Custom grind camshaft for nearly stock 350

[mechanicalman]

Originally Posted by Cgoldhill

Sorry for the double post, the damn forum keeps logging me out mid post reply.
Posted via Mobile Device

The thing about narrow LSA is that it increases overlap, and increased overlap favors top end power and decreases low end power, despite the fact that it also helps low RPM cylinder filling so it's a two-edged sword that, IMO, is only applied in racing particularly short track circle racing and also larger cams (drag racing) MUST employ narrow LSA just to keep cam timing appropriate so again the double edged sword cuts both ways.

There are some OLD, old stock chevy cam grinds from long ago that employed some short duration with narrow LSA. They would actually be an improvement on your stock cam for LOW END ONLY power band 1,000-3,200 RPM. Might be a Band-Aid solution for the time being? Not for me though.
http://www.competitionproducts.com/E.../#.VVy1EE3bJdg

Some general cam info copied/pasted from Crankshaft coalition:

Lobe separation angle (LSA)

The lobe separation angle, sometimes called lobe displacement angle, is a measurement in camshaft degrees that states how far apart the maximum lift points of the exhaust and intake lobes are. This number is ground into the cam and can't be altered without physically changing the camshaft lobe profiles.

Narrower LSA:

A narrower LSA will increase overlap. This has a tendency to reduce engine output at lower RPM and increase engine output at higher RPM. A narrower LSA tend to make more peak power but a little less average power.
Moves torque to lower RPM
Increases maximum torque
Narrow power band
Builds higher cylinder pressure
Increase chance of engine knock
Increase cranking compression
Increase effective compression
Idle vacuum is reduced
Idle quality suffers
Valve overlap Increases
Natural EGR effect increases
Decreases piston-to-valve clearance

[edit] Wider LSA:

A wider LSA tend to make less peak power, but a broader powerband. Changing the LSA also changes the valve timing events; opening the exhaust valve sooner and closing the intake valve later, both of which affect how the engine ingests air.
Raise torque to higher RPM
Reduces maximum torque
Broadens power band
Reduce maximum cylinder pressure
Decrease chance of engine knock
Decrease cranking compression
Decrease effective compression
Idle vacuum is increased
Idle quality improves
Valve overlap decreases
Natural EGR effect is reduced
Increases piston-to-valve clearance

Overlap

Area 1 is for street towing, 2 is regular street, 3 is street performance, 4 is street/strip, 5 is race, and 6 is Pro race.
"Overlap" represents the amount of duration in camshaft degrees when both the exhaust and intake valves are open at the same time. For a single cam engine this factor is ground into the cam and can't be changed without physically altering the camshaft lobe profiles. On a dual overhead camshaft (DOHC) engine overlap can be altered with adjustable cam gears. Adjusting one or more cams closer to TDC increases overlap. Increasing duration at the same LSA will increase overlap. Decreasing LSA at the same duration will also increase overlap.

Overlap is usually not found printed out on the cam card, but it's easy to calculate.
Add the intake opening point BTDC to the exhaust closing point ATDC.

If the intake opening and exhaust closing points aren't known, you can estimate the overlap by using the advertised duration (or duration @ 0.050" lift, etc.) and the lobe separation angle.
Add the intake and exhaust durations,
Then divide the results by 4,
Then subtract the lobe separation angle,
Then multiply the results by 2
The result is the overlap

[mechanicalman]

Originally Posted by Cgoldhill

Sorry for the double post, the damn forum keeps logging me out mid post reply.
Posted via Mobile Device

Some good reading:
http://www.crankshaftcoalition.com/w..._compatibility
With your set-up, 307 gear ratio in a pickup, you would lean toward more cam vs compression ratio in regards to the chart to avoid ping, just a tad.
This will explain why.
http://www.crankshaftcoalition.com/w...amshaft:metal:

[gvnick]

There is a reason you dont find small duration cams with a 108 LSA. LSA is just a byproduct of how much duration you want and where you want the valve events happening. A big duration cam needs a tighter LSA to keep from holding the intake open too long or opening the exhaust too soon. A small duration cam really doest work with a tight LSA because these valve events would end up in the wrong places, or compromises would be made for no reason other than hitting that 108 number that doesnt mean anything.

Pick your duration and ICL, put the LSA where it makes sense.