In the picture you see a small port in the middle of the head between the valve ports. What is this port for? When I pulled my Torker 340 intake the PO had blocked these off with a piece of stainless steel between the head and the manifold.

Not knowing what is was for but obviously there for reason, I left them open and the stainless steel pieces remain on the work bench.

Any idea's?

 

I believe you are referring to the heat crossover pathways. They are not used with headers.

 

If it's not used with headers does that mean it opens up into the exhaust manifolds. A passageway between the exhaust manifolds through the intake manifold?

 

That port is used to pass exaust gas up through the original intake manifold. That would heat the manifold and the choke box letting the choke open as it was heated. It is not needed if you use an electric or manual choke. It was also where the EGR valve draws in exaust gas if it was equipped with one on the original manifold. I have always blocked that passage off when it was not needed.

 

Lot of halfway wrong information here

Your original exhaust manifold one one side has a thermostatic butterfly, that when cold, partially "plugs up" that side of the exhaust. This creates pressure which forces exhaust gas up through the intake, under the carb, and out the other side.

It IS still open with headers, it's just that there is no butterfly valve in the headers. The crossover would still work with headers to some extent.

Also, it is not ONLY to heat the choke. It is ALSO to heat the under--carb area and improve fuel atomization when cold. In some cases "it doesn't have to be" all that cold. Certain temperatures down into the 50'sF with high humidity can cause poor fuel atomization and IN SOME ENGINES like Corvair/ VW sand buggies, etc, and six cylinder engines with headers and aftermarket manifolds---can cause ACTUAL CARB ICING. I've seen ice under aftermarket VW manifolds on an 80* San Diego day!!!!

(Google stuff like "carb heat", aircraft)

Depending on where you live (north) and whether you expect decent cold drivability and mileage, as opposed to a ***** out hot rod, as to whether I'd plug those openings.

 

Thank you all very much!

If there is a thermostatic butterfly in one of the exhaust manifolds, and it was "stuck" partially closed, what effect would this have on the motor?

When we ran the engine (for about five minutes) after changing the intake, I did rev her up just a little. Then I walked behind the truck to find a enormous spray a black crap that came from only one side of the exhaust. It has dual exhaust.

I suppose this could mean there is a restriction on one side that was partially relieved ater opening up the crossover?

Oh how the plot thickens.....

Love this stuff,
Thank you
Joe.

 

It would partially convert the car to a single exhaust.

 

As well as decreasing mileage and performance, I'm sure

 

What kind of vehicle is it in..By looking at the picture I am thinking pick up truck. The manifolds look similar to magnum manifolds as such there would be no thermostatic exhaust valve. Look down on the passenger side exhaust manifold and you will see a little metal contraption right above the flange that bolts to the down pipe. That is where the valve would be.

 

It's a '72 340 in a '90 Dakota.

I'll check it out.

Thanks guys.

Joe.

 

With the intake gaskets, a lot of people will not cut the hole in them to allow the gases to warm the intake. Over time though, the heat and gases eat away at the gasket and will create a small hole (nothing to get worked up or worried about though). For a race only vehicle, I wouldn't worry about them. For a road vehicle, I would cut the hole in the gaskets.

 

I think this "Thermostatic butterfly" you are referring to is the heat riser. These are more often rotted away and gone rather than being restrictive.

 

Yep it appears to be there. A large bulge in the passenger side exhaust manifold just above the flange. The bulge has what looks like a pipe plug in it.

From the reading I've been doing, this port is plugged off in race applications to keep the intake cooler as to not atomize the fuel as much.

I will be drag racing the truck, however I am glad I left the plugs out. The truck idles better (of coarse it still cold out) and it seems like a minor thing in the overall scheme of things. Probably better working the way the engine was designed to work is my thinking.

Thank you all very much for your help.
This is a great forum and a bunch of great guys.

Joe.

 

a comedian in the house!!