Heater core shut off valve

[SCOTI]

Originally Posted by RichardJ

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.

[pwdcougar]

Originally Posted by SCOTI

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

[SCOTI]

Originally Posted by pwdcougar

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.

[Killer Bee]

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

[Richard]

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.

[Andy4639]

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.