Header primary sizing and questions....
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Header primary sizing and questions.... Ok, I am building my car, will be strip street duty. I have rod ended suspension and other stuff most dont consider "daily driver" friendly.
Engine, 347ci, 11.5:1 ETP 11* 225 heads, 231/242 .637/.622 114* cam and a bunch of other stuff. I am running a Rossler TH350 with T Brake and 4000 stall, will be swapping rearends sometime in the near future. I ordered a Corsa CB but stuck on the headers. 1 3/4" or 1 7/8", or a stepped variety. I did have Jet Hot LTs and TDs but sick of the always loudness. I'd love QTP's 1 7/8" but dont thing that I can get a set anytime soon, so since I have time, figure I'd post up and see what the concensus is with the draggers. Thanks guys.
Charlie
*EDITED* Forgot to mention the little fact that I will be spraying this with a little 250-300 shot occasionally, and most likely a 150-200 frequently! Edited this part 18 Nov
Engine, 347ci, 11.5:1 ETP 11* 225 heads, 231/242 .637/.622 114* cam and a bunch of other stuff. I am running a Rossler TH350 with T Brake and 4000 stall, will be swapping rearends sometime in the near future. I ordered a Corsa CB but stuck on the headers. 1 3/4" or 1 7/8", or a stepped variety. I did have Jet Hot LTs and TDs but sick of the always loudness. I'd love QTP's 1 7/8" but dont thing that I can get a set anytime soon, so since I have time, figure I'd post up and see what the concensus is with the draggers. Thanks guys.
Charlie
*EDITED* Forgot to mention the little fact that I will be spraying this with a little 250-300 shot occasionally, and most likely a 150-200 frequently! Edited this part 18 Nov
Last edited by CAT3; Nov 18, 2005 at 12:13 PM.
if you're spinning below 6500 stay with 1 3/4 from my experience. I didn't gain anything untill then with my 408. a different application than yours, but that is my advice.
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Got a deal in the works, but leaning towards the 1 3/4 with merge type collectors. I shouldnt be going past 6500 that much. I only spin the stock bottom to 6900 or so now with the smaller TSP 231/237 cam. Hoping the new engine wont need to go as high, the power is supposed to be up to 6500, so that might help.
Just as 383ss said you probably wont pick up any power until high rpm, you want to keep the entire power curve good for dragracing not just high rpm. The better alternative is to go with Kooks stepped headers, I have 1 3/4 to 1 7/8 stepped Kooks on my Vortech 382ci, you keep the low end power and gain a little up top also. 
1-3/4" Should be fine for your application if on stock cubes and not going to spin past 7 grand. Your cam already has a big amount of exhaust bias (for your n2o setup) so I wouldn't even worry about stepped headers.
Nate
Nate
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Glad I posted this. Gives me a little better feeling with the pending order, just gotta wait for Barry to get into work and check his email 
I knew that larger primaries kill off some low tq and add top hp, but didnt realize the rpm related vs cubes issue. Thanks.
Charlie
I knew that larger primaries kill off some low tq and add top hp, but didnt realize the rpm related vs cubes issue. Thanks.Charlie
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Originally Posted by SUX2BU
my friend was cam only and gained 10 rwhp over 1 3/4 pacesetters. i'll be getting some 1 7/8" x 3.5" kooks for my bolt on car soon.
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Originally Posted by 383ss
thats a mistake IMO, especially for just a bolt on car. the 1 3/4 will make way more TQ down low and you won't gain much if any up top.
ffff i totally agree with 383ss in my experience i had the same results and i learned the hard way when i bought a set of kooks and picked up nothing, good for nitrous though there is no need for a 1-7/8 header on o 347 unless you are spraying
Last edited by soldeir; Nov 18, 2005 at 10:24 AM. Reason: fffff
A smaller and longer primary will, on most occasions run quicker than a short big tubed header. Like some have said, the 1 7/8" might make the peak number look real nice but under the curve is way more important for quick ET's.
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I think everyone is badly underestimating the exhaust needs of a big squirt of nitrous! It depends on how often you're going to use the 300 HP setting, and whether you want the car at its best on or off the juice, but remember: With 300 HP worth of N20, you're passing an additional 50% or so of exhaust, equivalent to a 540 c.i. all-motor! If it were me, I'd be choosing between an off-the-shelf 1 -7/8" and a custom 2" to 2 -1/8" system.
The 11 degree longer exhaust duration is good for nitrous, but you should install the cam with at least 6 degrees advance, to get the exhaust valve open early enough to blow down all that extra exhaust. The advance will make the cam act a little milder off the juice, but will pay dividends when spraying. According to David Vizard, with the advanced indexing and longer exhaust duration, a "200 shot" system will deliver closer to 300 HP, due to reduced exhaust pumping losses, with no additional stress on the motor.
The 11 degree longer exhaust duration is good for nitrous, but you should install the cam with at least 6 degrees advance, to get the exhaust valve open early enough to blow down all that extra exhaust. The advance will make the cam act a little milder off the juice, but will pay dividends when spraying. According to David Vizard, with the advanced indexing and longer exhaust duration, a "200 shot" system will deliver closer to 300 HP, due to reduced exhaust pumping losses, with no additional stress on the motor.
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From: Sierra Vista, AZ
Originally Posted by MadBill
I think everyone is badly underestimating the exhaust needs of a big squirt of nitrous! It depends on how often you're going to use the 300 HP setting, and whether you want the car at its best on or off the juice, but remember: With 300 HP worth of N20, you're passing an additional 50% or so of exhaust, equivalent to a 540 c.i. all-motor! If it were me, I'd be choosing between an off-the-shelf 1 -7/8" and a custom 2" to 2 -1/8" system.
The 11 degree longer exhaust duration is good for nitrous, but you should install the cam with at least 6 degrees advance, to get the exhaust valve open early enough to blow down all that extra exhaust. The advance will make the cam act a little milder off the juice, but will pay dividends when spraying. According to David Vizard, with the advanced indexing and longer exhaust duration, a "200 shot" system will deliver closer to 300 HP, due to reduced exhaust pumping losses, with no additional stress on the motor.
The 11 degree longer exhaust duration is good for nitrous, but you should install the cam with at least 6 degrees advance, to get the exhaust valve open early enough to blow down all that extra exhaust. The advance will make the cam act a little milder off the juice, but will pay dividends when spraying. According to David Vizard, with the advanced indexing and longer exhaust duration, a "200 shot" system will deliver closer to 300 HP, due to reduced exhaust pumping losses, with no additional stress on the motor.
I like the sounds of that. Even more so since Ed Curtis ground the cam, for my application, and included weight, cubes, nitrous etc, although I dont have all the specs, I know he said it will F&cking Rock on the sauce, cant wait to find out.
Who makes 2" primaries? Curious of course. Off the bottle, not to worried about, the rest of the car will take care of itself. What I dont want is backed up exhaust pressure killing off power on the bottle. I bet if 1 7/8" are this tight, the 2" will be a cramp plus!
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" <Quote: Who makes 2" primaries? Curious of course. Off the bottle, not to worried about, the rest of the car will take care of itself. What I dont want is backed up exhaust pressure killing off power on the bottle. I bet if 1 7/8" are this tight, the 2" will be a cramp plus!" >
That's a good enough question to launch a new thread!
I'm working on the specs for a killer 433 c.i. road race Corvette, and it looks like it needs as much as 2 -1/8" primaries (depending on how much power the owner decides upon)
That's a good enough question to launch a new thread!
I'm working on the specs for a killer 433 c.i. road race Corvette, and it looks like it needs as much as 2 -1/8" primaries (depending on how much power the owner decides upon)
