1 3/4-1 7/8 stepped vs. 1 7/8
10-18-2010, 02:48 AM
#22
Very curious about this also.Would like to know more.Mr. Tooley can you give us anymore insight to this?I need to pick something out for my setup and have been wondering what would work best with my new heads (stage 3 AFR's on a 402)With a 200 shot,and six speed
10-18-2010, 10:13 AM
#24
I can't see there being enough of a difference between the 1 3/4" and 1 7/8" to necessitate a stepped setup. The "stepped header is supposed to make the torque of 1 3/4 with the topend power of 1 7/8" isn't really true because the 1 3/4" doesn't make any more torque than the 1 7/8 at any point.
Also, going small to big slows exhaust velocity, so to increase scavenging (at least based on what I've read), you'd actually want a 1 7/8" header that steps down to 1 3/4" - that way, the velocity increases in the smaller pipe diameter, causing better evacuation in the larger diameter pipe. I can see how having the smaller diameter at the exhaust port would increase velocity there, but you're still going to lose velocity, and thus create turbulence, when you bump up to the bigger pipe diameter.
It'd be interesting to see this kicked to advanced tech to see what the smart guys think.
Also, going small to big slows exhaust velocity, so to increase scavenging (at least based on what I've read), you'd actually want a 1 7/8" header that steps down to 1 3/4" - that way, the velocity increases in the smaller pipe diameter, causing better evacuation in the larger diameter pipe. I can see how having the smaller diameter at the exhaust port would increase velocity there, but you're still going to lose velocity, and thus create turbulence, when you bump up to the bigger pipe diameter.
It'd be interesting to see this kicked to advanced tech to see what the smart guys think.
10-18-2010, 08:57 PM
#25
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i read this out of this book i bought dyno-proven gm ls1 thru ls7 performance parts by richard holdener
test engine was a ls2 on a engine dyno with open headers. quote in this case replacing the 1 3/4 hooker competition headers with custom step headers resulted in a sizeable power gain past 4500. The custom step headers were worth as much as 13 hp over the smaller hooker on this ls2 appplication . The step headers improved the torque above 4500 rpm but lost 6 to 8 ft-lbs down below 3500 rpm. the custom steps were 1(3/4) stepped to 1(7/8). the test engine was a stock gmpp ls2 crate engine equipped with a fast 90/90
test engine was a ls2 on a engine dyno with open headers. quote in this case replacing the 1 3/4 hooker competition headers with custom step headers resulted in a sizeable power gain past 4500. The custom step headers were worth as much as 13 hp over the smaller hooker on this ls2 appplication . The step headers improved the torque above 4500 rpm but lost 6 to 8 ft-lbs down below 3500 rpm. the custom steps were 1(3/4) stepped to 1(7/8). the test engine was a stock gmpp ls2 crate engine equipped with a fast 90/90
10-18-2010, 09:52 PM
#26
if you are already running a 1 3/4 header then there is no point at wasting money for 1 7/8 header. But if you do not have any headers and are in the market to buy some, i would go with 1 7/8. TSP sells 1 7/8 priced around 5-600 bucks i think.
10-18-2010, 11:23 PM
#27
The custom step headers were worth as much as 13 hp over the smaller hooker on this ls2 appplication . The step headers improved the torque above 4500 rpm but lost 6 to 8 ft-lbs down below 3500 rpm. the custom steps were 1(3/4) stepped to 1(7/8). the test engine was a stock gmpp ls2 crate engine equipped with a fast 90/90
10-18-2010, 11:34 PM
#28
i read this out of this book i bought dyno-proven gm ls1 thru ls7 performance parts by richard holdener
test engine was a ls2 on a engine dyno with open headers. quote in this case replacing the 1 3/4 hooker competition headers with custom step headers resulted in a sizeable power gain past 4500. The custom step headers were worth as much as 13 hp over the smaller hooker on this ls2 appplication . The step headers improved the torque above 4500 rpm but lost 6 to 8 ft-lbs down below 3500 rpm. the custom steps were 1(3/4) stepped to 1(7/8). the test engine was a stock gmpp ls2 crate engine equipped with a fast 90/90
test engine was a ls2 on a engine dyno with open headers. quote in this case replacing the 1 3/4 hooker competition headers with custom step headers resulted in a sizeable power gain past 4500. The custom step headers were worth as much as 13 hp over the smaller hooker on this ls2 appplication . The step headers improved the torque above 4500 rpm but lost 6 to 8 ft-lbs down below 3500 rpm. the custom steps were 1(3/4) stepped to 1(7/8). the test engine was a stock gmpp ls2 crate engine equipped with a fast 90/90
10-19-2010, 01:14 PM
#29
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10-22-2010, 07:06 PM
#37
A typical header has a single diameter primary the full length.
