Is it necessary to dremel the welds inside the header and reweld it on the outside?
Does it make a differance?

Thanx

 

Korean headers?

 

Damn typo! Can a moderator change that to "JDM" please.

 

changed

 

Thank you

Now about that porting....

 

don't understand your question.... what do you mean by "necessary"...


D

 

Well I guess it isnt "necessary"..the header will bolt on regardless...

But does it help out alot to port it out vs non-porting?

 

of course it helps.

D

 

I'm interested in this to, does anyone have any test/dyno results or flow tests to share???

Sam

 

i have dyno of ported JDM, with removed anti-reversion chamber, and coating. with a 2.5" carsounds cat, and a hack job of the connection to the b-pipe. problem is, i don't have good before-hand numbers... and i didn't bother to get a dyno run prior to porting the header. and, it's on a mustang dyno, so everything looks about 15% lower. check my site, there's pics of the before and after process with the header.

D

 

Thanks D, yours sites really good

I presume the anti-reversion chamber is in the collector where 4 goes into 1, does this mean you remove the inside layer of the collector and make it a true 2.5" all the way to the cat???

Sam

 

it's not completely 2.5"... i forget the exact dimension.... but yeah, remove the inner pipe wall, it's still necked down further back (upstream) in the collector to i believe <60mm. talk to SMS if you're interested, he'll have more details... but yeah, on the site, there should be before and after pics of the collector. and yeah, my dyno sheet should be in the directory, but it's pretty useless for comparison, i'm too lazy to find the link (on super slowzor connection).

D

 

Nice pics! The USDM header is different compared to a Eurospec one. Interesting..... The A-pipe is the same though.....

 

you're is an actual mild/SS steel 4-2-1 correct? not a cast piece like the USDM.... i've never seen pics... got any?

D

 

I ported mine out by just flattening the welds, not removing them . So we did not weld the exterior pipes. It worked pretty well, much nicer that the stock welds, and we still kept the structural integrity by leaving material and smoothening the humps. I have been told that you can get a 4whp gain by porting the primaries and re-doing the collector. Some guys have reported up to 7whp gains, but that sounds kind of optimistic to me. good luck.

Joey

 

not sure i follow your logic there....

 

If you "flatten" out the welds to the level of the primaries you may be able to get away without laying down another bead around the primaries/flange to reinforce it since it's minimal material you're removing....It's fairly effective since the gas is only going to be able to "see" the primaries after it gets past the header gasket. Although it is still my recommendation to weld up the primaries before porting it out--make sure you have that sucker bolted up/clamped the f down to an appropriate torque block so the flange doesn't warp during cooling.. The biggest fear of porting out the header is getting too aggro and actaully cutting into the primaries, this effectively thins out the wall thickness and results in a stress riser... (If you want to take it to the umpteenth level, additionally smoothing out the welds so there is a radius or transition from the flange to weld would just be candy).

Oh, and if you don't have a die grinder and a carbide tip, and you're gonna get wicked with the Dremel tool, at least go out and buy a carbide bit...unless you like to just sit there and grind and grind and grind away...

-Geo

 

minimal... hrm, i'm gonna have to disagree with that, those welds are pretty big... relative terms i guess..

agree with that 100%

heh, the grinding away with the dremel does languish on a bit... 60grit sanding wheels work aight tho...

D

 

D,

I was looking at your S&M Racing site and I really like the port work on the flange/primary area. I'm about to take delivery of a new JDM 4-1 header like yours (minus the porting, welding, & coating of course), and I'd like to perform similar mods to mine. I'm pretty clear on what you did to the primary/flange welds, but what work did you do to the collector area? Thanks in advance.

 

removed anti-reversion chamber

 

Is there an easy way to do it? Or is it really as hard as it looks?