Results 1 to 12 of 12

Thread: Holley 4 barrel carb. How much HP+ ?

  1. #1
    Registered User
    Member ID
    CZCC-15708
    Join Date
    Dec 2007
    Location
    Lithuania
    Posts
    13

    Default Holley 4 barrel carb. How much HP+ ?

    Hi everyone, i have 4 barrel holley carb in 71's 240z. How much hp it approximately add?
    P.S. sorry for my bad english

  2. #2
    Registered User Weasel73240Z's Avatar
    Member ID
    CZCC-14988
    Join Date
    Sep 2007
    Location
    Taunton, Massachusetts
    Age
    50
    Posts
    483

    Default

    I'm no expert on this, but I think most people on here would agree that running a Holley 4bbl probably doesn't improve power or performance with an L24 engine. You would probably make better (and more efficient) power with the original twin SU's.
    Paul Martin
    1973 240Z HLS30-127623 (10/72)
    4.11 R-180, 79 ZX 5-speed, ZX Distributor, ZTherapy SU's

  3. #3
    Enjoying the ride... 240ZMan's Avatar
    Member ID
    CZCC-4803
    Join Date
    Aug 2003
    Location
    Castle Rock, Colorado
    Posts
    565

    Default

    I agree with Weasel73240Z. A larger carb will only increase power if the original was too small to provide enough air and/or fuel to the engine. In the case of our Zs, the stock SUs can provide more than enough air/fuel for a stock L6, and even for most modifications.
    Daniel
    '73 240Z
    Castle Rock, CO

  4. #4
    Registered User
    Member ID
    CZCC-15708
    Join Date
    Dec 2007
    Location
    Lithuania
    Posts
    13

    Default

    So what is that carb for?

  5. #5
    Registered User MikeW's Avatar
    Member ID
    CZCC-3294
    Join Date
    Dec 2002
    Location
    Atlanta, GA, USA
    Posts
    2,739

    Default

    Quote Originally Posted by Greddy View Post
    So what is that carb for?
    Big American V8 engines.
    -Mike
    Add your Z to my online spreadsheet registry

  6. #6
    Enjoying the ride... 240ZMan's Avatar
    Member ID
    CZCC-4803
    Join Date
    Aug 2003
    Location
    Castle Rock, Colorado
    Posts
    565

    Default

    Quote Originally Posted by Greddy View Post
    So what is that carb for?
    A common problem with the SUs is that the throttle shafts wear out, begin to leak, and make tuning difficult if not impossible. Since new SUs aren't readily available, some have switched to 4 barrels (others to weber DGVs, etc). I've read of people who have properly set up small 4 barrels on Zs with good results. But they didn't achieve MORE power than with properly set up SUs.

    If your setup is working well, then go drive it and have fun!

    BTW, ZTherapy is a good source of rebuilt SUs that solve the leaking shaft problem.
    Last edited by 240ZMan; 12-13-2007 at 12:24 PM.
    Daniel
    '73 240Z
    Castle Rock, CO

  7. #7
    Registered User
    Member ID
    CZCC-15708
    Join Date
    Dec 2007
    Location
    Lithuania
    Posts
    13

    Default

    thanks for everybody for your answers.

    Off topic. What are other ways to increase HP? My Datsun has performance exhaust system, does it increase hp?
    Last edited by Greddy; 12-13-2007 at 01:02 PM.

  8. #8
    Registered User MikeW's Avatar
    Member ID
    CZCC-3294
    Join Date
    Dec 2002
    Location
    Atlanta, GA, USA
    Posts
    2,739

    Default

    HP is increased either with more displacement (i.e., going from 2.4 to 2.8 liters) or by making the engine consume more fuel/air. Because the SUs supply exactly the right amount of fuel for the amount of air coming in you need more air. That's why bigger carbs don't help without the additional air flow. A different camshaft is one way to make the engine consume more. Polishing/porting the intake manifold can also make a slight improvement. The performance exhaust may help a little but it usually goes along with the other changes.

    By far the easiest way to make the engine draw in more air is to force it in. The most common way to do this is a turbo charger. The simplest way to do that is to simply swap engines from a later model 280ZX Turbo. This has the added benefit of increasing the displacement at the same time. Another way to increase displacement is a new crankshaft. If you can find one the crankshaft from a diesel Maxima gets you from 2.8 to 3.1 liters.
    -Mike
    Add your Z to my online spreadsheet registry

  9. #9
    Biafra for President e_racer1999's Avatar
    Member ID
    CZCC-6883
    Join Date
    Jun 2004
    Location
    San Diego
    Age
    38
    Posts
    2,171

    Default

    ^must add to mike's post in regards to the crankshaft 'stroker' motor; it requires different pistons and rods to get to 3.1L. you would need 240SX (KA24) pistons milled down, as well as 240Z connecting rods.
    Jason King
    6/72 240Z / HLS30 89646 (Yellow)
    1996 Infiniti I30 *I finally have all Nissans again!*
    1971 510 4door (wife's car)
    IZCC Member #14186

    Quote Originally Posted by xray View Post
    As unfortunate as it may be, if you want to vintage race, go Euro....If you want to race for real, stick with the Z!

