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2 bolt mains vs. 4 bolt mains....

Discussion in 'The Hokey Ass Message Board' started by Roothawg, Oct 4, 2010.

  1. Roothawg
    Joined: Mar 14, 2001
    Posts: 19,008

    Roothawg
    Member

    I am just wondering if the 4 bolt main deal is really worth it?
    I mean I have read all the magazine articles, books etc. on splayed caps, 4 bolt mains etc.

    My question is this, for a guy on a budget, building a decent motor that sees the drag strip a few times per year, is it really worth the extra?

    Splayed caps can run into some serious money and if you are building a 350-450 hp motor, with no nitrous or supercharger, would you be better off spending money on other types of insurance? Like better rods or a forged crank?

    I'm just asking for opinions here. Not wanting a brawl.

    And just for the record, I have only owned one 4 bolt main.:cool:
     
  2. JeffreyJames
    Joined: Jun 13, 2007
    Posts: 16,597

    JeffreyJames
    Member
    from SUGAR CITY

    Now I know nothing and am no expert but weren't all the early Chevy V8's 2 Bolt mains and they saw plenty time on those drag strips. I think that for something like running 8 second passes you'd hardly notice. But again I know nothing.
     
  3. rjaustin421
    Joined: May 1, 2009
    Posts: 337

    rjaustin421
    Member

    "I am just wondering if the 4 bolt main deal is really worth it?
    I mean I have read all the magazine articles, books etc. on splayed caps, 4 bolt mains etc.

    My question is this, for a guy on a budget, building a decent motor that sees the drag strip a few times per year, is it really worth the extra?

    Splayed caps can run into some serious money and if you are building a 350-450 hp motor, with no nitrous or supercharger, would you be better off spending money on other types of insurance? Like better rods or a forged crank?"

    I have had great success and long life with 2 bolt mains and a set of ARP main studs...as in I built a 10:1 oval track motor that won a ton of features until a rod kicked out 7 full seasons later. Go for a better rotating assembly, make sure the caps are tight in the register, get the block prepped with aligned honed mains, ARP main studs and cylinders honed with a torque plate and you will have a very stout piece. A good aftermarket balancer (TCI, Fluidamper etc) is added insurance if it fits your budget.

    The key is to have a budget and build within that amount.
     
  4. Satinblack
    Joined: Jan 1, 2004
    Posts: 970

    Satinblack
    Member

    Well for me every 2 bolt main i have owned has lasted forever every 4 bolt had problems. Maybe just the way things are for me, but thats how its been. I gladly use a 2 bolt
     
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  5. Roothawg
    Joined: Mar 14, 2001
    Posts: 19,008

    Roothawg
    Member

    I have always ran 2 bolt mains and I have them balanced, zero decked and use ARP bolts on everything. I have never ran a set of main studs, although I hear they are worth it. The motor in question will be around 12.5:1.
     
  6. BulldawgMusclecars
    Joined: Jul 15, 2010
    Posts: 508

    BulldawgMusclecars
    Member

    Most factory 4-bolts aren't any stronger than a 2 bolt, and some are actually a little weaker. I'll 2nd the use of ARP main studs as a little exta insurance. Of the few engine issues I have ever had personally, I have never had a problem related to the mains. Spend your money where the power is made...the top end.
     
  7. 2 bolt 400 SBC's have that little bit of extra metal in the area. I'm building a 400sbc, but it's 4bolt. I'm using a forged non-twisted crank, forged main caps an a girdle. With ARP studs, keeping it all together. Should be interesting with my Enderle 8 stack injector
     
  8. 1/2done
    Joined: Oct 29, 2006
    Posts: 597

    1/2done
    ALLIANCE MEMBER
    from Ohio

    2 bolt main/cast crank combo is good for ~650hp. I know guys that wind the crap out of them in dirt cars w/o a problem.
     
  9. dexleo2
    Joined: Jul 20, 2008
    Posts: 145

    dexleo2
    Member

    I run 2 bolts in my Stock car and I twist the sh*t out them. (6700 rpm) Never had one blow the bottom end. Make sure you use ARP studs in the mains and Rods. And spend the money to have the rotating assembly balanced and you will be fine.
     
