Cam talk

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Hey.... quit hiding behind the popcorn....

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What would the difference be with a cam at 108* LSA and one with 112* LSA? The motor being the exact same and the cam specs being the same except the LSA. What difference will it make to the motor and the performance on the car?

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A narrow LSA (in this case 108) will create more high rpm power, the wider LSA will create more low end torque, all other things being equal.

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That may apply to some of the brands of motor with non true wedge heads, not to Mopars, even Hemi motors
edit: Stick shift drag motors like wider seperation usually, more power up top, automatic trans Mopar cars with stock type heads like less LSA and that ends up making more torque and power down lower in the usable RPM that the heads will work in

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LCA is all relative to the amount of duration. More duration with the same LCA = more overlap. You will see as the duration starts to get large most times the LCA will be dialed in wider as well. By altering the installed intake centerline you could have the intake closing point at the same location with both cams mentioned. Many variables here. Cams and converters. Get em right and your a Hero. Get em wrong and your a Zero.
Doug

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Example...

General consensus by many is to widen lobe centre when running nitrous , this hinges on the fact tight lobe centres will have some of that nitrous go straight out the tail pipes @ overlap , the reason for the 'wider' lobe centre is to increase duration on exhaust lobe , take a look @ these two camshafts , all valve events are identical except exhaust opening..............

260/260 110 lsa/110 icl
IO 20/IC 60
EO 60/EC 20
40 * overlap

260/268 112 lsa/110 icl
IO 20/IC 60
EO 68/EC 20
40 degrees overlap..............

Overlap is identical on these two camshafts , lobe centre was spread in order to lengthen exhaust duration (nitrous) , get valve events were they should be & LSA will follow.

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port size is important. A very large engine like a 535bb mopar with poor flowing 906 ported heads will swallow most all the cam you can throw at it and it won't pull power past 5800/6000. Try that with a 1970 ford boss 302 (huge Big block type ports)and you have an engine that won't get out of its own way till 6500 rpm. BUT, with the right cam it will make 650 hp at 9500! That was done in a HotRod article back in the seventy s. All they did was blue print the motor, no head porting, put in a big rollercam, and went modified class racing. AS I recall they were shifting that deal close to 10,000 rpm with stock ports.
The 906 head motor has so much port velocity it is hard to screw up with cam specs that are off. I went from a 590 cam installed at 108 to 112 and I didn't see any difference! A 286 @ .050 roller with .750 lift went in, and it only raised the power peak about 300 rpm, but the motor responded with a 5 mph gain in the quarter.
The Boss motor would be very touchy about late intake closing, because there is no velocity to help cover it up till very high rpm. It also will need a lot less duration for the same rpm. The 286 duration cam in that motor might even be too much at 9500, because the ports flow so well they don't need the extra time to fill the cylinder.

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Greg,
Nice reply, very informative. You're absolutely right on cylinder fill and duration. The cam out of my Hemi99 engine has 20* more duration on the exhaust side. They are trying to help the poor exhaust port with it's puny(compared to the intake) valve keep up with the huge port and valve of the intake.

The valve is also being lifted 1.050" so the efficient, huge intake port with a 2.55 valve diameter doesn't need a ton of intake duration to cylinder fill. The exhaust is a different story as it's an afterthought in a pro stock head and needs all the help it can get!

The cam in your 440-1 headed engine probably has more duration @.050 on the intake than my PS Hemi!!