Ever use a REAR bypass hose for cooling? - Page 2 - Chevelle Tech
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post #16 of 59 (permalink) Old Jun 14th, 20, 1:12 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 was planning on drilling .718" hole, (23/32" drill bit that a 1/2" NPT tap calls for) in each of the two rear manifold bosses, and using one of these stainless steel 1/2" NPT 90 deg. fittings threaded into each of the two bosses, with a 3/4" diameter heater hose which would connect the coolant flow from one head to the other, just like the front casted part of the manifold does. The 3/4" diameter heater hose would pass across the rear of the manifold, in front of the distributor.

I dont see where that will do anything at all to be honest with you. The water pressure will be the same on both sides and there will be very little flow between them.


The front is only connected together so that the water from both sides can get to the thermostat housing. The water gets pumped into the block from the water pump in the front on each side, goes back through the block then up in the back to the heads and back to the front to exit through the thermostat housing. The two sides are independent.
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post #17 of 59 (permalink) Old Jun 14th, 20, 1:37 PM
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I wouldn't bother connecting the two at the rear together, unless you're going to "Y" or "T" them to the front. Honestly I would run one side rear to front before I'd do that.(choose the side with the rear most cylinder) There is some engineering precedent for this as Pontiac allowed the rear passenger side head to flow through the heater core, then back to the suction side of the water pump. This served to equalize coolant flow and provide heat. Sometimes engineers are pretty smart 😉
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post #18 of 59 (permalink) Old Jun 14th, 20, 1:55 PM
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Re: Ever use a REAR bypass hose for cooling?

Billy
Appears the only issue you are trying to fix is the temp going up before the thermostat opens because you have no bypass with a bunch of unnecessary crap,,,,,,,,,,,,
Sometimes simple is better.........
You can drill the front of the intake if you must but I can tell you I do not have one BBC with that hose unless it is a stock deal
All you need is the correct thermostat with the bleed holes to get both the trapped air & to bypass when the unit is closed
https://www.summitracing.com/parts/emp-301
Or,, just drill yours
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post #19 of 59 (permalink) Old Jun 14th, 20, 7:17 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
Billy
Appears the only issue you are trying to fix is the temp going up before the thermostat opens because you have no bypass with a bunch of unnecessary crap,,,,,,,,,,,,
Sometimes simple is better.........
You can drill the front of the intake if you must but I can tell you I do not have one BBC with that hose unless it is a stock deal
All you need is the correct thermostat with the bleed holes to get both the trapped air & to bypass when the unit is closed
https://www.summitracing.com/parts/emp-301
Or,, just drill yours
Thanks for chiming in Mike. I'll place the sender in the manifold like I always did with my SBC engines. But I haven't drilled any holes in the manifold yet. Thank you for the link. I know that it's a popular thing to just drill holes in the thermostat or get one with holes already in it, and I understand that your suggestion for me to do that is due to it being the easier way to take care of this and be done with it. Since I have the manifold off, now was/is the time to consider the bypass fitting in the manifold rather than thinking about it after it's bolted on.

I suppose if I was going to play devil's advocate here just to shuffle the deck so to speak to get some more viewpoints, I could go as far as to ask that if I'm going to use a thermostat with small holes drilled into it, then why use a thermostat at all? Why not just remove it all together? With holes in the thermostat, it's never really closed. I mean with the factory type front bypass hose, you still allow the full open/full closed mode of the thermostat the way it was designed to work. I'm not meaning to split hairs here. Either way will get the job done I suppose, and your suggested method is easier since it allows me to avoid having to drill and tap a hole in the front of the manifold.

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post #20 of 59 (permalink) Old Jun 14th, 20, 7:51 PM
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Re: Ever use a REAR bypass hose for cooling?

We tried the hoses (front to back) on the dyno and at the track with our Super Stocker........ no difference. Now in a roundy round car ,maybe.
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post #21 of 59 (permalink) Old Jun 14th, 20, 8:32 PM
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Re: Ever use a REAR bypass hose for cooling?