  10. Deuce Roadster
    Joined: Sep 8, 2002
    Posts: 9,520

    Deuce Roadster
    Member Emeritus

    In a SBC ... I believe a 2 bolt block is as good as a 4 bolt up to 550/600 HP.
    With a BBC ... I want a 4 bolt main ... every time.

    Disclaimer :
    Both my 32's and my current project truck engine are SBC's with 4 bolt mains ...
    :rolleyes: :eek:
     
  11. squirrel
    Joined: Sep 23, 2004
    Posts: 44,251

    squirrel
    Member

    Probably doesn't matter in 98% of applications

    true story: tore apart the virgin 350 in a late 70s one ton truck, had a short main cap bolt rolling around in the oil pan. I think they put the extra bolts in because it was cheap insurance against not tightening one on the assy line
     
  12. #### Bingo !! We have a winner. Spend the extra dough on a good balance job !! Get the crank to spin like a gyro and you'll be suprised on how long a 2-bolt block will last you !!! >>>>.
     
  13. RodStRace
    Joined: Dec 7, 2007
    Posts: 2,229

    RodStRace
    Member

    So is this a street car that will get a blast down the strip, or an all out race car that only gets used a couple times a year?
    Maybe you plan on running E85?
    12.5 is not a street friendly ratio for gas....
    I'm no Chevy guy, but I have hung around a few. Go with better hardware, machining and parts. The block isn't the issue, unless you are hitting the spray or winding it real tight....
     
  14. Racewriter
    Joined: Nov 14, 2008
    Posts: 780

    Racewriter
    Member

    Not overly necessary for a street engine. Have the crank balanced, make sure it gets good oil to it, and you're fine.
     
  15. RichFox
    Joined: Dec 3, 2006
    Posts: 9,830

    RichFox
    ALLIANCE MEMBER

    The Specter Enterprises A/Blown Gas Streamliner was making plenty of runs last week at over 400 MPH. 485 inch Cadillac. Turbocharged on gas with a cast crank and 2 bolt mains. More than 650hp? A lot more.
     
  16. What Eng Pro said....you dont need 4 bolt mains.

    Wayyyy overrated for what you are asking of the engine.

    Balance and run some nice ARP studs.

    Done.

    Rat
     
  17. madgrinder
    Joined: Feb 5, 2005
    Posts: 324

    madgrinder
    Member

    2-bolt and a cast crank... I prefer a soft cast-crank because it will BEND and make racket so you have time to shut it down.

    When a forged crank goes, it just shits parts everywhere :)
     
  18. Roothawg
    Joined: Mar 14, 2001
    Posts: 19,008

    Roothawg
    Member

    Strictly track, just don't have a lot free time , so it won't see the track more than a couple times per year.
     
  19. fab32
    Joined: May 14, 2002
    Posts: 13,988

    fab32
    Member Emeritus

    After dozens of blocks (both 2 and 4 bolt) I can report a 2 bolt block with studded mains will hold as much power (with all else being equal) as a 4 bolt in a non supercharged application. I used to have a high performance engine shop and specializing in Chevys for street, oval track and drag applications. I built engines for the poorest and richest patrons in this area. Some of the most expensive engines to leave my shop went head to head with relative budget builds and save for the exotic roller setups and trick of the week components the "budget" setups never shamed themselves in competition.

    Frank
     
    Last edited: Oct 4, 2010
  20. chop32
    Joined: Oct 13, 2002
    Posts: 1,077

    chop32
    Member

    I ran a .060 over 12:1 327 with 2 bolt mains through three years of street racing, Wednesday night bracket racing and heavy stop lite flogging (I was young once) with no problems.
    It was balanced with a stock small journal steel crank, and I used good main and rod bolts.
     
  21. I would agree with these guys in general- with a caveat.

    It is certainly possible to make a lot of power with 2-bolt mains, as various examples have shown.

    However, so much of this depends on the tune. One guy can have serious cap walk at the 400 hp level, caused solely by detonation from a bad tune...while the guy next to him is making much more power with no problems with the same basic short block....because he knew how to properly read spark plugs.

