static and dynamic compression and pump gas

Discussion in 'Small Block Mopar Engine' started by dirty white boy, Sep 30, 2018.

  1. dirty white boy

    dirty white boy 47 yr old Juvenal delinquent

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    would a well tuned small block with 10.37 static compression with good quench, and 7.89 dynamic compression and cranking pressure of 159.1 run on good pump gas? AJ/FormS how 7.89 dynamic gonna work with 2800ish stall in a 904 with 4:10 gears and 28 inch tire?
     
  2. clinteg

    clinteg Well-Known Member

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    Do you have aluminum or iron heads? That’s low enough DCR for either. 8:1 iron and 8.5:1 for aluminum is the rule of thumb. Seen some builds here get away with a bit more with aluminum heads.
     
  3. dirty white boy

    dirty white boy 47 yr old Juvenal delinquent

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    iron heads with quench pads, these compression figures are done with max quench in mind...DWB!
     
  4. clinteg

    clinteg Well-Known Member

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    I’m betting you’re fine. Watch the timing and read the plugs. They will tell you how much timing the fuel can take with your combo.
     
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    • rumblefish360

      rumblefish360 so close yet so far away

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      Yes and no and with more and/or less compression.

      Confused?

      Hers why.....

      As well as the above mentioned head material, aluminum or iron, you left out the other important items starting with the cam. And to a lesser degree, the cars weight, converter, gears etc.... and why is that important, it’s the whole package that also effects the front part on back to the rear z

      Back to the engine part of it and the second most important part of “why?” Or “can I “ or “is it possible“ to get it to work.

      The real upfront issue is what your willing to accept. Timing of the distributor and available fuel is the other components of the question.

      If there is to much compression you’ll need to up the octane and/or retard the distributor timing.

      In a word, you need balance!!!
       
    • dirty white boy

      dirty white boy 47 yr old Juvenal delinquent

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      hyd roller 235 duration .522 lift, 3000lb duster. 2800 converter and 4:10 gears as posted above. thanks!
       
    • rumblefish360

      rumblefish360 so close yet so far away

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      Ah yes, I sit corrected, my bad!
       
    • AJ/FormS

      AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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      AJ's 2cents
      I'm guessing that's a a 340 with a 284 roller, but whatever it is it's about an ICA of 68*;
      At the track; it should be dynomite,and on pumpgas, I wanna say perhaps a little under-geared,but time will tell
      On the street, it would normally be a lil soft on the bottom. However the 2800TC and 3000pounds will get you past that and the 4.10s should rocket you into next Tuesday; get a bigger gastank and have fun.I love the 2800/904.Mine with a 318, has a nice little hit.
       
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      • dirty white boy

        dirty white boy 47 yr old Juvenal delinquent

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        its a 318. cam is crane mutha thumper - High performance street/ strip, needs 9:1 compression, 2500+ stall, intake, gears and headers, rough idle. Hyd roller 2200 to 5900 20-601-9 291THR7 291 311 235 249 .522 .509 107° ica at 66, 5 degrees advanced 71 recomended. no street/all race! hoping to get lighter than 3000lbs and deeper gears is an option to, being only 1/8th mile tracks near me, i know cam to big, if it dont work ill have it reground, maybe a bigger stall. thank for your thoughts!
         
      • AJ/FormS

        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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        Oh-oh; you tricked me. That's Ok, I deserved it....
        How did you get 7.89/159.1? What elevation did you punch in? bore and stroke is?
        With a 66* Ica, the Wallace will not spit out your numbers for me, not even a stroker.Only a 4.07x3.315 gets me close to your numbers.

        In any case, in a 318 that's gonna be a very high power peak, maybe as high as 5600, and a still higher shift-rpm, maybe 6400, and a trap-rpm of maybe 5800. And it is gonna use a lotta,lotta fuel. But I like it. Once on the pipe it is gonna be smokin' hot.
        Don't forget to do the appropriate oiling mods, for sustained hi-rpm useage.

        I take it back, 4.11s might be right for the quarter, maybe 4.88/5.13s to use 3 gears in the Eighth. I used 3.55s, but I have an unusual transmission. I love 1/8mile door-slammer racing.
        I'd probably swap out that 2800 for something closer to the torque peak like maybe a 3800. I'm not a racer so I'm kindof guessing.
         
        Last edited: Oct 1, 2018
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        • dirty white boy

          dirty white boy 47 yr old Juvenal delinquent

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          rutt row what rover??
           
