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heat riser operation question

743 Views 3 Replies 3 Participants Last post by  RB69SS396Conv
69 Chevelle, which way is the exhaust heat riser valve full open? with the vac on the canister, or with no vac on the canister. need to know which direction to tie it off in until I change the manifolds to headers.

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Vacuum applies the heat riser. (closes the butterfly valve)

Thanks, it comes off tomorrow. So when cold, the therm switch in the water neck is open, allowing vacuum from the manifold through the switch, then pulls in the vacuum piston. Once the water temp warms up, the switch closes off the vacuum, I suppose the switch also has a vent to release the vac as well?

Thanks for the info. I now know which way to tie it off until I install the headers.
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