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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
![]() Join Date: May 2007
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 |
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?
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 |
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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#7 |
Senior Member
![]() Join Date: Dec 2013
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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#8 |
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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#9 |
Registered User
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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#10 |
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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#11 |
Registered User
Join Date: Nov 2014
Location: Lincoln City DE
Posts: 1,292
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Re: T-stat to drill a hole or not to drill a hole?
My t-stat has patina ...
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#12 |
Senior Member
![]() Join Date: Oct 2009
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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#13 |
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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#14 |
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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#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 |
Post Whore
![]() Join Date: Feb 2016
Location: Portland Oregon
Posts: 11,154
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Re: T-stat to drill a hole or not to drill a hole?
It isn't anything new. It is an old racer modification. I was doing it back in the 80's. The reason is that it makes it easier to vent air out when refilling the water. Used to be you were allowed to dump the water out of your radiator between rounds and refill it to cool the motor down for the next round. Some guys used to put little valves in the top of the intake water passages to vent air too.
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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#17 | |
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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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#18 |
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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#19 |
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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#20 |
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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#21 |
Special Order
![]() ![]() Join Date: Nov 2004
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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#22 |
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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#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?
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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#24 |
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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#25 |
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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