longer exhaust duration?
longer exhaust duration? My mods are in the sig I am wondering if I should get a cam with a longer exhaust duration since I have shorty headers which I already know don't scavenge the exhaust no where near as efficient as long tubes. I am not going to change the headers, but I am going to get the largest cam that is still streetable and use it with my stock heads. So do you think a longer exhaust duration would make more power with my restrictive shorties? I am looking at making the most power possible through shorties.
I don't need to beable to pass emissions I have an underground source for that. I want maximum power and still be streetable. I was thinking 231/237 range of cams or
even bigger. Will a longer exhaust duration help with my exhaust set up?
even bigger. Will a longer exhaust duration help with my exhaust set up?
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Jrp perhaps missed that you have 1.85 SLP rockers. So I would stay with a cam that is less that 0.550 lift.
Comp 216/220, 0.525/0.532 114 lsa would be good for you for around 370>380 rwhp with a pulley.
You could always addnitrous if more power is desired
Comp 216/220, 0.525/0.532 114 lsa would be good for you for around 370>380 rwhp with a pulley.
You could always addnitrous if more power is desired
I bought my shorties before my emmissions hook up and I don't want to spend the money to replace my whole exhaust it flows good enough for me
I have no cats and also a electric cutout when needed. I will not be using my SLP 1:85 rockers I will use my stock ones with this new cam. Back to my main question for the third time will a longer exhaust duration make more power with my exhaust set up?????????????????????????????????? its only one question. Also I am going with a much larger cam than the one you mention that is a puny cam I want 230 and greater durations with up to .625 lift I will be running 921 dual valve springs or the new patriot dual valve springs good to .650 lift.
I have no cats and also a electric cutout when needed. I will not be using my SLP 1:85 rockers I will use my stock ones with this new cam. Back to my main question for the third time will a longer exhaust duration make more power with my exhaust set up?????????????????????????????????? its only one question. Also I am going with a much larger cam than the one you mention that is a puny cam I want 230 and greater durations with up to .625 lift I will be running 921 dual valve springs or the new patriot dual valve springs good to .650 lift.
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Verdad Gallardo then why is thunder racings t rex cam making 455 rwhp with stock heads???????????????????????? these ls heads have never reached their limit to date. We run out of piston to valve clearance before we max out the heads now back to my question for the fourth time will increased exhaust duration make more power with my setup?
So your saying shorter exhaust duration will make more power so your saying go with a reverse split cam like 231/228? I thought those grinds were designed for really efficient exhaust systems and ported exhaust ports?
Last edited by 52172; May 2, 2004 at 04:04 PM.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
If what u say is true, why do "nitrous" friendly cams favor more exhaust?
Because there is a bigger charge to exit through the exhaust, therefore more exhaust valve opening time.
With unported exhaust port (Less cfm) and a more restrictive exhaust manifolds, exhaust valve need to close quicker. So a reverse split will do just that and be more efficient for max power.
Because there is a bigger charge to exit through the exhaust, therefore more exhaust valve opening time.
With unported exhaust port (Less cfm) and a more restrictive exhaust manifolds, exhaust valve need to close quicker. So a reverse split will do just that and be more efficient for max power.
Predator z are you sure about the reverse split because I have people telling me the opposite to lengthen to exhaust duration because of its ineficiency. I vote leave the exhaust valve open longer to let the gases out because of the lower cfm on the exhaust side. Your theory makes a little sense though you say close it earlier because the exhaust ports can't handle the added flow. Who is correct?
Originally Posted by PREDATOR-Z
With unported exhaust port (Less cfm) and a more restrictive exhaust manifolds, exhaust valve need to close quicker. So a reverse split will do just that and be more efficient for max power.
