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Thanks, a very good thread I referenced before doing this. I think when you say closed you're describing cold but I welded the valve in the hot position, which is the position on the right in the picture below. Logic being I don't intend to drive my 40 in the winter and it has been operating the last few years with it flapping in the breeze. Headers don't use a heat riser and work just fine. If I welded it in the cold position it would be an obstruction to smooth exhaust flow and continue to warm the carb beyond what was intended possibly cracking the intake. I feel like removing it all together would create a void in the elbow that would be a detriment to exhaust flow where you would have turbulent air swirling in the corner and continue to heat the intake. So I welded it in the position it was designed to be in when hot.
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Pighead's reply in post #21 is more inline with my thinking: "The manual makes for funny reading in a few places, I figger it was just a bad day at the translator's typewriter..." hahaha.
EDIT:
I drew this cross section to illustrate what I was concerned about if I removed the riser all together. I think it would both impact flow and continue to warm to intake without a block off plate.
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