# ‘65 heater core delete question



## JesseLyon (Sep 13, 2020)

Hey all, so I removed my heater core a while back cause it was a leaky mess and decided not to replace it, as I don’t drive the car in the Canadian winter or rain. Since then, I’ve been running the heater hose from the water pump directly to the port on the back of the engine, but I’m wondering if I can remove that completely and just cap off both ports. I’m assuming not, as it needs this connected in order to circulate coolant, but can I get a confirmation on that?


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## Jerry H. (Mar 19, 2020)

I used the block off plugs on my 65 with no problems. Farthest it was driven at one time was about 40 miles. Many short trips and a few 1/4 mile trips. Be sure and check the plugs every year as they are easy to crack and leak.


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## Old Man Taylor (May 9, 2011)

They've always been blocked on my racecar.


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## JesseLyon (Sep 13, 2020)

Jerry H. said:


> I used the block off plugs on my 65 with no problems. Farthest it was driven at one time was about 40 miles. Many short trips and a few 1/4 mile trips. Be sure and check the plugs every year as they are easy to crack and leak.


Very cool (pun intended), thx guys!

What are you using to block these off? Can you post a photo, or link to anything available off the shelf?

cheers
JL


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## GTOJUNIOR (Aug 7, 2011)

The block off plates are available from several vendors, you will also need to find or make a dash plate.


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## JesseLyon (Sep 13, 2020)

Thanks!

what do you use to cap off the ports on the engine and water pump?


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## JesseLyon (Sep 13, 2020)

Found this online which could work nicely...I guess im just not quite sure how they’re supposed to attach to the water necks? 









Coolant Block off Plate (o-ring type) : USRT, Usually Sideways Rally Team


There's a hole where you don't want it. BLOCK it off with this bolt on part.



usrallyteam.com


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## Old Man Taylor (May 9, 2011)

They make rubber caps that slip on, but carry spares just in case.


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## PontiacJim (Dec 29, 2012)

JesseLyon said:


> Found this online which could work nicely...I guess im just not quite sure how they’re supposed to attach to the water necks?
> 
> 
> 
> ...



Hmmm. Those look like replacements for your intake manifold water neck. I don't think you want to block off the engine coolant going into the radiator?

Measure the ID of the water pump water-to-heater hose outlet and the water outlet nipple on the back of the head. Then go to your local auto store and ask for a rubber expansion freeze plug. Enclosed a photo of what you are after. It slips into the pipe end and you simply tighten it down snug - not over tight. Never had one pop out in my experience, but not a bad idea to have a spare or hose/clamps the length needed if you should get stuck out on the road - not knowing how far you go with the car.


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## JesseLyon (Sep 13, 2020)

PontiacJim said:


> Hmmm. Those look like replacements for your intake manifold water neck. I don't think you want to block off the engine coolant going into the radiator?
> 
> Measure the ID of the water pump water-to-heater hose outlet and the water outlet nipple on the back of the head. Then go to your local auto store and ask for a rubber expansion freeze plug. Enclosed a photo of what you are after. It slips into the pipe end and you simply tighten it down snug - not over tight. Never had one pop out in my experience, but not a bad idea to have a spare or hose/clamps the length needed if you should get stuck out on the road - not knowing how far you go with the car.
> 
> View attachment 138379


Hah! Right you are re that block off plate. My bad. Wouldn’t wanna do that. 

That plug you mention above looks perfect. Didn’t know they made such a thing. You guys are making my day, appreciate all the helpful advice.

Cheers,


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## Jerry H. (Mar 19, 2020)

JesseLyon said:


> Very cool (pun intended), thx guys!
> 
> What are you using to block these off? Can you post a photo, or link to anything available off the shelf?
> 
> ...


I don't have any pics, but I used the type that slipped over the top and attached with clamps. The brand I used was Dorman; off the 'Help' display at most auto parts stores.


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## lust4speed (Jul 5, 2019)

Never saw any block off caps that didn't rot away in a very short time. One of my friends had a cap rot off before he was able to finish the car and take his first ride. Best to use a 3" or so length of heater hose with the appropriate plug stuck in the hose. Looks strange but a sparkplug fits perfect in the 3/4" hose. Run a fake sparkplug wire to it and confuse the hell out of onlookers. At least the hose will go for many years before needing replacement.


