GT 250 expansion chamber

triplesmart · Post by **triplesmart** » Mon Jan 20, 2014 2:29 pm

Hello,

I want to build a pair of expansion chambers for my '78 GT250. Before I'm start welding, I want make a trial version of paper....so I'm searching for the flat patterns of the cones for printing. Is there anybody out there who is able to help me?

Regards

Dirk

titan performance · Post by **titan performance** » Mon Jan 20, 2014 3:45 pm

You may need to create your own beam compass if you don't have one, but the system is relatively simple. Turning the route of the pipe is not quite so simple....
http://craig-russell.co.uk/demos/cone_calculator/" onclick="window.open(this.href);return false;

tz375 · Post by **tz375** » Mon Jan 20, 2014 4:08 pm

Dirk, do you mean that you need someone to design the chambers for you or do you have a design but need someone to translate that design into templates?

triplesmart · Post by **triplesmart** » Mon Jan 20, 2014 5:58 pm

titan performance wrote:You may need to create your own beam compass if you don't have one, but the system is relatively simple. Turning the route of the pipe is not quite so simple....
http://craig-russell.co.uk/demos/cone_calculator/" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Thanks for the link. For turning the route, i think i'll use a M3 threaded rod with a couple of M3 Nuts and paper discs where the pipe diameter changes.

Dirk

triplesmart · Post by **triplesmart** » Mon Jan 20, 2014 6:08 pm

tz375 wrote:Dirk, do you mean that you need someone to design the chambers for you or do you have a design but need someone to translate that design into templates?

Mabe somebody built one in the past....and would be so nice to give me the flat patterns.
Otherwise....I found some exhaust calculations software for download....but most of them are unable to "unroll" the cones.....there is a laser cutting company nearby, but they need a .dsx file for cutting. And I have no clue to translate my cones into auto-cad files. Rolling the steel flat patterns and welding is no problem, I need help in designing. For expamle...how to design a angled/curved cone? Sorry, but it's my first trial to do this, hope for your understanding.
During 1984/85 I rode a GT 250...and this is my trip back to my teenager age...normally I ride 4-stroke british bikes.

Regards

Dirk

PS
I hope this is understandable...mabe I have to improve my english

Suzukidave · Post by **Suzukidave** » Mon Jan 20, 2014 6:21 pm

Here is something that will help http://www.conelayout.com/" onclick="window.open(this.href);return false;

sohospeedshop · Post by **sohospeedshop** » Mon Jun 22, 2015 5:34 pm

I just finishedy second pair...you still need help?

Suzukidave · Post by **Suzukidave** » Mon Jun 22, 2015 6:26 pm

Any pictures ?

smokin_blue · Post by **smokin_blue** » Tue Nov 03, 2015 5:29 pm

I built these around 1990 for a '74 GT250 with stock port timing and they worked well. Don't know if your '78 is any different. I then used them when I dropped the T350 top end on. I know I have dimensions and patterns some where I just haven't been able to locate them recently.

You can check out more details about the bike and build at my website at

http://www.street-unique.com/SmokinBlue/SmokinBlue.html

My main page is
http://www.street-unique.com/

GT 250 expansion chamber

GT 250 expansion chamber

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