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Hey gang, I'm finally installing vintage ac in my chevelle and ran across multiple posts stating not to block off the heater core circuit. My vintage ac system comes with a heater shut off valve that does not have a bypass on it so I'm going to need to find something to make this work. Has anyone used the LOJ bypass block? This would allow me to use my supplied vintage ac valve, but I'm wondering how others have solved this issue. Thanks guys!
I used a couple Dorman tees (1/8" 'bypass') - allows coolant to bypass all the time, but is small enough to not impact heater effectiveness when the valve is open. Not as pretty, but it works and was cost effective.
I'm running 2 swaps with conventional heater block off valves, no issues.
I did look into a 12V 4 port bypass valve if issues came up. There's a OEM Lincoln 12V valve that would work. IIRC it's from an LS, about $100.
Interesting topic. I’m doing a VA install right now on my Chevelle, which I spoke directly to VA about before I purchased it. I informed them specifically about my setup being a Chevelle with an LS swap, and never once did they mention to me about this bypass being necessary. In fact, this is the first I’ve ever heard of thus issue.
Why do folks say that a bypass is necessary? Is it just for trapped air purposes?
Interesting topic. I’m doing a VA install right now on my Chevelle, which I spoke directly to VA about before I purchased it. I informed them specifically about my setup being a Chevelle with an LS swap, and never once did they mention to me about this bypass being necessary. In fact, this is the first I’ve ever heard of thus issue.
Why do folks say that a bypass is necessary? Is it just for trapped air purposes?
The heater core lines are used to circulate coolant through the engine to keep the entire engine at a stable temperature. If it’s blocked off, hot spots develop. Coolant must be able to flow at all times.
The heater core lines are used to circulate coolant through the engine to keep the entire engine at a stable temperature. If it’s blocked off, hot spots develop. Coolant must be able to flow at all times.
Never heard that either. I’ve seen more than one, meaning multiple road race cars, and drag racers pull the spouts out of the pump, use a NPT tap to thread the holes, and plug them off with threaded plugs. Totally possible to get the air out of the engine without the heater lines blocked off.
I don’t see how the heater lines have anything to do with coolant flow in the engine. There are lots of guys out there using the VA setup with any cooling issues, with LS engines. I’m sure this will make burping the engine harder, but just like an OEM application, turn the heat to hot, turn the fan control to high, before you attempt to get all the air out.
What am I missing here?
For long term use, what 8lug says is right. Don't go by what drag racers do. They only run hard 1/4 mile at a time. There is a good and basic reason things are done as stated. If it didn't have to be, nobody would push the idea. And just because you haven't heard of something, doesn't make it not so.
This isn’t a debate. You asked, I answered. If you don’t think they have anything to do with the flow in the engine, then it’s clear you don’t even understand the circuit in the engine, or you think this is the 30’s and coolant only flows when the thermostat is open. Have fun with your blown engine. I’m done with you.
Every aftermarket AC company has a switch in the lines that completely shuts off the flow of hot water through the engine. They sell thousands of these. Engines are not blowing because of it. People also run blockoffs left and right without incident; neither might be ideal but clearly neither are going to give you a "blown" engine, whatever that is.
This isn’t a debate. You asked, I answered. If you don’t think they have anything to do with the flow in the engine, then it’s clear you don’t even understand the circuit in the engine, or you think this is the 30’s and coolant only flows when the thermostat is open. Have fun with your blown engine. I’m done with you.
Not debating with you...sure didn’t mean to hurt your feelings mister 8 lug.
I guess all those folks running a VA system will blow their engine?
I was seriously asking a question to you, when I said what am I missing.
For long term use, what 8lug says is right. Don't go by what drag racers do. They only run hard 1/4 mile at a time. There is a good and basic reason things are done as stated. If it didn't have to be, nobody would push the idea. And just because you haven't heard of something, doesn't make it not so.
What about the road racers? They run for very long periods of time like this.
Why would Vintage Air sell a system that will hurt my engine?
I can’t find an answer here for some reason?
If there is a “good and basic reason” for this G, can you elaborate for me? Obviously 8 Lug got mad at me when I asked why...
I seriously doubt running with a full shutoff will blow any engine. I DO think, however, that running with the lines flowing all the time is the way the engineers intended for them to run. It likely has to do with keeping the whole system flowing to avoid any stagnation or corrosion, more to keep the system in better general health. But blowing any engines? Nah.....
PS- I don't get hot tempered when someone disagrees with me. This is a forum, after all, where diverse ideas will be presented and debated.
