Editing DynoSim combinations (section)
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===400 SBC with Vortec heads=== This combo is best at building a lot of torque in the 3,500 rpm range. L31 heads on a 406 will not lend themselves to top end hp, so use them where they work the best. On a 400 ci engine that will be to make bottom end and midrange torque. *Keith Black [http://www.summitracing.com/parts/SCA-25700P/ p/n KB168-030 hypereutectic pistons]. *Scat Pro Stock 5.7" rods. These rods are clearanced for the cam right out of the box. Minimum clearancing may be necessary at the pan rail for the big end of the rods. 6" rods can cause the wrist pin to get up into the oil ring land. This adds a little more complexity and more things to go wrong than if you were to use a 5.7" rod. With nominal +/- 66cc heads (production head combustion chamber volumes are often larger than published data), these [http://www.summitracing.com/parts/UEM-KB168-030/ 22cc D-cup pistons] will produce 9.6:1 static compression ratio. An added benefit is the tall 1.433" compression height, meaning less block deck to cut off to reach a target squish of 0.035" to 0.045". Besides boring and honing, machine shop work will include align honing the main bearing bores and cutting the block decks square and to the proper deck height to work with the piston compression height and gasket thickness to set the squish. Stock block deck height is +/- 9.025". The height of your stack of parts will be 1.875" for the crank throw radius, 5.700" for the connecting rod center to center and 1.433" for the piston compression height, for a total of 9.008". Using a gasket thickness of 0.039"/0.040", the block decks will have to be cut 0.017" to reach a zero deck. This will put the squish at 0.039" or 0.040", depending on the head gasket used. Decking the block will also insure that the block decks on all four corners of the block are the same distance from the main bearing centerline, meaning that static compression ratio will be closer to equal across all cylinders and will also contribute to the heads and intake manifold lining up and sealing the way they're supposed to. Thinner shim head gaskets used to be available for the 400, but not any longer. If 350 shim gaskets are drilled for steam holes, they might have a large enough bore diameter to work on the 400 block, but this has to be carefully checked to be sure there's no overhang of the gasket into the bore. If the shim gasket intrudes into the cylinder/chamber, it could be a potential cause of pre-ignition/detonation. It's better to use a composition gasket that is engineered for the purpose and cut the decks accordingly. Speaking of steam holes, the heads will have to be drilled for them. [[Drilling steam holes in smallblock Chevy heads]] has info on this procedure. This build uses a low-cost hydraulic flat tappet cam and the stock L31 valve springs and retainers. The rpm limit with this motor will be 5000, so there's no need to make any changes to the heads except maybe replacing the seals, unless there's a need for new springs. If you want to keep some safety margin (total of at least 0.050" between the 5 coils, and a safety margin for retainer-to-seal clearance), then you should limit valve lift to 0.420- 0.450". There's no need for 1.6 ratio rockers for this build, either. Crane has a cam that uses easy ramps and will fall right into the static compression ratio range we will use in this motor. #10017 has an operating range of 1800-5400. [http://www.summitracing.com/parts/CRN-100172/ '''Here's'''] the p/n 100172 kit which includes lifters. Always buy quality lifters. Get them with the cam if possible. Crane's description says this cam needs a 2500 converter, but with the amount of torque the engine will make down low a stock converter and a 3.50 gear will suffice. The lobe separation angle of 106 degrees will help make the bottom end torque that's needed for a stock converter and 3.5:1 range rear gears. The 0.450" lift will work with the stock springs and retainers. Be sure to use feeler gauges between the spring coils at full valve lift to insure that the springs don't stack solid. In theory, they shouldn't, but they have to be checked to be sure. Use 16-18 degrees of initial advance with an additional amount of mechanical advance to bring the total initial and mechanical to 34 degrees. That's all you need with these heads. You need more at the crank than you would with a stock cam though, for the motor to idle properly. We need to bring the idle down for use with a stock converter so we don't have to stand on the brake pedal at stoplights. See [[Hot rodding the HEI distributor]] for details on this and for using a vacuum advance. To the long block, add an Edelbrock Performer RPM intake manifold and top it off with a rebuilt [http://www.edelbrock.com/automotive_new/mc/carbs_acc/carbs_access_main.shtml Edelbrock] Thunder series AVS 650 CFM manual choke carburetor, p/n 1805. Also get the Edelbrock choke cable p/n 8013. Mount a 14" x 4" air filter on top. Stack two 14 x 2's if you can't find a 4" thick element. This (and any) motor needs to breathe. Bolt on a pair of long-tube 1-5/8" to 1-3/4" headers and connect the two sides of the exhaust system by using either an X or an H pipe right after the collectors. Use the mufflers of your choice. ====Results==== :'''RPM HP TQ''' *1500 122 426 *2000 174 457 *2500 217 457 *3000 268 470 *3500 315 475 *4000 354 465 *4500 380 441 *5000 373 392 *5500 326 311 There you have it boys and girls, a tire-shredding motor with a "flat-as-a-table" torque curve and a cam that will have a slightly rough idle so the OP can pose cool down at the Sonic Drive-In. When using a flat tappet cam, break in is ''uber'' important. Read up on what to do and how to do it [http://www.crankshaftcoalition.com/wiki/Camshaft_install_tips_and_tricks '''here'''].
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