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View Poll Results: Should you replace the Head Bolts on rebuild?

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  • No; not needed.

    19 63.33%
  • Yes; always replace them if they are originals

    11 36.67%
Results 1 to 19 of 19
  1. #1
    Join Date
    Feb 2006
    Location
    Wichita, KS
    Posts
    611

    Default Replace Head Bolts?

    On a basic stock 455 rebuild do you replace the head bolts?
    (Iron head 72 455)
    I have searched the forums and not found a true answer. I have had some tell me it is cheap insurance. In the past I never did, but now I'm wondering....
    John Jones
    72 Skylark
    Wichita Kansas

  2. #2
    Join Date
    Mar 2002
    Location
    St Louis
    Posts
    9,975

    Default Re: Replace Head Bolts?

    Depends on your build. Stock rebuild I would check them for stretch and reuse them once. Boosted or high compression I woud replace with ARP bolts or studs
    John & Terry Kemper
    GSCA #4322
    BPG #1373
    72 Stage 1 Suncoupe
    72 Stage 1 Suncoupe clone
    70 Sportwagon

  3. #3
    Join Date
    Feb 2002
    Location
    Oakland Gardens, N.Y.
    Posts
    21,422

    Default Re: Replace Head Bolts?

    I'd replace them. ARP's are nice, and not that expensive.
    Larry
    1998 "Fully Optioned" SC3800 Riviera
    70 GS 455 Stage1, TSP 470, 602 HP@ 5900, 589 TQ @ 4900
    TA Hyd Roller Cam, 230*/238*, 112, .544"/.577" lift, 4-7 swap
    MSD Digital 6+, Ignitionman Distributor w/MSD trigger
    1967 BT Switchpitch ST-400, Gear Vendors OD
    with TSP 3200/1800 converter
    AED 1000 HO Carb, 800 CFM 7042240 Quadrajet
    8.5 10 bolt, 3.73's
    11.67 @ 115.49 MPH
    Larrymta@verizon.net, GSCA #291
    BPG # 1063
    N.E. GS/GN Club Assistant Director

  4. #4
    Join Date
    Feb 2006
    Location
    New Hampshire
    Posts
    3,583

    Default Re: Replace Head Bolts?

    It is not necessary, but recommended.


    In a nutshell: modern cars with aluminum cylinder heads have a "stretch" type bolt that is designed the stretch a certain amount, also known as "torque to yield" bolts.
    "Stretch" bolts MUST be replaced every time they are removed, because they have already "stretched" to their design limit, and after a few heating/cooling cycles, will never contract to their original size/strength.

    Cars with cast iron heads use a standard type bolt that can be reused. Not a bad idea to measure it, and on a rebuild, I would probably replace them just for safety's sake, seeing as they are 40 yrs old.
    No, its not a chevy motor

    Steve Mario

    '71 Skylark, street/strip beater w/JW and T/A goodies!

    (JW prepped 462 short block, ported T/A Stage 1 TE heads w/stage 3 valves, 1050 Dominator, Super Scavenger headers, 3400 stall TH400, runs on pump gas, and leaves brown skid marks on the passenger seat.)

  5. #5
    Join Date
    Feb 2002
    Location
    Sacramento CA area
    Posts
    3,157

    Default Re: Replace Head Bolts?

    I've not replaced on multiple rebuilds and never had an issue (my current engine has been built twice since it was OEM). That said, the idea of a measurement prior to reuse seems like a good idea. But is your time costlier than the replacement cost of bolts?
    BadBrad
    '70 GS455 - Power Brute Super T10 4spd
    ex. '70 GSX
    New Project: 2000 Mercury Grand Marquis - for the kids to drive.
    New Muscle: 2013 Ford Taurus SHO - Twin Turbo Terror

    Spare 455 on the stand, just in case!


    Slideshow of BadBrad's Car: http://s517.photobucket.com/albums/u...view=slideshow

  6. #6
    Join Date
    Nov 2010
    Location
    Simi Valley, CA
    Posts
    2,614

    Default Re: Replace Head Bolts?

    I've rebuilt dozens of engines over the years, but not with the stretch bolts. I got out of the biz awhile back when I gradjamatated college and went to work as an engineer. I've never replaced anything but the occasional bad head bolt. Mind you, almost all of it was stock, but one example is my '66 LeMans with a Stage III 400 engine. I didn't change the head bolts out on it, and I was running 11.5"+ to 1 compression...about 195 psi a hole compression pressure. Boy, it liked that premium gasoline. Often.
    '68 Buick Skylark California GS
    '00 Chevy Astro Van
    '70 Chevy 3/4 Ton Longhorn Custom Camper, numbers matching

  7. #7
    Join Date
    Sep 2004
    Location
    Michigan, USA
    Posts
    14,960

    Default Re: Replace Head Bolts?

