2 BOLT VS 4 BOLT MAIN POWER CAPACITY

Discussion in 'High Performance Modifications' started by nova75mike, Feb 19, 2018.

  1. GoldenOne7710

    GoldenOne7710 Veteran Member Lifetime Gold Member

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    Jun 23, 2004
    Athens, GA
    Use premium hardware combined with a balanced rotating assembly, no reason why it couldn't live a long, reliable life. It isn't always about power output, but more of how much time will it spend above 6K rpm for sustained periods. A cruiser with limited track time...no problem.
     
  2. budro6968

    budro6968 Veteran Member

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    Apr 2, 2016
    Jax Florida
    I have had lots of buddies use the 2Bolt through 500+ and not a problem. Keeping it oiled helps. Most problems were either over rev and float the valves or lean out. I have seen the wrist pin move in to the cylinder wall. One guy just had it sleeved and went back to racing on dirt track. It lived another 2 seasons. Then he went with a different engine.
     
  3. Jeep43

    Jeep43 Veteran Member

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    Mar 30, 1999
    Connecticut
    Whats the cost difference between 2 bolt studs and line hone vs install of splayed caps??
     
  4. nova75mike

    nova75mike Veteran Member

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    Mar 20, 2008
    Etters, PA
    My machine shop is very reasonable on pricing, but the conversion is very labor intensive. splayed main caps, $190. Machining and line boring, $250-$275. 4 bolt main stud kit, $95 or bolts $45. so between $500 and $600 depending, OR I just buy the main stud kit for a 2 bolt for $60-$65. I'll probably just lower my HP goal a bit and stud the 2 bolt mains, and be done with it.
     
  5. nova75mike

    nova75mike Veteran Member

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    Mar 20, 2008
    Etters, PA
    I knew I wanted more power and more cubic inches, so I sold the entire engine to a buddy for dirt cheap and built my first 406 roller motor. He is still running that same, sleeved, 355 in his 67 Chevy II to this day.
     
  6. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

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    Jun 22, 2003
    Endicott, NY
    There are many "opinions" as to which is stronger: two or four bolt main.

    I’ve built every factory SBC there is (262, 265, 267, 283, 302, 305, 307, 327, 350, and 400). Almost all the early engines except the 350’s and a few 400’s had two bolt mains and some of them (the 283, 302, and 327's) lived at unbelievable RPMs (10,000 RPMS and higher in AF/X race cars!).

    As stated in other posts, replace the main cap bolts with top quality main studs and there should be no problem. This ASSUMES that the original main caps are tight in the block. IF, however, they are not tight in the block (and you can afford them) the next best option is to have billet main caps installed. Get the billet splayed four bolt caps for the three center caps plus the billet front and rear main two bolt caps.

    THEE weakest link in all SBC’s is the rod bolts. Get good quality rods with top grade rod bolts!

    IMHO, THEE most important next steps is to have (but not limited to) a balanced rotating assembly, blueprint the motor (cc and properly port the intake and heads, decking the block, degree the cam in, etc.), new SFI approved harmonic balancer are absolutely essential to building a motor.

    Then there is the endless list of other parts: windage tray (which requires special main studs to attach it to), crank scraper, oil gallery restrictors (if you run a solid lifter cam), top quality head bolts (or studs), oil pump & pickup, high capacity oil pan, etc. (this list can go on and on to infinity $$$$!).
     
  7. nova75mike

    nova75mike Veteran Member

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    Mar 20, 2008
    Etters, PA
    I hear ya Cardinal. I was planning on running a deeper than stock Moroso pan with scraper, ARP hardware everywhere I possibly can. The rotating assembly is a Scat steel crank, a set of their pro rods with 7/16 cap screws and Wiseco forged pistons. SFI flexplate and balancer, etc. Profiler heads that I'm likely to get from Speier Racing Heads, waiting for a reply to an email I sent to them, and a Hydraulic roller (specs up in the air due to rpm limits).
    All the smaller cubic inch motors had the benefit of short strokes which are a bit lighter and easier to get higher rpm. that is my main concern with a heavy, long stroke crank. I'll lower my rpm expectations and hope the engine will be happy. I'm going to my machine shop tomorrow and I'll chat with my engine builder about everything. He's built lots of engines for me and the only issue I ever had was the piston pin in that 355.
     
  8. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

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    Mar 25, 1999
    San Jose, CA, USA
    Yeah at that point - I'm starting to think about an aftermarket block. CNC is selling fully prepped Dart blocks for ~$1900; after all of the other machine work needed for a rebuild the price isn't that much worse. Especially considering the Dart Block will survive a small nuclear blast (and a 4.25" stroker crank).

    Or like you said, a $65 main stud kit for the 2-bolt... ;)
     
  9. 77 cruiser

    77 cruiser Veteran Member

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    Nov 17, 2006
    Frostbite Falls MN
    That's a good deal when you consider boring, torque plate hone, decking, & line hone could easily run close to a grand.
     
  10. nova75mike

    nova75mike Veteran Member

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    Mar 20, 2008
    Etters, PA
    Well, it looks like splayed 4 bolt caps are in my future. My machinist actually has a set of splayed caps off another engine and he will fit them to my block for $250, cant really beat that. I just have to buy a new stud kit for them. So at least I now know how much "piece of mind" costs.
     
    Cardinal likes this.

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