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Old 04-06-2021, 11:48 AM   #26
SCOTI
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Re: Heater core shut off valve

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Originally Posted by RichardJ View Post
The first image below from Summit looks very close to the cross-over used with 60's 289 fnords. The other images, also on Summit are from 4 Seasons that have internal valves. 4 seasons has a variety of manual cross-over styles, also shown in Summit.
That's the early version of it. Thanks for adding that to the info.

The unit I've seen is a billet piece. Very clean unit. I'll post up the info as soon as I can access it but it's basically just a higher-end (and more expensive) version of the early variations in your provided link/s.
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Old 04-06-2021, 12:51 PM   #27
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Re: Heater core shut off valve

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Apparently some later model vehicles require flow on the path to the heater core or suffer cavitation issues. I recently learned this & was not aware. These set-ups actually have a bypass that stops flow to the heater core (similar to these cut-off valves) yet allows for the loop to still circulate.

I learned about them on various LS swaps I've seen on the web.
Yes I found this out when I bypassed the heater core on a 97 Buick Century. The heater core is an integral part of the cooling system. I installed a bypass valve that was for a Ford Ranger
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Old 04-06-2021, 01:52 PM   #28
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Re: Heater core shut off valve

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Yes I found this out when I bypassed the heater core on a 97 Buick Century. The heater core is an integral part of the cooling system. I installed a bypass valve that was for a Ford Ranger
I never gave these much thought.

I had a primitive bypass set-up (as in using what I had available for free vs spending money for something that may not impact my issue) for my 74swb @ one point. I was struggling w/heat soak on the a/c & wanted to see if blocking the hot-water flow to the heater core helped. I built a similar, simple hand valve set-up as it's what I had available for testing.

I knew there were early OE versions of a vacuum/temp actuated bypass valve (from GM) available but wasn't going to spend the money for one just to find out it didn't make a difference for my needs.
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Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive.
It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar.....

Cubic inches is like Indiana Jones with a cheap pistol.
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Old 04-06-2021, 02:06 PM   #29
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Re: Heater core shut off valve

wait... what?? there's a valve that does this?

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Old 04-06-2021, 02:21 PM   #30
Richard
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Re: Heater core shut off valve

I believe the two types of vacuum operated valves for 67-72 trucks are different. If I recall correctly the early one without bracket is normally closed and later one with bracket is normally open. Both could be used together to create a bypass.
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Old 04-06-2021, 08:09 PM   #31
Andy4639
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Thumbs up Re: Heater core shut off valve

I had a hard time getting mine to burb when I installed it. I finally had the front end jacked up and took the 2 small steam ports loose on the front of the engine. That seemed to do it. Haven't had any more issues since. That was back in 2014. That I know of any way the truck runs cool even with the AC on.
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