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98 vortec questions

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Old 10-18-2014, 09:35 PM
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98 vortec questions

Hey all.

Got a few questions that I can't seem to find answers to anywhere.

Bit of info before I proceed. The car is a 1987 camaro with p/s heater and ac delete. Motor going in is a carbed 1998 vortec 5.7.

1. I'd like to know if I can use a electric 35gpm 12volt, 7amp draw waterpump
(If so, what do I do about the "bypass" I keep reading about and can't make sense of)

2. Is there room in our cars to use a low mount passenger side alternator.

3. If using a electric water pump, do I buy a crank pulley and alternator bracket for a short water pump or long?

Any advice would be greatly appreciated as I would like to start buying parts and get this motor in asap
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Old 10-19-2014, 12:17 AM
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Re: 98 vortec questions

1-i think 35 gpm would be enough for non-highway use-"bypass"coolant flow passes coolant past the thermostat wax chamber so the thermostat will begin to open once the temperature of bypass flow gets to thermostat opening temp.
Never tried it myself,but i presume no thermostat will be needed if water pump is controlled in a manner to maintain proper engine temperature.
2-yes,depends on alternator and pulleys used.
3-depends on alternator size and location-if electrical load is fairly low,a small japanese alternator could be used-mounted low and using short pulley
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Old 10-19-2014, 09:35 AM
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Re: 98 vortec questions

Originally Posted by Dombant View Post
(If so, what do I do about the "bypass" I keep reading about and can't make sense of)
When the thermostat is closed, there is no water flowing from the engine to the radiator. Therefore, the water pump can't pump any more water into the block. Pre-Vortec SBCs have an internal passage (attached picture) that allows water from the block/head/thermostat area to flow into the water pump for circulation.

SBC engines with Vortec heads and/or block do not have this passage, so like a BBC, needs an external thermostat-bypass... which can be just a hose from the intake to the pump.

There are a couple ways to accomplish this:
1) remove thermostat. BUT, you need to control the water(pump) to allow the engine to warm up sufficiently.
2) add a big block style (3" long or so) manifold-to-waterpump hose.
3) have a heater core hooked up, to serve as the bypass. The factory from-manifold, to-radiator heater hose routing will also accomplish bypass.

If I could not explain it good enough, here is a quote I found:
"Engines with thermostats don't allow any water to move in the front of the intake if you don't run a bypass. The water gets very hot in the heads during warm up and since the water is not moving, the heads just keep getting hotter and hotter until enough heat wicks up to the front of the intake/thermostat and allows it to open. Thermostats open and close during engine operation and what will happen is that the temperatures in the heads will swing wildly and not as well controlled as it will if you DO run a bypass. The internal bypass in the older blocks is only on one side because that is all you need to let the water move.

Pictures:
1) bypass port on water pump, that works with PRE-Vortec engine
2) Vortec block, missing the internal bypass passage.
3) BBC bypass hose. Note: the fitting has a small passage so it doesn't bypass too much water.
Attached Thumbnails 98 vortec questions-bypass.png   98 vortec questions-no-bypass.jpg   98 vortec questions-bbc-bypass.jpg  
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Old 10-09-2018, 05:12 PM
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Re: 98 vortec questions

Originally Posted by MoJoe View Post
When the thermostat is closed, there is no water flowing from the engine to the radiator. Therefore, the water pump can't pump any more water into the block. Pre-Vortec SBCs have an internal passage (attached picture) that allows water from the block/head/thermostat area to flow into the water pump for circulation.

SBC engines with Vortec heads and/or block do not have this passage, so like a BBC, needs an external thermostat-bypass... which can be just a hose from the intake to the pump.

There are a couple ways to accomplish this:
1) remove thermostat. BUT, you need to control the water(pump) to allow the engine to warm up sufficiently.
2) add a big block style (3" long or so) manifold-to-waterpump hose.
3) have a heater core hooked up, to serve as the bypass. The factory from-manifold, to-radiator heater hose routing will also accomplish bypass.

