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Just put a valve in each heater hose and be done with it.
You need one in each hose if not hot coolant will transfer heat into the heater core. I shut mine off in the summer to help keep the cabin a little cooler and open in the winter for heat.
Granted I am in central AZ. so I drive my cars year around. If you need the defroster on any given day just carry a pair of gloves and open the valves with you hands. ALL problems solved.
There is currently a similar thread on General section on this subject, with the same arguements on how many valves and where. What I will add here, as I always do, is that when my heater system in my 77 was full hooked up, with factory NOS vacuum operated valve in line, when the heater switch on the console was OFF.......I could drive the car on the hottest summer day in PA and the inside of the car was as comfortable as outside the car....with the T-tops off and windows down. What I am saying is that there was ZERO heat transfer into the inside of the car that made it any more uncomfortable than a 95 degree day is driving the car without AC. With no hot water flowing into the heater core......no heat coming into the cabin.
My car is rebuilt. All the factory designed components in the car have to have the same integrity as Chevrolet built the car to have....heater box seals have to be intact, the foam collar needs to be across the bell housing, the hood seal at the back of the hood has to be intact, there can be no holes in the firewall or dry rotted rubber seals failing, you have to have insulation on the firewall that is functioning, floor insulation that is functioning, etc etc. Those are the real problems. So bypassing the heater core on my car would NOT make it one bit better. I know many disagree. (For those following my thread on 406 SBC problems.....I am bypassing my heater for other reasons).
Last edited by Shovels and Vettes; Aug 4, 2022 at 07:55 AM.
Just put a valve in each heater hose and be done with it.
You need one in each hose if not hot coolant will transfer heat into the heater core. I shut mine off in the summer to help keep the cabin a little cooler and open in the winter for heat.
Granted I am in central AZ. so I drive my cars year around. If you need the defroster on any given day just carry a pair of gloves and open the valves with you hands. ALL problems solved.
If there is a closed valve in the hose going from the intake manifold to the heater core, how is hot coolant getting into the heater core? Magic? Does the valve in the return line de-activate the magic, somehow?
If there is a closed valve in the hose going from the intake manifold to the heater core, how is hot coolant getting into the heater core? Magic? Does the valve in the return line de-activate the magic, somehow?
Scotty
I really don't want to get into this p****** match, but before I sign off for this morning, I have to comment on your thread. I am not scientist,....but I do know a little. There is no hot coolant FLOWING into the core. BUT....the coolant in the engine transfers heat to the coolant in the hose from the intake....which transfers heat to the valve.....which eventually continues to transfer heat to the coolant on the opposite side of the valve, as well as engine compartment heat transferring heat to the hoses / coolant inside. NOW.......how long this takes, or how much heat, I have no idea. I suspect it takes awhile, and is by no means equal to actual hot coolant flowing into and out of the heater core. So.....if folks want to argue about it......I submit the above. Lets talk about reality.
But....more importantly.....as I posted above....the way more important part of all of this is that the seals, doors, insulation, functionality of the valves and switches is what really makes the difference in heat transfer into the car. Bypassing the heater system is a band-aid approach, but truthfully,....it works. But lets keep all the facts and truth in mind, without nonsense drama and theories.
So, let me get this straight,....for those that see the "defroster" as a must have in a C3 Corvette.......what you are saying is that a typical classic C3 Corvette owner is out driving around in conditions that require a defroster to be functional. Ok....if that is true, you got me. IF, it is true.
But the typical C3 Corvette owners I have known and come across on this forum, are lucky to drive the car 500 miles a year. (their words, not mine).......and 99% of that time its done on a sunny, rain free day, from their garage over to the Taco Bell parking lot, which typically may not exceed 10 miles away, and then they spend two hours with their lawn chair, picture books and stuffed animals sitting behind the car, while old men walk around and puff their chests out with all their BS ego. Then, after the two hour exhausting event is over....they drive back to their garage, only to possibly repeat that same thing next month. Otherwise,....they occasionally leave their Lazyboy to go out in the garage and look at the car once a week, IF it is convenient. IF they work on anything,.....its trying to make the "vacuum" system work....or maybe getting those most important feature to work....the fiberoptic light system to make sure we are immediately aware that a marker light bulb has failed.....ha ha ha.ha.....!!
Ok...to those of you who drive your C3 Corvette alot, and in reality, more than I do (last year 8000 miles),......and IF you choose to do this in the conditions that would cause your windshield to fog up, how about this. Carry a rag under your seat.....and when it does fog up on the inside,....reach the two feet ahead of you and wipe it down. Problem solved. However......in MY driving experience, of 5000-8000 miles a year in MY C3 Corvette. in Western PA.....a fairly wet and humid area.....I have only had a windshield fog up partially ONE TIME....and that was leaving a motel in the early morning hours, after attending Carlisle, and was on the 3 hour drive home. I survived without issue. With T-tops off, windows down...the way I drive the car 99.9 % of the time.....it only took a minute and all was clear.....in the meantime...the rag worked perfectly.
