Ever use a REAR bypass hose for cooling? - Page 3 - Chevelle Tech
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post #31 of 59 (permalink) Old Jun 15th, 20, 1:56 PM
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Re: Ever use a REAR bypass hose for cooling?

I've run the hose from rear to just under the thermostat for each side, always seemed to keep the engine more temps unified and friendly, never had a problem doing it. There were other brands of engines that had cast in side to side passages at the rear of their V8 engines, no problems with those, either.
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post #32 of 59 (permalink) Old Jun 15th, 20, 4:16 PM Thread Starter
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Re: Ever use a REAR bypass hose for cooling?

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Originally Posted by Wolfplace View Post
....On the factory bypass you have to remember it is not circulating through the radiator just the engine & returning to the water pump so it will naturally come to temp quicker than a bypass hole in the thermostat which returns to the radiator so although the end result should be the same there is a difference in the two systems
Yes, that's what I was talking about in post #23. So I'm leaning towards drilling and tapping the manifold while I have the thing off. Like Mark said, I can always just close them up again with pipe plugs if I wanted to.

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Originally Posted by Dave Ray View Post
I've run the hose from rear to just under the thermostat for each side, always seemed to keep the engine more temps unified and friendly, never had a problem doing it. There were other brands of engines that had cast in side to side passages at the rear of their V8 engines, no problems with those, either.
Thank you for mentioning that. I thought I had seen pics somewhere of certain engines with intake manifolds that were plumbed like that before. I just cannot remember what they were, nor where I've seen them. I wish I could see for myself exactly what directions the water pump pushes the water through the engine and manifold, and how that current is effected by a bypass hose vs. not having a bypass hose, as well as how external add-on hoses might effect the current and flow, (if at all).

For instance: does the water pump draw the water from one side of the block, and push it through the other side while the thermostat is closed? And if so, which side does it draw from? And once the thermostat opens, and the water pump is drawing the water from the lower radiator hose, does it then push the water into both sides of the block, or does is still draw from one side and push it through the other side of the block? Do any of the two small ports at the top of the GM Long pumps draw water in, or do they both push the water out? And how might all that be effected by the bypass hose in the front of the block? Can anyone say for certain without actually sticking the lower radiator hose in a bathtub full of water with the hose still clamped to the pump, and finding a way to spin the pump to see for them self??

Has anyone here ever dismantled a GM water pump and had a look at the shape of the impeller? I cannot say that I have. If I did, then maybe I would have a better understanding of exactly how these mechanical pumps navigate the water through the engine block, and through the manifold.

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post #33 of 59 (permalink) Old Jun 15th, 20, 5:16 PM Thread Starter
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Re: Ever use a REAR bypass hose for cooling?

I just found this....it begins to answer some of the questions I had in my last post here in this thread.....I was thinking that the BBC front OE type bypass hose pushes water from the pump into the manifold, but the guy in this video below here says "NO".....


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post #34 of 59 (permalink) Old Jun 15th, 20, 6:05 PM
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Re: Ever use a REAR bypass hose for cooling?

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Originally Posted by BillyGman View Post
I just found this....it begins to answer some of the questions I had in my last post here in this thread.....I was thinking that the BBC front OE type bypass hose pushes water from the pump into the manifold, but the guy in this video below here says "NO".....

YouTube

Billy
I just got done explaining that to you in post 30???

Pay attention,,,,,,,,, there may be a test

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post #35 of 59 (permalink) Old Jun 15th, 20, 6:22 PM
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Re: Ever use a REAR bypass hose for cooling?

Billy,

Don’t do it. Your making this way more complicated than it needs to be.
If you are dead set on doing this - IMHO - only use a AN -4 braided hose from each head to the front of the manifold water jacket. They will really only be steam relief holes. You don’t want to change the pressure pathway of the coolant returning to the radiator.

On that manifold I would put the coolant temp probe in one hole and the electric fan temp probe in the other. If not running electric fans plug it.

I’ve never run the factory bypass up front. This just continually circulates hot coolant bypassing the thermostat, if you run one.
I’ve always used a restrictor washer in the thermostat housing.
It takes a little longer to heat up, so what. These cars don’t get driven in the winter in CT.

With a good radiator on a 90 degree day the fans never come on while driving on the highway. Fans typically cycle on @ 180 and off @ 190 no matter what the ambient air temp is.