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Originally Posted by BillyGman View Post
Thanks for chiming in Mike. I'll place the sender in the manifold like I always did with my SBC engines. But I haven't drilled any holes in the manifold yet. Thank you for the link. I know that it's a popular thing to just drill holes in the thermostat or get one with holes already in it, and I understand that your suggestion for me to do that is due to it being the easier way to take care of this and be done with it. Since I have the manifold off, now was/is the time to consider the bypass fitting in the manifold rather than thinking about it after it's bolted on.

I suppose if I was going to play devil's advocate here just to shuffle the deck so to speak to get some more viewpoints, I could go as far as to ask that if I'm going to use a thermostat with small holes drilled into it, then why use a thermostat at all? Why not just remove it all together? With holes in the thermostat, it's never really closed. I mean with the factory type front bypass hose, you still allow the full open/full closed mode of the thermostat the way it was designed to work. I'm not meaning to split hairs here. Either way will get the job done I suppose, and your suggested method is easier since it allows me to avoid having to drill and tap a hole in the front of the manifold.
By crap I mean all the extra hoses from the rear etc.
We use these in some circle track deals to enhance cooling but this is a totally different application

Don't think the holes are going to pass as much water as no thermostat or one that isn't there....
Also how much water do you suppose is going through that bypass hose in comparison to the hole or holes in the thermostat?
The holes will cause the warm-up to be slower (as will the factory bypass) but the thermostat is still a big restriction until open so I would suggest you do not run without it, very hard on a street deal you need to get the water temp up unless you like water in your oil
The biggest deal is you need the oil to get hot like 200+ or the condensation will not burn off.
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post #22 of 59 (permalink) Old Jun 14th, 20, 8:35 PM Thread Starter
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Re: Ever use a REAR bypass hose for cooling?

I'm mostly focused on wanting to be sure I can have the cooling system circulating as well as possible to avoid hot spots, and avoid detonation with a fairly high static comp ratio on pump gas, with the OE four core radiator and a mechanical water pump. I'm not looking to make more power by altering the coolant system. Avoiding stagnancy and hot spots in the heads and block is my goal. I'd like to rely on the OE radiator and OE type water pump if I can. How much the .400" increase in deck height on an iron block plays a role in this equation, I don't know.

My thinking was if I can adopt a way to keep the water flowing and moving around the the heads, even in the rear section of the engine near the firewall where it's furthest away from the water pump, even before the thermostat opens, it might prevent the water from sitting in any one spot and getting ready to boil before the thermostat opens. Even if the water moves around in a circle, at least it would still be moving around and helping to wick away some of the heat that the heads are developing in any one or two hot spots. That was the theory being tossed around in my mind, but IDK, maybe it's nothing but a theory. That's why I decided to consult all of you about this. I appreciate everyone's participation so far. It's very helpful to me.
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post #23 of 59 (permalink) Old Jun 14th, 20, 8:56 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
....
Also how much water do you suppose is going through that bypass hose in comparison to the hole or holes in the thermostat?
The holes will cause the warm-up to be slower (as will the factory bypass) but the thermostat is still a big restriction until open so I would suggest you do not run without it, very hard on a street deal you need to get the water temp up unless you like water in your oil
The biggest deal is you need the oil to get hot like 200+ or the condensation will not burn off.
I never thought about water in the oil Mike. yeah, that would obviously be a no no. And yeah, I wasn't seriously considering running without a thermostat. Sometimes I have to go into devil's advocate mode to get you and some of the other knowledgeable and seasoned builders/racers to share more and dumb it down for me.

ofcourse the factory type 3/4" diameter bypass hose is going to move more water than a couple small holes drilled into the thermostat will. Your point is well taken and acknowledged. It just seems like it would be a little different with the bypass hose since it's moving the water around a little more while the thermostat is still completely blocked, and before hot water begins flowing past it and into the upper hose and onto the radiator. I was even thinking about attaching a small 6" aluminum finned heat sink between the two rear manifold bosses that I was going to drill and tap, just to wick away some extra heat, ( like the in-line finned heat sinks they sell for the cooling of the transmission fluid) but that probably would be more effort and expense than it's worth, since one 6" long heat sink likely wouldn't make much difference, if any at all. But like I said, I'm just brain storming a little bit while I still have the manifold off.

