Intake Manifold Exhaust Cross-Over Leak?

[rmartens]

My '56 Century has always had a small exhaust leak in the crossover in the bottom of the intake manifold. I recently saw a photo of the underside of an intake manifold and noted there is a small cover plate. I was able to locate and order a gasket for the cover plate.

Apart from a bad gasket, are there other "typical" exhaust leak points? In the cover plate? In the casting itself?

Before I dig in, should I plan on doing additional work while the manifold is off? Pull the valley pan, replace the gasket, and clean out any sludge in the valley?

I'm guessing I'll also need to replace the intake manifold gasket. Would it pay to clean the ports a bit with a die grinder?

Thanks for your input!

Rick

[JohnD1956]

When mine leaked it was the metal cover that rusted through. I had a plate cut from sheet steel and used that instead.

Not sure of your other questions although this is a prime time to clean and paint the valley cover.

[Smartin]

The underside of the intake has a "plug" that will rust through. I've been told it's replaceable, but is better to find another intake.

[JohnD1956]

Not to argue, but the older generation 322 cu Nailheads had a plate, like mine, that is held on with two bolts. I understand by the time the 364 cu came along in 57 the plate was changed to something akin to a soft plug. Can someone else confirm this, as I am not certain when the plug was incorporated?

[rmartens]

While contemplating this repair, I also read in my shop manual last night that there is some filter material in the crankcase ventilation system intake (before the road draft tube) built into the valley pan.

Is this material cleanable or replaceable, or should I just leave it alone. I'm thinking it might be well clogged or saturated after 50 years and maybe I need to take care of all of this at the same time.

Thoughts? Experience?

[old-tank]

Rick

The valley pan needs to be taken apart by drilling the spot welds on the bottom side. There is some aluminum mesh like in AC filters (that is what I used to replace). It will either be clogged or if ever tanked at a machine shop (caustic), the aluminum will be mostly destroyed.

Reassemble by welding, brazing or JB weld.

Willie

[Smartin]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JohnD1956</div><div class="ubbcode-body">Not to argue, but the older generation 322 cu Nailheads had a plate, like mine, that is held on with two bolts. I understand by the time the 364 cu came along in 57 the plate was changed to something akin to a soft plug. Can someone else confirm this, as I am not certain when the plug was incorporated? </div></div>

Ah...I had no idea. Thanks for the clarification.

[Gene Brink]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RTMartens</div><div class="ubbcode-body">I also read in my shop manual last night that there is some filter material in the crankcase ventilation system intake (before the road draft tube) built into the valley pan.

Is this material cleanable or replaceable, or should I just leave it alone. I'm thinking it might be well clogged or saturated after 50 years and maybe I need to take care of all of this at the same time.

Thoughts? Experience? </div></div>

Can be cleaned though Willie is right - if it was ever hot-tanked it probably was destroyed. I cleaned by submerging the valley cover in a shallow pan in kerosene for a few days and then rinsing with fresh kerosene until it ran out clean. You will be able to see some of it through the vent holes. Worth trying before disassembly and rebuilding. Good luck.

[old-tank]

Some more points as to why I vote to disassemble: the filter media is there to intercept oil droplets so none is lost out the draft tube...the intercepted oil drains back into the engine maybe with some of the crud that was loosened by attempts to clean; if you take one apart it will be apparent that that is the only way to clean; clogged media will result in too much pressure build up in the crankcase causing leaks; it will take 2 hours tops and can be done without disturbing pretty paint on the topside if you use JBweld.

Willie