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Discussion Starter · #1 ·
I recently bought a nice 56 Belair that has a strange cooling system modification that I have never seen before. The previous owner drilled and installed a hose on both sides of the engine from the bottom of the block water jacket to the water pump discharge. I assume it was to allow a 3/8" stream of water to enter the block below the number 5 and 6 cylinders rather than flow along the normal route through the front of the block. Is anyone out there familiar with this modification or have an opinion as to why it might have been done. The engine is a small block chevy equipped with Edelbrock aluminum heads. Thanks in advance.
 

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Just a thought!!
Possibly due to minimal coolant flow in the rear of the engine and possible cavitation or air lock may be the reason this was done.
 

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Looks like a bypass to me. All it's doing is recirculating some "warm" water back into the "cool" water, robbing some of the flow to the heads, where all the heat is. Fortunately the lines are probably too small to do much harm.
 

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Discussion Starter · #5 ·
i was hoping someone would have seen this modification before and could shed some light on it. I thought it might be similar to the Ramjet modification discussed in the sticky in this forum but it appears not. Hopefully someone will see the picture one day and know what it is for. Thanks for the comments though, much appreciated.
And to all of you veterans out there, thanks for everything.
 

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That's a roundy round trick.
Sometimes they go from front to rear coolant crossover on the manifold.
It's to help with hot spots and air pockets in the coolant system.
NOTE: sometimes a reverse flow water pump is used with this system.
If you ever have to replace the w/p, make sure you know what it is.
 

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Looks like a bypass to me. All it's doing is recirculating some "warm" water back into the "cool" water, robbing some of the flow to the heads, where all the heat is. Fortunately the lines are probably too small to do much harm.
The lines are connected to the high pressure (discharge) side of the pump. In a stock engine the water pump pushes coolant in the front of the block and out the top at the front of the intake manifold. With the stock setup circulation is higher in the front of the engine and the back cylinders run hotter. I believe the idea was to send some cool water from the pump to the back of the engine. For this to work it might be necessary to place a slight restriction where the cool water enters the front of the block to force cool water through the lines to the back of the block.

If it were my car I would plug the lines off and see if there was any difference in cooling.
 

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I recently bought a nice 56 Belair that has a strange cooling system modification that I have never seen before. The previous owner drilled and installed a hose on both sides of the engine from the bottom of the block water jacket to the water pump discharge. I assume it was to allow a 3/8" stream of water to enter the block below the number 5 and 6 cylinders rather than flow along the normal route through the front of the block. Is anyone out there familiar with this modification or have an opinion as to why it might have been done. The engine is a small block chevy equipped with Edelbrock aluminum heads. Thanks in advance.
That is part of what used to be a very popular circle track cooling system modification in an effort to better equalize the cooling in a 4.125" bore siamese cylinder wall chevy block. Water from the pressure side of the pump was pushed up through the bottom of the block through the water drain holes. The second part of this modification was additional holes were also drilled and tapped in the rear of the intake manifold to intersect the water holes in the head. In the center of the intake manifold slots were milled and additional holes drilled into the water jacket in the head.Some after market head manufacturers such as Brodix actually drilled and tapped the holes for you,especially in the spread port version of their heads. Hoses were then plumbed from the rear holes teed into the center holes and then were connected to a spacer under the water outlet. This was said to prevent hot spots due to steam pockets and low water flow and aid in keeping bore straightness and circularity thus improving ring seal and lowering the risk of cylinder wall cracking. It was very popular to do this in the 80s and 90s
 

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Let me explain my thoughts on this a bit more.

The block drains are only 1/4" NPT. There's no way you're pushing any significant flow from fittings on the water pump, through 15"-18" hose, and through a 1/4" NPT fitting on the block drain. You'll still have most of the flow going through the 5/8" or so holes on the water pump directly into the block. And the flow that goes into the drain ports is far away from the heads where the coolant needs to go. The other half of this is that Chevy and the aftermarket head gasket suppliers limit the flow through all the holes in the head gasket so that all of the cylinders in the head get a pretty even flow from the block. What I'm saying is that what you do to the block doesn't matter, the flow to the combustion chamber is controlled by the head gasket.

On the other hand, having a fitting/line at the rear of the heads back to the crossover at the front of the intake makes some sense. If there are air/steam pockets on cylinders 7 or 8, that gets relieved and returned eventually to the radiator.

So, bottom line, the stuff on top is ok, the stuff on bottom makes little sense. At least to me.
 

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An Aussie guy John Bennett developed a similar system some time back. He relocated the thermostat to the lower hose and used two hoses tapped into the rear of the intake. Was designed to better distribute the water to the rear of the block. He also reworked the water pump to better control the flow. A few guys I know used they system and said it really worked.
Google John Bennett cooling system and you might find some background info.

Cheers, Des
 

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Let me explain my thoughts on this a bit more.

The block drains are only 1/4" NPT. There's no way you're pushing any significant flow from fittings on the water pump, through 15"-18" hose, and through a 1/4" NPT fitting on the block drain. You'll still have most of the flow going through the 5/8" or so holes on the water pump directly into the block. And the flow that goes into the drain ports is far away from the heads where the coolant needs to go. The other half of this is that Chevy and the aftermarket head gasket suppliers limit the flow through all the holes in the head gasket so that all of the cylinders in the head get a pretty even flow from the block. What I'm saying is that what you do to the block doesn't matter, the flow to the combustion chamber is controlled by the head gasket.

On the other hand, having a fitting/line at the rear of the heads back to the crossover at the front of the intake makes some sense. If there are air/steam pockets on cylinders 7 or 8, that gets relieved and returned eventually to the radiator.

So, bottom line, the stuff on top is ok, the stuff on bottom makes little sense. At least to me.
I agree with your opinion and would add that we actually did a considrable amount of testing in regards to cylinder bore geometry during that time period. Our focus was mainly in regards to sonic testing cylinder wall thickness and then based on that what was the bore geometry at engine build time vs when the engine came back for freshening.Engine leak down information also was included in the test as well. We noted the cooling system setup as part of that. The bottom line was that there was no measurable difference unless the wall thickness dropped below .200 or so then big changes would often happen. We did see more change in a new block vs a overbored seasoned block. Based on that we did some pre-seasoning tests by heating the block to 190 in an oven for 8 hrs and saw some improvement but finally not worth the trouble and time to do..
 
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