489 Cam Selection
 

WICH CAM WOULD BE BETTER,CRANE 139721 OR 139731(OR SOMTHING DIFFERENT).MY SETUP------4.280 BORE,4.25 STROKE,RPM AIR GAP,750 CFM EDELBROCK,STAINLESS MARINE WITH SHORT RISERS TO CORSA SILENT CHOICE,9:1 COMPPRESION,AND MERLIN OR EDELLBROCK RPM HEADS(NOT DECIDED YET).CONCERNED ABOUT REVERSION IN SILENT MODE AND RUNNING OUT OF CARBURATION.

You should run the 731 camshaft to make maximum power at 5200 rpm. With only 226 degrees of intake duration and 112 degrees of Lobe Sep Angle you shouldn't have any problems with water ingestion at an idle. The intake lobe centerline is at 107 degrees advance. Retard the intake lobe centerline to 110 degrees advance and you will pick up some additional power.

By combining the 110 degree intake lobe centerline with higher compression from Edelbrock Aluminum marine heads the engine should really come alive.

Have fun!
Sincerely
Dennis Moore

DENNIS ARE YOU SUGESTING RUNNING THE EDELBROCK HEADS WITH THE 9:1 PISTONS TO GET CLOSE TO 10:1 COMPRESSION.91 OCTANE IS MY LIMIT LOCALY.WHAT ABOUT AN ISKY 228/238 ROLLER CAM.IVE HEARD THER ROLLERS ARE A BIT MORE DURABLE.

Exactly what pistons do you have? Are they flat or do they have a dome?

Yes, the Isky camshaft will work but you will have to get a custom ground camshaft with 112 degrees of Lobe Sep. Angle. Most Isky camshafts are ground on a 108 LSA.

By the way, I like the 750 Edelbrock Performer Square Bore carburetor for your combination.

Dennis Moore

IT'S A NEW MOTOR I'M PUTTING TOGETHER AND I WAS PLANNING TO USE SRP 9:1 DOMES IF I USE THE MERLINS, OR FLAT TOPS IF I USE THE EDELBROCKS.ISKY CAM 396275/284------224/[email protected],275/284 ADVERTISED,.553/.578 LIFT,112LC.I WAS ASSUMING THE 112 WAS THE SEPARATION ANGLE?

Sounds like a good camshaft but I don't see the need for 14 degrees more exhaust duration than intake duration. If you cut down the exhaust duration to 230 you would have less valve overlap and could increase performance by running a tighter lobe separation angle.

The stock camshafts are single pattern (same amount of intake duration as exhaust duration) 224/224 intake/exhaust duration @ .050 lift.

Running 12 to 14 degrees more exhaust duration has always seemed a little excessive to me and not necessary when you consider that the intake valve/intake port is so much larger than the exhaust valve/exhaust port.

If there was such a disparity in the intake to exhaust flow ratio you would think that the original engineers would have simply increased the exhaust valve/exhaust port size.
Dennis Moore

OOPS! 228/[email protected]. I HEARD THAT ISKY LIFTERS WERE MORE TOLERANT TO LIFTER MISALIGNMENT THAT SEEMS TO BE QUITE COMMON IN PRE GEN V1 BLOCKS. WHAT ABOUT STATIC COMPRESSION 9 OR 10 TO1.