Engine/Transmission (1994 - 1998) What is this part of the head?

[LVJUNIOR]

I bought a ported cylinder head made in Brazil. I transfered all of the plugs and bolts from my stock head and intalled it. I had a huge boost leak out of the ports on the underside of the intake manifold in the cylindrical part near the center of the manifold. My stock head had this same configuration with no plugs and worked fine. The new head leaks like the Titanic.



I have pluged the large hole in the bottom and the side hole almost centered on the cylinder. What is this fore and do I need to plug the other two holes as well.

 

[MBanning]

That is a built in fuel filter head, it is used in different applications. You do not need to plug the holes. MBanning

 

[LVJUNIOR]

I didn't plug the holes and my truck wouldn't get out of its own way. I was blowing boost right out of the holes. Plugged the holes and got boost back.

 

[PToombs]

Sounds like they ported into the fuel transfer area. Since you don't use this filter area, just plug them up and you should be fine. They are all connected so plug them all. You should be able to blow air in to test it.

 

[hsmith]

Also, that hole is not npt. It is straight threads. Npt plug may work though since you will not need it in the future.

 

[LVJUNIOR]

The guy who ported it put the markings on it. I think he re-tapped it for npt. The threads do not match my stock head.

 

[Joseph Donnelly]

The boss inside the intake plenum was ported away for better flow, and the remaining parts of the fuel filter passages were tapped NPT.

 

[LVJUNIOR]

I just plugged the bottom 3/8" NPT and the 1/4"NPT above it. Do I need to tap the other medium sized hole and the small hole as well or are these unaffected by the porting.



By the way, thank you for the help with the head.

 

[hdm48]

Yea, that boss is for the fuel filter and heater used on the first gens. When I port a head, I permanently plug the hole on the bottom and the one right above (inlet/outlet), then I remove 90% of the boss inside the manifold for a little better flow.