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## JesseLyon (Sep 13, 2020)

lust4speed said:


> Never saw any block off caps that didn't rot away in a very short time. One of my friends had a cap rot off before he was able to finish the car and take his first ride. Best to use a 3" or so length of heater hose with the appropriate plug stuck in the hose. Looks strange but a sparkplug fits perfect in the 3/4" hose. Run a fake sparkplug wire to it and confuse the hell out of onlookers. At least the hose will go for many years before needing replacement.


good tip. I like the plug wire idea 

I looked for some expansion plugs as mentioned by Jim, but can’t find anything small enough. I need a 5/8” for the water pump outlet, and 1/2” for the one on the head, and they just don’t seem to make them that small. Found some rubber caps that fit, but like you said, worried about them rotting or blowing off. Maybe a rubber plug inside first, then cap and hose clamp could work?


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## Old Man Taylor (May 9, 2011)

lust4speed said:


> Never saw any block off caps that didn't rot away in a very short time. One of my friends had a cap rot off before he was able to finish the car and take his first ride. Best to use a 3" or so length of heater hose with the appropriate plug stuck in the hose. Looks strange but a sparkplug fits perfect in the 3/4" hose. Run a fake sparkplug wire to it and confuse the hell out of onlookers. At least the hose will go for many years before needing replacement.


My block off caps were very thick, and I never hade a problem with them. However, on the racecar I used screwed in plugs.


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## JesseLyon (Sep 13, 2020)

Old Man Taylor said:


> My block off caps were very thick, and I never hade a problem with them. However, on the racecar I used screwed in plugs.


So finally got my tri-power running and idling ok today, except now its overheating like crazy. Had quite the rad cap blowout! The only thing I can think of is the heater hose I removed and capped off, discussed in this thread. Going to put the hose back on and see if the recurculation helps.


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## lust4speed (Jul 5, 2019)

The coolant flow is basically from bottom of radiator through block to the back of the heads and forward through the head to the cross over and to top of radiator. The heater outlet in the head actually robs some of the coolant that would otherwise be flowing through the head helping to cool it. Adding the hose back in allows some of the coolant to bypass directly back to the pump with only part of it's job done. The stock heater nipple only has a 1/4" hole in it and a thermostatic spring in front of that further limits flow. Pontiac was very careful to not re-route too much coolant to the heater.

I'd be looking for a stuck thermostat. As a test, remove the thermostat and take a test drive.


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## JesseLyon (Sep 13, 2020)

lust4speed said:


> The coolant flow is basically from bottom of radiator through block to the back of the heads and forward through the head to the cross over and to top of radiator. The heater outlet in the head actually robs some of the coolant that would otherwise be flowing through the head helping to cool it. Adding the hose back in allows some of the coolant to bypass directly back to the pump with only part of it's job done. The stock heater nipple only has a 1/4" hole in it and a thermostatic spring in front of that further limits flow. Pontiac was very careful to not re-route too much coolant to the heater.
> 
> I'd be looking for a stuck thermostat. As a test, remove the thermostat and take a test drive.


Very good info, thank you! I will try thermostat first.


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## JesseLyon (Sep 13, 2020)

lust4speed said:


> The coolant flow is basically from bottom of radiator through block to the back of the heads and forward through the head to the cross over and to top of radiator. The heater outlet in the head actually robs some of the coolant that would otherwise be flowing through the head helping to cool it. Adding the hose back in allows some of the coolant to bypass directly back to the pump with only part of it's job done. The stock heater nipple only has a 1/4" hole in it and a thermostatic spring in front of that further limits flow. Pontiac was very careful to not re-route too much coolant to the heater.
> 
> I'd be looking for a stuck thermostat. As a test, remove the thermostat and take a test drive.


Removed thermostat and no issues now. It was a brand new heavy duty thermostat right out of the box from AEMS (N140LW ), so Im a bit surprised. In any case, thanks very much for the advice! Maybe I'll just leave it out


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## lust4speed (Jul 5, 2019)

I always test new thermostats in a pan of water on the stove with a thermometer. Started with a candy thermometer and finally bought a multi-meter with a probe that is more accurate. Anyway, only about one in four was anywhere near the rated opening point, and even stranger was the more expensive ones were more at fault.