If I could not explain it good enough, here is a quote I found:
"Engines with thermostats don't allow any water to move in the front of the intake if you don't run a bypass. The water gets very hot in the heads during warm up and since the water is not moving, the heads just keep getting hotter and hotter until enough heat wicks up to the front of the intake/thermostat and allows it to open. Thermostats open and close during engine operation and what will happen is that the temperatures in the heads will swing wildly and not as well controlled as it will if you DO run a bypass. The internal bypass in the older blocks is only on one side because that is all you need to let the water move.

Pictures:
1) bypass port on water pump, that works with PRE-Vortec engine
2) Vortec block, missing the internal bypass passage.
3) BBC bypass hose. Note: the fitting has a small passage so it doesn't bypass too much water.

Reviving this thread! Thanks for a very informative reply regarding the Vortec heads and cooling considerations. Question... I have a small block 350 GM Performance turn key crate motor with Vortec heads which I just inherited. The block itself DOES have the internal bypass passage on the passenger side where the water pump mounts. This indicates to me that the Vortec heads were used on a "non-vortec" block. Would I still need to run a external coolant bypass hose from the manifold to the water pump? Currently, it does not have one installed but the motor is running hot. One of the main reasons I discovered when pulling the pump was that it was the wrong rotation pump. I am replacing it with the correct pump but I still wonder if i need to hook up a bypass hose since my block has the internal bypass passage.
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Old 10-09-2018, 10:29 PM
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Re: 98 vortec questions

That IS a good description with pictures from MoJoe. I didn't know any of that.

My SBC education continues....
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Old 10-10-2018, 09:43 AM
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Re: 98 vortec questions

Originally Posted by DynoDave43 View Post
That IS a good description with pictures from MoJoe. I didn't know any of that.

My SBC education continues....
I spoke to a tech guy at GM Performance Parts yesterday who assured me I would still need to run the external coolant bypass hose between the intake manifold and the water pump even if my block has the coolant bypass passage which Vortec blocks don't have. The issue is with the Vortec head since it does not have the coolant circulation passages that non-Vortec heads have. So even if the block has the bypass passage, the coolant will simply reach a dead-end where it meets the Vortec head.
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Old 10-11-2018, 08:57 AM
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Re: 98 vortec questions

That is a good point: Even if the pump and block have the bypass, because the stock Vortec head does not have the passage, you have to run the external bypass.

One of my preferred tips is to drill a 1/8" hole or two in the thermostat. This will prevent any air/steam from backing up behind the thermostat... which insulated the stat from the heat, preventing it for opening. It will also provide a little bypass and circulation. I don't know if this is enough for closed-thermostat operation.

Does the engine run hot all the time? Or only until the thermostat opens? Does the upper hose get hot? (To indicate the thermostat DOES open). Take the radiator cap off before it is hot, run the engine until it it hot/over-heating... Do you see water flowing through the radiator?
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Old 10-11-2018, 11:20 AM
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Re: 98 vortec questions

I know it sounds odd but after I replaced the water pump on my 79 block with vortec heads with a new one I had all sorts of overheating issues on the expressway. Went through tried everything new thermostat, head gasket check, leak down, radiator flush and new waterpump. Everything was perfect as soon as the thermostat opened while I was idling. Added a bypass and no more issues sense.

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Old 10-11-2018, 02:41 PM
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Re: 98 vortec questions

Originally Posted by imyourmaster View Post
I spoke to a tech guy at GM Performance Parts yesterday who assured me I would still need to run the external coolant bypass hose between the intake manifold and the water pump even if my block has the coolant bypass passage which Vortec blocks don't have. The issue is with the Vortec head since it does not have the coolant circulation passages that non-Vortec heads have. So even if the block has the bypass passage, the coolant will simply reach a dead-end where it meets the Vortec head.
I have drilled more than one Vortec head for the missing passageway using the head gasket as a template.

If you are using a factory 3rd gen cooling system the heater core is perfectly adequate as a bypass itself and you do not need an external bypass of any kind.

Drilling the thermostat is also a great way to bypass water if you need it.
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