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View Full Version : Header weld pics before/after


JOEX
12-19-2002, 06:53 PM
Here are some pics of what I did. Any input appreciated:)
1.

http://mypeoplepc.com/members/joe340/sitebuildercontent/sitebuilderpictures/0004.jpg
JOEX
12-19-2002, 06:54 PM
2.
http://mypeoplepc.com/members/joe340/sitebuildercontent/sitebuilderpictures/0006.jpg
JOEX
12-19-2002, 06:55 PM
3.
http://mypeoplepc.com/members/joe340/sitebuildercontent/sitebuilderpictures/0007.jpg
JOEX
12-19-2002, 06:56 PM
This one didn't turn out as well as I had hoped...
4.
http://mypeoplepc.com/members/joe340/sitebuildercontent/sitebuilderpictures/0009.jpg
JOEX
12-19-2002, 06:57 PM
Last one...
5.
http://mypeoplepc.com/members/joe340/sitebuildercontent/sitebuilderpictures/0011.jpg
toby400ex
12-19-2002, 07:07 PM
wow, those things are dirty:eek:
JOEX
12-19-2002, 07:19 PM
Carbon from inside got onto my fingers and I handled the headers afterwards. Thanks for your input.

Joe
12-19-2002, 09:42 PM
You need to remove some more material from the top and sides especially.
JOEX
12-19-2002, 09:53 PM
Can you explain futher? How/why does that make it better?

Joe

edit: I don't want to lose structural integrity.
Deathbringer
12-20-2002, 08:28 AM
So what is the difference, am I missing something? :huh
Extremeracer167
12-20-2002, 09:16 AM
You wont lost any strength. What this does is just allows it to flow better. What uwant is to just ahve a nice gradual transition until it gets to its full size. U dont want any edges in there. Just a nice smooth flow. Once u get that, u will be set.
4punksdad
12-22-2002, 05:44 PM
looks good..........let us know if it makes a difference.
JOEX
12-22-2002, 05:51 PM
I had it out once...It felt a little snappier, but I also replaced and tightened:eek: the plug at the same time...Does it make a difference? Little if any noticable difference I think, but I need to ride more:)

Joe
Deathbringer
12-22-2002, 08:45 PM
Yeah let us know what happens with this project.
Moded86R
12-24-2002, 08:13 PM
I agree I would remove a little more.

Whenever I did this to my stock 300ex header I didn't remove very much at first.I also didn't notice any difference.So then I removed more and made it a nice transition.Like extremeracer said.Then I even had to rejet.It did make a difference.I was very happy with it.

I have the header pipe welds ground,350x airboot and rejetted carb.And it runs pretty dang good.I raced a 250x with a freshtop end fmf complete exhaust and cam.We ran pretty much dead even.I weighed a little less than him though.
JOEX
12-24-2002, 10:50 PM
The welds are ground down flush to the inside diameter of the actual haed pipe. I don't see where grinding them further would be better. Other than tapering the small lip near the opening.

Am I missing something?

Also, my understanding is the 300 has the 250 head and responds better to head/port mods than the 400. I could be wrong though.

Thanks for for all the input:)

Joe
Moded86R
12-24-2002, 11:00 PM
The little "Lip" there is what I was refering to.I took my 300's header off tonight.I am getting ready to cut it and make it similar to an FMF powerbomb.It will look bone stock.Hopefully run a little better than now though.THen I am going with a slip on.Not sure which one.Probably a t-4 or pro-meg though.

Anyway.After I think about more.Whenever the exhaust exits.That flange is acctually pretty much as big as the exhaust port is anyway.So enlarging it would create turbulence.And acctually counteract what we are trying to do.

If I am wrong please tell me.
JOEX
12-24-2002, 11:17 PM
Heck, I don't know what is right or wrong:p

I do know that "port matching" is very important for flow. That is theory I was working off of. Just trying to even everything out. This mod maybe "free" and relatively easy, i'm thinking that it should be left to the pros to be truely effective.:)

Air flow is a science that most of us don't fully understand and could very well but making worse by messing with it.

It would be nice to hear some input from professonal enigine builders on this subject:)

Joe
Moded86R
12-24-2002, 11:23 PM
Exactly.That thought didn't even cross my mind until that moment.I don't know to much about air flow.I do know that the smoother the transition the better.I will have to check this out a little bit.If you could get the port and the inside of the header to match.Essentially it couldn't get any better.Of course if it is tapered gradually it will have a little bit more low end torque due to more back pressure.

The Stock 300ex is tapered though.Just a little bit later down the header.
DEAL
12-25-2002, 09:37 AM
I did it to my bone stock 400ex and i lost a little low end, i could notice the diffrence.
0240099r1
12-25-2002, 09:44 AM
looks good.............
12-25-2002, 10:57 PM
Also, my understanding is the 300 has the 250 head and responds better to head/port mods than the 400. I could be wrong though. From what I understand the head on those are a bottleneck for air flow and when ported (correctly) the restriction is removed and results are good even on a basicly stock motor with intake and exh mods.