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Old 11-12-2008, 09:31 PM   #1
williaty
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Default When Is It Worth Porting/Polishing/Gasket Matching An Exhaust?

My OBX EL headers showed up tonight. They're probably the crappiest made car part I've ever bought. One of the biggest problems is that none of the actual tubes mates cleanly to any of the flanges. The worst offenders are the primaries where they mate to the dual-port engine block flanges. They're offset and the pipes are considerably bigger than the holes in the flanges. Placing a Subaru gasket on the flange shows that the holes in the OBX flange are WAY smaller than the holes in the gasket.

Is it worth dremeling out the holes in the flanges to make a smooth transition to the pipe? Won't this just leave a sharp transition from the block to the flange? Is it worth cleaning up the edges between the header and the intermediate pipe and the intermediate pipe and the midpipe?
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Last edited by williaty; 11-12-2008 at 09:38 PM.
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Old 11-13-2008, 10:20 AM   #2
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i havent recieved mine yet maybe in a few hours. tracking says its out for delivery.

arent these modeled after a much more expensive brand? i wonder if they have the same set up, and they flow better because of a venturi effect . does anyone have the" more expensive brand" and can confirm or deny.

maybe opening up the hole at the flange flange accually takes away from the flow? i dont know if we can answer this without testing . do you have a shop vac and a flow meter? you could make a seal on the shop vac with a good glob of vaseline .

in saying all that my gut feeling is to bore that bitch out! i have to wait until mine show up to really see how bad they are but when you say " worst car part ever" ohh man im getting so bummed .
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Old 11-13-2008, 12:23 PM   #3
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just got em!!!!! dude your funny. they look fast!
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Old 11-13-2008, 02:07 PM   #4
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just got em!!!!! dude your funny. they look fast!
They're real Monets though. They look all shiny and awesome for 5 feet away. Go look at them up close though. Run your fingers around inside the ports at the top, etc. You'll see what I mean.


Either that, or I got the worst set ever made.
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Old 11-13-2008, 02:45 PM   #5
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i see where your talking about at the block flange. do you know the i.d. of the exausht port on the block? i think if the port hole is smaller then there is no issue. if its the same size then there is no issue. because the flange will just act as an extension of the exausht port like a strait pipe.until it hits that lip . i dont think it would cause restriction because its not bigger up stream . until it hits the bend . and by that point it opens up.

if the port hole is bigger then looks like some boaring will be needed for us both. well not needed but wtf if im gonna do it should do it right.

the rest of the piping looks great and the rear flange looks solid . its obviously strait up bolt on cat delete for the < = 05.

its only that little piece thats where ill have it extended. cut the resonator off have the guy weld in the 2.25 hfc possibly a new boss is needed have to see what the guy says . and just have him extend it to the mid pipe with some 2.25 , it just seems easier to do all the mods on that piece. then have the guy make me a custom mid pipe with resonator(s)
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Old 11-13-2008, 02:51 PM   #6
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No, I'd love to know the ID of the port in the block. If you toss an OEM gasket onto the header, there's like 1/8" all the way around that needs ground off the flange. I don't know of any way to figure that out right now other than to drop the current header off the block and measure the block itself. The pisser of that is that doing so will cost me a set of gaskets, which isn't cheap.
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Old 11-13-2008, 02:51 PM   #7
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u think id be able to fit this resonator on the mid pipe. 4.5" x 6.75" x 14" Long Inlet/Outlet Size: 2.25"
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Old 11-13-2008, 02:52 PM   #8
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definitely. Probably even 2 of them.
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Old 11-13-2008, 02:53 PM   #9
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im thinking that one and then a smaller one after it
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Old 11-13-2008, 02:55 PM   #10
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doesnt anyone here work at a dealership? im sure there is a block laying around somewhere. any one work at a junk yard ect? or does anyone on here just have an ej25 block around?
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Old 11-13-2008, 08:11 PM   #11
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You two need to get a room. Either that or find the PM button. ;p
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Old 11-13-2008, 08:39 PM   #12
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id grind the flange ID's to match the gasket. i mean, you are not going to hurt anything. The exhaust is going to tumble horribly going from a larger exhaust port to a small flange opening and then back to a larger volume primary. matching the flange to the gasket (or better yet, the primary if its not bigger than the gasket and then tapering it so at the engine side of the flange its gasket matched and then it smoothly tapers to match the primary ID) would at least eliminate one of those transitions. if i remember right, the exhaust gaskets are very close to the exhaust port ID's... just enough meat on the heads to let the gasket crush and end up very close to flush with the ID of the exhaust ports. Have a dremel handy when you pull your current headers and check it out. "modify as necessary" as we say in the aviation maintenance industry.
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Old 11-13-2008, 09:47 PM   #13
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I have a EJ253 block laying around.
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Old 11-13-2008, 10:07 PM   #14
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Default dude

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I have a EJ253 block laying around.
dude hook us up!!!!!!! you mind?
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Old 11-14-2008, 06:53 AM   #15
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When you unbolt your stock header, you'll see that the exhaust ports on the head are also smaller than the gasket. At least 1/16", maybe more......(I've been playing with singleport EJ22 stuff lately).

