This is an old school JG turbo manifold. Stock D-series runners welded to a new plenum.




Biggest concern - The water ports are welded shut. Now I'm not concerned about the smaller one because it just feeds the IACV and TB. But the larger port is for the U-hose that connects to the thermostat housing.

What is the purpose of the U-hose? I started to study the water flow but I didn't quite figure it out. I know that when the thermostat is open, the flow is as follows:

Pump -> Block -> Head -> Upper Rad Hose -> Lower Rad Hose -> Thermostat -> Water Pipe -> Back to pump.

But when the thermostat is closed, where does the coolant go when it gets the the head? Does it flow through the U-hose and back to the water pipe? I don't get how that port can be welded shut. Some insulating gaskets also block off the port.

(The blue is the U-hose)

 

Here is how I picture it with the Thermostat closed:



So with the U-hose port sealed off, the coolant can't exit the head?

 

I would just drill out the big lower one and re tapp it and plumb it man

 

I'd rather figure out it's purpose, then determine whether or not to use the manifold. It can't be drilled/tapped now that the plenum is welded on. No room to get in there.

 

It's a coolant bypass, it allows a small amount of coolant flow before the thermostat opens.

 

So removing it will make the coolant stagnant? Won't that create hotspots, as well as put excessive strain on the water pump?

 

No, it's not a straight shot from the flange to the port. It makes a weird turn.


Besides, that's not the point. I'm not trying to figure out how to put a new port on. I'm trying to figure out exactly what the port does and if there's any detriment to not having it.


After all, it's not like JG accidentally plugged the port. It's a $500 manifold and the port was obviously filled for a reason. I just don't know what that reason is.

 

Midnight bump for knowledge.

 

call JG and ask them?

 

just drill the welded spot from the back, not the plenum side.

you need that bypass there to circulate the coolant to the themohousing. i didint hook that "hole" up before and had problems with the car running hot. and air bubbles.

 

Damnit, then why did JG do that? I thought it would create air pockets.

And while I can drill the hole from the flange side, I can't tap it from there too. Maybe I'll just drill out the small hole and rig that back to the thermo housing. The big port is a lost cause.

 

Anyone recognize what fuel rail would fit? I know it's not a y8 rail.

 

you can drill and tap the thermostat housing and you'll be fine. I just did it on my car and the temp stays the same.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed &raquo;</TD></TR><TR><TD CLASS="quote">Anyone recognize what fuel rail would fit? I know it's not a y8 rail.</TD></TR></TABLE>

y8 and y7 fuel rails are 2 bolts...
d15b7, d16z6 etc are 3 bolts like your new manifold...

about the coolant thing, I'd call JG and ask them.
I'd also like to know, so if you get an answer, let us know.

 

here is how i did mine with the same manifold only for a B series mine was plugged too haha

 

And i also just had to tap for a fitting so my brake booster would have vacuum and i through a few others in for other little things like regulater and boost gauge

 

The purpose of the U-hose is to allow some coolant to pass at the rear of the thermostat which once up to temperature will alow it to open . if this hose is blocked off no coolant will flow to the thermostat thus it will be closed and your car will over heat . this can only be blocked off if the thermostat is removed or drilled out to allow coolant flow to the rear of the thermostat.

hope this helps!

 

How long does it take for the car to warm up if the thermostat is removed?

It's not too cold where I live (SoCal). It never freezes, but some cold mornings in the winter are about 40*.