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02-22-2018, 03:57 PM | #1 |
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T-stat to drill a hole or not to drill a hole?
I am getting ready to replace my thermostat and was wondering if it is necessary to drill a 1/8 hole in it before installing , if so what are the benefits? I heard that by drilling a hole it could cause the temp to fluctuate. The PO did not drill holes in the current thermostat and the temp is at a constant 190.
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02-22-2018, 04:04 PM | #2 |
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Re: T-stat to drill a hole or not to drill a hole?
If it ain’t broke, don’t fix it. I’ve never drilled a hole in one, never had any issues either.
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02-22-2018, 04:20 PM | #3 |
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Re: T-stat to drill a hole or not to drill a hole?
Necessary? No. Helpful? Yes. It allows the engine and radiator to be completely filled with no air pockets being trapped. Drilling one or or two 1/8" holes in a thermostat creates no issues or fluctuating temps that I've ever seen. Many thermostats nowadays come with holes already in them....
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02-22-2018, 04:30 PM | #4 |
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Re: T-stat to drill a hole or not to drill a hole?
X2.
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02-22-2018, 05:12 PM | #5 |
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Re: T-stat to drill a hole or not to drill a hole?
They have the jiggle thing in them though.
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02-22-2018, 10:01 PM | #6 | |
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Re: T-stat to drill a hole or not to drill a hole?
Quote:
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02-22-2018, 05:42 PM | #7 |
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Re: T-stat to drill a hole or not to drill a hole?
Always drill two holes in them, it stops air pockets.
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02-22-2018, 05:45 PM | #8 |
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Re: T-stat to drill a hole or not to drill a hole?
Never drilled holes in any of them over 45 years ,So now it's the thing to do ?
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02-22-2018, 06:13 PM | #9 |
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Re: T-stat to drill a hole or not to drill a hole?
Millenials...
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02-22-2018, 06:32 PM | #10 |
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Re: T-stat to drill a hole or not to drill a hole?
Apparently it's the in thing to do now. This thread is the first I've heard of it!
-klb
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02-22-2018, 06:50 PM | #11 |
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Re: T-stat to drill a hole or not to drill a hole?
It also helps with aluminum heads because it is not as much of a shock due to temperature change when it opens.
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02-22-2018, 09:09 PM | #12 |
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Re: T-stat to drill a hole or not to drill a hole?
Just a tad overkill - but yes one 1/8 inch hole drilled helps for the purpose of air pockets
Last edited by hjewell2; 02-22-2018 at 09:11 PM. Reason: mis spelled |
02-22-2018, 08:05 PM | #13 |
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Re: T-stat to drill a hole or not to drill a hole?
I have heard of this before (recently), but have never done it. It came up in a discussion about the lack of wp bypass passage in the L31’s vortex heads and this was brought up as a possible mitigation. Having said all that, I HAVE had an air pocket in a rad and, if this would prevent that. I’m all for it. But I do wonder why, if it’s such a good idea why they didn’t come like this originally and still don’t as far as all the replacements I’ve bought.
What is this jiggle thing you speak of Demian?? Hey! I used to live in Lake Forest!! |
02-22-2018, 08:58 PM | #14 |
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Re: T-stat to drill a hole or not to drill a hole?
I had a Corvette years ago. And they are notorious for running hot. The person that built my motor. Put a bleed hole in the thermostat. And it did run cooler. I think maybe it helps with extra circulation. But it seem to work for me. Just my two cents.
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02-22-2018, 09:46 PM | #15 |
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Re: T-stat to drill a hole or not to drill a hole?
A bypass hose is what you need not a hole in your thermostat especially on a vortec. The bypass hose keeps the water circulating through the heads eliminating hot spots. I have never know a SBC to have a problem with air pockets, these old trucks ran with air in the radiator.
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02-23-2018, 01:27 PM | #16 |
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Re: T-stat to drill a hole or not to drill a hole?
Thanks Fellas! I don't have any issues with my engine running hot and if the cooling system is bled correctly wouldn't you not have to worry about air in the system?
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02-23-2018, 11:46 PM | #17 |
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Re: T-stat to drill a hole or not to drill a hole?
FWIW I drilled one very small hole in mine. The heater core looks to be higher than the top of the radiator and I did it to purge air pockets faster. Some thermostats already have a hole with a rivet looking piece that accomplishes the same thing. I have heard of guys propping a thermostat open with an aspirin on reassembly to let air out then the aspirin melts away and the system goes back to working normally. Without a hole I imagine air could accumulate around the thermostat and it would not open as soon but once it did it would purge the air. Probably over thinking it a bit but love the trucks.
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02-23-2018, 11:57 PM | #18 |
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Re: T-stat to drill a hole or not to drill a hole?
I haven't ever seen an actual flow diagram of the coolant circulation system of a Chevy engine, but I suspect that the bypass port in the SBC water pump or the bypass hose in a BBC probably covers this issue.
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02-24-2018, 09:50 AM | #19 |
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Re: T-stat to drill a hole or not to drill a hole?
Is it necessary to drill a hole in the thermostat? No, or they would come with the hole already drilled. Is it an effective way to keep a truck running cool as that thermostat allows in a wider set of circumstances? Yes. Is there any negative affect from drilling al 1/8" hole? No, only good. I never did it in all my years till a friend who is an ace mechanic suggested it when my truck seemed to run a tad hot after fresh heads bumped my compression. I'm a baby boomer and he is generation X. If it's a millennial thing to do, there's at least one good thing we can credit them . But I think it's an old school track trick that has found it's way into the mainstream.
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02-24-2018, 11:16 AM | #20 |
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Re: T-stat to drill a hole or not to drill a hole?
Drill
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02-24-2018, 02:49 PM | #21 |
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Re: T-stat to drill a hole or not to drill a hole?
Years ago I rebuilt a SBC and upon its first run my 50/50 mix kept spewing out of the radiator overflow and fill hole like a coffee pot peculator!
Assumed it was an air pocket trapped in there somewhere and was causing steam. Removed the thermostat and drove a few days and eventually it settled down, so I put the stat back in. I read someplace that the hole causes the engine to take a bit longer to warm up but can be helpful if the stat should seize closed. |
02-24-2018, 02:56 PM | #22 |
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Re: T-stat to drill a hole or not to drill a hole?
Small block Chevrolets have an internal bypass in the water pump, do they not? Seems redundant...
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02-24-2018, 03:09 PM | #23 |
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Re: T-stat to drill a hole or not to drill a hole?
Could very well be, that was my first rebuild and really don't know what was causing that problem.
ETA: Oh I think I see what you're saying, didn't know SBC water pumps had a bypass. ...oops! Last edited by BRL; 02-24-2018 at 03:28 PM. |
02-24-2018, 10:38 PM | #24 |
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Re: T-stat to drill a hole or not to drill a hole?
Vortecs don't have the water pump bypass. Also the water pump bypass is a pencil sized bypass the heater bypass circulates a lot more water. Another thing is the bypass does not send coolant back to the radiator, it just circulates it through the block and heads.
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02-25-2018, 08:43 AM | #25 |
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Re: T-stat to drill a hole or not to drill a hole?
It's not redundant to improve the flow of the bypass when it seems to be insufficient. These trucks came with a reliable ignition system. So someone could say going to HEI is redundant under the same logic.
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