Announcement Announcement Module
Collapse
No announcement yet.
Compression question Page Title Module
Move Remove Collapse
X
Conversation Detail Module
Collapse
  • Filter
  • Time
  • Show
Clear All
new posts

  • Compression question

    How do i figure out compression.. i tried the calculator go about on a few times but my math is way off.

    im redoing my 454 block as im sure everyone has read..

    it is .30 over so a 461.

    heads are 119cc

    edlebrock performer air gap intake

    cam is a elgin prostock .576 lift .050 duration

    i would like to know if i can get this set up and be able to run pump gas etc. street/strip. http://www.summitracing.com/parts/ESP-B11000030/

    im not sure on gasket thickness etc, or deck clearance..


    at this point its over my head and any help would be greatly appreciated... thanks
    Drag Week 2011: Finished with best pass of 12.21 at 107mph

  • #2

    Re: Compression question

    You are missing some data points in the calculation. The flat top pistons make this easier with their 3 CC valve reliefs. You have your bore size, stroke, combustion chamber volume and you might assume safely that the pistons will be zero deck, that is not down in the bore. So you add the compressed gasket volume, here you have to take the spec from your gasket of choice, lets say .45. So you can readily calculate static compression with any of the available online calculators.

    You haven't posted the necessary numbers for the cam specs so you can't calculate dynamic compression which is a better way to access pump gas suitability of the overall combination. I didn't give you the answer because all of the necessary data points aren't present. I did give you enough to go and get the data and then plug in the numbers. I like the calculators on the Wallace Racing site. Tell us what you find out.
    Drag Week 2012 - Winner Street Race Big Block Naturally Aspirated - Big hat no horses Drag Week 2013 - Watching the live feed Drag Week 2014 - Maybe I'll go faster with a 1000 fewer pounds?

    Comment


    • #3

      Re: Compression question

      Thanks for the info.. ill try to dig up those other numbers tonight and keep pluggin them in..

      appreciate the help
      Drag Week 2011: Finished with best pass of 12.21 at 107mph

      Comment


      • #4

        Re: Compression question

        Its going to be around 8 to 1

        The cams going to be key with this low of static comp.
        2007 SBN/A Drag Week Winner & First only SBN/A Car in the 9's Till 2012
        First to run in the .90s .80s and .70's in SBN/A
        2012 SSBN/A Drag Week Winner First in the 9.60's/ 9.67 @ 139 1.42 60'
        2013 SSBN/A Drag Week, Lets quit sand bagging, and let it rip!

        Comment


        • #5

          Re: Compression question

          Found a different set up that is a little better on compression i think.. www.eaglerod.com part number 18002

          says 10:1 with my application.

          im guessing a dome piston isn't that great for a shot of nitrous though?? im undecided if i will spray or not. but it is all set up for it......
          Drag Week 2011: Finished with best pass of 12.21 at 107mph

          Comment


          • #6

            Re: Compression question

            Domes are a requirement for compression. But most of the big N2O users have what they call "softened" chambers. Not much quench area, etc. But still manage 13:1 or so. You won't do that with your engine. I see nothing wrong with a dome- I am headed that way.
            Why think when you can be doing something fruitful?

            Comment


            • #7

              Re: Compression question

              At 10 to 1 your not stopping any flame travel with that small of a dome
              2007 SBN/A Drag Week Winner & First only SBN/A Car in the 9's Till 2012
              First to run in the .90s .80s and .70's in SBN/A
              2012 SSBN/A Drag Week Winner First in the 9.60's/ 9.67 @ 139 1.42 60'
              2013 SSBN/A Drag Week, Lets quit sand bagging, and let it rip!

              Comment


              • #8

                Re: Compression question

                using nitrous on a dual plane intake is ok but it helps to put a spacer on the intake. just spray it and have fun i have a nice 150hp tune from monty at drag week 2010. its 65n 52f 5psi fp retracted tip plugs around a ngk 8 heat range 28* timing total 100+ fuel. if using pump gas 93 fuel i use a tune of 42n 36f 5psi 28* total timing stock plugs works great
                Drag week 2009 Quickest street rod
                Drag week 2010 Quickest street rod

                Comment


                • #9

                  Re: Compression question

                  been doing a little more research and decided i would try and go with a 489 stroker kit. ive been crunching some numbers and as far as i can tell this set up would give me 10 to 1 i believe??


