DynoSim combinations
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| + | I took this directly from a response on a thread where a rodder wanted to use a 400 block and L31 heads.... | ||
| + | I would advise against max hp in favor of building for max torque in the 3,500 rpm range. L31 heads on a 406 will not lend themselves to high hp, so I would use them where they fit best, low rpm torque. I'd use Keith Black hypers, #KB168-030, hung on 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. | ||
| + | http://www.summitracing.com/parts/SCA-25700P/ | ||
| + | 6.0 rods get up into the oil ring land and I do not advise more complexity and more things to go wrong than you need in an engine build like this, particularly for a beginner. With nominal +/- 66cc heads (production heads usually pour larger than published data), these pistons, with a 22cc D-cup 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". | ||
| + | http://www.kb-silvolite.com/kb_car/...php?action=comp | ||
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| + | Machining operations to the block, besides the boring and honing to +0.030 oversize, will include align honing the main bearing bores and cutting the block decks to square and to the proper block deck height to work with the piston deck 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". If we use a gasket thickness of 0.039"/0.040", then we will have to cut the block decks 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. Some fellows have used 350 shims and drilled them for steam holes, but the bore of the gasket is iffy with the larger 400 bore. If you get any of that thin shim out into the cylinder/chamber at all and it glows hot, it could be a potential trouble spot for pre-ignition/detonation. 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. Here's the tutorial.... | ||
| + | http://www.gregsengine.com/converti...ads-to-400.html | ||
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| + | I'm going to waver from my usual roller tappet song and dance here and suggest a low-cost hydraulic flat tappet cam because we're going to use the stock L31 valve springs and retainers. Our rpm limit with this motor will be 5000, so we don't need to do any changes to the heads except maybe replacing the seals, unless of course if you want to pony up 60 bucks for fresh springs. Chevrolet says if you want to keep some safety margin (total of 0.050" between the 5 coils), then you should limit valve lift to 0.430". We can move into the margin a little with this low rpm motor and use a cam with 0.450" lift if we need to. I would advise against the use of an extreme energy type cam and also against the use of rockers in excess of 1.5:1 ratio in this build. | ||
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| + | 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. Here's the 100172 kit which includes lifters. Always buy your lifters with the camshaft....that way you know they were produced by the camshaft grinder, not some fosdick Chinese outfit.... | ||
| + | http://www.amazon.com/Crane-100172-...r/dp/B000CIRW8I | ||
| + | Crane's description says the cam needs a 2500 converter, but with the amount of torque we're gonna produce down low, I'd be thinkin' stock converter and a 3.50 gear. The lobe separation angle of 106 degrees will give us the bottom end bias we need and the 0.450" theoretical lift will work with our 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 theory doesn't always agree with reality. Use 16-18 degrees of ignition lead at the crank with an additional amount at the weights to bring the total initial and centrifugal 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. | ||
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| + | OK, we have a long block. Now, let's bolt on an Edelbrock Performer RPM intake manifold and top it off with a rebuilt Edelbrock Thunder series AVS 650 CFM, manual choke carburetor #1805. Also get the Edelbrock choke cable #8013. | ||
| + | http://www.edelbrock.com/automotive...c/thunder.shtml | ||
| + | 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 motor needs to breathe. Speaking of that, bolt on a pair of equal-length, long-tube 1 3/4" headers and fashion either an X or an H pipe right after the collectors. Mufflers of your choice, but run the pipes to the rear of the car. Nothing is more "trailer park" than terminating the pipes under the car . | ||
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| + | 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. | ||
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| + | The OP should read this tutorial over as many times as it takes to make good sense of it and understand completely what it says...... | ||
| + | http://www.crankshaftcoalition.com/...tips_and_tricks | ||
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