A real 565 hp (give or take) to rear wheel BBC produces some serious heat.
I’d rather wait a little longer to drive off than chance overheating.

A stocker is a lot more forgiving.

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Last edited by bradley67; Jun 15th, 20 at 6:40 PM.
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post #36 of 59 (permalink) Old Jun 15th, 20, 6:53 PM
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Re: Ever use a REAR bypass hose for cooling?

Quote:
Originally Posted by BillyGman View Post

For instance: does the water pump draw the water from one side of the block, and push it through the other side while the thermostat is closed? And if so, which side does it draw from? And once the thermostat opens, and the water pump is drawing the water from the lower radiator hose, does it then push the water into both sides of the block, or does is still draw from one side and push it through the other side of the block? Do any of the two small ports at the top of the GM Long pumps draw water in, or do they both push the water out? And how might all that be effected by the bypass hose in the front of the block? Can anyone say for certain without actually sticking the lower radiator hose in a bathtub full of water with the hose still clamped to the pump, and finding a way to spin the pump to see for them self??

Has anyone here ever dismantled a GM water pump and had a look at the shape of the impeller? I cannot say that I have. If I did, then maybe I would have a better understanding of exactly how these mechanical pumps navigate the water through the engine block, and through the manifold.
BBC and the similar SBC water pumps....the small hose connections to the pump body, and the inlet hose from the radiator feed coolant into the center front face of the pump impeller.....the spinning impeller throws that coolant outward where it is collected by the internal shape of the pump body cavity and routed into the block through both legs of the water pump.

The better Air Conditioning/Heavy Duty application pumps, and many aftermarket pumps have a cast iron (aftermarket cast aluminum) curved vane impeller. The standard application factory pump is just a stamped steel impeller that looks almost identical to a stock stamped alternator cooling fan.

This vid is a more modern LS pump i believe, but the principle is the same and he explains the cavity's and functions well.

A lot of neat info and pics on the FlowKooler site too that may help your understanding of how water pumps work.
https://www.flowkoolerwaterpumps.com/
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post #37 of 59 (permalink) Old Jun 15th, 20, 8:22 PM
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Re: Ever use a REAR bypass hose for cooling?

Quote:
Originally Posted by BillyGman View Post
Has anyone here ever dismantled a GM water pump and had a look at the shape of the impeller?
Round?

Sorry Billy, I had to...
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post #38 of 59 (permalink) Old Jun 16th, 20, 6:13 AM Thread Starter
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Re: Ever use a REAR bypass hose for cooling?

Quote:
Originally Posted by Wolfplace View Post
Billy
I just got done explaining that to you in post 30???

Pay attention,,,,,,,,, there may be a test
Let me explain. What I learned specifically from the video that you didn't make mention of is the flow direction inside the front bypass hose... I thought that when a front bypass hose is used by connecting it to the top of the water pump, that coolant then gets pushed up into the front face of the manifold by the pump. But what that guy in the video is explaining is that flow is actually in the exact opposite direction than I thought it traveled in, because it's getting drawn into the top of the water pump through that small bypass hose. Not being pushed out of it. I told you that you gotta "dumb-it-down" for me son.

I also thought that the paddle-like fins of the impeller were shaped in such a way that it drew water into one mounting leg of the pump, and out of the other mounting leg. But based on the other video, it looks like my thinking was wrong about that too, since the impeller pushes water out of both of the legs and into both sides of the engine block. At least that's what's being said.

Quote:
Originally Posted by bradley67 View Post
Billy,

Don’t do it. Your making this way more complicated than it needs to be.
If you are dead set on doing this - IMHO - only use a AN -4 braided hose from each head to the front of the manifold water jacket. They will really only be steam relief holes. You don’t want to change the pressure pathway of the coolant returning to the radiator.

On that manifold I would put the coolant temp probe in one hole and the electric fan temp probe in the other. If not running electric fans plug it.

I’ve never run the factory bypass up front. This just continually circulates hot coolant bypassing the thermostat, if you run one.
I’ve always used a restrictor washer in the thermostat housing.
It takes a little longer to heat up, so what. These cars don’t get driven in the winter in CT.

With a good radiator on a 90 degree day the fans never come on while driving on the highway. Fans typically cycle on @ 180 and off @ 190 no matter what the ambient air temp is.

A real 565 hp (give or take) to rear wheel BBC produces some serious heat.
I’d rather wait a little longer to drive off than chance overheating.

