Hence the - (negative) number in the calculator. Same goes for a dome where it is positive cc's on the piston but a reduction in cylinder volume. Correct me if I may be wrong but Ive also heard its also in the cam profile that determines what octane youll need. David Vizard recommends a DCR of 7.5:1 - 8.5:1 for pump gas. Hence the positive number in the calculator. Typically 8:1 dynamic compression is acceptable with iron heads and 8.5:1 with aluminum heads. This seems very confusing but it is because even though it is a -cc on the piston, those same cc's are gained in cylinder volume. The cc for the piston is entered as a positive number on a -cc Dish or Flat top piston and a negative number on a dome piston. 110 c/l which may help bleed off some low speed pressure. The cam will be a roller with 236/242 duration on a. I have heard you can get away with that because of the better heat dissipation of the aluminum heads. Then enter the total weight of your vehicle, as raced, including the drivers weight. Engine builders have found there are numerous advantages of a smaller journal size, the most significant being that it slows the bearing. This is a rough estimate +/- 10 on the way you do your compression test. For a Chevrolet 350, the traditional rod journal size is 2.1 inches. Compression Ratio and PSI Compression Test I agree no, not really 9.6 135 PSI 10.1 145 10.5 158 11.0 175 180 is very high - this motor will need liquid dynamite to run without pinging. Tire Diameter Tire Diameter (MPH x Gear Ratio x 336) ÷ RPM. To use this horsepower calculator enter the mph trap speed at the 1/4 mile mark from one of your dragstrip ET slips. Note: You can also take this Compression Ratio Calculator tool for a spin. The compression ratio will be approximately 11:1. Engine Rear Wheel Horsepower Calculator Based on total vehicle weight and 1/4 mile MPH. 99Based on the DOHC 6G72, this engine has a reduced compression ratio (8:1) to accommodate the boost pressure from twin turbochargers and twin air-to-air. 050 cam, with a 108 LSA has a cold cranking compression of 175 psi. For example, my 540 BBC motor with 10.75:1 static compression ratio ( 7.43 to 1 dynamic compression ratio) and a 266/272 at. And you can see this even on a compression test. Apparel, Cups, Decals, Books, Gift Cards It will have flat tops and 64cc aluminum heads. A narrower LSA cam will close the intake valve sooner than a wider LSA cam.Your Marvel Mystery Oil and a six pack and get ready to party. Light, non-nasty grease, your handy dandy plexiglass or lexan sheet, Enter a positive number for aĭished or dimpled piston. Natural, 15:1 Max Compression Ratio, Inline, Buick, Chevy, Each. EnterĪ negative number for a domed piston. Compression Ratio Calculators 1/4 Mile & Acceleration Calculators Coming Soon. do it yourself or call the piston manufacturer. 2 Note: You can also take this Compression Ratio Calculator tool for a spin. Switching to 92 or 93 octane would allow the compression to be in the 10-1 range. Correct Compression Ratio (CCR) CCR FCR (Altitude/1,000) x. From what I read the Vortec heads will allow a half point higher in compression without pinging. The closer you get to pushing any limits, the more important the small details become. In my opinion, 8.5 to 1 would be good if using old style smog heads and running on 87 octane or less. At TDC the piston will "rock" so be careful in 020-inch thinner head gasket will produce a 3.5-percent increase in compression ratio, or just over a quarter-point in a typical small-block Chevy build. On 113/135" ORCA motors it is 0.00 because they use metal seals and no head gaskets.ĭistance between the flat top surface of the piston (not the top of aĭome or the bottom of a valve relief) and the top of the cylinder.Įnter a negative number if the piston's flat surface sticks up past the Combustion chamber volume- How much open space is in the head above the cylinder. It's usually 0.040", but not always.for example, on K1200 BMWs it is 0.070".
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