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the exhaust side is along for the ride.

The one thing I dont like about split duration cams is that the extra lift and duration isnt needed , alls its doing is mucking up the charge on overlap with the extra degrees of overlap.

Unless that extra overlap is needed to assist with scavenging {And probably not} its a waste of extra valve movement and duration IMO, for the most part. mike

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& i always figured you were a split kinda guy.

There is know answer , every cam guy has differing views & will grind two different cams for the same application , some of these guys are pretty sharp , but not sharp enough to know exactly what cam that engine wants , the fast guys spend all there time on the dyno going through hundreds of cams , it's IMPOSSIBLE to spec the perfect camshaft for a given engine period.

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It is interesting that the big power-adders (Supercharging, Turbocharging, and NOS) all work on the principle of packing more oxygen into the combustion chamber. Turbo even does it at the detriment of exhaust flow, yet a big percentage of performance cams favor the exhaust side...

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Motors running nitrous want that exhaust valve opening pretty soon on power stroke to avoid overheating/detonation , hence the reason for the split........

I changed out the single for a split when i started running the bottle , basicly wanted the split pattern to behave pretty similar to the single pattern on the street , here's the two camshafts , notice overlap remains the same for the two cams as does IVC , only difference being EVO , these are the #s @ 050".

#1
270/270
112lsa
110icl
IO.25/IC.65
EO.69/EC.21

#2
270/278
114lsa
110icl
IO.25/IC.65
EO.77/EC.21

both had pretty similar street manners.

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Let me pose this question a little differently...
What would be the result of using a cam with more exhaust duration than was necessary? Obviously, we would have a bit more overlap and contaminated charge but how would the engine react?

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It is interesting that the big power-adders (Supercharging, Turbocharging, and NOS) all work on the principle of packing more oxygen into the combustion chamber. Turbo even does it at the detriment of exhaust flow, yet a big percentage of performance cams favor the exhaust side...

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Motors running nitrous want that exhaust valve opening pretty soon on power stroke to avoid overheating/detonation , hence the reason for the split........

I changed out the single for a split when i started running the bottle , basicly wanted the split pattern to behave pretty similar to the single pattern on the street , here's the two camshafts , notice overlap remains the same for the two cams as does IVC , only difference being EVO , these are the #s @ 050".

#1
270/270
112lsa
110icl
IO.25/IC.65
EO.69/EC.21

#2
270/278
114lsa
110icl
IO.25/IC.65
EO.77/EC.21

both had pretty similar street manners.

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Hey Ad How did they compare at the track? on and off the bottle?

On a side note, the vast majority of cams that Indy Cylinder Head supplies / recommends are split pattern. Whilst these guys may not be the easiest to speak to over the phone, I'd bet they've used some dyno time trying different types of cams and maybe found whats best for Indy heads. Sorta tells me something

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I have heard that certain heads with very good flowing exhaust ports (compared to exhaust) can over-scavenge the cylinder and actually suck a lot of the intake charge into the header, where it continues to burn and overheat the pipes. With some of the intake charge lost, power would be down.

Perhaps over-camming the exhaust would do the same.

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I spent a bunch of money dyno testing camshafts on my 470 low deck motor. It had exhaust manifolds and lots of people told me that I would need extra duration on the exhaust side to compensate for the manifolds. Turns out that the very best camshaft for that engine was the old school Mopar .528 solid flat tappet.

I suppose if I was given unlimted funds I could find a camshaft that was even better than the .528. And perhaps, after hunreds of dyno pulls the very best cam might well be a split pattern cam. But I called it quits after spending a couple of grand on cams and dyno time.

As far as I know, nobody knows the answer to this question. It is fairly easy to get a 90% correct answer to the question, but I don't think anyone has ever really figured it all out. If they had, then there wouldn't be any need for all of the dyno testing that goes on every day at all of the engine shops around the world.

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Let me pose this question a little differently...
What would be the result of using a cam with more exhaust duration than was necessary? Obviously, we would have a bit more overlap and contaminated charge but how would the engine react?

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You know, there is not a single man or company that has it all figured out to the point where they can spec the PERFECT cam for an engine without some type of compromise. This could be debated for ever and ever...and probably will be...LOL!!!!!

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Yep--fixed cams are always a compromise. Well, except for applications where an engine operates at a steady rpm and load performing some sort of work.

Thats why variable valve timing has so much potential! V-tec etc.

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On a side note, the vast majority of cams that Indy Cylinder Head supplies / recommends are split pattern. Whilst these guys may not be the easiest to speak to over the phone, I'd bet they've used some dyno time trying different types of cams and maybe found whats best for Indy heads. Sorta tells me something

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Hi Tig , maybe you can ask Indy the reason for going split with their heads next time you speak to them , my bet is they don't know.

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How many times do you here guys on here telling others to advance the heck out of the off the shelf MP grinds? , the one's i'm talking about are the single pattern grinds , why would you want to advance more than MP recommends? , one reason maybe the cam is too big for the application? , another reason is maybe some guy fitted this cam & it ran like a dog on his combo? , maybe another guy found he picked up some advancing intake centre line? , what does all this tell you? , THE CAMSHAFT IS WRONG FOR THE APPLICATION , any time a camshaft has to be advanced more than 4 degrees from straight up then go look for another camshaft , most guys on here who found power by advancing ICL are street guys , this gets back to my earlier post of contaminated intake charge , no way that motor picked up any power going 8 degrees advanced , only benefit would be seat of the pants , mostly being idle characteristics/part to mid throttle , any torque gained down low would be killed off up top.

All you guys running excessive advance maybe go get another cam , will certainly pick up on the big end.

Ever wondered why intake cenreline has to be advanced 4 degrees on most all off the shelf grinds?.............chain stretch is poor excuse , gear wear being another poor excuse , anyone wanna touch on the real reason?

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You need to talk with some of the guys in the EM Challenge...they will change your mind about how much of a tuning tool a camshaft can be.

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I could'nt agree more , but these guys are trying to wring out every ounce of power & don't mind pulling the motor appart to get there , most guys on here wanna fit & forget , how much power are they leaving on the table?

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You need to talk with some of the guys in the EM Challenge...they will change your mind about how much of a tuning tool a camshaft can be.

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I could'nt agree more , but these guys are trying to wring out every ounce of power & don't mind pulling the motor appart to get there , most guys on here wanna fit & forget , how much power are they leaving on the table?

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On a side note, the vast majority of cams that Indy Cylinder Head supplies / recommends are split pattern. Whilst these guys may not be the easiest to speak to over the phone, I'd bet they've used some dyno time trying different types of cams and maybe found whats best for Indy heads. Sorta tells me something

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Hi Tig , maybe you can ask Indy the reason for going split with their heads next time you speak to them , my bet is they don't know.

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As long as they know from results that they worked best for those heads then that will do for me
FWIW this cam 320 / 320, 288 / 288 @ .050 .691 when installed 4 degrees retarded (@ 112) from the recommended 108 picked up 2 tenths. We were just looking for a little more top end and it worked but what was that telling us?