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  • #61
    > - Vol of any Cyl = (pi/4 * Bore² * Height)/1000
    > - Compression Ratio (CR) = (Cyl Vol + TDC Vol)/TDC Vol
    > - Top Dead Center Volume (TDC) = Piston Vol + HG Vol + Combustion Chamber Vol
    >

    Jake, how do you measure the combustion chamber vol? Do you do similar liquid measurement with the head upside down?

    I also wonder how much of the measurement can be based on written specs or actual measurement of every component. Eg should we trust the stated height of the HG from manufacturer, or should we measure it manually? Would the HG height be less after it's installed? How to compensate the difference (if any) for the CR calculation?
    Similar question on other parts like crank stroke and rod length. Do you measure everything yourself?

    Thanks,

    -Fred

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    • #62
      Originally posted by m3pat2 View Post
      Hi Jake...I love your work. Very meticulous. When I was building my engine, I created a diagram to help me think through my block measurements and also to calculate my compression ratio (diagrams help me visualize better). Hopefully this will help others too.
      Thanks Pat! That does help. I wonder if something like that can be made so that you can enter in the data and make sure everything agrees? I'm working on an Excel product but it's only a chart right now. I think you can make diagrams that you can make entries on. That would be nice.

      Originally posted by M-tinker View Post
      Jake, how do you measure the combustion chamber vol? Do you do similar liquid measurement with the head upside down?

      I also wonder how much of the measurement can be based on written specs or actual measurement of every component. Eg should we trust the stated height of the HG from manufacturer, or should we measure it manually? Would the HG height be less after it's installed? How to compensate the difference (if any) for the CR calculation?
      Similar question on other parts like crank stroke and rod length. Do you measure everything yourself?

      Thanks,

      -Fred


      Hi Fred,

      I don't think crank and rods necessarily need to be measured except when it comes to verifying oil clearances. But for things like checking crank throw and rod length I think just measuring piston pop-up is going to tell you right there if there is a variance. If there is one then I'd look at the piston first.

      The HG figures I quoted are known factors. I did pull out an old stock HG and measure it and it came out spot on at 1.76mm (compressed). In fact that reminds me, I meant to specify that those HG height figures are as compressed, not as they come out of the package. We only want to know installed height of course.

      The head is measured in much the same way as the piston tops. I did a big write-up on CC the combustion chambers a few years back but the picture links are broken. One of these days I'll reload all those pictures and fix that thread. In the mean time here are some pictures from the other day on this current project.

      This is the rig I use. It has 3 specialized adjustable legs that get bolted to the head, these are used for leveling and they make the job very easy and quick.






      Then I use a bridge fixture and pointer for full indication. The moment the chamber is full the fluid connects with the pointer giving a very positive indication; you can't mistake it. The fluid surface tension does not affect this as some may think. You simply zero out the pointer and you're set. No vaseline needed to seal up a peice of plexiglass or the necessary clean-up afterwards. Oh, here's a few close up pictures of what I'm talking about.










      I've used the old plexiglass trick but this way is much quicker and less messy. Precision and repeatability are key. Some are fine just using a syringe graduated to .5cc. You can get much more accurate measurements if you go just a bit further and buy a dedicated buret and stand. For about $100 you now have the capability to accurately measure down to .1cc. And it makes a difference!

      2 problems with the plexiglass method, the thin film of vaseline used to seal it to the head is a varible and it does contribute. Also, for repeated tests you have to clean it off and re-apply. Using a buret and pointer is the way to go.

      Oh, and here' s that link to the other write-up. Maybe later I'll include the entire write-up in this thread for completeness.

      http://www.s14.net/forums/showthread.php?t=22308

      Jake

      Comment


      • #63
        Great thread and detail, loving the big clear pic's too.
        Keep it coming

        Comment


        • #64
          Thanks Jake. Sorry the question just popped up. I didn't bother to do a search. The other thread is just as entertaining to read, even without the pics

          It's funny the picture above shows a much shorter spark plug tip under the liquid, compared to the one in the next cylinder. It almost looks like the spark plug wasn't seated all the way (which I'm sure it's not the case).