A stocker is a lot more forgiving.

https://www.enginebuildermag.com/201...g-accessories/
Now that I'm understanding what the actual flow path of the water is, (as a result of those two videos) I agree with you on forgetting about the hoses being plumped from the rear of the manifold to the front. Yes I agree that it might upset the flow path of the water, and make cooling worse!!! I think while I have the manifold off the engine, I might drill and tap those two rear holes and put pipe plugs in them for now, just in case I decide to try installing the temp sender back there in the future, or if I find any gadget to thread in one the holes which can bleed off air without leaking any coolant out of it, ( I've never seen one like that though). I'm not quick to agree with you about your claim of the use of a front factory type bypass house bypassing the thermostat, because plenty of flow will still pass through the thermostat and into the radiator once the thermostat opens. I don't see any way that the front bypass house would stop or even significantly reduce flow past an open thermostat.

Quote:
Originally Posted by Ericnova72 View Post
BBC and the similar SBC water pumps....the small hose connections to the pump body, and the inlet hose from the radiator feed coolant into the center front face of the pump impeller.....the spinning impeller throws that coolant outward where it is collected by the internal shape of the pump body cavity and routed into the block through both legs of the water pump.

The better Air Conditioning/Heavy Duty application pumps, and many aftermarket pumps have a cast iron (aftermarket cast aluminum) curved vane impeller. The standard application factory pump is just a stamped steel impeller that looks almost identical to a stock stamped alternator cooling fan.

This vid is a more modern LS pump i believe, but the principle is the same and he explains the cavity's and functions well.
Inside a chevy water pump -- how it works - YouTube

A lot of neat info and pics on the FlowKooler site too that may help your understanding of how water pumps work.
https://www.flowkoolerwaterpumps.com/
Thanks. I had just found that same video yesterday and I was watching it. I'll take a look at the FlowKooler site too. Thank you

Quote:
Originally Posted by MarkP View Post
Round?

Sorry Billy, I had to...
Hahaha...yeah yeah yeah.....I meant the fins or the shape of the fins on the impeller. They kind of remind me of the stator fins of a torque converter.

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Last edited by BillyGman; Jun 16th, 20 at 6:37 AM.
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post #39 of 59 (permalink) Old Jun 16th, 20, 4:01 PM
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Re: Ever use a REAR bypass hose for cooling?

There are two types of pump impeller used for Chevy water pumps. One is a cast iron closed fin impeller design, with the rear of the fins closed off. Second is a stamped steel impeller, with an open back between fins. There are rivited in place block off plates available that close off the open fin impellers, making them like the cast iron closed back ones in function.

The stamped open fin impellers have too much coolant bypass to be effective in cooling.

Use the closed back impeller, or, if you only have the open impeller, Flow Kooler used to have the block off plates to close the backs of the open fin impellers.

There were a small number of factory cast manifolds that had the rear cross over cast into the manifold, and a couple of aftermarket ones did the same, can't remember just who did them. The passage went from one rear water port to the one on the other side of the manifold, not the way I do them, rear port to just under the thermostat, each side separate frm the other until they reach the thermostat housing.
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post #40 of 59 (permalink) Old Jun 17th, 20, 1:40 AM Thread Starter
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Re: Ever use a REAR bypass hose for cooling?

Quote:
Originally Posted by Dave Ray View Post
There are two types of pump impeller used for Chevy water pumps. One is a cast iron closed fin impeller design, with the rear of the fins closed off. Second is a stamped steel impeller, with an open back between fins. There are rivited in place block off plates available that close off the open fin impellers, making them like the cast iron closed back ones in function.

The stamped open fin impellers have too much coolant bypass to be effective in cooling.

Use the closed back impeller, or, if you only have the open impeller, Flow Kooler used to have the block off plates to close the backs of the open fin impellers.

There were a small number of factory cast manifolds that had the rear cross over cast into the manifold, and a couple of aftermarket ones did the same, can't remember just who did them. The passage went from one rear water port to the one on the other side of the manifold, not the way I do them, rear port to just under the thermostat, each side separate frm the other until they reach the thermostat housing.
Thanks for that info Dave. I have no idea which type of impeller my Weiand #8242 pump has, and that model had been discontinued, and replaced by the model #9242.

