rear intake manifold coolant reroute note

[vector1]

some of you guys put coolant lines off the rear of the intake manifold to keep out the hot spots off the rear of the heads where air pockets form.

i did some rerouting on coolant lines today and was wanting to restrict these lines which are 3/8" so they wouldn't flow much coolant, just let the air pass.

i took out the fittings which were 3/8" npt x -6 flare and drilled the inside pipe portion and threaded for 1/8" npt and installed brass plugs and redrilled to 1/8" for the restriction.

works good so far.

[vector1]

the 1/8" restriction each side might be a little large, if i do it over would prob use 1/16".

i can watch the coolant circulate with the electric pump.

[HighPlainsDrifter]

Hi,
The head gaskets have a front stamped in them, this provides a small coolant hole in front and a large hole at the rear to allow the rear to cool better. Unless you are an all out racer it is not needed to add another passage. I have raced for years without any trouble.
Perry.

[vector1]

yeah, i know it is possibly not needed, but putting my engine together i noticed a place in the back which would hold an air pocket and found others doing the same thing i was thinking, i asked on an advanced type engine building forum and found others doing this, as well as the gt40 forum.

also helps to bleed the air out the back. noticed on filling this time the engine took all the coolant and then some. didn't have to run the engine and refill multiple times.

[Jerry Clayton]

Would you care to explain why you are using an electric pump????

[vector1]

probably don't have a real good reason. found a good deal on one and just wanted to try it. i've heard good and bad and have yet to see how it works first hand.

it's nice to be able to circulate coolant with a flip of the switch though. if it gets hot on track i'll just have to switch it out for a belt driven unit, but 10-20 minutes on track with an aluminum engine shouldn't get too hot i wouldn't think and is another reason i was concerned with keeping the thing cool and not getting any hot spots so i did the coolant lines off the rear.

i'm also using npg which is waterless and doesn't require a pressurized system so i don't have to mess with the water and additives and anti-freeze stuff.

[Rick Parker]

If you are describing a connection from one side to the other at the rear of the manifold, I think that would only equalize pressure within the water jackets on each side of the engine. Not transfer any significant amount of coolant (?)

[vector1]

Originally Posted by Rick Parker

If you are describing a connection from one side to the other at the rear of the manifold, I think that would only equalize pressure within the water jackets on each side of the engine. Not transfer any significant amount of coolant (?)

that is correct, except there is a hose teed off this to a low pressure area.

[Rick Parker]

Where is it reconnected to low pressure.

[vector1]

yeah, i thought about this after i posted, it is ran to the top of the header tank.

i guess low pressure or suction is considered to be from waterpump inlet to radiator tank side, and high pressure is after waterpump through block out thermostat to other radiator tank side.

the bottom of the header tank is connected to the low pressure side, so the line off the back of the manifold is connected to the top of the header tank.

[vector1]

well sheet, that didn't work. it seems to work fine when cold at a standstill, but when warm the header tank fills up quicker than it can lose it, so it was blowing coolant out the tank. after it was warm i could run the pump and watch the tank fill up.

i'll have to either restrict the bleed off the back some more or ****can the whole setup and just keep the system closed without the tank, or plumb the bleed to a different location. i thought i had it plumbed correctly from my research though.

richard advised me not to run the header tank and guess i'll have to listen a little better next time.

[392cobra]

Chevys do this by routing it back to the thermostat housing.

[vector1]

i thought about that and still might do the routing to the thermostat housing. i think the problem on reflection was the cap on the header tank is not sealed.