longer exhaust duration?
as already stated you'll want a longer exhaust duration. but you best bet is to just eliminate the restriction in the fist place and get long tubes. then feel free to run any cam you want and not be hindered.
TECH Enthusiast
Joined: Mar 2004
Posts: 647
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From: Australia
There is no restriction between 2 headers of similar primary pipe size but different primary pipe length. The difference is simply where the torque becomes usable. Longer tubes will bring torque on earlier than shorter, but for stock heads and cams it aint gonna matter diddly squat.
Tri-Y are good for NA cars with cams of increased overlap. If you blow, then 4-1s are the best bet.
All things equal, a short 4-1 and long 4-1 setup of equivalent pipe diameter will not theoretically yield any difference in peak power.
Tri-Y are good for NA cars with cams of increased overlap. If you blow, then 4-1s are the best bet.
All things equal, a short 4-1 and long 4-1 setup of equivalent pipe diameter will not theoretically yield any difference in peak power.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
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From: BFE
Originally Posted by arron
reverse split is to compensate for lack of "intake" same goes true but opposite for standard split.
With a set up like his, personally I would prefer a short "reverse split" with 0.570's range lifts and 110 lsa on XE-R lobes.
Something like 228/226, 110lsa. (I've always been a bit unusual)
Proper tuning (Wide band) would be a must.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
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From: BFE
Originally Posted by 52172
predator-z your theory may be way off!!!!!!!!!!!!!
Longer intake open=bigger charge=bigger bang=more pressure=quicker exit time.
Of course this is under normal atmospheric pressures and not under boost.
Someone may ask me: So why do stock cams play more on exhaust? and the answer is simple: Emissions.
Last edited by PREDATOR-Z; May 3, 2004 at 06:14 AM.
Staging Lane
Joined: Feb 2004
Posts: 76
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I think there is a dynamic of reveres split cams that is not being taken into consideration here. One reason that they work well is the fact that they have alot of overlap. When the exhaust valve is exhausting gases during the overlap it creats a suction next to the intake valve to start the charge coming in. The larger the opening during this event the less velocity of the exhaust gases and the less suction / vaccuum is present next to the intake valve. The smaller exhaust opening (i.e. reverse split) during overlap the faster the velocity of the exhaust gas and more vaccuum is created. To a point. It is a balancing act here.
I read an artical somewhere and came up with this theory. Please refute me if I am wrong.
I read an artical somewhere and came up with this theory. Please refute me if I am wrong.
I want decent torque down low to still be streetable with my 3:42 gears yet my target operating range will be the top end from 3000-6800 rpm. My shorties arent really that restrictive in reality they are dumping into nothing but straight pipes into a high flow 2.5 in Y pipe then out a cutout. there is no backpressure or not much at all. I think my exhaust is great. My intake is even better with CAI,lid, smooth bellow, 85 mm MAF,ported TB into a ported Lingenfelter intake. I think I will get a custom cam grinded and then tuned at So Cal Diablo with my Predator and the cam will be in the 231/237/ .595,.595 on a 112 lobe separation. Should be good for 420 rwhp with a good tune. I'll keep people posted once I get the dyno tune numbers. I may even go with one of the xer grinds with a 234/240 duration. I will use the new comp 921 valve springs for maximum life and durability. Should be a long tube equiped killer!!
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Brett Foote TECH Senior Member
Joined: Mar 2004
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From: BFE
Good luck,
But just to let you Know, Colonel one of the cam GURUs here makes 420 with a 224/220, .581/.581 116lsa (MTI stealth 2) and a good set of heads. Sounds stock too
Overcaming doesn't make sense to me.
If i were to put JBA's on my 01, I would gain maybe 2-3 rwhp max. They are restrictive.
BTW I'm not bashing, just my view of things.
But just to let you Know, Colonel one of the cam GURUs here makes 420 with a 224/220, .581/.581 116lsa (MTI stealth 2) and a good set of heads. Sounds stock too
Overcaming doesn't make sense to me.
If i were to put JBA's on my 01, I would gain maybe 2-3 rwhp max. They are restrictive.
BTW I'm not bashing, just my view of things.
Last edited by PREDATOR-Z; May 4, 2004 at 03:16 PM.
TECH Fanatic
Joined: Nov 2001
Posts: 1,248
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From: Kansas City, MO
You can obviously do anything you want, even if it is incredibly silly. 
You're extremely overcamming for a target rpm, but if you're wanting to follow the herd...you're on the right track.
You're extremely overcamming for a target rpm, but if you're wanting to follow the herd...you're on the right track.
Originally Posted by DenzSS
You can obviously do anything you want, even if it is incredibly silly.
You're extremely overcamming for a target rpm, but if you're wanting to follow the herd...you're on the right track.
You're extremely overcamming for a target rpm, but if you're wanting to follow the herd...you're on the right track.
What cam would you recommend?
Thanks
John
why do you think I am extremely over camming when my target rpm is 3000-7000 rpms. everyone with the tsp 231/237 cam is shifting at 6800 and no higher this is the cam I am considering and is in my target rpm's. I think you are making an incorrect statement by saying I am overcaming. There is no such thing as overcaming with these ls1 motors the thunder racing t rex cam is like a 247/251 cam and it makes 455 rwhp through stock heads!
Put that in your pipe and smoke it! The bigger the cam you put in the more power the motor will make period. You will run out of piston the valve clearance before you can say that motor is overcammed. Why don't you elaborate on a situation where the person was overcammed. These long durations just move the power band up to higher rpms and my target range is pretty mild rpm range. I will probibly be shifting at 6800. Lets hear you fire back now.
Put that in your pipe and smoke it! The bigger the cam you put in the more power the motor will make period. You will run out of piston the valve clearance before you can say that motor is overcammed. Why don't you elaborate on a situation where the person was overcammed. These long durations just move the power band up to higher rpms and my target range is pretty mild rpm range. I will probibly be shifting at 6800. Lets hear you fire back now.
Yes I am open to suggestions what cam would you recommend for me DenzSS? I want over 400 rwhp and have just enough torque to beable to drive it on the street with 3:42 and run like a raped ape when needed. Seek and destroy those fords.
TECH Fanatic
Joined: Nov 2001
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From: Kansas City, MO
It's pretty obvious you've already made up your mind. No use wasting my time or yours. Most who need advice won't ask for it, most who ask for it are looking for someone to agree with them.
All I have to say is take a look at the big cams that make the most power...G5X2, TSP 231/237, TREX...they are all exhaust biased...look at any SBC racing cams...they are all exhaust biased. I personally chose a single pattern cam for various reasons, but knew that I was leaving power on the table. It's a fact, longer exhaust duration cams make more peak power...low and midrange suffer though.
TECH Senior Member
Joined: Nov 2001
Posts: 9,246
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From: Troy, AL
I think you should use a cam with at least 260 on the intake and 280 on the exhaust. Use a 102 LSA and advance it 10 degrees....that'll get you back below a 7000 shift point and will work GREAT with your 3.42 gears! Afterall, bigger IS better, right? Oh yeah, just a small side note...you'll need to idle it at 2500 RPM but hey, you can still call it streetable if you want. You'll be the envy of every dyno racer with this BIG 'ole whompin' bumpstick! 
JUST KIDDING!!!
LS1Tech.com...the land of 12 second BIG DYNO DADDY cams and 10 second baby cams...go figure.
JUST KIDDING!!!
LS1Tech.com...the land of 12 second BIG DYNO DADDY cams and 10 second baby cams...go figure.