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Discussion Starter #1
My first '04 had 1-3/4 Dynatech LT's, my '06 had Kooks 1-3/4 both fit well. This time around I decided to roll the dice and tried to save a few hundred dollars with JBA LT's. I never could get clearance on the steering shaft, not even with new poly mounts.

I pulled the JBA's, returned them and ordered a set of Kooks 1-7/8. The Kooks have plenty of clearance on the steering shaft, but are hard against the transmission cooler lines. Anyone else have this issue?

I know the 1-7/8 will obviously be a tighter fit than 1-3/4, but the trans line wants to go through the centerline of the primary tube. I guess I'm going with -AN hose on the trans cooler.
 

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Discussion Starter #3
I tried bending them, but the area is so tight that I didn't have much success and I wasn't pulling the DS header back out. I had planned on running -6 AN lines at some point anyway to put an aftermarket cooler in line with the radiator.
 

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Got the trans lines taken care of and pulled the mids out of the box to install them. They are missing the hanger brackets.:mad:
502093
 

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Discussion Starter #7 (Edited)
Lol. :rolleyes: 2004 mids have hanger brackets. See the difference?
502122
 

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What is the point of larger tubing when it’s reduced at flanges?
I'm not sure, my cat-back is 2.5" so it had to reduce somewhere.
 

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What is the point of larger tubing when it’s reduced at flanges?
it is a bit dumb, but the reduction may or may not be a significant restriction. the farther you get away from the engine, the less the exhaust sizing matters. stuff cools and slows down on the way out... at least the neck down on the kooks isn't as abrupt as i've seen.
 

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it is a bit dumb, but the reduction may or may not be a significant restriction. the farther you get away from the engine, the less the exhaust sizing matters. stuff cools and slows down on the way out... at least the neck down on the kooks isn't as abrupt as i've seen.
^^^Exactly. On my Kooks cats, they are three inches all the way through, even the flanges are three inches. They just bolt right up to a 2.5 inch opening in the catback. Doesn't seem to cause any restriction or problems.
 

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^^^Exactly. On my Kooks cats, they are three inches all the way through, even the flanges are three inches. They just bolt right up to a 2.5 inch opening in the catback. Doesn't seem to cause any restriction or problems.
How do you know? Tested on dyno 2.5” vs 3” cat back?
Maybe it’s just fine. Depending on hp level. But if hp level calls for tubing larger than 2.5” (over 500-550 crank hp), it may be restrictive.
If hp level is under 550 crank hp, installing 3” midds may be rubbing you of hp and tq.
Reducing tubing diameter anywhere after headers collectors is probably counterproductive.
There is also turbulence at transition point that effectively reduces exhaust flow even further.
Exhaust science is complicated but there are some general rules. If anything, it should be progressively larger tubing towards the end, not smaller. It has to do with reducing back pressure and diffusing the gases at exhaust exit.
Check out exhaust systems on race cars. No bottlenecks and abrupt transactions there. In some cases, megaphones at the exit.
Smaller diameter tubing is always used upstream, close to the heads, for scavenging effect. Scavenging effect is happening in headers. More downstream you go, less scavenging effect is possible. All this is just theoretical. Only testing can give you real answer. I am just being skeptical based on basics.
 

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i think it is pretty verified that 3" mids on most 5.7/6.0 LS combos with long tubes is better than 2.5" mids.

you have to consider it is acting as part of the header collector, and not just exhaust piping...

but it's just theory, ultimately. you can be our own richard holdender and dyno every combo yourself, and post the results, if you want. (y)
 

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i think it is pretty verified that 3" mids on most 5.7/6.0 LS combos with long tubes is better than 2.5" mids.

you have to consider it is acting as part of the header collector, and not just exhaust piping...

but it's just theory, ultimately. you can be our own richard holdender and dyno every combo yourself, and post the results, if you want. (y)
I think you are not too far from the truth here. Maybe just little too broad. It would have to depend on LT tube sizing and collector configuration too. It is all about matching all the components of the complete system. In OP's case, I would agree that 3" mids are way to go with 1-7/8" headers, heads and cam. I am just skeptical about 2.5" cat back. May be slight mismatch there. That's all.
Let Richard be Richard; he said banana in the exhaust doesn't help ;)
 
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