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Posted by Sherman in Idaho [24.32.202.166] on Wednesday, February 27, 2013 at 14:27:29 :
In Reply to: Re: Freshening up a 251? posted by Sterling From TX [99.98.76.231] on Wednesday, February 27, 2013 at 12:55:20 :
The plumbing is separate. It's the manifold connection for the PCV valve. If you follow it, you'll see it connects to a hole on the rear passenger side of the block, up pretty high, where it can suck crankcase fumes into the intake.
The heat riser is a choke-like contraption that directs hot exhaust up into ports under the carburetor to help vaporize the gas and prevent carb icing in cold weather. Some are thermostatically controlled, via a big "clock" spring and a weight. Some just have a slotted sheet-metal lever with a pointer on it that you manually move to "summer" (no heat) or "winter" (max heat) position or somewhere in between as suits you. The thermostatic ones usually don't get stuck because they're always vibrating and moving around. The manual ones are usually stuck, and the only way to unstick them is to pull the whole manifold assembly and separate the intake and exhaust. If you try to unstick it by forcing the lever, you will just strip the lever out of its little swaged hole on the end of the shaft. Now might be a good time to make sure yours moves.
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