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Discussion Starter · #1 ·
I am installing the FCS/BB. Before I go grinding anything down, I want to be clear on a few things....

1. Where did this instruction come from?
2. What exactly is it talking about?.....pictures would be cool if anyone has them.
3. Is this a requirement or an option?

Big Bore KIT porting only done on exhaust port;

with stock crank:

widen to 31 mm

raise roof 2mm

=============

with SFC

exhaust port :

widen to 31 mm

raise roof 4mm

lower floor 1mm

==

warning :dont try to match exhaust chanell with port size or channel can bust open (holed) , so you can tapper cut only
Thanks.
 

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Instructions came from Tyler @ adrenalin-racing....
as to what they mean? i dunno, id just pay the 15 bucks and let them do the porting for me.
 

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Discussion Starter · #3 ·
I know it came on a printed paper with the parts from Tyler, but is he the original source of it or is IP2 or someone else? I don't want to go porting things that shouldn't be and were just from a random post from someone who doesn't really know.

Also, which exhaust port is this refering to? On the case or on the head? I measured the port on the BB head and 31mm extends all the way to the bolt holes.
 

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The instructions were written by IP2.

Note - The BB kit I received already had exhaust port work and piston indexing done to it. I have not yet measured it. Waiting for it to come back from SME Racing. I found that some kits came this way and others did not. It was the luck of the draw when ordering the BB kit. The indexed piston won't work with the stroker crank without modifying the top of the transfer ports. :(
 

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Discussion Starter · #5 · (Edited)
Transfer ports being the 2 slots on the side of the barrel? Sory don't know all the terms yet.

My BB says "Not Ported" in white crayon on the top.

My BB piston looks like this.

http://www.socomzone.com/cag/bb_piston.jpg

Indexing would have flat areas right? Mine is a complete dome.

This is how much porting would take off on the outside of the head exhaust port according to the instructions with FCS/BB.

http://www.socomzone.com/cag/bb_head.jpg

I'm guessing that the porting is supposed to be on the inside to match the stroke of the piston, because outside it would nearly hit the bolt holes. Really uncertain though and I am not sure how you would do that accurately. I know it says tapered but not sure where and in which direction.

:confused:
 

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Yes, the transfer ports are the 2 channels/slots cut into the sides of the cylinder.

Yes, the piston would have small flat cuts at the top on the sides near the rings.

As for the porting instructions I find them kind of confusing. He says not to match the exhaust channel with the port size. I take this to mean that the inside port width (where piston is) should be 31mm but the outside port width where the exhaust pipe sits cannot be 31mm. He also says to raise the roof by 4mm and lower floor by 1mm which I read as raise the exhaust port where the piston is by 4mm and lower it by 1mm. So...as far as I can tell the inside port width and height would be larger than the outside port width and height where the exhaust pipe is which would be strange unless there is casting imperfections. Or I could have it all backwards.


As for my pictures you can see the piston indexing that was done. On the cylinder picture you can barely see the widening they did on the inside of the exhaust port.
 

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Discussion Starter · #7 · (Edited)
That makes sense. It looks like the problem with the indexing and the FCS would be that it would extend a gap in the piston and transfer port because of the longer stroke.

What I don't get now is how the heck you are supposed to accurately taper the inside of the port. I can't fit a caliper in there to measure and am not sure if a file would fit. I guess you can use the end of the caliper for the "roof" and "floor" from the top. Still will be hard to get it exact.

Speaking of the "roof" and the "floor", which is which? I was thinking "roof" being near spark plug and "floor" being the large opening, but I'm not sure. From your picture I would think this is right because if you can't use the indexed piston with the FCS, that should be showing a 2mm roof x 31mm width porting.

The 31mm width porting would also have to be very steep because the cylinder wall is not very thick.
 

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Discussion Starter · #8 ·
Initial Calculations

Just keeping some notes here...

--------------------------------
BB (non-ported) exhaust port
--------------------------------
inner dimensions = 11mm x 24mm*
outer dimensions = 16mm x 25mm
--------------------------------
updated inner dimensions (BB only)
= +2mm roof, +3.5mm right, +3.5mm left
= 13mm x 31mm

updated inner (BB+FCS)
= +4mm roof, +1mm floor, +3.5mm right, +3.5mm left
= 16mm x 31mm
--------------------------------

*Took the inner dimensions by making an imprint with a post-it.
 

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Am I mistaken or wasn't there a picture of the inside of the cylinder with the port work done to it on here?
 

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DarkSide said:
anyone do their own porting yet?
Yes I did.

Matched the ouside of the exhaust to the pipe.
Inside of port I.........
Widened it to 31mm
Raised it 4mm
Lowered it to match top of piston.

Widened the case 2mm to match ported barrel.
 

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Discussion Starter · #12 ·
WFO what did you use to port it and how did you know what measurements you took off? It's a pretty small barrel so I want to be careful on it.
 

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What did u use to messure the opening a standard ruller?
 
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