  10. #10
    Registered User
    Member ID
    CZCC-5121
    Join Date
    Oct 2003
    Location
    Seattle, WA
    Posts
    2,362

    Default

    Quote Originally Posted by MikeW View Post
    Big American V8 engines.
    You mean small American engines don't you? Can't run a big V8 off of a puny 390. It's a popular spec carb for 2.3L Pintos in dirt track racing.

    I agree with 240ZMan as to the purpose of that conversion. If you've got a set of tired SU's and you've never heard of ZTherapy and don't know how to diagnose or fix SU's, a 4 barrel conversion can get the car running strong again. Probably not as strong as properly refurbished SU's, but well enough to make it seem like a big power increase over tired SU's.
    Jon

  11. #11
    HS30-00352, HS30-101370 240znz's Avatar
    Member ID
    CZCC-1608
    Join Date
    Jan 2002
    Location
    New Zealand
    Age
    51
    Posts
    984

    Default

    Biggest performance gains are all down to head work. But you really should be thinking about modifications as an on going thing. You'll get very little increase in power by just putting a set of extractors on it. To get the best out of them you really need to look at the carbs, ignition, cam and head work upgrades together. They are all related one way or another. Careful and educated planning is the key. Read up all the tech articles you can and build a picture of what you are after rather than fitting parts in a piecemeal fashion.

    One of the easiest mods to is change your diff to a 3.9 or 4.11. Just remember that that alone will increase acceleration but decrease top speed. Trade off's are everywhere.
    Zed not Zee

    HS30-00352 still being rebuilt (year 6)
    HS30-101370 chopped in half

    CZCC #1608

  12. #12
    Express Japanese Taxi ozconnection's Avatar
    Member ID
    CZCC-10105
    Join Date
    Nov 2005
    Location
    Sydney, Australia
    Age
    53
    Posts
    304
    Blog Entries
    1

    Smile

    I have an L28 that runs a Holley 465 on an Arizona manifold imported from the USA. Bought it off ebay. I also have a Clifford 4 barrel manifold for the 4bbl conversion. Very different results from each of them. The Arizona is a torque manifold by design. The Clifford sacrifices low speed torque for a lot more power up top all else being equal. Admittedly, the Arizona 4bbl needed a lot more 'tuning' of the carb to get it working right, but it's worth the effort.
    I have played around with different sized carbs too, one being a spreadbore vac secondary 650, an annular booster square bore vac sec 600 and the 465 and they are all reasonable performers. The best for low speed torque is a close run between the 650 (small primary throttle bores) and the 465. The 600 produced the most power on the Clifford manifold. The 465 on the Arizona produces a low speed torque monster with a stock cam when the cam is also advanced (positition 3 on the stock cam sprocket). This is how my car is set up at the moment. Throttle response is excellent with the 4bbl setup and economy isn't half bad either. Like I said, it takes time to get it right but the results are there if you're prepared. BTW, I also recommend some mixture metering device to see where your mixtures are at. I use the Innovate wide band O2 sensor thingy. Best tuning tool I ever bought.
    Check out my engine and car on youtube. (Dyno run Datsun 280C).
    All the best with your 4bbl project.
    Mark.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	engine bay dec 07 006 smaller.JPG 
Views:	1583 
Size:	289.3 KB 
ID:	20974  
    Last edited by ozconnection; 12-14-2007 at 03:03 AM.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Triple Carb vs. Holley 4BBL Carb
    By red_dog007 in forum Carburetors (S30)
    Replies: 41
    Last Post: 12-04-2007, 09:53 PM
  2. Holley Carb - Manual or Automatic Choke ???
    By moritz55 in forum Help Me !!
    Replies: 4
    Last Post: 08-21-2007, 05:26 AM
  3. 6 carbs???
    By kmack in forum Carburetors (S30)
    Replies: 41
    Last Post: 05-11-2005, 11:30 AM
  4. L24 horsepower
    By zeiss150 in forum Help Me !!
    Replies: 43
    Last Post: 07-01-2004, 04:24 AM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •