![]() I'll bet you never get to 32* before you get detonation with a 8-71 and pump gas. Too much total timing and your run into detonation. You'll have to do alot of T&T on the combo to get it dailed in right, but start with low timing. you will need 1/2" pickup welded in your tank, and use 1/2" fuel lines. If you go lean with a blower kiss the engine goodbye. Altitude plays an important role in determining compression ratios. You'll need atleast dual 600 cfm carbs, and you better get good at carb tuning to get them both dailed in right. The formula for calculating your exact final compression ratio is as follows: Final Compression Ratio (FCR) (Boost÷14.7) + 1 x CR. My engine builder is getting near the end of my build. Example: For an engine with 4.030-inch bore and a 3.00. Swept Volume (Cylinder Diameter / 2) Squared x 3.14 x Stroke. Cam specs: Lift 600/583 Dur 50 243/251, centerline: 103/104, LS: 109. Compression Ratio (Swept Volume + Clearance Volume) / Clearance Volume. Heres my combo: 489, (30 over stroked 454, gen 4 block) 049 heads, 219/188 valves, 290cc on flow bench, Howards 'big daddy rattler' hydraulic roller. Inside No 9, BBC Two, review: Friday 13th is unlucky for some as the. higher flow aftermarket water pump, and an alum 2 1" row rad in the biggest size you can fit. I need some input on compression with my 489 build. Calculator will immediately calculate with selected distance unit. The 8-71 is gonna build alot of heat so you will need a great cooling system. If your engine checks out with around 170 to 185 psi of cranking pressure, then youre. For a SBC street 8-71 blown engine look for 1-3/4 tube headers and 3" dual exhaust pipes with great flowing mufflers like dynomax bullets or ultra flos The key here is to give you one more tuning device you can use to dial in your engine to perform better. You'll also pretty much have to have aftermarket heads (alum. : The Compression Ratio (CR) of an engine is the ratio of the cylinder volume compared to. Determining what the compression ratio is after the intake valve closes provides valuable information about how the engine will perform with a particular cam and octane. You don't want a big cam cause it will "bleed off" your boost. Dynamic Compression Ratio (DCR) is an important concept in high performance engines. ![]() Building a boosted engine is very diff than N/A. ![]() Use forged pistons (not cheap junk) go with ross, JE, SRP, etc, Good forged rods with ARP cap screws, Forged aftermarket crank, Look into "blower cams" with a LSA of 114-116. BBC Blown BBC Drag Racing Drag Racing Engines Racing Engine Builder Supercharged. Of the variables, the most important is cam timing which has a dramatic effect on your 'dynamic' as opposed to your static compression ratio. compression ratio too high blower drive ratio improper timing poor. 050' number when your cam is a brand like Comp Cams which typically only provides you with an IVC. This calculator is useful for finding out your IVC. 050' lift by inputting intake & exhaust duration. Find out your camshafts valve timing events. If the bore and stroke measurements are in inches then the result from the formula above will be in cubic inches. Engine displacement is often measured in liters, cubic centimeters, or cubic inches. Roots blowers can't get away with the compression and boost that a centrifugal superchargers (pro charger, paxton, vortech), and turbos can.įor a pump gas street type blown engine I would run 7.5:1 to 7.8:1 SCR. Use this calculator to see what the effect of bore, stroke, rod length, cam timing, compression ratio, boost pressure and altitude is on your dynamic compression ratio. Camshaft Valve Timing Degrees Calculator. displacement 0.78539816339 × 11.56 × 3.6 × 8. You can return any new or unused item within 90 days of the date your item was shipped and we will refund the full purchase price.With an 8-71 you better have LOW compression and very good bottom end parts. Visa/Mastercard, Discover, American Express, Pay Pal, and Pay Pal Credit, Gift Cards, Summit Racing SpeedCard. ![]() Have questions? Our customer support team is available 7 days a week to help you. Stroke of your engines crankshaft Rod Length. This calculator will calculate both Static and Dynamic compression ratio. We’ll beat any advertised price on an in-stock product. Compression Calculator Enter the number of cylinders of your engine Bore. The static and dynamic compression ratio calculator. We're confident our prices are the lowest. Over 1 Million parts from more than 1000 trusted brands, more parts added all the time. We ship in-stock parts via ground shipping the same day if ordered by 8:00 pm EST. Just place an order over $109, and we'll drop the shipping and handling charge. You need to work all this out then use the effective dome volume number for a particular piston and run all those numbers on a compression calculator.
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