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Discussion Starter #1 (Edited)
I really wasn't sure where to post this. Figured I would try this section. I've been building my little svt focus (don't laugh) for a while just as a fun car. Here is the setup.
2.0 dohc 4 cyl (almost identical to a mod motor 4v), 13:1 compression, 235/225 cams, sheet metal intake, direct port nitrous.

Car makes 170 wheel at 7500 rpm on motor.
270 on the 100 shot and lots more to go when I jet up.

Now my question. The factory header on these is VERY good. It's a 4-2-1 design with 1 3/4 primaries. Car has 2.5 inch exhaust on it. Now I plan on making it a full 3 inch. But my question is on the header design. Would I see more power going to a 4-1 header with a 3 inch merge collector? Is there software to help me design the header better? Should I go to 1 7/8 cause of the heavy nitrous? Stepped headet?


There is not much reliable info on these setups as the na route is seldom used. But I know you guys are WAY more knowledgeable than me.


Basically help me build a header lol that way i don't end up with a header that makes less power than stock
 

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Do a search on merge collectors.

A 4-2-1 is the way I would go.

I am just a crash test dummy, so keep that in mind.
 

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Throttle's Performance
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Basically help me build a header lol that way i don't end up with a header that makes less power than stock
buy Pipemax to start with.

build the header with the most gentle, swooping bends you can
don't build the header too big.
4-2-1 will destroy a 4-1 on that application.
buy your bends/merge collectors from SPD or Burns
quality of bend and quality of tube fit is important, spend a lot of time on tube fit.

ICE EngineWorks header mock-up kits can really help you fit the header to the car without having to do a lot of cut/weld trial and error.
 

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Discussion Starter #4
buy Pipemax to start with.

build the header with the most gentle, swooping bends you can
don't build the header too big.
4-2-1 will destroy a 4-1 on that application.
buy your bends/merge collectors from SPD or Burns
quality of bend and quality of tube fit is important, spend a lot of time on tube fit.

ICE EngineWorks header mock-up kits can really help you fit the header to the car without having to do a lot of cut/weld trial and error.
exactly what I was looking for...

so question.. since I already have a 1 3/4. 4-2-1,am I better off just changing the collector on my existing header to 3 inch over 2.5 and let it ride?
 

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Throttle's Performance
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exactly what I was looking for...

so question.. since I already have a 1 3/4. 4-2-1,am I better off just changing the collector on my existing header to 3 inch over 2.5 and let it ride?
There is more in tube fit, gentle bends, and the overall design of the header than a simple collector change will give you. The factory bend radius suck. The factory merges suck. There is a lot to it.

Go over to Speedtalk and search posts by "Exhausted". You have a lot of reading to do.
 

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Discussion Starter #6
There is more in tube fit, gentle bends, and the overall design of the header than a simple collector change will give you. The factory bend radius suck. The factory merges suck. There is a lot to it.

Go over to Speedtalk and search posts by "Exhausted". You have a lot of reading to do.


Thank you very much....:)
 
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