    For a stocker I'd reuse them, but just to be sure I'd let the engine go through a heat cycle or two and retorque. The trick is to put a witness mark on the head bolt and the head, back off the bolt a bit, then sneak back up on the original torque spec. Usually all the bolts will take a bit more rotation past the original mark, but if one or two stand out because they need substantially more rotation than the others, the fastener may have reached its yield strength.

    Devon
    Fuel & Brake Systems Engineer
    "I can live with doubt and uncertainty and not knowing. I think it's much more interesting to live not knowing than to have answers which might be wrong." - Feynman
    "Good data is precious. The problem I have is when some damned fool fails to use it properly." - Slingerland

  8. #8
    Join Date
    Mar 2003
    Location
    Peoria, IL
    Posts
    281

    Default Re: Replace Head Bolts?

    Here's the torque professional purist answer: Yes. Always replace a bolt that has been subject to torque as it will have stretched under that load.

    In practice, if the threads are clean and everything looks fine, probably 90% of people will re-use those bolts and not experience any issues.
    -Keith
    1974 455 Apollo

    "Buick Impala? Buick never made an Impala!......No, Buick Apollo, Like the Rocket ship!"

  9. #9
    Join Date
    Mar 2002
    Location
    St Louis
    Posts
    9,975

    Default Re: Replace Head Bolts?

    Might stretch the threads before the bolts, 455 have BIG BOLTS
    John & Terry Kemper
    GSCA #4322
    BPG #1373
    72 Stage 1 Suncoupe
    72 Stage 1 Suncoupe clone
    70 Sportwagon

  10. #10
    Join Date
    Jul 2002
    Location
    the cold north
    Posts
    807

    Default Re: Replace Head Bolts?

    The intake bolts are huge to.
    Bob Gable
    70 GS Foe Fiddy 5

  11. #11
    Join Date
    Nov 2010
    Location
    Simi Valley, CA
    Posts
    2,614

    Default Re: Replace Head Bolts?

    Quote Originally Posted by DaWildcat View Post
    For a stocker I'd reuse them, but just to be sure I'd let the engine go through a heat cycle or two and retorque. The trick is to put a witness mark on the head bolt and the head, back off the bolt a bit, then sneak back up on the original torque spec. Usually all the bolts will take a bit more rotation past the original mark, but if one or two stand out because they need substantially more rotation than the others, the fastener may have reached its yield strength.

    Devon
    Back in the '60s, part of a tune up was to retorque the head bolts, if you went to the dealer, at least on Chevies. You can see that in some of the old shop manuals.
    '68 Buick Skylark California GS
    '00 Chevy Astro Van
    '70 Chevy 3/4 Ton Longhorn Custom Camper, numbers matching

  12. #12
    Join Date
    Sep 2004
    Location
    Michigan, USA
    Posts
    14,960

    Default Re: Replace Head Bolts?

    Quote Originally Posted by Keith2k455 View Post
    Here's the torque professional purist answer: Yes. Always replace a bolt that has been subject to torque as it will have stretched under that load.
    Keith, I'd love to know more from what you said, and know right away that I have no special knowledge about fasteners other than a tube nut or two.

    But since the purpose of a "bolt" is to stretch and impart a bit of clamping in its application because of it, is there a reason it won't do the same job over and over again as long as it hasn't been forced past it's elastic limit?

    Of course thread wear plays a part if we're talking on the receiving end, the block.

    Devon
    Fuel & Brake Systems Engineer
    "I can live with doubt and uncertainty and not knowing. I think it's much more interesting to live not knowing than to have answers which might be wrong." - Feynman
    "Good data is precious. The problem I have is when some damned fool fails to use it properly." - Slingerland

  13. #13
    Join Date
    Feb 2006
    Location
    Wichita, KS
    Posts
    611

    Default Re: Replace Head Bolts?

    Thanks guys, this started with some friends as we discussed rebuilds. In the past (back in the 70's) I had never replaced any fastners. One of the guys in my group said after some issues he had he always replaces head bolts (of course he can do that for $35). Another who builds lots of engines said he doesn't and has never had a failure. So the debate started. As I'm ready to drop the heads on my 455 I began to wonder.. should I spring for the $70... I didn't on mains and rods wish I had(to late now).

