbs. The RPM is around 1,500 to 6,500 RPM which is close to what I am running with my current dual plane.

    3. Three Two Barrels - This was the final set up I was looking at. According to the description the RPM range is from 1,500 to 5,500 RPM. I do see an advantage of running on a single a 350 two barrel for most of the driving until the pedal is punched and the end secondary carbs will come in. The linkage is a progressive linkage so it can be dialed up like a manual transmission and set any way I like for the end carbs to kick in.

    My questions is has any one run these set ups? If so, any suggestions? I must admit nothing looks more bad ass than a tunnel ram sticking out of the engine bay with velocity stacks but I am also trying to keep performance in mind. The car runs fine now minus some dieseling due to low octane fuel. (Which if anyone has any suggestions on an octane booster that would be appreciated as well.) Almost forgot, the rear end is a GM 10 bolt 8.2 with a 3.23:1 rear ratio. It is also a posi rear.

    Thanks for the information all you fine Hambers out there.
     
  2. I have a complete 3X2 set up ready to run , if you are interested.
     
    falcongeorge likes this.
  3. aaggie
    Joined: Nov 21, 2009
    Posts: 2,530

    aaggie
    Member

    Your current setup is probably the best for daily driver street use. Maybe go up to a 750 Holley with vacuum secondaries or a Qjet. Multiple carb setups are mostly multiple problems.
     
  4. Personally, I like a belt driven intake manifold with a 750 Eddy on top... ;)

    IMG_4205 - Copy.JPG
     
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  5. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,791

    tfeverfred
    Member Emeritus

    Yea, maybe. But what I don't get, is how could the factories run multiple carbs on cars that came with a warranty? What makes doing it, so damn hard today? Hell, the cabs today are better than the ones in the 50's and 60's! So, what's the mystery and fear in doing it now? Have we gotten impatient, so we don't take the time in setting it up correctly? Threw away the instructions? Or maybe the guy down the street couldn't do it right, so we all got scared and ran into our single 4bbl closet, where it's all warm and safe.

    So, why is a multi-carb set up, so damn scary? Just curious.
     
  6. steinauge
    Joined: Feb 28, 2014
    Posts: 1,507

    steinauge
    Member
    from 1960

    IME there is nothing especially" scary" about multi carb setups if you start out with good carbs and know what you are trying to accomplish.The 3X2 setup as you said is nice and tractable due to running most of the time on the center carb.Once you have the linkage set up the way you want it it isnt likely to change.Same with 2 four barrels.If you start with a 3X2 install the manifold and carbs and get the car running and dialed in on the center carb. Connect the end carbs linkage and adjust it so that the end carbs start to open at about half throttle(or wherever you like) and drive the car.I generally just close the pilot screws on the end carbs and remove or immobilize the choke plates.I generally do not disable the accelerator pumps on the end carbs although many people do.2X4 sets up the same way except you dial the engine in on the rear carb and then connect the front carb and adjust.
     
  7. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 31,178

    Jalopy Joker
    Member

    option #2 - looks/performance= Cool
     
  8. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    I would do #2, or #3 before #1.

    Tunnel rams can be difficult to get good off-the-line performance out of. It can be done, but it takes work and patience.

    I'd lean towards #2, with vacuum secondaries.
     
  9. Nocero
    Joined: May 16, 2002
    Posts: 489

    Nocero
    Member

    I started out with a tunnel ram with Holley 450's it didn't work well for my combination
    I ended up with a edelbrock c26 dual quad with edelbrock 500's and a milder cam and am much happier.
    The top end horse power may be less but it is much more usable and the car is faster.
    I have a 355 with about 11-1
    Cam choice will make a big difference as to how well either combo works.
     
  10. rails32
    Joined: Oct 29, 2008
    Posts: 110

    rails32
    Member

    your manifold with a bigger carb will be the best set up for all around street driving. multi carb set ups look good on hoodless cars but can be a pain in the ass trying to find old carbs from factory set ups that are any good are 50 years old. new carbs are not sized or calibrated for multi use, do not even consider Edelbrocks dual quads
     
  11. The compression the poster stated is to high for a blower. I would go with 2x4 or 3x2 setup. Dont be afraid of multi carbs or tuning , After all, every carb needs some tuning for your application.
     
  12. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    I have had excellent results with Edelbrock dual quads.
     
  13. Joliet Jake
    Joined: Dec 6, 2007
    Posts: 536

    Joliet Jake
    Member
    from Jax, FL

    Tunnel Rams work just fine on the street, don't let anyone convince you otherwise. I have never ran one with an automatic though. I run Edelbrock on mine, been trouble free. It all depends on the look your after. Back in the 70s in ran a tunnel ram year round, in Illinois.
    image.jpeg
     
  14. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,245

    theHIGHLANDER
    ALLIANCE MEMBER

    You really want to raise a single finger to conventional street intake/carb set ups?
    [​IMG]
    Find a used 750 Dominator to throw on top of it, maybe a decent 4 hole spacer to keep throttle response crisp n clean. Not practical but not much of what we do is either. Just sayin...
     