I seriously doubt running with a full shutoff will blow any engine. I DO think, however, that running with the lines flowing all the time is the way the engineers intended for them to run. It likely has to do with keeping the whole system flowing to avoid any stagnation or corrosion, more to keep the system in better general health. But blowing any engines? Nah.....
Of course it won’t. Prolly the silliest statement I’ve ever read on here, and Tech is full of silly statements.
I put over 100k miles on my Nova swap, and my '33 Ford is sitting at 101k right now, both with Vintage Air, and never had an issue with cooling either one of them, and the majority of the driving time is during the hot summer months. My truck and Blazer I put a factory heater shut off that has a bypass built in it, no difference in running temps in any of them. Personally, I think if you get the air out of the system you'll be fine. Or, maybe I'm just really lucky...
Go here and scroll down ( http://www.pirate4x4.com/tech/billavista/Cooling/ ) for a schematic of how the folks that engineered the cooling system wanted it to work. I always thought bypassing a bit of coolant around the t-stat in the LS was for these 2 reasons --- 1) to make things a bit easier on the water pump when the t'stat is closed during a 'cold' start -- I know the 5.0L Ford motor I had in the car before had a small bypass hose for the same reason, reduces cavitation possibilities; and 2) to keep a bit of coolant flowing around the backside of the t'stat so that it gets a real-time coolant temp signal a bit quicker (as engine is warming up) than it would if no coolant was moving around the wax temp bulb. I suspect this helps with cold start emissions -- but it's just a guess on my part. Clearly, lots of people run without it and don't seem to have problems. For me, it was enough to see that the folks that designed the motor/systems wanted it that way -- so I followed their lead. No one 'has' to do it. I did it on mine. Opinions vary.
I'd add - the Vintage Air/Classic Auto Air stuff -- for vast majority of their applications, their systems were designed with the old school Chevy/Ford/Chrysler V8's in mind. They all had t'stats on the OUTLET of the engine (LS is on the inlet). They didn't change anything when the LS came out. Based on extensive conversations with both of them before I bought (I picked Classic Auto Air) -- they didn't seem to have a clue how the LS cooling set up was configured. I asked specifically about the 'bypass' and I pretty much got crickets. I even asked if I could buy a control valve that would work the OPPOSITE of the heater control valve - was open when the control valve was closed, and vice versa. Wanted to use it as a bypass between the hoses. Crickets again. My conclusion? Aftermarket A/C companies have their hands full just engineering a system that will work. They're happy to leave figuring out how the rest of the car's cooling system should function up to you/me.
Sorry gang, didn't have any intention of starting a debate over this. LOL. The system was designed to flow a certain way. I know several people that block it off and haven't had any known issues, but I decided to keep it working the way it was supposed to work.
I'd add - the Vintage Air/Classic Auto Air stuff -- for vast majority of their applications, their systems were designed with the old school Chevy/Ford/Chrysler V8's in mind. They all had t'stats on the OUTLET of the engine (LS is on the inlet). They didn't change anything when the LS came out. Based on extensive conversations with both of them before I bought (I picked Classic Auto Air) -- they didn't seem to have a clue how the LS cooling set up was configured. I asked specifically about the 'bypass' and I pretty much got crickets. I even asked if I could buy a control valve that would work the OPPOSITE of the heater control valve - was open when the control valve was closed, and vice versa. Wanted to use it as a bypass between the hoses. Crickets again. My conclusion? Aftermarket A/C companies have their hands full just engineering a system that will work. They're happy to leave figuring out how the rest of the car's cooling system should function up to you/me.
I'm pretty much in agreement with your assessment. The tech's at VA is not real well versed on any of this, and tend to answer technical questions with "this is how we do it." Some years back, I vented my frustrations with an acquaintance that turned-out to be a personal friend of the owner/president of VA. The next day, I get a call from the VA president; he was very forthcoming, and offered to assist me in any way he could. I thanked him.
On my Hot Rod Air system, I retained the stock Camaro vacuum controlled bypass. I used a normally closed/vented vacuum control valve which, if I recall correctly, is a Nissan part. When the heater request is sent, the VCV closes and vents, which terminates the vacuum to the HCV, which closes the bypass, and sends hot coolant to the heater core......That make sense? Works fine.
Makes sense to me Andy! My system is self contained -- CAA provided the control system as well as the HVAC hardware. There's no connection with the ECU at all. And given how air and coolant flow work in the system -- I want the control valve absolutely closed (no hot coolant at all in the heater core) unless I call for heat. So I had to create an alternative for the engine/coolant bypass that worked independent of the HVAC controls to be sure I kept hot coolant out of the air box -- unless I turn the 'heat' on.
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Heater core bypass block 
