Headers
06-12-2008, 03:00 PM
#2
4th Gear Member
Join Date: Oct 2005
Posts: 1,195
RE: Headers
They need to create a couple dedicatedthreads focused on sujects such as headers,tranny swaps, etc.
Headers, the biggest factor determining headers is your personal budget. Second is application and purpose. Headers can becheap or$600+, and I won't guess what customsrun. Application, long tube helps torque and hp on top end and are very good with high end motors that will see 6K rpm, tri-y's are good for low end torque, and better for stock performance motors. I haven't done a comparison with shorties, but I believe this would be better then the stock manifold where tight spaceis an issue. In my opinion, the three items that determine a good header, flange thickness, tube thickness, and coating. Remember, heat makes metal expand and contract, and the thicker the material, the less deformation you'll see. That's why good headers (thicker) rarely blow gaskets.
Which is best? it all depends on your application. For example, I have tri-y's on my 289, but if I was running a strong 347, i would seriously consider using long tube to help broaden the torgue band and get more hp on the top end. Maybe some of the mechanical experts can chime in here with the technical stuff.
Headers, the biggest factor determining headers is your personal budget. Second is application and purpose. Headers can becheap or$600+, and I won't guess what customsrun. Application, long tube helps torque and hp on top end and are very good with high end motors that will see 6K rpm, tri-y's are good for low end torque, and better for stock performance motors. I haven't done a comparison with shorties, but I believe this would be better then the stock manifold where tight spaceis an issue. In my opinion, the three items that determine a good header, flange thickness, tube thickness, and coating. Remember, heat makes metal expand and contract, and the thicker the material, the less deformation you'll see. That's why good headers (thicker) rarely blow gaskets.
Which is best? it all depends on your application. For example, I have tri-y's on my 289, but if I was running a strong 347, i would seriously consider using long tube to help broaden the torgue band and get more hp on the top end. Maybe some of the mechanical experts can chime in here with the technical stuff.
06-12-2008, 03:04 PM
#3
3rd Gear Member
Join Date: Dec 2006
Location:
Posts: 815
RE: Headers
Im no expert here.
It seems that everything I read points to long tube headers being the best for torque.
I have a mean lil 347 but run shorty's due to my front suspension time will tell but I may modify a pair of long tubes later on.
My old 289 ran great with the tri Y's.
It seems that everything I read points to long tube headers being the best for torque.
I have a mean lil 347 but run shorty's due to my front suspension time will tell but I may modify a pair of long tubes later on.
My old 289 ran great with the tri Y's.
06-12-2008, 05:04 PM
#4
6th Gear Member
Join Date: Aug 2007
Location: Elk Grove, CA
Posts: 5,896
RE: Headers
Long tubes flow better at higher rpm's, but they actually tend to hurt low-end torque because they reduce backpressureat lower rpm's (which relates to scavenging exhaust pulses; please don't try to claim any and all backpressure is bad). Tri-y's tend to make better low end and mid-range power, but won't flow as well at higher rpm's as long-tube headers. Shorties are much better than stock manifolds and are a great idea for space saving applications, but power tends to die off at higher rpm's where they don't flow well at all.
06-15-2008, 02:19 AM
#6
Yukon Cornelius
Join Date: Oct 2005
Location: deep in the heart of dixie GEORGIA
Posts: 11,808
RE: Headers
ORIGINAL: Starfury
Long tubes flow better at higher rpm's, but they actually tend to hurt low-end torque because they reduce backpressureat lower rpm's (which relates to scavenging exhaust pulses; please don't try to claim any and all backpressure is bad). Tri-y's tend to make better low end and mid-range power, but won't flow as well at higher rpm's as long-tube headers. Shorties are much better than stock manifolds and are a great idea for space saving applications, but power tends to die off at higher rpm's where they don't flow well at all.
Long tubes flow better at higher rpm's, but they actually tend to hurt low-end torque because they reduce backpressureat lower rpm's (which relates to scavenging exhaust pulses; please don't try to claim any and all backpressure is bad). Tri-y's tend to make better low end and mid-range power, but won't flow as well at higher rpm's as long-tube headers. Shorties are much better than stock manifolds and are a great idea for space saving applications, but power tends to die off at higher rpm's where they don't flow well at all.
+1
06-15-2008, 07:42 PM
#8
6th Gear Member
Join Date: Aug 2007
Location: Elk Grove, CA
Posts: 5,896
RE: Headers
Untrue, unless they're too small for the motor. Then they'll work great at the bottom of the rpm range and die off as the exhaust flow gets choked up.