The OBX header has been around long enough that this new topic of the primary daimeters being small should have been questioned before. I'd bet a dollar that Pat Olson would've posted some sort of comparison if it looked like it was a design issue.

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Old 11-14-2008, 12:43 PM   #16
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http://www.rs25.com/forums/showthread.php?t=36449

1.5"

I'm not exactly sure how much you expect from a $300 header. The design is right for the car, but it's just quickly built.
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Old 11-14-2008, 01:09 PM   #17
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I have a stock BLOCK laying around, but not heads. What measurements do you need? And NA loves its' velocity, I'd say to port match your headers. Hell, I ground down some excess welds on my borla headers and it made things smoother.

And it shouldn't cost you new gaskets every time you drop the headers, you can reuse them. (yes i know the manual says you shouldn't) I haven't had any problems reusing head to header gaskets...at least a few times.
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Old 11-14-2008, 03:39 PM   #18
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They eventually wear out and start to leak, then they burn up. You're right though, I've re used them as well.

Jay
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Old 11-14-2008, 03:40 PM   #19
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I have a stock BLOCK laying around, but not heads. What measurements do you need? And NA loves its' velocity, I'd say to port match your headers. Hell, I ground down some excess welds on my borla headers and it made things smoother.

And it shouldn't cost you new gaskets every time you drop the headers, you can reuse them. (yes i know the manual says you shouldn't) I haven't had any problems reusing head to header gaskets...at least a few times.
if you dont mind can you confirm that its is 1.5''? the exhaust ports on the block.

after looking at these , i do think those lips might mess with the flow. i just hope that when i grind them down that the welds arent so thin that i make a hole and need them rewelded. i can see it coming.
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Old 11-14-2008, 03:44 PM   #20
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if you guys want something pretty to look at, get some TWE's Oh wait...you can buy 3 of the OBX's for that price

I know, I'm terrible

I would just try to grind off as many rough areas in the exhaust path as I can get to and throw them on the car TBH, as even in their "unoptimized" form theyve been shown to give some decent gains.
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Old 11-14-2008, 03:57 PM   #21
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if you guys want something pretty to look at, get some TWE's Oh wait...you can buy 3 of the OBX's for that price

I know, I'm terrible

I would just try to grind off as many rough areas in the exhaust path as I can get to and throw them on the car TBH, as even in their "unoptimized" form theyve been shown to give some decent gains.
you got ripped off if you bought twe's. $300 and a dremel and ill have function over form twe's .
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Old 11-14-2008, 04:00 PM   #22
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Default allthough

SuperStock 1.625" tubes, 2.25" Collector twes . mandrel bent piping though is sweet!!! maybe not such a rip off after all
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Old 11-14-2008, 04:26 PM   #23
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Quote:
Originally Posted by watchunglava View Post
SuperStock 1.625" tubes, 2.25" Collector twes . mandrel bent piping though is sweet!!! maybe not such a rip off after all
all those features are nice, but the bottomline with headers is always what kind of gains you'll be getting... 1-2hp over the obx's for 3x the price? hmmm

I've had TWE's before (bought used) they were a nice piece, but you're not going to be looking at it all too often once it's under the car
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Old 11-14-2008, 04:57 PM   #24
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all those features are nice, but the bottomline with headers is always what kind of gains you'll be getting... 1-2hp over the obx's for 3x the price?
I've seen dyno plots of the TWE high-flow 4-1 setup showing about twice the gain of the OBX. That's worth the money if you live in that income tax bracket.
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Old 11-14-2008, 05:42 PM   #25
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I've seen dyno plots of the TWE high-flow 4-1 setup showing about twice the gain of the OBX. That's worth the money if you live in that income tax bracket.
Really? was that car cammed? I've seen the OBX's on a relatively stock car gain about 10-15whp. I doubt the 4-1's by themselves gave me another 20-25whp...at least not when I had the car dyno'ed (unless I just suffered a 40% drivetrain loss )
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