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Old 12-14-2012, 03:03 PM
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Originally Posted by southernculture View Post
Hey y'all,
I am building a 350 for my rat rod, 1953 3 window chevy pickup, and I have a question on cam selection. I have the short block built. I have had the motor bored .040 over, new crank and .040 speed pro flat top pistons. The heads I have are 906 vortec heads. I had them worked, new springs and the heads cut to allow for .550 lift. valve job and the heads were decked. I am trying to figure out what cam to run. I plan on having a 3.08 rear end and the trans is manual. I want it to sound rough at idle and I want it to run well from at least 2000-6500. I dont have an intake or carb yet. Thanks for the help.
Shaun, here we go again. You cannot intelligently choose a camshaft for a motor until you know the static compression ratio. We can sort of figure most of the volumes because we've done it so many times, but we have no idea of the piston deck height on your motor. (the distance from the crown of the piston to the block deck where the heads bolt on). If you'll do a little work for us, we can figure it mathematically. Assuming you have a short block and have not bolted the heads on yet, turn the crank so that ANY piston is at the top of its bore. Using a steel rule, turn it on edge and lay it across the bore about a half inch from the edge of the bore on either side of the piston (looking at the piston as a clock face and standing at the side of the block, place the rule at 3 O'Clock or 9 O'Clock to prevent the piston from rocking on its pin and giving you an erroneous reading. Using a pack of feeler gauges, stack gauges together until you fill the gap between the underside of the steel rule and the piston crown. Turn the crank a little clockwise and counter-clockwise to make sure you have the piston at top dead center. Depending on the piston compression height and piston deck height, this could be anywhere from -0.020" (minus twenty thousandths) to about +0.055" (plus fifty five thousandths). Post whatever the figure is. Also, how much was taken off the heads? Each 0.007" (seven thousandths of an inch) cut equals about 1 cc.

Last edited by techinspector1; 12-14-2012 at 03:19 PM.
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