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Old 12-20-2012, 01:18 PM
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Here's a Dynosim I did a while back....
350 SBC L31 heads
Flat tappet hydraulic cam, stock self aligning (SA) rockers, some head work for better springs.
In this build, a tight budget is called for. To that end, use stock self aligning rockers. Lift is under a half inch, so the SA rockers should be OK. Check to see if using a -0.050" lock will be needed to insure the valve tip sticks up far enough above the retainer so that the retainer top surface doesn't get loaded by the side rails of the rail rockers. More on checking clearances, etc. under Resources, below.
Bore the block 0.030", use these or similar 12cc dished pistons w/5.7 rods.
Makes 9.6:1 static compression ratio. Cut block decks to zero and use a 0.040" head gasket.
Use XE274H Comp cam, installed at straight up.
http://www.compcams.com/Company/CC/c...x?csid=87&sb=0
Needs MINIMUM 2200 stall converter.
This cam closes the intake valve at 41 degrees ABDC @0.050" tappet lift and is all the cam you need to pull past the capability of the heads to flow. If you can't get the power you need from 1,800 to 6,000 with this motor, you need a bigger motor and bigger heads, not more cam.
Comp p/n 981 valve springs, p/n 750-16 retainers, p/n 630-16 keepers and stock 1.5 rail rockers. 1.250" springs should be OK because the cam is a moderate grind, hydraulic flat tappet.
Machine the OD of the guide bosses to less than the I.D. of the damper spring and cut for PC-type positive seals.
Cut top of guide for 0.550" play from bottom of retainer to top of guide seal. Pin the pressed-in rocker studs with this kit.
Performance Distributors custom curved HEI distributor, p/n 12720, or build your own from a GM HEI.
http://www.performancedistributors.com/gmssdui.htm
Edelbrock RPM Vortec intake mounting a 750 vacuum secondary carb of your choice. Edelbrock, Rochester 5 psi max at the inlet, Holley 6 psi max at the inlet.
http://www.summitracing.com/parts/EDL-7116
Performer RPM Vortec w/natural finish: p/n 7116, w/EnduraShine finish: p/n 71164, w/polished finish: p/n 71161, or look for a used manifold on craigslist to save a few shekels.
Long-tube 1-5/8" headers with X or H pipe right after the collectors, 2-1/2" to 3" pipes to the rear through mufflers of your choice.
Use 2200 or looser stall converter, shorter rear gears.
Results
RPM HP TQ
2000 138 364
2500 176 369
3000 224 392
3500 281 421
4000 331 435
4500 370 432
5000 402 422
5500 405 386
6000 375 328
Peak dynamic compression ratio 8.16:1 on KB's calculator.
Peak volumetric efficiency 97.2% @5000

Even with 10.0:1, use the same cam I used here. It will make 8.496:1 Dynamic Compression Ratio. Pay attention to the squish and set it at 0.035" to 0.045". A tight squish is the key to making high cylinder pressure on pump gas without detonation. Throw the shorty headers over the fence and pop for some quality long-tube 1 5/8" headers. I'd just as soon use the stock cast iron manifolds as to use shorties. Bolt on all the air filter element that you have room for. The motor has to breathe to make power, so don't choke it down with some fosdick undersized filter element (I like 14" x 4"). If you have room, 14" x 6" looks really cool in my opinion.
Nova Parts | K & N AIR FILTER ELEMENT 14" X 6" | Classic Industries

One more thing, if you chose those pistons because they were advertised as 10:1, the actual measured SCR will likely be less....and that's OK.

Last edited by techinspector1; 12-20-2012 at 01:34 PM.
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