          -Fred

          Comment


          • #65
            It's actually an optical illusion. They're all installed just as far. But the one you're looking at is under the surface of the fluid and so it distorts things.

            My camera is very old. And I've used it more in the garage than a 10mm spanner. Literally. It still takes nice up close pictures but it can no longer focus at things more than 5 feet away. I bought a new camera but the old one is still better for close up.

            Take care,
            Jake

            Comment


            • #66
              Jake +1 on the pistons if you get a design you are happy with.

              Great thread for a guy massing parts for his own rebuild.

              What springs are you going to run? Springs seem to have flared a new controversy.

              Cheers,

              Carl
              1989 e30 m3 Zinnoberrot/Grey 256k Track/M3T
              1991 e30 m3 Alpinweiß/Schwartz 81k Garage Queen
              1991 325iX Diamantschwarz/M-Tech 110k Snowmobile (For Sale)
              1991 325ic Macau Blau/M-Tech 178k M-Tech Cabrio 5spd (For Sale)
              2002 Chevy 2500HD 8.1 Vortec, Alison Tranny, 4.10 gears

              Comment


              • #67
                Carl,

                I'm running Supertech springs with stock retainers. They actually fit quite well together. Not as good as Schrick though. I was originally going to use Schrick but this head was packaged with the Supertech springs so I decided to give them a try. I was already familiar with the Schrick set up and I guess I wanted to see what this Supertech stuff was all about.

                Jake

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                • #68
                  What about valves?

                  Steve
                  Sport Evo No.47

                  My Sport Evo Restoration

                  Comment


                  • #69
                    All the pictures are now fixed in that older thread about CC'ing the heads.

                    http://www.s14.net/forums/showthread.php?t=22308

                    Steve,

                    Valves are Supertech as well. I'm actually kind of impressed with them. I'd rank them very close to Schrick.

                    Jake

                    Comment


                    • #70
                      see you haven't been cured of your OCD mate...

                      ;-)

                      Comment


                      • #71
                        Originally posted by Jake View Post
                        All the pictures are now fixed in that older thread about CC'ing the heads.

                        http://www.s14.net/forums/showthread.php?t=22308

                        Comment


                        • #72
                          Originally posted by UK215M3 View Post
                          see you haven't been cured of your OCD mate...

                          ;-)
                          And we're all better off for it...

                          Awesome thread Jake.

                          -Dietrich

                          Comment


                          • #73
                            Originally posted by UK215M3 View Post
                            see you haven't been cured of your OCD mate...

                            ;-)
                            The only cure is more cow bell. :ha:

                            Jake

                            Comment


                            • #74
                              Jake,
                              I am not getting involved ( I was accused of spamming even though I was not). I will NEVER post on this site again but... I am almost done with a complete 2.5 rebuild. I have lots of do's and don'ts. A big dont is 294 intake cams. THEY DONT FIT unless you grind down the intake wall. I leave it at that. I am part of the old ERT in Wilmington Delaware. We used to build Turbo kits for S14 motors. I was told by your Sciontologist like leader to not post again. I will not ever again, even though I have tons of info. Honestly he sucks and 2 middle fingers up (to make it a pair). I love these cars. If you need anything i am here (although this is going to be censored anyway) sheymeatverizondotnet

                              Comment


                              • #75
                                Sometimes the Schrick 292 cam fits, sometimes it doesn't. I'm told while duration and lift is always the same, sometimes they use different base circles. So if you get one that started with a larger base circle it will not fit. I have already checked mine and it fits. If it didn't the fix is very simple and common place. VAC even offers a replacement program with cam boxes that are on the shelf and pre-clearanced.

                                Jake
                                Last edited by Jake; 04-12-2010, 09:54 AM.

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