    I would also contend that certain engine designs are better able to "get away" with 2-bolt mains than others. I would have absolutely no problem with using a stock production 460 Ford block, which are all 2-bolt mains, to make 700+ hp. I've seen with my own eyes that they will easily handle much, much more and live for years (again...assuming a proper tune). I wouldn't try it with a 2-bolt BBC and expect it to last.
     
  22. guitar man
    Joined: Sep 13, 2010
    Posts: 210

    guitar man
    Member
    from Tulsa OK

    I had a 2 bolt main .030 over 400 sbc in a '73 cutlass supreme. It was built by a very skilled friend of mine. I never dynoed it so I don't know exactly what it was putting out but it would flat out carry the mail. I drove the crap out of it, broke a rocker arm one time and bent a pushrod another time but never had a bit of problem with the bottom end.
     
  23. Bib Overalls
    Joined: Aug 3, 2001
    Posts: 4,067

    Bib Overalls
    ALLIANCE MEMBER

    My engine building friend has stopped arguing about the subject. Folks just don't buy into the 2 bolt blocks. When he thinks a motor needs 4 bolts he recommends a 2 bolt block with splayed 4 bolt steel caps.
     
  24. Dynaflash_8
    Joined: Sep 24, 2008
    Posts: 3,012

    Dynaflash_8
    Member
    from Auburn WA

    i ran my old 59' 283 with 305 heads and a big cam hard with cast crank and 2 bolt mains. Shifted out of second at 6300. It flat hauled before the rings broke.
     
  25. HEATHEN
    Joined: Nov 22, 2005
    Posts: 7,592

    HEATHEN
    Member
    from SIDNEY, NY

    It always makes me laugh when I hear some Smokey Yunick wannabe tell me that the 4 bolt main Chevy 350s had "thicker main webs", or were made of "better metal". I never knew how that could be when both blocks had a 3970010 casting number.
     
  26. Mr Haney
    Joined: Jul 17, 2008
    Posts: 1,001

    Mr Haney
    Member

    Art Birchnaugh [ spelling ?] from the stick shift club, has been running small journal 283, 327's for years now. he has a non hamb freindly hornet wagon 4-door. the car has been altered front wheelbase, body shortened [ rear doors removed] runs a lenko box behind a 327 runs 10's. He is now attempting 9's with his new 2-bolt motor.

    most guys that race around here know Art. He works at NASA and fabricates EVERYTHING on his car NO SUMMIT RACING PARTS ANYWHERE !!!!
     
  27. Deuces
    Joined: Nov 3, 2009
    Posts: 17,976

    Deuces
    Member
    from Michigan

    '70-'71 Chevy and GMC pickups 4-bbl 350's all had the 4-bolt blocks and a forged steel crank... 3970010 block castings...
     
    Last edited: Oct 5, 2010
  28. Lucky3
    Joined: Dec 9, 2009
    Posts: 652

    Lucky3
    Member

    Chris,
    For the motor you reference, 2-bolt mains are fine and especially with good fasteners (ARP) that you mention. The rotating assy is where you need to focus. The comments above are spot on !!
    Good luck.
    Fellow Okie !
     
  29. mart3406
    Joined: May 31, 2009
    Posts: 3,055

    mart3406
    Member
    from Canada

    -------------------
    Thanks for bringing that up, that regarding
    the 3970010 casting number blocks. There's
    a lot of 'old wives tales, urban legends and
    misinformation regarding Chevy blocks with
    a "010" casting suffix floating around - such
    as - "they're all 4-bolt mains", "they're cast
    from better
    - ie - higher nickel and/or
    higher tin content iron", "they have thicker
    webs
    ", "better machining" etc., etc. - ad
    infinitum and ad nausium! None of this true
    - at least not *just because* of a 010 casting
    suffix. All a 010 suffix indicates is that the
    block has 4 inch bore size, nothing more,
    nothing less.

    Mart3406
    ===========================
     
    Last edited: Oct 5, 2010
  30. Roothawg
    Joined: Mar 14, 2001
    Posts: 19,008

    Roothawg
    Member

    Thanks Roger, I am just pondering a couple of things.
     

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