  15. I don't think you'll be able to use your HEI if you switch to a multi carb intake so you need to factor that into the equation.
     
  16. sedantudor
    Joined: Jan 28, 2012
    Posts: 129

    sedantudor
    Member

    Yes, a distributor change is in the near future after switching out the intake/carb set up. Thanks for pointing that out.
     
  17. sedantudor
    Joined: Jan 28, 2012
    Posts: 129

    sedantudor
    Member

    Thanks for the good advice all. I still interested in seeing more perspectives on the topic. Also, do any of you have an octane booster that you would recommend. I think another issue I am having is too low of an octane for the compression the engine has. Thanks.
     
  18. 4thhorseman
    Joined: Feb 14, 2014
    Posts: 261

    4thhorseman
    Member
    from SW Desert

    IMO I'd really consider the look I was after as well as the application in this case. I'm just speaking if it was mine and everyone has different opinions.

    The current combo is very mild but it don't have to appear mild. The ride in your avatar (hoodless and flamed) screams hot rod. Having a pair of carbs poking up out of that big, deep engine bay on top of a tunnel ram would complete it I think. There's currently a lot of empty black space up that fire wall. If you were to go with a street oriented TR (Edelbrock 7110) you'll have some street manners. They have narrower runners to maintain velocity. They say 3500 basement but that means when it starts really coming on. It's not dead below that. And your compression is a bonus to maintaining a healthy torque curve. But it won't have the same street manners as you dual plane. Now upstairs its going to be a different story. From 3500 to redline it ought to pull much harder than current unless its a very mild camshaft combo. Then you can run a pair of stacks or a scoop of choice and suddenly the engine becomes a focal point to the gawkers. If your piston to valve clearance is there I'd probably step up the rocker ratio and pick up 30 thousandths lift to take better advantage of the free'er breathing up top. And rear gearing is crucial. highway gears and a TR = tortoise.
     
  19. sedantudor
    Joined: Jan 28, 2012
    Posts: 129

    sedantudor
    Member

    The car in the avatar is the car I looking at upgrading. I personally have never run a tunnel ram but I was debating about stepping up the gears to a 3:73 rear ratio. The piston to valve clearance is minimal as I have domed pistons with 61 cc heads. (Not a typo, I know strange number. Heads are off of a 67 302 DZ with no accessory holes in them. At least that is what my research has led me to by means of the casting numbers.) The cam is moderate to semi- aggressive. If memory serves me right it is a comp cam with 520 lift on the intake side and a little less on the exhaust side. Thanks for the info.
     
  20. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,910

    dirty old man
    Member Emeritus

    Although I know that a good single 4bbl manifold with a Holley is prollt the most practical and a good deal easier to tune and maintain, because it was going in a Hiboy '31 roadster with visible engine, I wanted a more racey looking induction system.
    Not seeing, reading, or hearing much that I liked about street use of tunnel ram setups, and wanting more cfm carb flow than you can get with commonly available 2bbl carbs for a 3/x2 system, I went with 2X4 system.
    Ordered the full Edelbrock system in a package with hi rise air gap manifold, linkage and 500 cfm Edel AVS carbs calibrated to work on this setup.
    Pulled the tops and found float level settings off a bit and readjusted, other wise, they are straight outta the box. They look awesome, and run great, WFO or chugging around town. Originally I set linkage up for progressive operation, and it ran quite well and considering the cam I have, it's good around town
    But I got to thinking about how little that back 4 bbl was getting activated and worrying about this damn Ethanol spiked crap they're calling gasoline these days phase separating and causing some corrosion or sediment problems in the back carb bowl and innards.
    So I readjusted linkage to simultaneous operation, and have had it that way for over a year and I like it. Realize it might be different if I didn't have the AVS carbs which have an air valve butterfly on both secondaries similar to a Quadra-Jet, but I have no appreciable bog, maybe even a bit more "crisp" throttle response and feel. Can't comment either way about fuel mileage, but is that really important on a hot rod you only drive in good weather around town or on short trips outta town up to maybe a hundred or 2 miles?.
     
  21. Blues4U
    Joined: Oct 1, 2015
    Posts: 7,589

    Blues4U
    Member
    from So Cal

    I'll just leave this here....
    20160207_144702.jpg 20160207_144907.jpg
     
    Nocero likes this.
  22. yea a tunnel ram on a pro street car is tits. :rolleyes:

    I have run all 3 setups, even an early Edelbrock Breadbox. Of the 3 the 2x4 is the hot setup. At least that is my opinion.
     
  23. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,799

    jimmy six
    ALLIANCE MEMBER

    I've been running dual quads for 3 years with an automatic and progressive linkage and don't have any complaints.(WCFB's) They definitely have the cool factor. There are still a lot of 245-270 Corvettes running.. Good luck..
     

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