        • roccodart440

          roccodart440 Well-Known Member

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          Mine has 160PSI cranking compression with aluminum and a 240@.050 cam. Runs on premium. 34 total timing
           
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          • nm9stheham

            nm9stheham Well-Known Member

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            I've run iron heads on a 351C with quench at 8.3 DCR. Cranking pressures in the mid 160's at 1500' elevation IIRC. Had to be cautious with timing but it was fine for me as it was for general use, not racing. 3.08 rear axle, stock TC, and even towing with it are things that would tend to get you into 'detonation-land' but once I got the timing right, it was not a problem. Sorry, I can't give you timing numbers.... over 40 years ago LOL; it was not far beyond stock numbers but came in faster IIRC with the Accel distributor. Noticed a bit of a tendency to ping when going to sea level, so I was pushing timing as much as I could. 93 octane. 18-19 mpg at 65 mph so very small cam and lean carb.

            The current 340 in my son's 'cuda runs with quench gap in the low .040's, Edelbrock AL heads and 8.0 DCR; never has even suggested pinging. 155 psi cranking pressure at 2400' elevation. Timing: initial of 15 and total in the 36-ish range. Vacuum advance is used too as well as running AFR in the 15's for level cruise. 93 octane. With a 2200 stall TC, 3.55 rear gears, a light car, and no towing, I don't ever expect any issues.

            So what the OP has is quite doable, in my humble experience.
             
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            • mderoy340

              mderoy340 Well-Known Member

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              1/8 mile I would run the 4.10 with a 26" tire.
               
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              • roccodart440

                roccodart440 Well-Known Member

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                Depends where it makes power. This is why I love dynos. They are cheaper than tires and/or gears.
                 
              • RustyRatRod

                RustyRatRod Just another dumbass. Technical Editor

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                Closed chamber Cleveland heads? Those are very good for quench. That was cheatin. lol
                 
              • AJ/FormS

                AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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                How fast are you thinking that combo might run? Just asking, cuz I don't know.

                Ima thinking 85ish. Admittedly a guess.
                If 85 and with 4.10s and 26s, that would be ~4730 in direct,~6860 in second.
                Ima thinking that Thumpr cam in a 318 is gonna want to trap quite a bit higher than 4730, and a lot less than 6860,lol. And because it is a 318, and a dedicated race car, I would really really want to use up all three gears in that 904.

                To go 85 is 108 in the qtr, and that takes a W/P of 9.8; so at 3200pounds race ready will require 327hp or 1.03 hp per cubic inch, which is not a big stretch for this combo. Maybe it will go a lil faster, but I believe 85 is in the ballpark.
                IMO the 235/249/107 cam will peak around 5400/5600, so say 5500 and the 107cam is gonna roll over pretty quick, so I see a trap rpm of say 5700/5800. And with a 26" tire,that would take 5.23s, which rounds down to 5.13s
                And 5.13s might like that 2800TC, at least for a little while, cuz 5.13x2.45= a starter gear of 12.57, which at 2800rpm should be a reasonable launch, and if not, the 5.13s are gonna kick the Rs up pretty quick.
                Those 5.13s are good to 89mph@5900, if I'm wrong. To go 89 is 110 in the qtr, and a W/P of 9.3,so 344 horsepower or 1.08 hp/ cube;meh, probably not with this combo.
                Like I said, just guessing.
                 
                Last edited: Oct 2, 2018
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                • mderoy340

                  mderoy340 Well-Known Member

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                  A 318 is gonna need help with a 235@.050 cam to get going and good head flow to keep going and rpm at the top. 1/8 mile car needs gears to get the most. This is just general info. A 4.10 with 28" tire will be a 2 gear car in the 1/8.
                   
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                  • nm9stheham

                    nm9stheham Well-Known Member

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                    LOL yes they were. But actually mine were 2V open chamber heads with the TRW forged 'quench dome' pistons made to close up tightly on the plug side of the open chamber, with a fire slot through the dome.
                     
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                    • forphorty

                      forphorty Well-Known Member

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                      Think more 4500 stall. IMO converter is more important than gear.
                       
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                      • dirty white boy

                        dirty white boy 47 yr old Juvenal delinquent

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                        3.94x3.31 at 300ft above sea level 0 boost!
                         
                      • AJ/FormS

                        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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                        Ok got it; with an Ica of 69*

                        That is a very interesting cam, not for me tho
                         
                      • dirty white boy

                        dirty white boy 47 yr old Juvenal delinquent

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                        brand new hydraulic roller cam for use with factory roller lifters and all for 125 bucks and the ride figured give it a shot see how it dose!
                         
                      • Wyrmrider

                        Wyrmrider Well-Known Member

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                        69 is a long way from 54
                         
                      • AJ/FormS

                        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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                        Ica of 69 is the 20-601-9 cam, in at 103.5. (291/311/107 advertised)
                        On the 107LCA, that is ~4* advanced. The 69* is just what I had to input into the Wallace to match OPs numbers back in post #1, which were 159psi/7.89Dcr,and 10.37Scr@300ft elevation

                        Where does the 54 come from?
                         
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