What Straight-Edge for Checking Engine Surface Is Flat

Widget on 12/08/2023 - 15:31

Hi guys,

Doing a head gasket, I got the head machined but I suspect the engine block surface may not be flat enough. I'm using a Daytona DRM600 steel "precision cut" ruler, but I can't seem to get a good reading with it. Trying to hold it perpendicular to the block sometimes the 0.002" feeler would easily go under, but tilting the ruler a little forward or back I might not get the 0.002" feller gauge under. With that in mind, when I bought the ruler to use as a straight edge, I assumed it to be "straight", then later found out straight doesn't mean straight, it means mostly straight (some tolerances). I don't know what the tolerances are for the ruler, it could be anything. I'm waiting to hear back from 'Sydney Tools' (who said I can swap it, but that doesn't help with knowing tolerances).

Anyway, in say this, I'm considering getting a proper 'straight edge' with a tolerance of 0.001" or better, just so I can take into account the tolerance of it & so I can actually get a flat seating to using the feeler gauge on without having to worry about back/forward movement.

Ideally I'm looking for something around the 18' 400mm length (engine bay is a little crowded with the 600mm) with a tolerance of 0.001" or better, preferably close to the $100 price. I don't know if my Google search skills are lacking but I've been looking for about a week & can't find much other than a couple on Amazon (with some bad reviews about quality) & a couple at a woodworking / knife making stores, but they don't list information (tolerances) or answer their emails :/, & mostly they seem to be <300mm or 600mm>

I'm stuck. Any suggestions? Does anyone have experience here or have any leads on where I can try ?

Automotive Straight Edge

Comments

  • Typical16-bitEnjoyer on 12/08/2023 - 15:50
    +5

    My brother in christ, this is a bargain website.

    • Widget on 12/08/2023 - 16:50
      +9

      Any bargain straight edges around?

  • [Deactivated] on 12/08/2023 - 15:58

    hmmmm …. would a spirit level work?

    • Widget on 12/08/2023 - 16:52

      Not sure. I guess if it's flat, but the main issue is knowing just how flat so I can take that into account when using a feeler gauge. If I spirit level is 0.005" tolerance, that's a lot considering the surface of the block needs no more than 0.002'.

  • Malik Nasser on 12/08/2023 - 16:02
    +4

    Everything has a tolerance.
    Straight is a general term.
    As you have noted, you need to specify what tolerance you can accept, and get equipment to suit. A lot of general tools will not give you a tolerance, as they are not designed for your specific use case.
    Unless you know what tolerance the block needs to be, then measuring it is rather pointless. When you got the heads machined you could have also got them to do the block as well (matched machined).
    What tolerance can your head gaskets accept?

    Alternatively, go to a machine shop with your block and see if they can measure it up for you. Why purchase tools that you will only use once.

    • Widget on 12/08/2023 - 17:04

      I have no way of getting the block our of the car, unless (& I really don't want to do it, or know if I could actually do it), unless I strip everything out of the engine (pistons, crankshaft etc..) and unbolt the automatic transmission first (because I don't have a engine crane) then try and lift an empty cast-iron 4cyl block out of the engine bay (assuming it can be lifted by hand), but then that required replacing more parts/seals when reinstalling, that's why I prefer to get a straight edge so I have a far more accurate reading to know if I need it machined or if it's within tolerance of the gasket, then I can go from there.

      Gasket came in a VRS kit V2338SSY. According to https://www.aagaskets.com.au/PDF/BeforeYourHeadGoesOnTheBloc… (page 2 bottom right) it states,

      4 cylinder & V8 engines
      Length: 0.102mm (0.004”)
      Width: 0.051mm (0.002”)

    • Tricon on 12/08/2023 - 17:08

      As Malik has noted, you can go back to the same place the Daytona DRM600 came from and purchase this. It has a known tolerance and is certainly better than the DRM600; however, as Malik has further noted, everything is relative, and you may be OK as the gasket will accept the difference. If you discover that the block requires work, you can return it to the machine shop for required mating or research scraping. Good luck.

      • Widget on 12/08/2023 - 17:42

        hmm, whenever I looked at ST or TT website it never showed me these edges, always 1.4m+. Will have to check it out.

        Getting the block out is the big issue as I don't have the tools to do that. I would have preferred to get an accurate measurement of the surface before I went down that path. As for scraping, quite the skill, have seen videos on it, but it's a skill I have done of.