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post #24 of 59 (permalink) Old Jun 14th, 20, 11:09 PM
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Re: Ever use a REAR bypass hose for cooling?

I've run many BBC without the factory bypass but use the heater hose connections. Does the same thing.
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post #25 of 59 (permalink) Old Jun 15th, 20, 5:37 AM
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Re: Ever use a REAR bypass hose for cooling?

[QUOTE=Wolfplace;11319978]By crap I mean all the extra hoses from the rear etc.
We use these in some circle track deals to enhance cooling but this is a totally different application

Don't think the holes are going to pass as much water as no thermostat or one that isn't there....
Also how much water do you suppose is going through that bypass hose in comparison to the hole or holes in the thermostat?
The holes will cause the warm-up to be slower (as will the factory bypass) but the thermostat is still a big restriction until open so I would suggest you do not run without it, very hard on a street deal you need to get the water temp up unless you like water in your oil
The biggest deal is you need the oil to get hot like 200+ or the condensation will not burn off.

Curious to the size of hole you use in the thermostat?? Multiple holes??
Thanks in advance

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post #26 of 59 (permalink) Old Jun 15th, 20, 6:08 AM
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Re: Ever use a REAR bypass hose for cooling?

I think the ones I have are (3) 1/8” holes.
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post #27 of 59 (permalink) Old Jun 15th, 20, 7:26 AM Thread Starter
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Re: Ever use a REAR bypass hose for cooling?

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I've run many BBC without the factory bypass but use the heater hose connections. Does the same thing.
I've read that before, (I mean using the heater hoses and the heater core as a type of bypass). Am I reading you right? If I am, the issue with my car is that the heater core wasn't used by the previous owner since he drag raced the car only, so I haven't any doubt that the core is pretty much rusted out, and would leak coolant all over the place if I did attach the heater hoses to it. I don't plan on ever using the heater, so with this car, it's actually easier for me to drill and tap a hole in the manifold for a bypass hose before I install it onto the engine, rather than removing and replacing the heater core.

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post #28 of 59 (permalink) Old Jun 15th, 20, 12:13 PM
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Re: Ever use a REAR bypass hose for cooling?

If you run that intake without the bypass, run that 301 Stewart thermostat that Mike posted. With the bypass holes at the top of that cone in the center of the thermostat, I think the fluid flows past the spring allowing it to open faster. Plus, it will bleed the air out on the initial fill. It works well on my 502.

As far as the rear tubes, I really don't see how it would help. Just to keep you thinking: would it rob flow from the rest of the head if you installed them? I guess it wouldn't hurt to tap the manifold because you could always plug them if it doesn't work. I wouldn't install 1/2 npt maybe 3/8 or 1/4 npt. You wouldn't want a lot of flow.

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post #29 of 59 (permalink) Old Jun 15th, 20, 12:29 PM
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Re: Ever use a REAR bypass hose for cooling?

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Just to keep you thinking: would it rob flow from the rest of the head if you installed them?

Only if you put a Tee in it and run a hose up to the front. Otherwise a hose between the two sides is going to do pretty much nothing.
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post #30 of 59 (permalink) Old Jun 15th, 20, 1:17 PM
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Re: Ever use a REAR bypass hose for cooling?

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Curious to the size of hole you use in the thermostat?? Multiple holes??
Thanks in advance
I prefer a single hole about .187 or a couple of smaller holes
The linked EMP thermostat has three as I recall, been a while since I looked at one & it will slow heating quite a bit compared to a single hole or the factory bypass unless the newer ones have smaller holes,,
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

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