CH4B intake

[C500]

Does anyone know the purpose of the small hole in the underside of the Manifold? Looks original, is it necessary to have? Am having a hairline crack welded and wondering if I should also get the small hole filled at the same time? The pic below is not mine, but the same manifold and same hole.

[ws23rt]

That is a good question . I looks like it may open to the heat crossover chamber.

If it was mine I would tap it to the nearest pipe thread size for a pipe plug. That gives you a clean option to have it or not and save the welding hassle.

[Dino]

What the heck is that for??  Condensation drain?   

[birdsandbees]

Yes

[C500]

Condensation drain huh, better keep it operational then I guess. Was a bit gummed up

[birdsandbees]

That's just the heat cross over that has the well for the automatic choke.. NO. Pending what you're running for a carb it may not matter.

[C500]

That's just the heat cross over that has the well for the automatic choke.. NO. Pending what you're running for a carb it may not matter.

I currently have an Edelbrock 750 with auto choke. You're saying this hole needs to be there if you're running an auto choke?

(Thanks for the replies too everyone).

[myk]

I guess I'll keep mine plugged...

[b5blue]

I left mine alone. Put an air blower into it and you know if it's okay.  (My Proform 750 has an electric choke anyway.)

[BSB67]

You're saying this hole needs to be there if you're running an auto choke?

No.

[John_Kunkel]

I can't picture any scenario where you'd want exhaust gasses exiting the manifold.  As suggested earlier, blow air into the hole and, if it does lead to the crossover, plug it.

[C500]

I can't picture any scenario where you'd want exhaust gasses exiting the manifold.  As suggested earlier, blow air into the hole and, if it does lead to the crossover, plug it.

[Dino]

Maybe you can stick something like this in there?

[Ghoste]

I can't picture any scenario where you'd want exhaust gasses exiting the manifold.  As suggested earlier, blow air into the hole and, if it does lead to the crossover, plug it.

I thought it was just hot air from a dead point between exhaust ports in the head?  There isn't actually exhaust going through there is there?

[firefighter3931]

Most folks install the felpro #1215 intake gasket with a "performance" style intake which blocks off the heat crossover. Doing so keeps the intake manifold cooler and would make blocking off the hole (in question) a moot point.

My guess is that the hole is there to bleed off excessive heat from the intake manifold. 

Bottom line : install the 1215 valley pan and don't worry about the crossover bleed hole 



Ron

[cdr]

I can't picture any scenario where you'd want exhaust gasses exiting the manifold.  As suggested earlier, blow air into the hole and, if it does lead to the crossover, plug it.

I thought it was just hot air from a dead point between exhaust ports in the head?  There isn't actually exhaust going through there is there?

the exh port is open through that passage, when the heat riser is closed it forces the exhaust to flow through the passage under the intake into the other heads exhaust port.

[John_Kunkel]

I thought it was just hot air from a dead point between exhaust ports in the head?  There isn't actually exhaust going through there is there?

That's why we suggested blowing air through it...it is possible that that hole is isolated from the actual exhaust gas i.e. a heated passage for a choke stove.

[303 Mopar]

Most folks install the felpro #1215 intake gasket with a "performance" style intake which blocks off the heat crossover. Doing so keeps the intake manifold cooler and would make blocking off the hole (in question) a moot point.

My guess is that the hole is there to bleed off excessive heat from the intake manifold. 

Bottom line : install the 1215 valley pan and don't worry about the crossover bleed hole 

Ron

  This is exactly how I installed my CH4B, 1215 Felpro which includes 2 gaskets and the valley pan with heat crossover blocked.  Don't worry about the hole in the bottom of the manifold, but you need to plug the hole on the passenger side.

[John_Kunkel]

If that hole you plugged is the other end of the bottom hole in question, no need to plug it. I'm not familiar with that manifold but, if the bottom hole is the other end of the top hole, it's merely a hot air source for a divorced choke mechanism. 

[303 Mopar]

If that hole you plugged is the other end of the bottom hole in question, no need to plug it. I'm not familiar with that manifold but, if the bottom hole is the other end of the top hole, it's merely a hot air source for a divorced choke mechanism. 

The two holes are not connected.  I was having trouble setting the timing, and could swear I heard a vacuum leak but could not find one until I happen to look hear and saw the hole.  Once I plugged this, I was able to get the timing set.