We are on the edge of the desert and it's only another hour to Palm Springs so we get very warm and multiple tests of our club cars have proven that no thermostat and a perfectly working thermostat are equal in their abilities to keep the engine at it's lowest operating temperature during very hot days. For instance, temps outside around 105° to 110° and the other partial limitations of the complete cooling system produces say 175° with a 160° thermostat or no thermostat -- and don't believe the Chevy wife's tail of needing a restriction like a thermostat or Moroso ring to slow down circulation.

So hot summer days the car will be just as happy with no thermostat or a perfectly working one. That changes when the weather cools and neither the engine will be happy running too cool nor will the occupants trying to keep warm with a poorly performing heater.


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## JesseLyon (Sep 13, 2020)

lust4speed said:


> I always test new thermostats in a pan of water on the stove with a thermometer. Started with a candy thermometer and finally bought a multi-meter with a probe that is more accurate. Anyway, only about one in four was anywhere near the rated opening point, and even stranger was the more expensive ones were more at fault.
> 
> We are on the edge of the desert and it's only another hour to Palm Springs so we get very warm and multiple tests of our club cars have proven that no thermostat and a perfectly working thermostat are equal in their abilities to keep the engine at it's lowest operating temperature during very hot days. For instance, temps outside around 105° to 110° and the other partial limitations of the complete cooling system produces say 175° with a 160° thermostat or no thermostat -- and don't believe the Chevy wife's tail of needing a restriction like a thermostat or Moroso ring to slow down circulation.
> 
> So hot summer days the car will be just as happy with no thermostat or a perfectly working one. That changes when the weather cools and neither the engine will be happy running too cool nor will the occupants trying to keep warm with a poorly performing heater.


good idea, going to test it out on the stove today.

I’m in Vancouver, BC, and don’t drive the car in the winter anyway. I’ve also removed/bypassed the heater core, so I don’t really even see a need for the thermostat. Engine warms up fast enough, I’ll probably end up just leaving it out.

Thanks again for all the good advice, I’d be lost without this forum!


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## JesseLyon (Sep 13, 2020)

lust4speed said:


> I always test new thermostats in a pan of water on the stove with a thermometer. Started with a candy thermometer and finally bought a multi-meter with a probe that is more accurate. Anyway, only about one in four was anywhere near the rated opening point, and even stranger was the more expensive ones were more at fault.
> 
> We are on the edge of the desert and it's only another hour to Palm Springs so we get very warm and multiple tests of our club cars have proven that no thermostat and a perfectly working thermostat are equal in their abilities to keep the engine at it's lowest operating temperature during very hot days. For instance, temps outside around 105° to 110° and the other partial limitations of the complete cooling system produces say 175° with a 160° thermostat or no thermostat -- and don't believe the Chevy wife's tail of needing a restriction like a thermostat or Moroso ring to slow down circulation.
> 
> So hot summer days the car will be just as happy with no thermostat or a perfectly working one. That changes when the weather cools and neither the engine will be happy running too cool nor will the occupants trying to keep warm with a poorly performing heater.


good idea, going to test it out on the stove today.

I’m in Vancouver, BC, and don’t drive the car in the winter anyway. I’ve also removed/bypassed the heater core, so I don’t really even see a need for the thermostat. Engine warms up fast enough, I’ll probably end up just leaving it out.

Thanks again for all the good advice, I’d be lost without this forum!


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## JesseLyon (Sep 13, 2020)

Hey guys, it turns out the temp sending unit for my electric fan is cooked, and not turning the fan on anymore (hence the overheating problems). Easy fix...Question is, if Im running a 180 degree thermostat, what range should I choose to have the fan turn on/off at? its going to be installed in the top coolant hose returning to the rad, after the thermostat (Im out of ports in the stock tri-power intake, otherwise Id put it there). Im currently looking at one that turns on at 190 and off at 175. Or should I go lower, on at 180 when the thermostat opens, and off at 165? Thoughts?...









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