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Tips for changing Heater core for 78-87

36K views 27 replies 21 participants last post by  Simm 
#1 ·
I used this link to change my heater core on my 84. It made it simple with step by step instructions & with pics!! Hope somebody can use this !!

http://www.chevyasylum.com/core/
 
#3 ·
Nice link for the heater core. The problem I'm having is getting the correct heater core. The orig one has the 'v' in the top tank for the hold down clamp and the ground wire. The ones I've seen at the parts store have a flat top tank and therefore cannot be secured or grounded like before. Did you guys buy a core with the 'v' on the top tank? If not, how did you secure the tank and attach the ground wire? Thanks
 
#5 · (Edited)
I had to take the clip out and it fit fine. Mine came with instructions about the clip. At first i couldn't get the clip out it's just the angle has to be right and it slips out. I have my old one sealed up here it never leaked. I replaced it when i re-did all my air conditioning i had the cover off so might as well replace it too. You can have it just PM me your address and i will ship it from work ups no charge. :texas:

 
#4 ·
I did my 84 last year & Don't remember exactly what I did! I don't think I used the hold down clip & I striped the ground strap wire a little longer & wrapped it around one of the tubes with a hose clamp! & once the top cover went on it. It held down the core !!
 
#6 ·
I tried searching for the AC compressor forums with there are any threads but I'm new and am clueless how to use this site lol. Maybe ya'll can answer my question. I want the specs for my entire AC/Heating units. Primarily the compressor. I want to take it off the belt. I want to keep it attached and intact under the hood though. I want to use an electric motor of some sort and possible a second battery or more sup'd up alternator to handle the load. Gonna take my fan off the belt to and go with electric dual polar'd fans too. 25 horsepower at least goes to my belts, probably more, lik 35 on my setup. So I want to take it all off. ANY info on how much electric current would simulate the belt, and how much would the AC use running? to handle the weight differences I figure Ill use a fiberglass hood and a few mods to keep my power to weight ratio if not improve it.
 
#7 ·
When I did my heater core I added these shut-off valves to keep the hot water from circulating in the core during the summer months ! I always felt hot air coming out the bottom vents when the AC was off ! (NO MORE HOT AIR) & I open them up when it gets cold !! A few bucks each from lowes plumbing department.

 
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#10 ·
When I did my heater core I added these shut-off valves to keep the hot water from circulating in the core during the summer months ! I always felt hot air coming out the bottom vents when the AC was off ! (NO MORE HOT AIR) & I open them up when it gets cold !! A few bucks each from lowes plumbing department.

SLICK I'M ON MY WAY TO GET A SET.:You_Rock:
Didn't you have a vaccume switch between one of the hoses? Do you just take it off till winter or do you really need it?
 
#9 ·
86'kid
I admire your enthusiasm - BUT
If you want to keep your AC running it off an electric motor is going to be a real challenge. There is a much easier solution. A switch that the accelerator linkage hits when you open it wide open that turns the compressor off would be the first way I would go (factory did this on many models). To add the weight of an extra battery and a higher output alternator that will require a bunch more horses to turn plus the weight of your new electric motor and mounting brackets will probably slow you down more than just leaving the AC alone.
A nice intake, carb and set of headers will do more for your 305.
 
#13 ·
When I got my 84 when my dad passed the heater core was blocked off & no heater hoses. I checked into that vacuum heater valve but I put a different intake on & put a plug in the back of the intake where that hose goes in !! A Mechanic told me to put a manual valve on it & I checked all the parts store for that & they wanted a bunch of money for it !! like this 19.99 just for this little valve
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=BK_6601413_0328888996
It does get cold down here in north central Fl. in the 20's & 30's for a few weeks !!
So I need the heat for a little bit ! So I just open up the valves for a while !!
So I got these for cheap ! I don't have the emissions or the computer any more!
 
#18 ·
I am in the middle of doing this to my 86 w/ac. I am at the stage where I have a lot of gunk to come off before the cowl will come off. I don't know if there is an easy way to do this, but I will restart this mess tomorrow.
 
#20 · (Edited)
What is the ground strap on the top of the core for? Mine was cut. Do I need it?
Yes ! GM put it there for a reason ! The reason is heating core grounding strap prevents electrolysis . Electrolysis can cause heater core leaks because it can cause a breakdown in heater core material
 
#24 ·
I just did mine last Friday. I got rained out at work a being I was already PO'd I might as well get it out of the way. It was not the highlight of my day but is done now. One thing is to make sure you seal every thing up real good when you put it back together or you will have a leak in the cab on the passenger side.
 
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