                  http://www.summitracing.com/parts/SCA-1-42260BE/


                  im kind of confused though as to why some pistons are -cc and some positives?
                  Drag Week 2011: Finished with best pass of 12.21 at 107mph

                  Comment


                  • #10

                    Re: Compression question

                    -cc means it has a dish or valve reliefs in it so its negative volume
                    2007 SBN/A Drag Week Winner & First only SBN/A Car in the 9's Till 2012
                    First to run in the .90s .80s and .70's in SBN/A
                    2012 SSBN/A Drag Week Winner First in the 9.60's/ 9.67 @ 139 1.42 60'
                    2013 SSBN/A Drag Week, Lets quit sand bagging, and let it rip!

                    Comment


                    • #11

                      Re: Compression question

                      hmmmm.. soo since the last set up i had posted was a positive 28 would this one effect me running nitrous with a -17.00? and on the wallace racing calculator i was getting a 9.97 when i punched in my info although im not 100 percent sure on deck height and compressed gasket thickness?

                      i appreciate the help Jeff.... is there something i could read to educate myself more on everything motor wise? im kind of a big dumb dumb when it comes to this and have been guessing alot. i want to get my nova running but be somewhat aware of what the heck im doing haha.
                      Last edited by dougs67; May 17th, 2012, 07:54 PM.
                      Drag Week 2011: Finished with best pass of 12.21 at 107mph

                      Comment


                      • #12

                        Re: Compression question

                        The "How to build a Blah" Books are good for starting, taking it as general stuff, not the gospel. I tell my son watch those TV shows on the weekends. Auto Math is a great book. The Wallace site has plenty to play with and see what causes what to happen. I grew up with guys that pushed limits for their day, and one who never made it to the track, but built crazy motors with tons of power.
                        2007 SBN/A Drag Week Winner & First only SBN/A Car in the 9's Till 2012
                        First to run in the .90s .80s and .70's in SBN/A
                        2012 SSBN/A Drag Week Winner First in the 9.60's/ 9.67 @ 139 1.42 60'
                        2013 SSBN/A Drag Week, Lets quit sand bagging, and let it rip!

                        Comment


                        • #13

                          Re: Compression question

                          hmmmm.. soo since the last set up i had posted was a positive 28 would this one effect me running nitrous with a -17.00? and on the wallace racing calculator i was getting a 9.97 when i punched in my info although im not 100 percent sure on deck height and compressed gasket thickness?

                          i appreciate the help Jeff.... is there something i could read to educate myself more on everything motor wise? im kind of a big dumb dumb when it comes to this and have been guessing alot. i want to get my nova running but be somewhat aware of what the heck im doing haha.
                          I am currently building a 489 with Probe 18cc pistons (I think)- gives roughly 9.8:1. The pistons are .010" down in the hole, .040" compressed gasket, 119cc heads. If you calculated your compression using these numbers, you won't be far off. You will have around 10:1. Can we say 93 octane?
                          Why think when you can be doing something fruitful?

                          Comment


                          • #14

                            Re: Compression question

                            That will depend on many things. The intake valve closing has a bunch to do with it.
                            2007 SBN/A Drag Week Winner & First only SBN/A Car in the 9's Till 2012
                            First to run in the .90s .80s and .70's in SBN/A
                            2012 SSBN/A Drag Week Winner First in the 9.60's/ 9.67 @ 139 1.42 60'
                            2013 SSBN/A Drag Week, Lets quit sand bagging, and let it rip!

                            Comment


                            • #15

                              Re: Compression question

                              I am currently building a 489 with Probe 18cc pistons (I think)- gives roughly 9.8:1. The pistons are .010" down in the hole, .040" compressed gasket, 119cc heads. If you calculated your compression using these numbers, you won't be far off. You will have around 10:1. Can we say 93 octane?
                              Aluminum heads or iron can make a big difference, as much as a full point. The combustion chamber configuration is also big on top off the intake event timing Jeff mentions.
                              Drag Week 2012 - Winner Street Race Big Block Naturally Aspirated - Big hat no horses Drag Week 2013 - Watching the live feed Drag Week 2014 - Maybe I'll go faster with a 1000 fewer pounds?

                              Comment

                              Working...
                              X