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#1 |
Registered User
Join Date: Sep 2016
Location: Brentwood CA
Posts: 180
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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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#2 |
Moderator
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Location: Southern Cal
Posts: 20,005
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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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1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man |
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#3 |
Registered User
Join Date: May 2016
Location: Waverly, NE
Posts: 334
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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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1965 Malibu SS L79 Restoration Page 1965 Two-Door Wagon Project Progress Page 2006 Pontiac GTO Preservation Project Rich Cummings Last edited by Rich69shortfleet; 02-22-2018 at 07:27 PM. |
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#4 |
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![]() Join Date: May 2016
Location: Sackets harbor ny
Posts: 282
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Re: T-stat to drill a hole or not to drill a hole?
X2.
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#5 |
Registered User
Join Date: Aug 2016
Location: Lake Forest, CA
Posts: 2,177
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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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"Work hard, use your vacation days." 1970 C15 GMC Long Bed 1986 C20 Scottsdale 1983 K2500 Sierra Classic Suburban 6.2 Instagram: C10sofOC |
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#6 | |
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Join Date: Jan 2011
Location: Townsend MT
Posts: 1,725
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Re: T-stat to drill a hole or not to drill a hole?
Quote:
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#7 |
Registered User
Join Date: Jan 2015
Location: howard city mi
Posts: 83
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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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#8 |
Senior Member
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Location: Gods country East,Tn
Posts: 8,545
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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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#9 |
Registered User
Join Date: Aug 2016
Location: Lake Forest, CA
Posts: 2,177
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Re: T-stat to drill a hole or not to drill a hole?
Millenials...
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"Work hard, use your vacation days." 1970 C15 GMC Long Bed 1986 C20 Scottsdale 1983 K2500 Sierra Classic Suburban 6.2 Instagram: C10sofOC |
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#10 |
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Join Date: Oct 2016
Location: Dallas Texas
Posts: 3,091
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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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67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi 07 335 sport turbo 6sp 94 Trans Am GT LT1 6sp posi -- sold after 22yrs 99 540 sport V8 6sp -- sold 73 240z L24 4sp -- given to friend 68 C10 step 350/350 3.73 open -- sold |
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#11 |
Registered User
Join Date: Nov 2016
Location: Center ND
Posts: 73
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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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#12 |
Registered User
Join Date: May 2011
Location: mich
Posts: 655
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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 |
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#13 |
Senior Member
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Location: Godley, TX
Posts: 17,964
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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!! |
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#14 |
Registered User
![]() Join Date: May 2016
Location: Sackets harbor ny
Posts: 282
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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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#15 |
Registered User
Join Date: May 2016
Location: Henderson NC
Posts: 975
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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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#16 |
Registered User
Join Date: Sep 2016
Location: Brentwood CA
Posts: 180
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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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#17 |
Registered User
Join Date: Feb 2015
Location: TX Hill Country
Posts: 150
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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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#18 |
Who Changed This?
![]() Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,430
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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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#19 |
Special Order
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Location: Mt Airy, MD
Posts: 85,859
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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
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"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ Last edited by special-K; 02-25-2018 at 08:36 AM. |
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#20 |
Registered User
Join Date: Nov 2017
Location: JOPLIN MO
Posts: 59
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Re: T-stat to drill a hole or not to drill a hole?
Drill
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#21 |
Registered User
Join Date: Jun 2014
Location: Tahuya WA
Posts: 571
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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. |
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#22 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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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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#23 |
Registered User
Join Date: Jun 2014
Location: Tahuya WA
Posts: 571
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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. |
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#24 |
Registered User
Join Date: May 2016
Location: Henderson NC
Posts: 975
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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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#25 |
Special Order
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Location: Mt Airy, MD
Posts: 85,859
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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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"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ |
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