Boring the FPP

[Speedfreak]

What would it take to open the stinger back to the original opening? And how big are you going to make the headpipe? #0 is the man when it comes to this stuff so if he says that a 49mm headpipe and a stock opening will work for most applications then I would say run it that way.

 

[waxhead]

Ok so its an old post
what is the result of boring the pipe out
less or more top end
im not talking the stinger i am talking the header pipe and the manifold
My one is only 43mm

 

[dbrutherford]

I had Group K do mine because they have a fixture so once the head pipe and manifold are bored, the holes are concentric. Anyway they bored the manifold out to 48 and the head pipe out to 47 mm. Decent job and cost me around 100 with shipping both ways.

 

[steveyz250fpilot]

I had Group K do mine because they have a fixture so once the head pipe and manifold are bored, the holes are concentric. Anyway they bored the manifold out to 48 and the head pipe out to 47 mm. Decent job and cost me around 100 with shipping both ways.

If they have something that makes it concentric, why did you bore the manifold to 48 and the headpipe to 47? That sounds like a real nice area to start a buildup of carbon. How did you check your holes? Did you bolt the pieces up with something between them, then take them apart and look at how they lined up?

 

[dbrutherford]

If they have something that makes it concentric, why did you bore the manifold to 48 and the headpipe to 47? That sounds like a real nice area to start a buildup of carbon.

You are right, maybe it was the other way around, I will have to measure them again. I might have it backwards. But then again, 0.5mm isn't that much of an edge. I just remember old Harry K telling me something about one was bored a hair more than the other...

 

[steveyz250fpilot]

You are right, maybe it was the other way around, I will have to measure them again. I might have it backwards. But then again, 0.5mm isn't that much of an edge. I just remember old Harry K telling me something about one was bored a hair more than the other...

He didn't elaborate as to why he bores one bigger? I bet it is the headpipe, and I bet he does it to make sure he doesn't have any material in the line of fire coming out of the manifold..cause his bores ain't concentric! :scared:

just fawkin' with you knucklenuzzats :Banane26:

 

[dbrutherford]

I will just use my dremel to adjust it a little.... haha:buttkick: :stups: :nana: :moon: :Banane26: :spankme: :slap: :spank: okey:

 

[feartheride]

While this thread is back I have a couple ?'s

I have a B pipe I bought a while back. Looks like the chamber and manifold were opened a bit. The manifold is scribed on the gasget face 1435j and the head pipe face 1453. The chamber seems to be 25 1/2 in length and has a id of 47.5mm with a sleeve installed and a diverter in the middle.

I am thinking this pipe came off an octane and may have had some cleaning up by chuck

This will be used on one of my 85 mm bore motors

 

[Mouthfulloflake]

all of the chambers I have seen have that diverter in them near the stinger.

also, ive got a "supposedly" stinger mod from supertune, and it looks a little different than that.

who knows though...

While this thread is back I have a couple ?'s

I have a B pipe I bought a while back. Looks like the chamber and manifold were opened a bit. The manifold is scribed on the gasget face 1435j and the head pipe face 1453. The chamber seems to be 25 1/2 in length and has a id of 47.5mm with a sleeve installed and a diverter in the middle.

I am thinking this pipe came off an octane and may have had some cleaning up by chuck

This will be used on one of my 85 mm bore motors

 

[feartheride]

i am thinking the chamber is the way it came from factory pipe but was for the octane ???

 

[Mouthfulloflake]

for sure thats possible, I have ZERO knowledge of octane parts.

 

[#ZERO]

Ok so its an old post
what is the result of boring the pipe out
less or more top end
im not talking the stinger i am talking the header pipe and the manifold
My one is only 43mm

Boring out the head pipe diameter increases the chamber volume, which effectively broadens the power range. Its diverging walls reduce flow resistance both in and out of the cylinder. The burnt gases flow out easily with a minimum of turbulence and any fuel mixture which has spilled into the exhaust is rammed back into the engine more efficiently. Also by increasing the head pipe diameter with a shallow taper allows the exhaust gases to expand more gently. The result is a decreased loss of kinetic pulse energy than if the gases were to expand rapidly and abruptly on passing from a straight header into the diffuser section of the expansion chamber.

 

[waxhead]

Thanks
I aware of what it does i am just wondering if people found a gain where
I am chasing rpm with my setup it hits hard down low but im looking for more overrev and i was hoping this mod may gve more overrev
Has one done just this only and then bolted it back on and noticed if they got more low more top or more everywhere

 

[feartheride]

While this thread is back I have a couple ?'s

I have a B pipe I bought a while back. Looks like the chamber and manifold were opened a bit. The manifold is scribed on the gasget face 1435j and the head pipe face 1453. The chamber seems to be 25 1/2 in length and has a id of 47.5mm with a sleeve installed and a diverter in the middle.

I am thinking this pipe came off an octane and may have had some cleaning up by chuck

This will be used on one of my 85 mm bore motors

guess I will call factory pipe,but they will just tell me if it was desighned for the octane not how will hurt the performance on my 85 flat top motor