[torqjunki]

Although this is primarily a street car, I feel it may get more looks here. I have searched and read many threads on running two -6an coolant lines from rear of heads to front crossover. Some seem to feel they help while others say it does not and possibly is worse for cooling. This motor came set up this way, but did not use thermostat. I definitely want to run a thermostat. I will describe the motor and intended use and would appreciate opinions. Motor is 496ci IA-2 aluminum block with deck drilled in conventional locations for coolant passages. KRE d-port heads. Should mention that piston tops and combustion chambers thermal coated. 11:1 compression and Hyd roller. Will have traditional belt driven water pump. Mainly street with occasional strip. Should I ditch the additional coolant lines?

[gtofreek]

Seems to me like it would work better. Without those lines, the water has to travel back to the front of the heads, picking up even more heat along the way. Seems to me that if you ran that hot water from the rear of the heads to the crossover, via lines, rather than through the head, it would run cooler. That water wouldn't be collecting extra heat for the radiator to try to cool.

[Elarson]

If you run a little calculation of flow areas, you will find that a -6 hose has a tiny fraction of the flow area of the radiator hose and will not pass a significant amount of water. But there is probably some benefit if they tend to bleed air pockets out of the back of the head.

Worst case, I'd say they won't hurt anything.

Eric

[68azbird]

I used 5/8" pre bent heater hose into the standard heater hose nipple in cast iron heads. Don't know if it's a combination of proper divider plate clearance, airflow thru my copper 4 core radiator and the extra coolest lines but the water temp never goes over 185. This is from regular stop and go driving to cruising on the highway at 3500 rpm.

[Tom Vaught]

Quote from carb website: "In David Vizard's latest book on Holley, he writes about a gas mileage test he did with a SBC. His conclusion was (paraphrased): the worst mileage came from an unheated or only heat soaked manifold, better was the exhaust heated (but robbed 10 to 12 hp), and best gas mileage was achieved with a coolant-heated intake that held the manifold temperature to between 180* and 190* at a cost of only about 5 hp. This was accomplished by blocking the ports of the crossover and plumbing coolant through it from the radiator."

So Vizard apparently has data that says the "Water Heated manifold" concept works.

Tom V.

[gtofreek]

Tom, I think you read another post about running water through the exhaust crossover, but answered it on this thread. He's asking about taking water from the rear of the heads and bringing it up to the front water X-over.

[torqjunki]

I made a mistake on the hose size. It is actually -8an. Some of the searches have mentioned that this mod should be done with a restrictor and not a thermostat. Any thoughts on the thermostat with the coolant lines? Seems to me it should not hurt to run a thermostat especially if the bypass has not been blocked.

[Tom Vaught]

Originally Posted by gtofreek

Tom, I think you read another post about running water through the exhaust crossover, but answered it on this thread. He's asking about taking water from the rear of the heads and bringing it up to the front water X-over.

Sorry, you are correct.

My opinion on the water removed from the rear of the heads and going to the water X-over is that the hoses should be small and used only to remove trapped air at the rear of the heads and let it escape by feeding it to the x-over and later out the water over-flow bottle. You put a big line on the rear of the head you are basically by-passing coolant flow that should be going forward thru the cylinder head the was the Pontiac engineers designed the water flow prior to 1965.

The engineers screwed up when for a few pennies saving on hose they moved the water inlet to the heater core from the water cross-over to the passenger side rear heat nipple.
Now the passenger head cooled differently vs the driver's side head, (and that is a fact).

Tom V.

[gtofreek]

What about running a hose from the rear of the passenger side head, to the rear of the drivers side head? Then, if you wanted to run a heater, then you could tee off of this hose to the heater core.

[grandville455]

This New Build of mine, I am plugging the bypass on timing cover and water cross over, with a couple of holes drilled in the thermostat, and nothing plummed from the back of the heads to the cross over.

[BruceWilkie]

If you study the cooling scheme of 60 up Pontiacs (and differences from earlier reverse cooled system) you wil see that in 1960 they blocked off the three forward upper deck holes... this was done to prevent water taking a short cut from the block straight to the water crossover. http://www.pontiacsafari.com/EngineCooling/index.htm


IMO in normal street WET deck configuration adding lines at rear of heads to front crossover COULD create a shortcut there not allowing adequate flow across the top of heads.
As far as small hose there... IMO it MIGHT help eliminate trapped air, however with most engine installs the engine is tilted slightly nose up, therefore I question liklihood of air getting trapped all the way to the rear of the heads.

As an experiment... you could block the upper rear deck holes(to match your front upper deck), use restrictors on front crossover and hoses at rear that are sized so combined area of each return is equal to the normal front crossover area to balance flow out each end... this would force more water toward center of the block and then across to each end. This MIGHT help even up temps across the block. Maybe help center deck cooling.

[bigchief468]

I have used this setup for years with great sucess in my opinion. I use it in a race setup only. I like the idea that by touch the temp is the same (front to rear) versus without it. I like the idea of cooling temp. (front to back) is the same.

