[78mg]

Hello,

I recall reading somewhere that a tip for improving cooling in the 400 (I have a stock 67') is to add an additional heater hose nipple on the driver's side cylinder head (where there is simply a plug as standard) and then dog-leg the heater hose to run through both nipples.

Has anybody tried this and, if so, is it worthwhile? Could there be any downsides?

Thanks,
Michael

[lust4speed]

Coolant flow in a Pontiac engine is through the block front to rear, and then back through the head to the water crossover where it returns to the pump. The heater nipple robs some coolant flow that would normally help cool the passenger side head. The coolant goes through the heater core and shortcuts back to the intake port of the water pump. Maximum cooling will take place with both sides plugged. Older Pontiac engines didn't take the coolant from the head and took it from the water crossover - which was a better deal because it didn't bypass the head and the coolant going to the heater core from the crossover was hotter after making the return path through the head and absorbing more heat. I'm sure the bean counters had their way and the change was adopted to save a buck or two. A more conservative way of looking at it is the restriction built into the heater nipple reduces the amount of coolant flowing to the heater core to an almost insignificant amount.

[imposter]

or not

[Region Warrior]

The cylinder heads run hotter at the rear, so get'n some out helps, "BUT", sending back to water pump housing just puts more hot water back into engine.
Thats why you see guys run a water line from back of each head to front water cross over.

[Scarebird]

Originally Posted by Region Warrior

The cylinder heads run hotter at the rear, so get'n some out helps, "BUT", sending back to water pump housing just puts more hot water back into engine.
Thats why you see guys run a water line from back of each head to front water cross over.

Wouldn't that rob flow from the front of the cylinder heads?

[Pontirag]

and a rising tide raises all ships, the thermostadt determines how high the temp gets. and your theory only works, if at all when the heater is not used. When the heater is used it is a smaller radiator cooloing water. a nipple on both heads would at the least average the temp between cylinder heads. weather the heater is used or not.

the nipples I seen have a bi matellic coil in them that only expands when the head temp reaches a given temp.

[lust4speed]

Originally Posted by Region Warrior

The cylinder heads run hotter at the rear, so get'n some out helps, "BUT", sending back to water pump housing just puts more hot water back into engine.
Thats why you see guys run a water line from back of each head to front water cross over.

Although I'm not sure if there is any pressure differential over what is entering the crossover from the front of the heads. If there is not, then there won't be any movement of the coolant through the additional hoses - or at least not enough circulation to make any real difference.

I look at the flow chart in the Pontiac service manual a little differently. Much of the coolant proceeds to the rear of the engine and up through the rear part of the heads, and the front of the heads will be receiving much of their cooling from the rear of the heads - unless you pipe the coolant around the front. If this is the case, then the heater nipple robs the front passenger side of some coolant. The first design of the V8 had reverse cooling and did not use the head to supply the heater. Then the bean counters stepped in and shortcuts were taken to simplify the cooling system and reduce costs. Maybe the engineers simply found that the later cooling route was better or at least "sufficient". I suspect taking the heater supply off the rear passenger head was more of a necessary evil. Pontiac engineers knew the effects of stealing some coolant during the cold weather would be minimal when the heater would be used.

I always worry when we believe in some quick fix that goes against the multi-million dollar research results of Pontiac.

[Pontirag]

lust for speed"

"I always worry when we believe in some quick fix that goes against the multi-million dollar research results of Pontiac".

amen brother!

if i could just get a nickle for every time somebody tries to fix a cooling system when the problem lay elsewhere.

dont even get me started on aluminum radiators and flex fans