intake question
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Junior User
Joined: Aug 2006
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From: Eatonville ,Wa
intake question
im installing a edelbrock on my 86 f250 351w. my ? is what is the thing on the intake manifold that is on the driversside of the carb? it has a rod coming out of the intake and connected to some sort of vacuum valve. its in the way of my linkage, can i take it off and block the hole? thanks..... sorry camera isnt working so i cant post pics 
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Joined: Jan 2001
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From: Virginia
That sounds like the heat riser control. There is an exhaust passage in the center port of each head, and this lines up with a port on each side of the intake, with a passage under the carb. There is another valve in the outlet of one of the exhaust manifolds. When they close the one in the exhaust manifold, it forces the exhaust up underneath the carb to help it warm up and run during cold weather. The valve you are asking about controls the amount of flow also. I haven't figured out yet how the valves work together.
I would not block it off. If you want to take it out, I would plug any holes that would leak exhaust, but I would let the exhaust still run under the carb. The engine will run terrible if you block the exhaust passage off. I usually have good luck with leaving the ports open on either side of the manifold, and opening up or taking out the riser valve in the exhaust outlet. It doesn't force exhaust under the carb this way, but some does go through and it still seems good enough for it to run, if you keep the factory aircleaner and the hose from it to the shroud around the manifold.
I would not block it off. If you want to take it out, I would plug any holes that would leak exhaust, but I would let the exhaust still run under the carb. The engine will run terrible if you block the exhaust passage off. I usually have good luck with leaving the ports open on either side of the manifold, and opening up or taking out the riser valve in the exhaust outlet. It doesn't force exhaust under the carb this way, but some does go through and it still seems good enough for it to run, if you keep the factory aircleaner and the hose from it to the shroud around the manifold.
