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head warpage 200 1986

posted by  robert240 on  Tue Jan 28 10:16 CST 2014
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last visit: Tue Jan 28 15:43 CST 2014
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Hello -

I'm in the process of changing the head gasket on my 86 240 (B230F). The engine has never over-heated as far as I know. I'm measuring .012" of warpage corner to corner and middle side to middle side ... is that enough to take it to a machine shop?

Thanks!








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    head warpage 200 1986

    posted by  MrNabisco on  Tue Jan 28 22:34 CST 2014
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    last visit: Wed Oct 22 12:36 CST 2014
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    I'm going to chime in and say don't stop at skimming the head surface.
    Yes, disassemble the valve train and try to determine the camshaft condition.

    If the head has seen enough wear to warrant a deck shave then what about valve seats and guides? Why not have the head rebuilt and be dome with it? Sure it costs money, but it is an investment in more miles and now is the time to do it with the head already off.

    Knox did my head.
    https://www.facebook.com/KnoxMotorsports








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    head warpage 200 1986

    posted by  stealthfti on  Tue Jan 28 17:33 CST 2014
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    yes, 12 tou of warp would qualify for a resurfacing.

    BUT, I would suggest that you remove the camshaft and remeasure....hopefully using a "good" straightedge, Why? to remove any effects having the camshaft in place when you are checking the deck flat.

    Personally, I would pull the cam, remeasure the deck for warpage, and see if the 'warp' is a 'perfect' warp or if it is a twisted warp.

    By 'perfect', I mean that the deck is true side to side, but has a warp from end to end. By 'twisted'. I mean that the deck is twisted from end to end, with warpage more down one side than the other.

    Why bring this up? because I have installed a 'perfectly warped' 398 SCP head on my B21FT [it was warped 5 thou] using a Cometic MLS HG, [and did so with the camshaft NOT installed].

    I had zero problems with sealing compression or coolant: and had no prblems running 10+ psi of boost for well over 50K miles.

    I would probably do the same thing with a 12 thou perfectly warped head, BUT ONLY if using a Cometic MLS HG. Trying it using an OE style composite HG would not work.

    I realize that the usual approach is to just go have the head resurfaced, But, I don't care to lose any more alloy from a head deck than absolutely necessary.

    good luck, though

    TF








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      head warpage 200 1986

      posted by  someone claiming to be robertb on  Wed Jan 29 11:35 CST 2014 [RELATED]

      Thanks for everyone's feedback. I will remove the cam and re-measure the warpage as suggested, and inspect the journals.

      Fortunately I'm in no hurry since I'm resurrecting this car from the dead.








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      head warpage 200 1986

      posted by  3peat on  Tue Jan 28 20:45 CST 2014
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      last visit: Mon Oct 6 18:32 CST 2014
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      For the laymen out there, I take it this Cosmetic brand of head gasket - the "MLS" - is really a heavily padded type of head gasket that is ideally used in bridging the gap between two sometimes non-even surfaces?

      Laymen question number two deals with the skimming some metal off the head - why is that so bad?

      Link: http://www.cometic.com/automotive-gaskets.aspx








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        head warpage 200 1986

        posted by  stealthfti on  Wed Jan 29 06:16 CST 2014
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        last visit: Tue Jan 28 17:36 CST 2014
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        'MLS" stands for multi layer steel. Each of the three layers of steel are embossed, and the outer layers are coated with a fluoroelastomer [viton type] coating.

        You might take a look-see at my galleries on Pbase:

        www.pbase.com/stealthfti

        I have a couple of galleries dedicated to SOHC heads and headwork; and one concentrating on using the Cometic MLS head gasket.

        Re the comment on valve guides and seats: in all the years that I have been working on Volvo redbocks, I have yet to have to replace any valve guides or seats....on an otherwise usable SOHC cylinder head. i.e., a head NOT cracked, excessively warped or with camshaft jourmals chewed up.

        I realize that the common perception is that valve guides wear out over time. In pushrod motors, that is a valid perception. Not so much in one of our SOHC heads: the head design damn near eliminates any side loads on the valve stems and guides.

        Since most of the heads I do are for boosted motors, I prefer to have all the deck thickness that I can have. Which is why I prefer to not shave any more off the deck than absolutely required.

        TF








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          head warpage 200 1986

          posted by  Peetz on  Wed Jan 29 13:12 CST 2014
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          last visit: Thu Oct 9 10:18 CST 2014
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          My experience is different. I've replaced the guides intake and exhaust on B20's and B30's lots of times. I've had new exhaust valve seats installed on those engines due to valve bounce from weak springs which causes recession. I've installed new exhaust valve guides on B230FT's because the valves rotate so much they bell mouth the guide. For sure lots of times the guides are fine. They can also wear so about a quarter of the time they need replacing. If the head comes apart the guides have to be checked.







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    head warpage 200 1986

    posted by  Peetz on  Tue Jan 28 10:48 CST 2014
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    last visit: Thu Oct 9 10:18 CST 2014
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    That's a lot of warp. Normally they hump up in the middle between 2 and 3 when overheated. For sure it should be surfaced, and modern machines will do a job far better than the factory could back then. There is at least .020 inch allowance for machining so you're fine to have it done. Yank the cam and buckets out before taking it in. Keep the buckets in order, and change the dampers before installing them again.
    Be sure to blow out the oil gallery holes in the head that feed the cam bearings in case anything lodges in there during the machining before installing the cam.








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      head warpage 200 1986

      posted by  robert240 on  Tue Jan 28 11:10 CST 2014
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      Thanks, that is what I suspected. Yes the bump is between 2 and 3 so it must have over-heated at some point ...








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        head warpage 200 1986

        posted by  trichard on  Tue Jan 28 11:17 CST 2014
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        last visit: Fri Oct 24 05:52 CST 2014
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        anything over 5 000's requires machining. you have 12 which is a fair amount.

        really good machine shops can also use a press and heat for 8 or so hours to flatten badly warped heads. this will cost you more because the head must be dismantled before heating and pressing.







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          head warpage 200 1986

          posted by  robert240 on  Tue Jan 28 13:05 CST 2014
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          last visit: Tue Jan 28 15:43 CST 2014
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          The machine shop wants $62 to resurface (cut) the head, the you-pull-it charges $64 for used heads. I'm slightly concerned about the warpage affecting the cam, So I'm tempted to go find a decent used one.








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            head warpage 200 1986

            posted by  Volvo From Heck on  Tue Jan 28 13:29 CST 2014
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            last visit: Mon Oct 13 20:56 CST 2014
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            If you break the head down(remove valves)and then remount the camshaft you'll know quick enough if it can spin smoothly in the journals. You won't know anything about a p&p cylinder head till you get it off. -- Dave







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