Generally speaking, full length headers are designed to function at higher rpm's where performance motors are usually built to make power. At lower rpm's there isn't enough backpressure to get the exhaust pulses timed to pull exhaust gases out of the heads. As rpm's build, so does exhaust flow and backpressure. At a certain point you reach optimal backpressure where the exhaust pulses are timed perfectly, giving optimum performance. Shorties are designed more for low end (ie. normal street driving) power increases, which is part of why they're OE for fox bodies. Tri-Y's are optimized for low and mid-range power increases, but still don't flow quite as well above 4k as full-length headers do.
Of course, all of this changes as you change displacement. A set of Tri-Y's are great on a stock or mild 289/302, but probably won't flow enough to keep up with even a mild 347.
Basically, if you spend most of your time below 4k (as most people do), tri-y's and shorties are great. If you have a warmer engine and tend to take the engine past 4k a lot (ie. street/strip car), or if you have a stroker smallblock, long-tubes are the way to go.
Generally speaking, full length headers are designed to function at higher rpm's where performance motors are usually built to make power. At lower rpm's there isn't enough backpressure to get the exhaust pulses timed to pull exhaust gases out of the heads. As rpm's build, so does exhaust flow and backpressure. At a certain point you reach optimal backpressure where the exhaust pulses are timed perfectly, giving optimum performance. Shorties are designed more for low end (ie. normal street driving) power increases, which is part of why they're OE for fox bodies. Tri-Y's are optimized for low and mid-range power increases, but still don't flow quite as well above 4k as full-length headers do.
Of course, all of this changes as you change displacement. A set of Tri-Y's are great on a stock or mild 289/302, but probably won't flow enough to keep up with even a mild 347.
Basically, if you spend most of your time below 4k (as most people do), tri-y's and shorties are great. If you have a warmer engine and tend to take the engine past 4k a lot (ie. street/strip car), or if you have a stroker smallblock, long-tubes are the way to go.
06-15-2008, 09:47 PM
#9
5th Gear Member
Join Date: Sep 2006
Location: Australia
Posts: 2,266
RE: Headers
ORIGINAL: Starfury
Of course, all of this changes as you change displacement. A set of Tri-Y's are great on a stock or mild 289/302, but probably won't flow enough to keep up with even a mild 347.
Basically, if you spend most of your time below 4k (as most people do), tri-y's and shorties are great. If you have a warmer engine and tend to take the engine past 4k a lot (ie. street/strip car), or if you have a stroker smallblock, long-tubes are the way to go.
Of course, all of this changes as you change displacement. A set of Tri-Y's are great on a stock or mild 289/302, but probably won't flow enough to keep up with even a mild 347.
Basically, if you spend most of your time below 4k (as most people do), tri-y's and shorties are great. If you have a warmer engine and tend to take the engine past 4k a lot (ie. street/strip car), or if you have a stroker smallblock, long-tubes are the way to go.
. I have tri-ys on a GM race engine thats 355 cubes and around 520hp at the flywheel. I also have them on my 408 which (if ever finally sorted) should be closer to 600. Both cars need to operate across a broader rev range (3000 - 7000) unlike a drag car where you are up the top of the range all the time. The trick for non-stock engines is to make the tri-ys bigger at the primaries. For example, the exhaust port on a stock or mild windsor head is about 1 5/8" diagonally across. Most tri-ys and longtubes are sized accordingly.AFR 225s are 1 7/8" and almost square so you need a bigger primary pipe regardless of header style.
There's one other advantage of tri-ys and thats ground clearance. You dont have that 4 into 1 collector hanging down low under the car. thats my $0.02
06-15-2008, 10:18 PM
#10
6th Gear Member
Join Date: Aug 2007
Location: Elk Grove, CA
Posts: 5,896
RE: Headers
Well, I tried to keep it simple
There's a huge difference between a set of cheap import tri-y's (which are great for a stock or mild 289/302) and a set of large-primary Doug Thorley tri-y's designed for a performance motor. Tri-y'sare a great design when applied to the engine type they're designed for and will produce power over a broader rpm range, but at high rpm's (like you said, drag racing applications)it's hard to beat long-tubes.
There's a huge difference between a set of cheap import tri-y's (which are great for a stock or mild 289/302) and a set of large-primary Doug Thorley tri-y's designed for a performance motor. Tri-y'sare a great design when applied to the engine type they're designed for and will produce power over a broader rpm range, but at high rpm's (like you said, drag racing applications)it's hard to beat long-tubes.