11/26/2023 0 Comments Compression calculator bbc![]() (2) if in doubt, about how to do anything, on an engine, do some detailed research,įind and compare at least 3-5 valid trust worthy sources info, RESEARCH CAREFULLY THE COMPONENT INSTALLATION AND INTENDED USE , MAKE DARN SURE THE LIST IS COMPATIBLE WITH,Īnd AT LEAST SEMI-REASONABLY PRICED WITHIN YOUR BUDGET.įOR WHAT YOU INTEND TO BUILD AND RESEARCH THE RELATED MACHINE WORK, The first few rule's of GRUMPY'S engine assembly Not realizing or refusing to accept, its their own lack of grasping the concepts involved. Theres lots of guys that don,t comprehend the stress levels involved in spinning a longer stroke engine up over 7000 rpm,Īs a result theres a lot of guys who as a result get an expensive personal education in that area,of engineering stress management ,Īfter their engine "EXPLODED FOR NO REASON" and 90% plus will blame the machine shop , This is a good place to point out that ARP makes much stronger rod bolts and main cap studs,and that the better aftermarket forged 4340 forged connecting rods are far stronger than most OEM connecting rods and that a 7/16" arp rod bolt is on average 200%-250% stronger than a stock 3/8" OEM rod bolt.īalanced components tend to put significantly lower stress on the engine components So 48,000/7.5" of stroke =6400rpm, (7.5" is twice the engines 3.75" stroke) exceeding that is a reasonably sure way to over stress the engine or (get into valve control issues ( which is a different can of worms) On a 383 sbc the stroke is 3.75", so 4000fpm on a 383 is reached at 4000rpm x 12"(inches)= 48,000 inches per minute of piston travel Your fpm is found by multiplying the engine rpms x the stroke x 2 700 lift too breath to its potential, both engines would benefit from a tunnel ram intake and dual quads or a stack injection style intake Notice the pin height in the pistons pictured above allow a longer or shorter connecting rod lengthĮither engine will require a roller lifter cam with a fairly tight 109-111 lsa and about a. ![]() ![]() If you wonder why I suggest using SCAT (H) beam style cap screw connecting rods vs stock or most (I) beam designs this picture should show the increased cam to connecting rod clearanceĪfter market performance ,big block connecting rods come in several common lengths will equal the required piston pin height The blocks deck height, minus the connecting rod length, minus 1/2 the crank stroke. Remember the blocks deck height, minus the piston pin height minus 1/2 the crank stroke will equal the required connecting rod length 7854ġ/2 stroke + rod length+piston pin compression height,ĭue to head gasket thickness and what the piston deck height is are commonĬommon BB CHEVY piston compression heights are Yes Im assuming its a tall deck 10.2" block and a 4.25" strokeĪ 4.25" stroke,6.8" rod and 1.270 pin height, for that 10.2 deck height blockĦ.8" rod divided by a 4.25" stroke=1.6 ratioĭisplacement = bore x bore x stroke x 8 x. What length connecting rod and what piston pin height are you using, building the 496 BBC? Yes Im fully aware most people don,t bother to read the links and sub-linksīut for the few people on the web site that might prefer spending less time and cash replacing expensive failed parts,Īnd financing the machine shop owners vacations and paying his mortgage. It is likely your likely going to want heads with a 4.5 cross sectional area It will calculate the DCR based on the modified stroke length, which in turn is derived from the rod length and the IVC.Your looking at about 706 ft lbs on the 565 cubic inch engine. You can open the dynamic compression ratio calculator in our calculator's advanced mode. You can discover more in Omni's Carnot efficiency calculator. This is why the dynamic compression ratio (DCR) is dependent on the intake valve closing (IVC) point, which is expressed as an angle after the bottom dead center (ABDC). We can only speak about compression once the valve is completely closed. At that time, though, the intake valve is not yet closed, so no compression occurs – the air is "pushed out" through the valve. The piston reaches its lowest position (bottom dead centre) and starts moving up again. When it moves up, the volume inside the cylinder is compressed when it moves down, fresh fuel and air enter the chamber through the intake valve. ![]() In a combustion engine, the piston moves up and down. Why? It doesn't take into account the closing of the intake valve. However, this number does not perfectly describe reality. Using the compression ratio formulas above, you will be able to compute the static compression ratio. You may calculate it by multiplying the displacement volume by the number of cylinders. Our compression ratio calculator estimates the value of the CR and the total engine volume.
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