351c intake manifold question

Cougar Community Classic Cougar Maintenance Restoration and Repair
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I have 2 intake manifolds (edlebrock 2v and 4v). See photo. Not to sure which one to use on the original rebuilt 351c. Also would you recommend a valley pan (see photo) or using gel-pro 1240 intake gasket and why? I have watched lots of videos and no one has really given a reason for the pan vs the gasket

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So if you have 2V heads use the 2V intake, if you have 4V heads use the 4V intake. Look at the size of the intake runners in the heads. Use the intake that best matched the size of them. As for the valley pan, I recommend using it. The Cleveland engines did not have a pan in the underside of the intake to keep oil from roasting on the underside of the exhaust cross over. Though of you block that off you might not need it. If you plan to use a EFI unit like the Sniper, it is best to do that anyway.

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If you use the metal valley pan, do not put RTV around any of the ports. It will cook around the exhaust crossover ports and cause a big vacuum/exhaust leak.

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Thanks badcatt. Would you suggest measuring the runners with a tape measure to make sure the match is accurate? That valley pan has some rust on it. Would you suggest trying to cleaning that off or just purchasing a new one? If I can use it that would be great but I don’t want to damage the engine

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Thanks sfhess. I watched a video where they used black RTV under and on tops of the valley pans at the ends, not around the ports. Is there a gasket that needs to go between the valley pan and the intake runners and/or between the valley pan and the intake manifold?

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Do I need to run a 4 barrel carburetor with a 4V intake? does a 2barrel carb have to run on a 2V intake?

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The raised beads around the ports on the “valley pan” will crush down and will seal the manifold to the heads.

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Thank you sir. So no need for any gasket either above or below the “valley pan,” correct?

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Both of the manifolds you show use a 4-barrel carb. The 2V and 4V when discussing Cleveland intakes and heads has to do with the intake and exhaust port sizes. One only need to look at them to tell what one you have.

A person “could” run a 2-barrel carb on a 4V intake. But why? It would take an adaptor plate at the least and offer nearly no improvement in performance or fuel economy.

As for using the valley pan, you will still need to seal the front and back at what is called the China wall. I usually use a about 1/4 inch bead of a RTV silicone for that. Also it is not a good idea to use a used valley pan as the bead around the ports may not seal any longer.

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You will need to seal between the pan and the block at the front and back, as Badcatt mentioned. Sometimes they come with rubber pieces that you can use, or just use a bead of RTV. (this is from my experiences with Ford 400 engines)

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Sfhess, are you referring to the font and back “china Wall?” This valley pan come with 2 gaskets that looks like they go around the ports. Should I use those between the cylinder heads and valley pan around the ports? Or would you recommend using RTV (black), which I have seen or no gasket? Just curious

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There should be some sort of seal or RTV on the tops of the ‘China walls”.

The beading stamped in the port areas of the metal pan gasket should be sufficient to seal the ports. RTV not recommended. I learned the hard way that RTV in the port area will burn and harden around the exhaust crossover passages, causing a big exhaust/vacuum leak. Using the provided port gaskets is up to you. FYI my experience with Cleveland-style engines is mainly on 400s.

Another tip: If you are working with the valve gear, use new bolts for the rocker arms.

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Thank you sir. i appreciate your time and badcatt’s help with this. Wish me luck I am trying to get all this in this weekend.