That's what I did.
Long tube headers, which Primary size is 'best'?
- Thread starter Shaun@AED
- Start date
That's what I did.
Thank you both... I think I am just going to pull the trigger on the 1 7/8ths. My goal is ~ 500 whp on an N/A dd.
Who makes stepped?
Pypes makes a stepped longtube, starts off with 1 3/4 primary at the flange and goes to 1 7/8
Maybe Shaun will chime in with his thoughts on these headers.
Fittament wise, how are the Pypes headers?
I have never installed a set of pypes, have done ARH and JPC headers, so I can't personally speak for the fitment on the pypes. Though from what I have read some guys have to shim the drivers side motor mount with a washer or two to clear the steering shaft. I can already tell you Shaun prefers the Kooks Longtubes/Midlength design, especially if you plan to run E85. The upstream O2 bung position is the best of all the longtubes out there, should not have any issues burning up O2s on E85.
'Nuff said....
Below is a dyno graph of the difference between 1 &3/4 headers vs 1 &7/8th. Different cars, but same setup on the fuel with the same timing and fueling, the only difference is the Primary diameter (same brand headers).
The smaller diameter primaries made 30+ TQ more down low and did not restrict top end power.
The smaller diameter primaries made 30+ TQ more down low and did not restrict top end power.
Mine fit perfectly, but the x-pipe with the flex pieces constantly hit the ground, and the O2 position kills sensors. Had to relocate, and still am replacing them every 10 races or so. Will go with Kooks at some point. Spend the money now, wish I had.
Thanks, Shaun. That's a huge chunk of power down where you feel it in every day driving. For an NA Coyote, looks like 1-3/4 is where it's at.
Knock it off.
CPRsm
Active Member
Below is a dyno graph of the difference between 1 &3/4 headers vs 1 &7/8th. Different cars, but same setup on the fuel with the same timing and fueling, the only difference is the Primary diameter (same brand headers).
The smaller diameter primaries made 30+ TQ more down low and did not restrict top end power.
Makes sense. A smaller tube is easier to get to seal w a smaller exhaust pulse, and create vacuum behind it at a lower rpm. A larger tube will take more rpm and mass thru the tube before it creates that seal.
Thank you, Beefcake. Once I have a better idea of when I will be home to do the work, I will see about reaching out to you. Right now I'm pricing shopping AM, CJPony, Lethal, and Kooks for prices. I'm trying to do a CJ mani, cai (RevAuto or FRPP), TB, Headers, H-pipe, Over-Axle w/o Resonators (Lethals?), GT500s and MGW shifter. Figured that would make for a great stage 1&2 of my build.
Stages 3-5 would be CJ cams, 302R heads, OPG, Crankshaft gear/sprocket, and then suspension. :burnout:
Below is a dyno graph of the difference between 1 &3/4 headers vs 1 &7/8th. Different cars, but same setup on the fuel with the same timing and fueling, the only difference is the Primary diameter (same brand headers).
The smaller diameter primaries made 30+ TQ more down low and did not restrict top end power.
Shaun@AED.... So, 1 3/4' would give a better torque in the lower RPM range. With my build above, would this would be the more optimal set for a DD, with limited drag/track time (3-4 times a year max)?
With big cams you will lose so much power under 4000 - 5500 (depending on the cams and how you install them) I'd imagine you'd want to keep as much low end power as possible.
Since the smaller 1 &3/4 are NOT a restriction in these all motor applications, my answer should be obvious.
Actually I am curious how the 1&5/8th Kooks would perform compared to the 3/4 and 7/8th now....
Didn't have ANY issues with the pypes headers hitting or rubbing on anything.
Thank you, Shaun@AED. I appreciate the info here and on all the other forums I've seen your name. This is my first time going deeper than the intake manifold and full exhaust.
This new still has a lot to learn!
Yes, absolutely.
The negative pressure pulse of the exhaust gasses should be at the exhaust valve when it is open on the next combustion cycle during the overlap phase in order to pull more exhaust thru the chamber and increase power output. The Length of the primaries determines the RPM at which this 'boost' in airflow thru the chamber will occur. The shorter the primary, the higher in the RPM band at which this will occur, the longer the primary the lower in the RPM band.
We've found via testing that the Kooks midlength headers have a boost in power around 6700-6800RPM. Longer primaries like ARH, Pypes, SW, and others give power boosts at much lower RPM's. With Cam timing changes we can move this RPM to some degree, but not much. Primary diameter can affect this as well if the gases slow down significantly due to the larger tube they have to fill. Slower exhaust gasses = lower RPM at which the negative pressure at the valve will occur, and it could also negate much of the effect of the negative pressure if the gasses slow down too much to fill the primary. IE, you CAN go 'too big' and hurt performance.
Basically the Shorty headers available are a bit too short for boosting power in the usable RPM range of these engines, and the long tube headers are so long they give benefits to mid range torque. The Kooks seem to be the best fit overall, although they are not perfect IMO.
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