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Old 09-30-2018, 03:56 PM
Festivus is offline
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Question
What headers fit a GP 123

I have one Pro Flow medium can and will buy one more to try cans on my GP 123 in my PAU Viper and will be ordering a PAU 35% Edge next week and another GP 123.
I have searched and cannot find much selection for a 90mm drop header for this engine.
I prefer to stay away from the adapters to run the DA 120 headers.
I was told the DA 100 has rectangle ports and the headers will "bolt right up".
If this is true it looks like Desert Aircraft sell a pair of 90mm drop headers at a very reasonable price.
DA sells flex headers and solid headers any pro or cons to either style?

After reading it appears the DLE 111 header will fit, maybe?
Any first hand knowledge will be appreciated.
Thanks
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Last edited by Festivus; 09-30-2018 at 03:59 PM. Reason: Add questoin
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Old 09-30-2018, 08:22 PM
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This may not be much help but I have owned a few 123s and used the adapters every time with great success every time.....but the adapters do cost $$$.
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Old 09-30-2018, 08:27 PM
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You can run the adapters ($49.95) or you can do some grinding on the DA-100 headers. The adapters/DA-120 headers will provide you a much better exhaust seal.
If interested I have the adapters in stock.
Dave
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Old 10-01-2018, 05:30 PM
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Dave and Super thanks for the info, I know the adapters have to be great quality, I was just trying to eliminate a item and see what header options are out there.
If I go the adapter route, any pro or cons to the flex header over the rigid header?
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Old 10-01-2018, 08:03 PM
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I have been running DA120 Headers directly to the GP 123 for a couple of yrs with no problems.
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Old 10-01-2018, 08:31 PM
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Quote:
Originally Posted by mikeh View Post
I have been running DA120 Headers directly to the GP 123 for a couple of yrs with no problems.
Ditto. I ground out the opening a bit on the headers to match the exhaust ports. Works great if ya grind them to match,
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Old 10-01-2018, 09:23 PM
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Quote:
Originally Posted by madinpensacola View Post
Ditto. I ground out the opening a bit on the headers to match the exhaust ports. Works great if ya grind them to match,
When you say DA 120 headers are you using the headers with the round port flanges?
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Old 10-01-2018, 09:52 PM
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Quote:
Originally Posted by Festivus View Post
When you say DA 120 headers are you using the headers with the round port flanges?
Yes
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Old 10-01-2018, 10:23 PM
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Thanks MikeH and Madinpensecola
I may have to give it a try.
Are you using the flex headers or rigid headers?
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Old 10-02-2018, 05:55 AM
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Quote:
Originally Posted by Festivus View Post
Thanks MikeH and Madinpensecola
I may have to give it a try.
Are you using the flex headers or rigid headers?
Flex with the heat tape you see on them from the factory. Use a dremel and grind the ports more square. Use the GP123 muffler gasket as a template on the header flange and mark areas needing adjusting with a sharpie.
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Old 10-02-2018, 05:56 AM
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If GP would keep their headers in stock we wouldn’t need this workaround.
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Old 10-02-2018, 08:36 AM
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My solution to use a match a DA50/100 port to a GP61/123 was to make an aluminum plate to match the ports. The bolt pattern is slightly narrower on the GP, but a file took care of that, but because of the difference in port heights there isn't much area on the top and bottom to seal which is what the plate fixes, plus it port matches. I didn't use any gaskets, just Red High Temp RTV, and it doesn't leak.

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Old 10-02-2018, 08:41 AM
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I found a picture of the plate.

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Old 10-03-2018, 09:28 AM
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What are the GP-61/123 exhaust port dimensions, and what is the center to center bolt hole spacing (I have an idea)?
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Old 10-03-2018, 09:52 AM
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Please, send me an E-mail as soon as this item is back in stock


Product information


Stainless steel engine flange to be welded on steel elbow



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This info from Topmodel web site for a header flange.
LF=27mm
HF=17mm
BA=38mm
OE=5.5
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Last edited by Festivus; 10-03-2018 at 09:57 AM.
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