  • Euphemistic on 12/08/2023 - 16:14
    +2

    I just use a 30cm wooden ruler borrowed from school.

    • pegaxs on 12/08/2023 - 16:31
      +1

      And see if your fingernail fits under it?

  • pegaxs on 12/08/2023 - 16:21
    +1

    You literally put it in the title/post… a straight edge. Or what you commoners typically call a "StEeL RuLeR". that, and some feeler gauges. That's about it. (Side note: the "straight edge" we have at work is about 500mm long, 50mm wide and about 10mm thick.)

    The best way to to just get the block machined with blue on it. I dont know what we call that shit at work. It's like a bottle of blue ink. Paint that on and take a light skim on the deck and it will instantly show you were the low spots are.

    The only other way I have seen it done and it's a butchers apron way of doing it, is with a heavy piece of machined bar. 1200 wet and dry pulled tight around it, blue ink on the deck face and just use it like a sanding block. high spots will be rubbed clean, low spots will have ink.

    Lastly… What is the specs for the block? If you are getting 0.002 but the spec is 0.005, dont worry, slap it together.

    • Tricon on 12/08/2023 - 16:58

      For the machinist blue, you can substitute a Texta.

    • Widget on 12/08/2023 - 17:17

      I have a "StEeL RuLeR", which could be out enough that I give the impression the block surface is way out of spec when it could be within spec. I also use feeler gauges.

      "Side note: the "straight edge" we have at work is about 500mm long, 50mm wide and about 10mm thick.)" well, that's likely a proper straight edge, something I'm looking for.

      I don't have a way to get the engine out of the car, nor do I want to strip it bare if I don't have to. It would be nice to have a 'straight edge' with a tolerance I know so I have something to work with.

      The blue dye is likely 'bearing blue' or 'prussian blue'. I don't have any, I thought about just using a permanent marker then rubbing it back with a flat sanding block/thick glass/machined block. I would need to get the surface to <20-30RA (what ever that means) apparently with my gasket (according to Permaseal).

      Specs according to Permaseal they say, https://www.aagaskets.com.au/PDF/BeforeYourHeadGoesOnTheBloc…

      4 cylinder & V8 engines
      Length: 0.102mm (0.004”)
      Width: 0.051mm (0.002”)

      • Tricon on 12/08/2023 - 17:26

        I thought about just using a permanent marker

        Absolutely

        • Widget on 12/08/2023 - 17:44

          $12.50! dreamin'.

      • pharkurnell on 12/08/2023 - 19:20
        +1

        which could be out enough that I give the impression the block surface is way out of spec when it could be within spec

        You could say the same for everythign on earth… if your that concerned, rip the motor out.

        • Widget on 12/08/2023 - 20:53

          The whole point of a straight edge is to accurately check that the head and block are straight within spec for a new gasket. There's nothing 'concerning' about wanting to do the job properly. I'm not going to rip the motor out if I don't have to, which is why I asked originally about a straight edge. If the block if within spec then I can just put the gasket on, but I need to find check if it is…

      • pegaxs on 12/08/2023 - 21:13
        +1

        The blue dye is likely 'bearing blue'

        Probably.. They just call it "Octopus piss/smurf spunk" at work :D

        And the straight edge we have at work, we got the machinist to make it. They are not cheap and this thing is super heavy. Not 100% sure what is is made of, but it is made to not flex or bend. I did hear what they made it out of, and I just know it's not "mild steel". Maybe stainless?

        You should be able to find them at your local engineering supplier though. They are not that hard to come by. But, take in a tub of KY when you get a price. ;)

    • Dslrfirst on 13/08/2023 - 09:29

      Blue engineers/marking fluid.

  • Nugs on 12/08/2023 - 17:15

    Do a gauge r&r of your ruler and feeler combo. That will tell you if it is a suitable measurement system.
    Gauge Repeatability & Reproducibility study is what it is called (I think)
    .

    • Widget on 12/08/2023 - 17:22

      What surface would I do the test on though? Wouldn't you need to know the tolerance of the surface so you can take that into account for each reading?

      • Tricon on 12/08/2023 - 17:24

        You require a Surface Plate

        • Widget on 12/08/2023 - 17:44

          Damn! still cheaper than I thought it would be though.