[Bnick166]

I used -10's....hope it's not going to create a problem.....pretty tall fill on the block as well (to the bottom of the water pump holes in the block. Planning on doing some street driving.

[Tom Vaught]

Bruce, My "Opinion" is based on some engine testing we did a few years ago where our instrumentation showed that the right cylinder head was not cooling as well as the left cylinder head. The engine was installed in the Vehicle position and angle.

Moving the water return to the heater from the rear of the right head to the front right cross-over point showed that the cooling issues went away with ONLY that change and the overall engine efficiency curves were much more even cylinder to cylinder.

So the comment is based on actual (very accurately documented data) over many tests on the same engine (condition A vs condition B).

Tom V.

[60man]

Originally Posted by Elarson

If you run a little calculation of flow areas, you will find that a -6 hose has a tiny fraction of the flow area of the radiator hose and will not pass a significant amount of water. But there is probably some benefit if they tend to bleed air pockets out of the back of the head.

Worst case, I'd say they won't hurt anything.

Eric

X 2......

[BLANK1]

Tom,
Do you have any pics of that setup?

[BruceWilkie]

Originally Posted by Tom Vaught

Bruce, My "Opinion" is based on some engine testing we did a few years ago where our instrumentation showed that the right cylinder head was not cooling as well as the left cylinder head. The engine was installed in the Vehicle position and angle.

Moving the water return to the heater from the rear of the right head to the front right cross-over point showed that the cooling issues went away with ONLY that change and the overall engine efficiency curves were much more even cylinder to cylinder.

So the comment is based on actual (very accurately documented data) over many tests on the same engine (condition A vs condition B).

Tom V.

I dont disagree... It never made much sense(other than hose cost, possibly more or quicker in-cabin heat???) to do it the way Pontiac did. My 55 and 59 Pontiacs took water from manifold to heater then returned to the radiator iirc.

Adding return lines from rear of heads(take heater out of picture) to crossover should create more flow to rear cylinder(s) in the block... not too sure it helps temp across or through the head.

The coolant temp at crossover can be different than temp in block or in the middle of the cylinder heads. Pontiac blocked upper front deck holes(1960 - newer) to slow the shortcut to the crossover... adding rear returns to front crossover the hose size determines amount of "short-cutting" from rear of block to crossover because the deck holes arent blocked on that end.
This might create a situation where water temps could read lower at crossover and cylinder jackets than they are at middle areas of the heads.

LMSracer has done alot of testing and likely knows what does work best as far as hose size, flow, and flow pressures/temps within the engine. He has several great posts/threads here(PY) on the subject.
Or contact Larry here... http://www.precisionautomotivespecialists.com/

[Skip Fix]

Originally Posted by gtofreek

What about running a hose from the rear of the passenger side head, to the rear of the drivers side head? Then, if you wanted to run a heater, then you could tee off of this hose to the heater core.

I T's the hoses on my 78 that way fro a long time.

My IA has two lines to the crossover and a thermostat.

Dave did you get the block water holes staightened out with the gasket?

[chuckies76ta]

Originally Posted by gtofreek

What about running a hose from the rear of the passenger side head, to the rear of the drivers side head? Then, if you wanted to run a heater, then you could tee off of this hose to the heater core.

I've done this also. I run from the back of both heads to a T fitting then through the heater core then back to the water pump. If you don't have the heater core just bypass it.

From what I understand the coolant flows up from the block through the heads through the heater core back to the water pump when the thermostat is closed. Plumbing in the back of the drivers head allows coolant to flow through heater core also. To me your trying to keep both heads the same temperature. The coolant will also flow from the block through the heads back to the water crossover and continue the process until the thermostat opens.

To me running lines from the back of the heads to the crossover won't work as well as plumbing them into the heater core return on the water pump. Simple reason is the engineers designed it so coolant will continue to run through the heater core. It will continue to move coolant from back of the heads to water pump through the block on a continues cycle. Thermostat will open and now start to move coolant through the rad back to engine. There are two systems at work here. A loop through the engine and the Rad loop

As far as air trapped in the back of the block it will migrate to the front of the crossover as soon as coolant starts to flow if there is any at the back of the heads because of the engine tilt as one member pointed out . I always remove the pipe plug in the cross over when initallally filling rad with coolant as it lets air that is trapped out of the engine.

Anyhow. Just my thoughts
Charles

[Cliff R]

"Quote from carb website: "In David Vizard's latest book on Holley, he writes about a gas mileage test he did with a SBC. His conclusion was (paraphrased): the worst mileage came from an unheated or only heat soaked manifold, better was the exhaust heated (but robbed 10 to 12 hp), and best gas mileage was achieved with a coolant-heated intake that held the manifold temperature to between 180* and 190* at a cost of only about 5 hp. This was accomplished by blocking the ports of the crossover and plumbing coolant through it from the radiator.""

Still very good info Tom, and something you might want to mention next time the topic comes up over on the street section, and the arguments start raging on, especially from the guy who advocates running a cold intake on ALL his engines, even when driven in Northern climates in the dead of Winter......FWIW.....Cliff