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327 RPM limit on 2 bolt mains

Discussion in 'The Hokey Ass Message Board' started by Gotzy, Dec 13, 2013.

  1. Gotzy
    Joined: May 21, 2005
    Posts: 494

    Gotzy
    Member

    I suppose this I one for the engine builders really. I have a small journal 327 that will be built for a race only Model A roadster and I'm buying parts and want to make sure I head in the right direction.

    I'm building a screamer motor just because it will be fun with a manual trans behind it and want it to be comfortable to rev up to 8,000 rpm in case we get carried away, and everyone should do it at least once. I've got a forged GM crank, after market H beam 6.125" rods and will be using light forged pistons. Whilst the heads are iron I'll be using light weight valve train and solid lifter etc to cope up top which I'm all happy about.

    My main concern is main cap walk using on the 2 bolt setup. Ultimately I can't see the motor really producing more than 460hp / 400ft.lb (tops) so not really sure if its an issue. It will run good studs to mount a windage tray on as well so will have as good a clamping force as it can.

    I've read about main cap girdles but can't really see how they would prevent walk (or if they are even designed to) and would like to avoid spending £500 or more on fitting splayed 4 bolt caps as its a budget build for fun

    So what's the professionals thought or experiences?

    It will be a 2 or 3 run what you brung event car and not a serious competition can but I suppose the engine won't know the difference.

    Thanks in advance

    Stephen
     
  2. 66tintop
    Joined: Nov 7, 2012
    Posts: 450

    66tintop
    Member
    from Canada

    :eek:It will go 8,000 rpm twice, first and last all in one run best of luck ! Go for cover lol !
     
  3. txturbo
    Joined: Oct 23, 2009
    Posts: 1,771

    txturbo
    Member

    I use to spin mine up to a little over 6k on a regular basis. It was built to factory 350hp specs. The valves would start to float right about there.
     
  4. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    I'd have no problem with a 2 bolt sbc at those power levels. IMO, The bottom end will take more rpm than the valvetrain you are describing.
     

  5. nwbhotrod
    Joined: Oct 13, 2009
    Posts: 1,243

    nwbhotrod
    Member
    from wash state

    what he said
     
  6. Gotzy
    Joined: May 21, 2005
    Posts: 494

    Gotzy
    Member

    Out of interest then guys, what would fail?
     
  7. Larry T
    Joined: Nov 24, 2004
    Posts: 7,875

    Larry T
    Member

    Large journal or small journal?

    When I raced my Anglia (small journal 327), I ran 5.38 gears, wound it to 7000 and then shifted (4 speed) with a basically stock bottom end. If I were worried about it, I think I'd check how tight the main caps indexed into the block and run main studs instead of bolts.

    Yea, a 2 bolt main engine could blow the bottom end out on the first pass,..........................................but so could a splayed 4 bolt engine.
     
  8. treb11
    Joined: Jan 21, 2006
    Posts: 3,947

    treb11
    ALLIANCE MEMBER

    If you're gonna buzz that motor, the machining needs to be spot on. Rebuilder quality won't cut it. Align hone the mains at least and ditto on the main cap fit with studs.
     
  9. Gotzy
    Joined: May 21, 2005
    Posts: 494

    Gotzy
    Member

    SJ block Larry and planning on studs, line hone and balance
     
  10. primerhotrod
    Joined: Feb 2, 2013
    Posts: 98

    primerhotrod
    BANNED
    from ILLINOIS


    X2

    Quality block prep is key in this situation.
     
  11. We ran one at 7200 in a dirt modified. What will blow are your valve springs. We just staked the caps from walking and chamfered the edges of the bearings. Of course you will need to run a forged crank.
     
  12. 66tintop
    Joined: Nov 7, 2012
    Posts: 450

    66tintop
    Member
    from Canada

    :eek:Valve train will fail first unless you spend LARGE !
     
  13. isky1843
    Joined: Feb 3, 2011
    Posts: 157

    isky1843
    Member

    As for the 2 bolt mains withstanding 8000 RPM, yes they can and they will support even more if done properly. However, there are a lot of things that need to be done in order for it to survive. There is no doubt that a 4 bolt is stronger, and that a splayed 4 bolt is even stronger, but a 2 bolt can take a lot more than what most may think. I have personaly taken a 2 bolt 272ci (destroked 283) to 10k several times. To do this right, you will need extensive balance work, exceptional machine work and block prep, along with a very high quality rotating assembly. The best advice I can give you for building a high strung SJ327 is to buy Grumpy Jenkins engine building book and read it, and start saving your pennies. There is no doubt it can be done, but will it last? and for how long? Just some food for thought.
     
  14. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    This and this. But I kinda figured it went without saying.
     
  15. classic gary
    Joined: Sep 24, 2009
    Posts: 504

    classic gary
    Member

    main studs and the rest of your planed mods, but make sure the valve springs are enough to keep the valve float away, good plan. ive got one now that been to 7500 ALOT, and never missed a beat, the bottom end shows nothing bad.......
     
  16. Brad54
    Joined: Apr 15, 2004
    Posts: 6,021

    Brad54
    Member
    from Atl Ga

    My friend Lamar Walden had a 2-bolt small-journal 327 in his Pro Stock Vegas back in the early '70s, and he never had a problem.
    The small journal blocks have thicker caps than the large-journal blocks, so you don't get cap-walk or other issues.
    Also, if it's a small journal block, I don't think you have the meat there to put in 4-bolt caps--at least I didn't on my sj 283 with a 327 crank build.