      • Nugs on 12/08/2023 - 19:29

        Actually don't need to know the size/tolerance/variation of the samples, but careful selection of test samples improves the score (choosing samples at either end of acceptable range helps get a better result).
        Test is conducted on ten 'samples' which in this case would be ten places on your block. Mark them for position and also orientation of the straight edge to allow 3 measurements taken at the same place by two operators.
        Might sound over the top, but it's the way to determine if a measurement system is suitable for the task at hand.
        Having the block on a bench would allow the use of a height gauge with dial tip, much easier to perform measurements but understand your predicament
        .

        • Nugs on 13/08/2023 - 10:38

          Target value = 0 (perfectly flat)
          Tolerance = 0.05 (per permaseal info)
          .

  • Tricon on 12/08/2023 - 17:32

    It seems to be a common question. And now I'm off on a straightness rabbit hole.

    • Widget on 12/08/2023 - 17:47

      Signed up to practicalmachinist about an hr ago, have yet to have a look at the website. Ill check both links out. thanks, :)

    • pegaxs on 12/08/2023 - 21:16

      Add this video to your "flatness" rabbit hole… :D

    • OBEY YOUR MASTERS on 16/08/2023 - 08:04

      Careful, you're playing with fire. You may soon find yourself ordering a granite surface plate and scraping your own straight edges down to a small number of microns. Its a one way trip.

  • brendanm on 12/08/2023 - 17:37
    +3

    Mate, it's an old pulsar, just slam the head back on.

    • Widget on 12/08/2023 - 17:51
      +1

      Just because the car is old, isn't an excuse to do a poor job. Putting the head on with an out-of-tolerence block will just cause issues.

      • brendanm on 12/08/2023 - 18:08
        +3

        The block is cast iron. The odds of it being out of spec enough to matter are extremely low. It's also a graphite head gasket and not MLS, so has even more tolerance for error.

        • Widget on 12/08/2023 - 18:19
          +1

          Cast iron, but likely worn down in some parts particularly between cylinders. Odds low or not, if it's out for spec it's out of spec, but I need to know it's out of spec before continuing. It's MLS not graphite. Where did you read that ?

          • brendanm on 12/08/2023 - 18:42
            +1

            @Widget: My mistake, I was thinking of the ga engine.

            If it's out of spec, are you honestly going to remove it from the car, strip it down, and have the block decked?

            • Widget on 12/08/2023 - 20:46

              @brendanm: What are the other options? I've already had the head done & have a new VRS kit. My only alternative option it to remove the timing cover so it's out of the way, source a flat block from where where, cover all holes to prevent filings falling in then sand it flat. Both option require work. I've come this far, I certainly don't want to part it out (even more work), but I won't know my options until I check the flatness of the block, hence the need for something straight with a good tolerance.

              All good anyways,Ill call around to local machine shops on Monday, see what they say. Thanks for the feedback.

              • brendanm on 12/08/2023 - 22:59
                +2

                @Widget: The other option is to put it all together, with a 99.999% chance that it will be completely fine.

              • Dslrfirst on 13/08/2023 - 09:31

                @Widget: A small laser with the right tolerance?

        • Worf on 12/08/2023 - 19:13

          Hey brendanm, bit off topic, but what are your thoughts on replacing fuel filters (2009 Corolla, it’s in the fuel tank accessed from under rear seats)? Specifically, is it necessary (as a maintenance item - car runs fine, normal driving conditions) and if so, what service interval would you usually recommend?

          • brendanm on 12/08/2023 - 20:09

            @Worf: Definitely do it, just replace it at whatever interval Toyota recommends, probably in the 60-80k km range.

            • Worf on 12/08/2023 - 20:49

              @brendanm: Ok thanks mate. Looks like a pain in the ass to change. I wonder if it costs much more to just replace the whole assembly (including fuel pump) assuming you can buy a pre-assembled kit. Might call Toyota parts.

              Also, I bought that ate plastilube brake lube that you recommended, worked a treat, thanks!

              • brendanm on 12/08/2023 - 21:34
                +1

                @Worf: They aren't too bad, just have to make sure the O rings are all on correctly, it all clips together like Lego. Awesome, ate makes good stuff 👍

              • JIMB0 on 13/08/2023 - 11:02

                @Worf: Best to run the fuel level down before taking out the assembly. They never seem to have much crud in them so seems kinda pointless changing it, but you never know.