As far as Flow Kooler having those block off plates, thanks for the heads up, but if I'd have to remove the pump to change the plate, then I may as well buy a new pump while I have the old pump off of the block. Maybe I'll decide to get a Flow kooler pump in the future. I wonder how many guys here have used that brand of water pump, and what they thought about them.

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post #41 of 59 (permalink) Old Jun 17th, 20, 2:26 AM
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Re: Ever use a REAR bypass hose for cooling?

Get a Stewart water pump, unless things have changed NASCAR uses them. They have different ones available including the closed fin type. Mine is serpentine driven so the part number will be different, if I could find it.

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post #42 of 59 (permalink) Old Jun 17th, 20, 3:11 AM
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Re: Ever use a REAR bypass hose for cooling?

All the Weiand pumps I've ever looked at the inside use a curved vane, closed back cast aluminum impeller. I think most all you aftermarket pumps advertised as high volume or race pumps use good impellers, not the stamped cheapo's that are in stock replacement pumps.

FlowKooler doesn't offer the disc mod kit for stock stamped sheet impellers anymore....I've seen it from another source, but don't remember who it was.....might have been Summit or Jeg's house brand.
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post #43 of 59 (permalink) Old Jun 17th, 20, 3:13 AM Thread Starter
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Re: Ever use a REAR bypass hose for cooling?

Quote:
Originally Posted by Ericnova72 View Post
All the Weiand pumps I've ever looked at the inside use a curved vane, closed back cast aluminum impeller. I think most all you aftermarket pumps advertised as high volume or race pumps use good impellers, not the stamped cheapo's that are in stock replacement pumps.

FlowKooler doesn't offer the disc mod kit for stock stamped sheet impellers anymore....I've seen it from another source, but don't remember who it was.....might have been Summit or Jeg's house brand.
Thank you Eric

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post #44 of 59 (permalink) Old Jun 17th, 20, 8:14 AM
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Re: Ever use a REAR bypass hose for cooling?

Now that I'm understanding what the actual flow path of the water is, (as a result of those two videos) I agree with you on forgetting about the hoses being plumped from the rear of the manifold to the front. Yes I agree that it might upset the flow path of the water, and make cooling worse!!! I think while I have the manifold off the engine, I might drill and tap those two rear holes and put pipe plugs in them for now, just in case I decide to try installing the temp sender back there in the future, or if I find any gadget to thread in one the holes which can bleed off air without leaking any coolant out of it, ( I've never seen one like that though). I'm not quick to agree with you about your claim of the use of a front factory type bypass house bypassing the thermostat, because plenty of flow will still pass through the thermostat and into the radiator once the thermostat opens. I don't see any way that the front bypass house would stop or even significantly reduce flow past an open thermostat.

I never said it would STOP the coolant flow thru an open thermostat.
When the thermostat is closed the bypass hose does just that, it allows coolant to bypass the closed thermostat and recirculate to heat the engine up faster.
Now - if the engine is up to temp and the thermostat is open and also depending on what type of thermostat, that bypass continues to bypass SOME coolant. How much coolant it will bypass depends on what you have put in the thermostat housing, or not.
Water will always take the path of least resistance - remember the coolant pump is at work here also - pulling hot coolant from the intake manifold and mixing it with cool coolant from the radiator - so I would expect different volumes of coolant to be pulled thru the bypass -all the time - depending how open or not the thermostat is.
I just prefer to run a restrictor washer in the thermostat housing and no bypass hose. High horsepower big blocks produce a lot of heat. I know that’s stating the obvious! 😃

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post #45 of 59 (permalink) Old Jun 17th, 20, 1:53 PM
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Re: Ever use a REAR bypass hose for cooling?

Quote:
Originally Posted by BillK View Post
Also, If you don't have the front bypass hose that is most likely why you are getting the readings you have. That hose is to bypass some of the water around the thermostat to keep some circulation when the thermostat is closed.
With my old BBC engine it ran fine. Then somewhere I read to not use that front bypass. So I disconnected it.
I had problems after that and actually blew out the original copper/brass radiator.
Blew out one of the water hoses, it was a mess.

I got a cheapo plastic temporary hybred radiator after more than
one radiator shops told me mine couldn't be fixed any longer.

I reinstalled the bypass hose and didn't have the same problem again then with the old
engine and with my new engine and new aluminum radiator.

That was my experience with the front bypass hose, removed then installed.
Never used a rear bypass hose.

-- Spike
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