But lastly......if you just feel like its cool, or critical, or just the way you want to do it,.....to make the old, vacuum actuated and controlled heat systems in these cars functional....go for it. But remember......modern Chinese junk parts are one major challenge....and it requires that YOU, the owner, know how to fix all this stuff, and secondly.....keep it maintained. I choose the far easier way.....and to just bypass the garbage that is completely unnecessary for the real life conditions I operate the car under. Both choices are acceptable....mine leaves me for alot more time enjoying and driving the car.....and less time trying to fix it.
wow that is absolutely spot on 👍!! All of these corvette owners just look at there car with a cup of coffee and a cigar and bark out orders what to do . Meanwhile they drive their car 10 miles a month 🤣🤣
wow that is absolutely spot on 👍!! All of these corvette owners just look at there car with a cup of coffee and a cigar and bark out orders what to do . Meanwhile they drive their car 10 miles a month 🤣🤣
and some people respond to a three year old post to **** on corvette owners again
didn’t realize it was a 3 year old post. You must be one of the 1o mile drivers
Well... wrong, I drive my corvettes every week of my life, I don't concern myself with miles or value but I certainly wouldn't condescend other corvette owners for not thinking the same way as me... I mean that would just be arrogant right.
Last edited by Golfobsessed; Mar 14, 2025 at 07:03 PM.
Howdy, rather than post something new vs. old...here's my addition. Pictures tend to put things into perspective. As the title indicates, from my 1981 Vette, 350SBC. My heater core line (from the water pump) gave up the ghost...hot coolant spray everywhere. A pin hole can cause quite the havoc in an engine bay. From what I've read and have confirmed through my own experience...the water pump fitting/hose is 3/4" and the intake is 5/8". I've decided, as most have done, to bypass the whole affair vs. going gung-ho and replacing heater core. Down-time means less time on the road....not a good thing. My heater core had also leaked into the passenger side (foot carpet area), since purchase. The decision was a no-brainer and a good excuse to tackle the task, eh? Once I cut half of the lines leading from the intake and water pump into the heater core....I purged the heater core from any residual coolant using an air compressor. Quit a bit spurted out from the core...basically a mini-radiator. Yes, a messy endeavor. Here's some pics along my journey; mostly the heater core side of the house. The pics (heater core fittings) are as you see them, ride is drivers side, left is passenger. The bigger fitting (left side) is 3/4", smaller fitting (right side) is 5/8". Nothing rocket science, you actually don't need to jack up the vehicle...you can reach into the area from underneath the vehicle, passenger side. Feeling around for the hose clamp, undoing it....cutting/scraping the melted and fuzzed rubber hose from the brass (copper?) fittings with a razor and your done. Cleaned it up with #0000 steel wool and anti-seize helps. The pics show the different sizes of the fittings visually, becomes apparent which goes where if you wish to swap out the core down the road and run the hose lines back to the engine. Completed the job with some rubber plugs from Dorman name brand; a pkg assortment from Canadian Tire; had the 3/4" and 5/8" and a bunch of others conveniently in one pkg. (note: the edging along the core housing, surrounding the fittings is uber-freaking sharp!!).
Last edited by 1981c3Corvette#; Jun 30, 2025 at 10:24 PM.
Reason: accuracy
Just get one of these by Gates to connect the hoses together. That's what I did on my 1971 as it had an aluminum radiator and overflow tank that has the pressure cap on it instead of the radiator. I had to do it this way because if I didn't I'd have to eliminate the overflow and install a radiator with a cap on it.
May be different on cars with the cap on the rad. Mine has been on there for 15+ years without issues.
Mine has an elbow hose, but basically same with adaptor fittings. Will end up having silicone caps replace both at intake/pump fittings...clean it up a bit.
Last edited by 1981c3Corvette#; Jul 1, 2025 at 06:50 AM.
Reason: accuracy
Plastic has no place in your cooling system*. I tried one of those 5/8 to 3/4 adapters to make the loop. When I removed it in a year or so (to install plugs) it cracked open. Imagine if that had happened on the road. I'll stick to plugs.
*Unless you are BMW, or almost any cheap, modern radiator.
Plastic has no place in your cooling system*. I tried one of those 5/8 to 3/4 adapters to make the loop. When I removed it in a year or so (to install plugs) it cracked open. Imagine if that had happened on the road. I'll stick to plugs.
*Unless you are BMW, or almost any cheap, modern radiator.
So you installed a plug at the intake and the pump?
So you installed a plug at the intake and the pump?
Absolutely. On an SBC, no bypass is needed. On a big block, YMMV. I think there is a separate bypass between the intake and the pump, but read up on that before you change anything.
If you want heater function in the winter, your best bet is a pair of valves and some insulation. Read @interpon's writeup on that. But even that solution will conduct heat from the engine compartment, simply by having the filled hoses present (insulation helps slow this down). https://www.corvetteforum.com/forums...e-79-w-ac.html
Plugs are pictured below (the intake plug is being used as another temperature sensor).
The gates product I posted is well up to the job. Been doing the job for 20 years now. BTW. ALL modern vehicles have PLASTIC coolant reservoirs..........just saying
Absolutely. On an SBC, no bypass is needed. On a big block, YMMV. I think there is a separate bypass between the intake and the pump, but read up on that before you change anything.
If you want heater function in the winter, your best bet is a pair of valves and some insulation. Read @interpon's writeup on that. But even that solution will conduct heat from the engine compartment, simply by having the filled hoses present (insulation helps slow this down). https://www.corvetteforum.com/forums...e-79-w-ac.html
Plugs are pictured below (the intake plug is being used as another temperature sensor).