                • Worf on 13/08/2023 - 11:31

                  @JIMB0: Thanks mate, had some fuel pump related recall ages ago and they said the same thing (less than half a tank of gas).

                  Been looking at fuel filter replacement videos and it looks a bit fiddly with lots of plastic clips that could snap. I think I could pull it off, but I could also stuff it up and be stranded… (and I’d need to buy an in tank fuel filter removal tool as well). What difficulty would you rate it (say on a scale of 0-10). Might get a quote from my local mechanic.

    • Muzeeb on 12/08/2023 - 18:33
      +3

      it's an old pulsar

      I thought OP was rebuilding an N54B30T0 or similar. Just slap it together dude. That's what Nissan would have done anyway.

      • Widget on 12/08/2023 - 20:47
        +1

        Nissan would have made sure the deck was within spec. no point shucking it on if it just gonna cause another fail…

    • pegaxs on 12/08/2023 - 21:20
      +2

      Old Pulsar!!! hahaha…

      Here I was thinking it was a open deck engine or wet/dry liner block that needed to be dead flat.

      But yeah, I agree… steel rule, feeler gauge, if it is basically flat, just slap the head on it and go.

      A proper straight edge would cost more than the car :D

      • Widget on 12/08/2023 - 23:43

        No point using a steel ruler unless you know for sure it's got good tolerance. As long as "basically flat" is within spec, so be it, but you won't know if it's basically flat unless you check with an appropriate straight edge.

        Nothing wrong with a Pulsar. If you work on anything, do a proper job or don't do it at all, including an 'old Pulsar".

        Define "proper straight edge"?

  • Widget on 12/08/2023 - 20:48

    Thanks everyone, all good. I'll keep looking and ask some local machine shops about it. Enjoy your night.

  • mapax on 12/08/2023 - 20:57
    +5

    Maybe I missed it, but since you’ve already had the head machined can’t you just use that as your flat surface to test if your straight edge is close enough?

    • Widget on 12/08/2023 - 21:00

      I can try but I think it' gonna be too big. I need to check tolerances in different locations, it'll be hard to move the head around which the engine still in the engine bay. If the block was outside, might be doable…might be.

      • brendanm on 12/08/2023 - 21:35
        +3

        He is saying to check the ruler that you have for straightness against the head, as that was just machined it should be pretty much dead flat.

        • Widget on 12/08/2023 - 22:05

          oh… good idea

    • Widget on 12/08/2023 - 22:06
      +2

      Sorry mapax, misread what you wrote. Good idea checking the ruler against the machined block, i'll do that, see what it comes out as.

  • terrys on 13/08/2023 - 10:03

    One method I have used on cast iron heads will good success is an opto-alignable planar matrix with inherent visual vertex assessment capability, fine wet'n'dry and the previously mention bearing/engineers blue.

    https://www.bunnings.com.au/estilo-450mm-x-600mm-diamond-edg…

  • Rekorb on 13/08/2023 - 10:54

    You can always spray paint the head gasket with aluminium paint. That was an old trick my Dad taught me, make shure you do both sides.

  • ozbargainoid on 13/08/2023 - 12:29
    +1

    A ruler is too flexible to give you the accuracy you need to do what you want.
    You can buy a proper (stiff) straight edge from Hafco or Blackwoods.
    If its too long for the job at hand, just cut a bit off one end with a hacksaw or angle grinder.

  • OBEY YOUR MASTERS on 13/08/2023 - 12:30
    +1

    You need a precision straight edge like the one an engineer or machinist might use. Normal steel rulers are not straight edges.

  • PNW1 on 13/08/2023 - 13:03
    +2

    Aluminium tubing is generally straight.
    You could head down to Bunnings and check out 25mm square tubing or similar, which l believe is available in one metre lengths.
    Grab two pieces and holding them against each other, hold them up to the light to prove straightness.
    If light does not shine between the two pieces, this proves they are straight.

  • Taine on 16/08/2023 - 15:08

    Test the ruler against the machined head. You can quickly see if it has any uneven spots with a powerful torch, looking for light under the edge.

    If most of the edge allows no light through, but a few areas do - mark the problem areas and check the block with the 'good' bits of the ruler.

    If there's any resistance at all when pushing the 0.002" feeler through your head will seal up fine.

  • Tricon on 13/09/2023 - 21:01

    Here is the way to make a flat edge. At about the 8 minute mark starts the specifics however the whole video is useful.

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