Camshaft FAQ

The chart below lists a “ballpark” range of camshaft durations to consider running based on the intake runner volume of various RHS® cylinder heads. Keep in mind that unless you run a high valve lift (above .550”) camshaft with the 220 & 235cc heads, you may not realize any performance advantage over cylinder heads with smaller intake runners. Note that we do not make a recommendation based on advertised duration because the wide range of methods by which camshaft manufacturers rate advertised duration makes it a poor indicator by which to compare camshafts.

Remember that this is a general guideline, and your intended application, advice of your engine builder, technician, etc. should always take precedence when it comes to cam selection on an individual basis. Note that you can also get help with camshaft selection by either Emailing RHS® or contacting COMP Cams® CAM HELP™ at (800) 999-0853.   

Small Block Camshaft Guidelines Based On Intake Runner Volume*

Small Bore/Short Stroke
Cubic Inches Intake Runner Volume .050" Camshaft Duration
Up to 350 CID 170-180cc 210-225°
302-350 CID 200-210cc 215-235°
347-400+ CID 215-220cc 230-245°
383-421+ CID 235cc 240°+
Large Bore/Long Stroke
Cubic Inches Intake Runner Volume .050" Camshaft Duration
Up to 350 CID 180cc 210-225°
302-350 CID 200-210cc 225-235°
347-400+ CID 215-220cc 230-245°
383-421+ CID 235cc 240°+

Big Block Camshaft Guidelines Based On Intake Runner Volume*

Big Block Chevrolet
Cubic Inches Intake Runner Volume .050" Camshaft Duration
468-500+ 320cc 250° +
500-565+ 360cc 275° +

*General recommendation only –not meant to replace other methods of camshaft selection. Note that camshaft/head recommendation “up to 350 CID” should also be taken to include 351W and other Small Block Ford engines.