My cam has a split duration 222 intake and 226 exhaust.

Why do cams have split durations while others have the same? What are the pros/cons of split durations?

And..how much of a gain would there be from say a LPE 219 cam to a hydraulic non-roller cam with the same specs?

 

IMOP it's to help the exhaust side ......????

 

Split duration cam specs, also known as 'dual pattern' cams compensate, as comp pointed out, for the weaker exhaust flow in most heads. So cams are are ground with more dusration and higher lift to even this out as much as possible.

When looking at cyclinder head flow numbers, there is a relationship between intake flow and exhaust. the higher the percentage of flow relationship between the two, the better a single pattern cam would work..

 

Because of the cylinder head and other flow for intake vs. exhaust.

If you just have headers, a cam with more exhaust duration would be good; for example.

There probably wouldnt be any gain from a 219 to a flat tappet with the exact same specs, more likely a very slight loss.

 

I basically figured that a 219 cam would make more power than a non-roller hydraulic cam with the same specs, but how much?

Rather than converting an older 2pc rear main seal non roller block to a roller block ( $$$ I don't have), I just figured on having a cam with the same specs, or maybe throw 1.7 rr's on (if cheaper route) to give me .525 lift.

My cam has very low lift (my machinist picked it for whatever reason before I knew anything -- I still don't) and I just wondered why he chose the split duration and such a low lift?

My mod list is..

383 stroker @ 9.3:1 - 9.5:1
LPE super ram plenum and super ram base
Cut air lid with K & N filter
LPE 58 mm throttle body
TNT 150 hp wet nitrous kit
FMS 30 # injectors
MSD 6AL
Ported L98 # 113 aluminum heads
NGK TR6 @ 0.038"
8 mm Taylor Spiro Pro Wires
AFPR currently set at 41 p.s.i
Centerforce Dual Friction Clutch
B & M Ripper shifter
DRM aluminum single mass flywheel
Throttle body bypass
"Frisbee" removed
Keith Black pistons
5.7" Eagle rods
Clevite 77 bearings
ARP bolts and studs
Moroso Accusump oil sump
ZF Docs C4 Beam Plates
COMP Cam 222/226 @ 0.050
valve lift int .464 exh .464
lobe separation 114
intake centerline 110
Valvoline VR1 Racing Forumula 20w50
Internally balanced SCAT 383 stroker crank
Breathless Performance Air Pump Eliminator Bracket
Modified Mass Air Flow sensor with screens and heat
sink removed
2 1/2" dual exhaust all the way back, no cats, to 2
chamber 40 series Flow Masters
GSS340M Walbro 255 lph fuel pump with "hot wire" kit
from Racetronix
Ceramic coated Hooker Super Comp Headers # 2149 (1 3/4"
primary to 3" collector)

 

I could only guess at the exact numbers, but i would say it would be more than a slight loss. The biggest benefit of a roller cam is the area under the curve, due to the agressive ramp profile the roller cam can get away with. It will hit it's lift much sooner and hold it longer than any flat tappet cam will.
You say you don't have the money for the conversion. Can you save for it? It will be worth it if you can.

 

[SNIP=black_89_vette]I basically figured that a 219 cam would make more power than a non-roller hydraulic cam with the same specs, but how much?

Rather than converting an older 2pc rear main seal non roller block to a roller block ( $$$ I don't have), I just figured on having a cam with the same specs, or maybe throw 1.7 rr's on (if cheaper route) to give me .525 lift[SNIP]

No need to convert the block itself, just use what are commonly referred to as "retro-fit" rollers lifters.

Actually, I feel that "retro-fit" is a term best applied to the late 80's setup that GM came out with in factory engines. Roller cams have been used in both SB and BB Chevy engines well over 30 years, long before GM began installing them in factory engines. So GM's version should be referred to as the "retro-fit" roller engines, not the other way round.

Tests done by a couple of the mags has shown about 30-35 HP increase when comparing hydraulic roller cams with a comparable flat tappet version. Comparable because there's no way to duplicate the aggressiveness of the roller cam's ramps' in a flat tappet profile.

Longer duration on the exhaust is used to improve exhaust flow on heads that have deficient exhaust ports and/or more restrictive exhaust systems. The longer exhaust duration on split duration cams also helps intake filling at higher RPMs. An intake to exhaust flow ratio of less than 70% calls for a split duration cam but when the ratio increases to 80% or more, a single pattern cam may show better power.

I say "may" because other variables effect which is better. Many of the the most popular cams are of the split duration variety with the difference between intake duration and exhaust duration ranging from 4 degrees to 14 degrees or more.

When you look at how restrictive the entire exhaust system is (from head port to muffler tip) a split duration cam makes sense.

Jake