Heat Riser

I'm swapping out the 352 engine in my '66 for another 352 from a donor '66. At some point my original engine had the heat riser disabled by removal of the butterfly plate in the casting. The donor engine has a heat riser with the butterfly plate intact but the spring holds the plate open when cold instead of closed. The picture shows the springs of the two units and that they are installed opposite from each other. The unit on the right is the intact unit with the plate open when cold. Has someone removed and reinstalled the spring the opposite way? I am still running with single exhaust. I disabled the riser in my '65 when I went to duals but I know it's there for a purpose in the single exhaust system. Any thoughts? Steve
Get your truck running, then if you want to go back and fiddle with it for kicks & giggles you can have at it, otherwise...................
John
I would HIGHLY recommend you consider changing the exhaust over to the later style without the heat riser valve. While you have the engine(s) out, it is much easier to solve problems such as extracting broken bolts.
Word of advice: Be sure to consider the issues it presents when working on exhaust.
The exhaust manifold for the valve is unique - the exit port is cast with a flat surface, not a rounded one. You cannot use an exhaust donut there.
If you replace the exhaust manifold, use one from a 360/390 to get the donut shaped casting.
However, this means you will need to change the downpipe, as the original one is too short.
When I changed mine out, I used the left and right side pipes from Advance Auto, specifying those from a '76 F-150 with a 390.
They fit my 352 perfectly.
I left it that way until I changed to a 460 dual exhaust.
Fits: 1965/67 F100/350 352 // 1973/76 F100/350 360/390.
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