I can't Find The Correct Thermal Vacuum Switch Chevy 350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Cadillac Kid · 07-18-2017, 01:57 PM

Hello everyone. The original thermal vacuum switch (TVS) on my chevy 350 does not open anymore when It gets to temperature. I need a replacement. All of the replacements I can find are 3/8 in size. The hole in my thermostat housing is 3/4 in size. I even bought a replacement just for fun and the threads on the new (TVS) are way to small and it just sits loosely in the thermostat housing.

Where can I find a functioning (TVS) that has 3/4" threads?
I could bypass the switch but I would really rather have it working properly as intended. Does anyone have one for sale? My engine is a 1974 Chevy 350.

Thanks

-Gavin

**kwmech** · 07-18-2017, 05:09 PM

Um, change t-stat housing to accept smaller threads?

**kwmech** · 07-18-2017, 10:11 PM

Troll on the loose!!!!!!!!!!!

Cadillac Kid · 07-19-2017, 02:36 AM

^^^Not sure what you mean by that sir??

I bought a new T stat housing awhile ago for my truck because the original was cracked. I looked at thermost housings online for early 80's 350's and they have two threaded ports on them with plugs if you dont use both holes. One of the threaded holes looks like the correct size for the new (TVS). I guess I'll have to buy one of those to make it work with the new vaccum switch.
Makes me wonder why they would sell you a thermostat housing (like the one I bought) that you can't obtain a proper thermal switch for? Oh well..

-Gavin

SkinnyG · 07-19-2017, 03:09 AM

Just buy a thread reducer.

Any decent auto parts store should have one that will work.

Tash4 · 07-19-2017, 08:36 AM

The threads should be pipe thread, 3/4 pipe is huge. I have seen 3/8 & 1/2 but never 3/4. parts books call them ported vacuum switchs if we are talking about the same part. As skinnyg said an adapter might be your only option. Good luck.

**kwmech** · 07-19-2017, 11:38 AM

Quote:

Originally Posted by Cadillac Kid

^^^Not sure what you mean by that sir??

-Gavin

There was a spammer plugging up all the threads with his crap. Looks like they were all deleted

Cadillac Kid · 08-03-2017, 09:20 PM

Found one with the correct threads. BWD #EC968
Around $8.99 at orilleys. I was going to use a pipe reducer as skinnyg suggested, but the parts store ordered a handful of these switches for me and this was the right one.

Thanks for the suggestions.

-Gavin

07-18-2017, 01:57 PM	#1
Cadillac Kid Registered User Join Date: Jun 2016 Location: Redondo Beach, CA Posts: 72	I can't Find The Correct Thermal Vacuum Switch Chevy 350 Hello everyone. The original thermal vacuum switch (TVS) on my chevy 350 does not open anymore when It gets to temperature. I need a replacement. All of the replacements I can find are 3/8 in size. The hole in my thermostat housing is 3/4 in size. I even bought a replacement just for fun and the threads on the new (TVS) are way to small and it just sits loosely in the thermostat housing. Where can I find a functioning (TVS) that has 3/4" threads? I could bypass the switch but I would really rather have it working properly as intended. Does anyone have one for sale? My engine is a 1974 Chevy 350. Thanks -Gavin __________________ Keep on truckin'

07-18-2017, 05:09 PM	#2
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,596	Re: I can't Find The Correct Thermal Vacuum Switch Chevy 350 Um, change t-stat housing to accept smaller threads?

07-18-2017, 10:11 PM	#3
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,596	Re: I can't Find The Correct Thermal Vacuum Switch Chevy 350 Troll on the loose!!!!!!!!!!!

07-19-2017, 02:36 AM	#4
Cadillac Kid Registered User Join Date: Jun 2016 Location: Redondo Beach, CA Posts: 72	Re: I can't Find The Correct Thermal Vacuum Switch Chevy 350 ^^^Not sure what you mean by that sir?? I bought a new T stat housing awhile ago for my truck because the original was cracked. I looked at thermost housings online for early 80's 350's and they have two threaded ports on them with plugs if you dont use both holes. One of the threaded holes looks like the correct size for the new (TVS). I guess I'll have to buy one of those to make it work with the new vaccum switch. Makes me wonder why they would sell you a thermostat housing (like the one I bought) that you can't obtain a proper thermal switch for? Oh well.. -Gavin __________________ Keep on truckin'

07-19-2017, 03:09 AM	#5
SkinnyG Registered User Join Date: Feb 2012 Location: Beautiful BC, Canada, eh?! Posts: 2,246	Re: I can't Find The Correct Thermal Vacuum Switch Chevy 350 Just buy a thread reducer. Any decent auto parts store should have one that will work. __________________ 1961 Apache: "Grabber Orange" Shortboxed, pancake, step-notch, air-ride, boosted-LS 1977 Silverado: Shortboxed & dropped, potato-potato V8 Pontiac Firefly (Chevy Sprint): The ultimate engine swap: 5.7L in a 1.0L bag Lotus Super 7 Replica: Scratch-built street-legal rollerskate

07-19-2017, 08:36 AM	#6
Tash4 Registered User Join Date: Sep 2016 Location: Pinhook Mo Posts: 120	Re: I can't Find The Correct Thermal Vacuum Switch Chevy 350 The threads should be pipe thread, 3/4 pipe is huge. I have seen 3/8 & 1/2 but never 3/4. parts books call them ported vacuum switchs if we are talking about the same part. As skinnyg said an adapter might be your only option. Good luck.

08-03-2017, 09:20 PM	#8
Cadillac Kid Registered User Join Date: Jun 2016 Location: Redondo Beach, CA Posts: 72	Re: I can't Find The Correct Thermal Vacuum Switch Chevy 350 Found one with the correct threads. BWD #EC968 Around $8.99 at orilleys. I was going to use a pipe reducer as skinnyg suggested, but the parts store ordered a handful of these switches for me and this was the right one. Thanks for the suggestions. -Gavin __________________ Keep on truckin'



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