Re: Cam profile / AQ271
You can install a roller cam follower system, but unfortunately, it is not as good as what GM came up with in the later engines. They have a great follower (lifter) keeper system that requires the engine block to be machined for the keepers and spring tray........, but it sounds like your block is an early block.
However, it can be done with components other then GM OEM parts.
As for profile.... here is a cut-n-paste from another forum where several of us are helping a man with cam selection.
This is by Dave M on the BOC:
First off lets start with a stock 260 hp merc type cam shaft ( pretty much the same for all 260 hp marine cams)
the specs are as follows:
202 duration intake
214 duration exaust
395 lift intake
404 lift exaust
Many of the marine cams seem to be st up on a 112 lobe seperation with a 110deg. center line.
Ok Now the max cam shaft for the chevy small block with an out drive for comp cams will be the 12-236-3
Here are the specs for that cam:
CL12-236-3 - Comp Cams 'Xtreme Marine' Hydraulic Flat Tappet Camshafts Details
Chevy 262-400ci Small Block 1955-98
*Note: In order to use these camshafts in 1955-57 265ci blocks, it is necessary to machine a small groove in the rear main journal of the cam to allow oil flow to the top of the engine.
Biggest cam for inboard/outboard, good mid-range with excellent response, noticeable idle.
Operating Range: 1300-5500 RPM
Duration Advertised: 262° Intake / 268° Exhaust
Duration @ .050'' Lift: 218° Intake / 224° Exhaust
Valve Lift w/1.5 Rockers: .462'' Intake / .477'' Exhaust
Lobe Separation Angle: 112°
Any more duration and lift you will increase the possibility on water reversion in the exaust only to ruin your new engine. Also with a cam this size and that much duration the hammer effect on the out drive from the duration is hard on the out drives to you have to be careful with it. Those are the two reasons that is the biggest cam for a small block.
Now having said that you are building a 383 so with the increased cubic inches you can get away with a little more duration as the more cubic inches it tends to calm te engine down as far as cams go.
The cam that they told you to use from Comp Cams is not a marine engine cam so I am a little surprised.
Here are the specs for that cam:
Operating Range: 1800-6000 RPM
Duration Advertised: 274° Intake / 286° Exhaust
Duration @ .050'' Lift: 230° Intake / 236° Exhaust
Valve Lift w/1.5 Rockers: .490'' Intake / .490'' Exhaust
Lobe Separation Angle: 110°
Notice that the operating range for what they gave you is clear up to 6000 RPM. I bet if you look at the curve for that cam you will be out of the peak operating range for cruising which is going to be some where around 3000RPM or say 80% of 4500 what ever that is. My opinion is that you can do better than that but then I am not a cam spe******t either but I do have alot of experience in this not just as a desk top computer cam suggester but as one who knows what works by actual experience
Now look at the operating range for the 12-236-3 it is closer to the 5500 RPM range and of you look at the curve for that came it is real close to where you want to be cuising and will give you better low end and better fuel economy at cruise speeds.