    John
    John Jones
    72 Skylark
    Wichita Kansas

  14. #14
    Join Date
    May 2002
    Location
    the Seasonally Frozen Wastelands
    Posts
    2,394

    Default Re: Replace Head Bolts?

    It is ABSOLUTELY POINTLESS to measure a used head bolt to see if it's stretched, UNLESS you have measured that very same bolt when it was NEW, so you have a basis for comparison. If the bolt is .001 longer after being used, it's now a paperweight.

    Since none of us measured the original bolts before GM installed 'em, there's no point to wasting time measuring what comes out of the engine.

    That said, there is NOTHING wrong with the quality of bolts that GM used to install the heads, and GM is very unlikely to have over-torqued them.

    I would re-use them without hesitation provided they aren't obviously damaged.

  15. #15
    Join Date
    Jun 2007
    Location
    Washington State
    Posts
    1,504

    Default Re: Replace Head Bolts?

    Quote Originally Posted by Keith2k455 View Post
    Here's the torque professional purist answer: Yes. Always replace a bolt that has been subject to torque as it will have stretched under that load.

    In practice, if the threads are clean and everything looks fine, probably 90% of people will re-use those bolts and not experience any issues.
    Isn't every installed bolt 'torqued? Just because a torque wrench isn't used does't mean it doesn't have a torque value to it. So is there a minimum torque, according to the purist, or is he saying to never re-use ANY bolt?
    _____________

    Jeff ~

    Buicks
    1965 Skylark Hardtop
    1965 Skylark Convertible

    The Others
    1966 Pontiac Lemans
    1967 Ford Mustang - for sale
    1987 Camaro IROC

  16. #16
    Join Date
    Feb 2010
    Location
    Framingham, Ma
    Posts
    2,812

    Default Re: Replace Head Bolts?

    In all my time working on various makes/models I've only ever replaced bolts that were torque-to-yield, or that were stripped/rounded/corroded. I generally find the problems people have are with the holes that the bolt goes into more than the bolt itself. Can't tell you how many times I take out a bolt and find on reassembly that the hole is partially stripped and the bolt just spins without actually seating. In these cases the bolts need to be replaced because the hole needs to be rethreaded.

  17. #17
    Join Date
    Oct 2008
    Location
    erie pa
    Posts
    528

    Default Re: Replace Head Bolts?

    276 lbs cranking pressure. 6400 rpm's on stock head bolts all day long. 360 quatermile runs on my engine after 80,000 miles on them from GM before I rebuilt it. Now it's been on it's second freshening up still using them. GM tech manual says nothing about new head bolts when replacing a cracked head or a rebuild from a cracked piston or ring replacement. Just retorque them as instructed by devon, chris
    Last edited by C.Rob; 03-30-2011 at 09:14 PM. Reason: Spelling
    BIG BLOCK POWER HOUSES
    (1) 1970 Stage 1 pure stock 3.64 Posi
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  18. #18
    Join Date
    Aug 2004
    Location
    Florida
    Posts
    2,158

    Default Re: Replace Head Bolts?

    Quote Originally Posted by C.Rob View Post
    GM tech manual says nothing about new head bolts when replacing a cracked head or a rebuild from a cracked piston or ring replacement. Just retorque them as instructed by devon, chris
    I have never replaced a head bolt on a stock rebuild of any early v-8, v-6, i-6 or i-4. As long as the bolt is in good condition and it is a stock rebuild I can't think of any reason to replace them.
    Steven

    1965 Skylark - Best 1/4 Mile 11.05 @121.31 ~ Best Nitrous 10.04 @ 133.35
    10 Second Drag Strip Video - http://www.youtube.com/watch?v=kKABJ...2&feature=plcp
    Past Buicks:
    64 Buick Special
    63 Buick Invicta Wagon (The Battleship Invicta)
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    87 T-Type Turbo

  19. #19
    Join Date
    Mar 2006
    Location
    NW Florida, originally from Southern Wisconsin
    Posts
    3,695

    Default Re: Replace Head Bolts?

    I've never replaced a head bolt on any stock or modified small or big block I've ever built. I've even dumped my pail of bolts out to find bolts with the best looking heads, not knowing what they came out of or how many miles were on them and I have never had a problem.
    Bill

 

 

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