I'm getting dumber by the day - please help

[foothilltom 33]

Hey guys, I've spent the past 60 minutes searching online and can't find an explanation.  Probably because I don't know how to even phrase my question:

• What the hell is the center port on this Edelbrock Performer 351 intake manifold?  Is it a water port?
• There is an equivalent port on my cast iron 351W heads, but NOT on my aftermarket aluminum heads
• Do I need a different intake for these non-standard heads?
• Is it OK to just cover over the port on the intake with a gasket?

Picture #1 is the intake with a blue circle around the port in question.  The other picture is my after-market head w/out said port.

This is related to my other post where I have managed to create a massive vacuum/coolant leak in my fresh 351W rebuild.  The more I look at things, the more confused I get.  Thanks very much for walking me through this (patiently). 

Tom

[whoapony 17]

It is a coolant port, you don't need it, your heads don't have the crossover and thats fine, they are aluminum.  Just use your regular intake manifold gaskets, the plus side is your air intake will run cooler now haha.

[ksquared 13]

That's the manifold heat port. The factory heads pass exhaust gas thru that port on the manifold from one side of the engine to the other to heat the manifold. That improves driveability on a cold motor by improving fuel atomization. Unless you live in cold country, I don't think you will miss it. Most folks who are after more performance prefer a cooler manifold for a potentially denser charge. The system used a thermally operated valve on one of the exhaust manifolds to create the back pressure to push the warming exhaust back thru the port. As the exhaust got warmer, the valve opened up until very little exhaust was sent back thru the port. It was common for those valves to freeze in the closed position causing a rather hot intake manifold and reduced performance from exhaust restriction. Not terribly important on a grocery getter but anathema to guys like us :-)

[foothilltom 33]

God dang, I learn something every day.  Thanks very much, fellas.  Bless this forum.

 

Tom

[whoapony 17]

8 minutes ago, ksquared said:

That's the manifold heat port. The factory heads pass exhaust gas thru that port on the manifold from one side of the engine to the other to heat the manifold. That improves driveability on a cold motor by improving fuel atomization. Unless you live in cold country, I don't think you will miss it. Most folks who are after more performance prefer a cooler manifold for a potentially denser charge. The system used a thermally operated valve on one of the exhaust manifolds to create the back pressure to push the warming exhaust back thru the port. As the exhaust got warmer, the valve opened up until very little exhaust was sent back thru the port. It was common for those valves to freeze in the closed position causing a rather hot intake manifold and reduced performance from exhaust restriction. Not terribly important on a grocery getter but anathema to guys like us :-)

Yup, I realized this after i wrote that i went to change it haha, coolant shoulda been EGR at least what I was thinking.

[1969_Mach1 333]

22 hours ago, foothilltom said:

Hey guys, I've spent the past 60 minutes searching online and can't find an explanation.  Probably because I don't know how to even phrase my question:

• What the hell is the center port on this Edelbrock Performer 351 intake manifold?  Is it a water port?
• There is an equivalent port on my cast iron 351W heads, but NOT on my aftermarket aluminum heads
• Do I need a different intake for these non-standard heads?
• Is it OK to just cover over the port on the intake with a gasket?

Picture #1 is the intake with a blue circle around the port in question.  The other picture is my after-market head w/out said port.

This is related to my other post where I have managed to create a massive vacuum/coolant leak in my fresh 351W rebuild.  The more I look at things, the more confused I get.  Thanks very much for walking me through this (patiently). 

Tom

From the gasket imprint on your cylinder heads, it looks like the gasket wasn't covering the tops of the intake ports.  Hence, the large vacuum leaks.  And from the gasket imprint on the intake manifold, you had the wrong intake gaskets for the rectangular shaped water ports on the cylinder heads.  Try the Fel Pro Performance or the Edelbrock intake gaskets I referred to on your other thread. 

[ksquared 13]

I just had barely related thought about exhaust back pressure. I've heard from some who should know better that engines run better or make more power if the exhaust system has some back pressure. Anyone ever heard that? I think I heard it in a muffler shop once as well as in a speed shop. Is there an emoticon for rolling eyes? It can often be difficult explaining the truth. I'm sure that isn't the case on this forum :-)

[barnett468 418]

2 hours ago, ksquared said:

I just had barely related thought about exhaust back pressure. I've heard from some who should know better that engines run better or make more power if the exhaust system has some back pressure. Anyone ever heard that? I think I heard it in a muffler shop once as well as in a speed shop. Is there an emoticon for rolling eyes? It can often be difficult explaining the truth. I'm sure that isn't the case on this forum :-)

It's not that simple.

[RPM 1,190]

13 hours ago, barnett468 said:

It's not that simple.

And since the replies to the answer are all over the board, this topic should be in its own thread.