Rear manifold/head coolant line size?

Tickler

Registered User
I just dropped in some 98 mustang HG's and I know most of the late 90's 3.8 mustangs have an extra coolant hose in the back of the intake manifold. I have not put my manifold back in yet, so I thought I'd put some hose barbs by my head's rear coolant ports.

My question is; How big of hole/hose should I tap for the lines, and where do they go from there?


Thank you kindly,
 
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I thought about doing something similar to open up the coolant passages bocked by the rear of the lower intake. I was thinking 3/8 hose barbs would be adequate, but haven't tried it yet. If you do this, let me know how it works out for you.
 
Basically you have to keep in mind the flow of the coolant through the motor, which is through the block to the back, up into the heads and back to the front of the motor. You don't interfere with that flow or you'll end up with dead spots that will boil out on you.

Some folks have thought about running a cross pipe from one head to the other head but if you really think about it, there will be no flow, as the coolant flows up into the heads on both sides at equal pressure... you would have to create pressure difference on one side to get actual flow from one side to the other, then of course your robbing from one head to cool the other head so you will have one head runner hotter than the other. Technically speaking, you would have to reflow the entire cooling system, and thats probably what they did with the newer model 3.8's.

In the long run, to get better cooling heads you probably should wait until the supposed new heads come out.
 
I totally see where your coming from, however; I'm Positive that two little 3/8" hoses shouldint stall flow anywhere, I can always crimp them alittle later. If you look closely at the mustang mls and maybe the tbird gaskets they are wide open at the back, and damn near closed at the front, Im just trying to help things along.
 
The gaskets have ports like that specifically to promote flow through the head due to the ports on the front of the block for the in and out of the water pump. I was considering the mod discussed here, but threw it out after looking at how the block and heads move coolant I figured I'd wait until I can really track the flow better.

There may be a way to improve cooling, but you need to keep in mind that engine power is optimized through heat and pressure. A cold motor isn't good, a too hot motor isn't good. A just right, hot motor is perfect. You could sure give it a try though if you want. Like you said, it would be easy to block off the ports if it didn't work out.
 
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