    For RPM, well, he was running Pro Stock with it, and beat Sox n Martin's Hemi cars. I don't remember what he said they twisted, but it was way the hell up there, and he told me that on the launch, he'd put his foot on the floor and the valve train float acted as his rev limiter until he side-stepped the clutch (Lenco).

    You won't have a problem, so long as you use good rods, forged pistons, and studs to hold the crank in.

    -Brad
     
  17. pitman
    Joined: May 14, 2006
    Posts: 5,148

    pitman

    In the olden days, only the Z28 was typically run up to 8k. I'd probably set up with a mid to upper end cam profile, with duration emphasized over lift, and shift at ~7.4-7.5k.
    There were a couple of 'best' oil pump strategies that helped too.
     
  18. Gotzy
    Joined: May 21, 2005
    Posts: 494

    Gotzy
    Member

    Happy with piecing together the valve train, question is about the 2 bolt mains only with intended rpm and power level.
     
  19. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    Valvetrain.
     
  20. pitman
    Joined: May 14, 2006
    Posts: 5,148

    pitman

    x2 with George. The launch w/sticky tires and max load conditions are the failure mode, yes guys?
    If you spin up, just make the valve train as robust as you can. The BBC's would shuck a stem 'keeper' off a valve, then it was over.
     
  21. Larry T
    Joined: Nov 24, 2004
    Posts: 7,875

    Larry T
    Member

    Now that you mention Z-28's, I believe the 67 models were 2 bolt main blocks.

    And I will guarantee you, drag cars were turning over 8,000 before Z-28's ever hit the showroom.
     
  22. primerhotrod
    Joined: Feb 2, 2013
    Posts: 98

    primerhotrod
    BANNED
    from ILLINOIS

    Since you said you are using iron heads, your first issue will probably show up in the castings. When the rocker stud bosses are cut for screw in studs and guide plates, they become weak, and love to crack do to gross lift, and spring pressure flexing the rocker studs. Titanium retainers, good lightweight roller rockers, and stud girdles will greatly help with avoiding this. Do not restrict oil to the top end, it is needed to help cool the valve springs.

    Your cam manufacturer will advise you on the proper spring and installed height. Follow this to the letter. There have been great improvements in valve spring technology in the past 10 years.
     
  23. I've heard of a shop class 327 build at a small town tech school that lived at 12,000 on a test stand in the mid-60s. (my brother was one of the students that built it) Most all of the money/work was in the valve train. Granted this engine never saw racing action, but the valve train has to live in either case. As primerhotrod said, springs have come a long ways, especially since the 60s!
     
  24. pitman
    Joined: May 14, 2006
    Posts: 5,148

    pitman

    Agreed, heh, recall the 301" chevs?
     
  25. TinShed
    Joined: Mar 3, 2011
    Posts: 553

    TinShed
    Member

    Most of what you need to know is covered, valve train and tune up at that rpm will need to be good to prevent major issues. Problem is at that rpm things go bad fast when they go bad.

    Is there a reason to spin it so fast. With cast heads will you be able to move enough air to make any power or do you want to tell people you spin it 8g?

    I have a small block ford with 2 bolt mains I shift at 7,400 but it has a heavily ported set of heads and intake on it, shaft rockers and a large billet core solid roller cam to do it. What cam, intake do you plan on and what do your heads flow?
     
  26. primerhotrod
    Joined: Feb 2, 2013
    Posts: 98

    primerhotrod
    BANNED
    from ILLINOIS


    Quality machine work will be the difference between an engine that lives or dies. The 2 bolt block is fine at the RPM and power level. Do not use the factory balancer, buy a ATI or Fluidamper.
     
  27. henryj1951
    Joined: Sep 23, 2012
    Posts: 2,306

    henryj1951
    Member
    from USA

    ran several 2bolts in the 9,000 10,000 area,
    found some old cam specs from (1975sorrynot1965info)
    .660in
    .637ex
    321*/329* 108 center
    roller cam
    HOT LASH .033+.033

    has been done -- can be done---
    titanium <---- everywhere (period)
    knifed-edged crank
    aluminum rods
    and the usual bla bla bla DRAG car (speak)


    :cool:
     
  28. chop32
    Joined: Oct 13, 2002
    Posts: 1,077

    chop32
    Member

    Id suggest good aftermarket main studs.
    Don't just go by the factory torque specs. The aftermarket studs will take more torque to reach the proper "stretch". This stretch is what gives you your proper clamping force.
    Ive witnessed a BBC with ARP studs where the mains were torqued to stock specs and upon teardown you could see where the caps had moved around quite a bit.
    In hindsight, staking the caps may have helped with this also.
     
  29. black 62
    Joined: Jul 12, 2012
    Posts: 1,895

    black 62
    Member
    from arkansas

    Smokey'sbc book ---published in Hot Rod around 67, answers all your questions also read what Joe Sherman says about 2 bolt studs---don't think you need to worry...
     
  30. 327Eric
    Joined: May 9, 2008
    Posts: 2,116

    327Eric
    Member

    I read an article done in the early 60's that 327 bottom ends ' were failing at about 7500 rpm , and the fix was a girdle.May have been in a Hot Rod Or Car Craft letters to the editor.
    I have a 327, studded, with ARP Studs and rod bolts. I have a scraper, and it is running K.B. Hypereutectics. In its first configuration, with ported 186 castings, we ran it to 7500 rpm multiple times daily. It is now running a factory z-28 solid cam, and ported 462's, being treated a little nicer, but still pulling strong.
     

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