216 Manifold gaskets

I have a 48 Chevy with the 216 stove bolt motor. The intake gasket is leaking and as I look it over there is another square gasket that looks like it separates the intake manifold from the exhaust manifold. Can someone tell me what the purpose is for this?? I think there has to be a plate or something that separates the exhaust from the intake. Do I really need to replace this gasket? I see the gaskets are available, any suggestions appreciated.

 

The exhaust manifold has a opening for heat to the solid intake manifold. There is a spring loaded ****erfly valve in the exhaust manifold for temperature control. Those exhaust manifolds frequently are cracked. Note; 216's have smaller intake ports than 235/261's Join the Inliners International Club. Newc

 

Thanks, any idea where I could see an exploded view of it?

 

The bottom of the intake is solid so where the intake bolts to the exhaust is separate. If you go to Best gaskets>Vintage engine> Chevrolet>50-52 complete set and look at the gasket 4145 in the middle of the layout of all gaskets it’s shown. As stated above it’s for carburetor intake heat for better fuel atomization.

 

Thanks for the reply, I see the gasket, still looking for a pic or drawing of the spring ***embly, is the spring something I should look at or just leave it alone and replace the intake -exhaust gasket?

 

Once the unit is free in the exhaust manifold cavity the outside “spring” will be set to close the exhaust off to the pipe withthe internal ****erfly. It holds very lightly in this direction and is easily moved by the weight on the outside. As an engine accelerates (rpm’s go up) the force of the exhaust opens the ****erfly inside. When the engine is warmed up the ****erfly it all works easier as the “spring” is bimetal.
In the 50-60’s and up ALL engine had a ****erfly flapper in one exhaust manifold on a V8 to force exhaust heat thru the intake. Most guys just removed them or wedged them open for performance.
In wet or salty areas of the country these were normally stuck.

 

Be aware that when you remove the intake/exhaust manifold from the engine, especially if you split the two from each other it will likely spring/warp and you will need to have the flanges ground flat to get them to mate to the head again. I pulled them off my 216 when I was a teenager just to clean etc, then found out the hard way they moved a bunch. Local old school shop had a belt grinder just for this and they did it for the price of a new coffee can.

 

Never thought about the manifolds springing, will the hold-down bolts not pull them back into shape? I seem to have lost vacuum to work my wipers and with some spray believe it to be an intake manifold leak, maybe a cracked manifold. Thanks for your reply.

 

I changed intake/exhaust on 216/235 and attached the on the head first with the 4 center bolts for the heat riser snug many times in my youth. After tightening the manifolds to the head I’d tighten the heat riser. Never cracked or had one leak.

 

sounds like a plan, thanks getting ready to pull it off the head today to get a good look at the intake, somehow I think it has to have a crack in it because of the lack of vacuum .