Thermostat By-pass Question - Team Camaro Tech
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post #1 of 14 (permalink) Old Jan 26th, 01, 12:17 PM Thread Starter
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I have a '96 truck vortec 350 in my '68 that is stock except for a performer RPM manifold. Before I put the manifold on the motor, I was checking out the thermostat by-pass hole in the block near where the water pump bolts on. I ran a plastic straw from a WD-40 can up through there, and it wouldn't go past the surface of the block. The water jacket of the head has a hole that would match up with this hole, but evidently the head gasket does not have a hole there. I knew that I had to have some kind of by-pass so that coolant would circulate in the block before it got hot enough for the thermostat to open, so I drilled a 1/4" hole in the thermostat flange. This worked fine in warm weather, but now my problem is that in cold weather, a 30 minute drive won't even get the engine up to even 160 degrees (engine runs poorly & no heat !) because all the water in the radiator is circulating all of the time. I don't know what kind of by-pass was used with the factory set up, some kind of hose, I guess. Does anyone have any idea of how to make a bypass around the thermostat ? I don't really want to pull the head and change the head gasket. Thanks, Ron.
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post #2 of 14 (permalink) Old Jan 26th, 01, 12:36 PM
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Sounds like that hole in the thermostat is causing your problem to me. It's not letting the thermostat do it's job of regulating engine temp. I'd get a new thermostat.

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post #3 of 14 (permalink) Old Jan 26th, 01, 12:54 PM Thread Starter
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Thanks for the reply, but I've got to leave in the thermostat with the hole until I can figure out some other way to by-pass it. There has to be some way for the coolant to circulate through the block before the thermostat opens to prevent hotspots. If the coolant didn't circulate, there's no telling how hot it would get around the head and cylinders before the area around the thermostat got hot enough to open. Thanks, Ron.
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post #4 of 14 (permalink) Old Jan 26th, 01, 04:41 PM
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Millions and millions of small-block Chevys run fine without an added bypass - you don't need it. Get a Robertshaw high-flow thermostat (available at any good auto parts store) and forget about it.

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post #5 of 14 (permalink) Old Jan 26th, 01, 04:49 PM
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Ron,
A 1/4" hole should not allow enough water flow to keep the motor from warming up, especially without the other bypass in the water pump. You might just have a defective thermostat, wont be the first time a new part is bad. All you really need to allow circulation is about a 1/16" hole in the thermostat.

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post #6 of 14 (permalink) Old Jan 26th, 01, 08:37 PM
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ok, edelbrock says to run a hose from the hole in the front of the manifold to the hole in the water pump. i did not do this as it is realy not needed it only aid's in a qicker warm up. replace your therm! get a high flow therm and you will be fine. worked for me! just take's a little longer to warm up in the winter is all.
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post #7 of 14 (permalink) Old Jan 27th, 01, 03:12 PM Thread Starter
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Thanks for the replies. I'll get one of those high flow units and put a 1/16" hole in the flange and see what happens.
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post #8 of 14 (permalink) Old Jan 27th, 01, 09:52 PM
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do not put a hole in it!!! you do not need it! just install it and go. by puting a hole in it you will not be happy. it should all ready be in it mine hade one all ready.

[This message has been edited by ilbl8 (edited 01-27-2001).]
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post #9 of 14 (permalink) Old Feb 4th, 01, 04:20 PM Thread Starter
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Well, I checked all the local parts places, and none of them have a thermostat that already has a hole in the flange. I did get a good quality Stant thermostat. I'll have to put a 1/16" hole in it since I don't have the normal by-pass in my engine. If that doesn't work, I guess I'll have to change the head gasket to one with a hole where the block by-pass is. Thanks, Ron.
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post #10 of 14 (permalink) Old Feb 5th, 01, 11:47 PM
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rons68,

Mr Gasket make's one. it is a high flow performance therm they go for around 10 buck's. you can get it is 180 or 195.
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post #11 of 14 (permalink) Old Feb 7th, 01, 07:17 PM
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If your car has a heater, isn't that a "bypass"?
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post #12 of 14 (permalink) Old Feb 8th, 01, 08:10 AM Thread Starter
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David, Thats a good question, and I don't know enough about how the cooling system flows to answer it. One of my heater hoses goes to a nipple on top of the water pump, and the other goes to a fitting on the front passenger side of the intake. With my situation of not having the internal by-pass in the block, I don't know if the coolant would circulate through the heater core and block, or just sit there while the thermostat is closed.
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post #13 of 14 (permalink) Old Feb 11th, 01, 07:09 PM
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it will act as a bypass, and you do not need one anyway. there are alot of car's with no heater in them runing around.

the bypass is to aid in warm up, with out it the motor take's alot longer to get to temp is all. also the bypass help's to even out the shock of the therm opening. that is to say when the therm open's a rush of cooler water enter's the motor realy fast, with the bypass this is a more even and smooth transfer.

[This message has been edited by ilbl8 (edited 02-11-2001).]
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post #14 of 14 (permalink) Old Feb 12th, 01, 07:36 AM Thread Starter
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I put in a new thermostat this weekend, didn't put a hole in the flange and it worked fine ! I let the car warm up before I drove it; I could feel the hot water going through the heater hoses before the thermostat even opened, so that told me for sure that the coolant was moving through the engine. I was creating my own problem, like you guys who responded told me. I guess I worry too much ! Thanks, Ron
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