Where to drill the 1" hole for heater core replacement - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 05-15-2018, 10:15 AM Thread Starter
 
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Where to drill the 1" hole for heater core replacement

I need to drill the 1" hole in the firewall to access the bolt holding the Heater core box on my 66 GTO. Does anybody have a photo of the hole they have drilled to replace their heater core? I don't want to drill more than one hole. A photo of one already done would help tremendously. Any advice on where to drill the hole would help too. Thanks!

Does anybody know where I can see the Pontiac instructions for this?
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post #2 of 4 (permalink) Old 05-15-2018, 02:19 PM
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It isn't on the firewall it is on the inner fenderwell.

On my '67 there was a dimple.
If you don't see a dimple look down between the fenderwell and firewall with a flashlight and you will see the nut.
Once you drill the hole use a 1/4" drive with an extension to break it loose and a magnetic driver to remove it so you don't drop the nut.
Post if you don't see the dimple and I will take a measurement for you.
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post #3 of 4 (permalink) Old 05-15-2018, 04:14 PM
 
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FWIW
If you get a long handled ratchet wrench set you can accomplish this without cutting anything.
My 66 has AC and I was able to swap out my Heater core in under 3 hours.
The nut can be accessed somewhat blindly but accessed none the less.
The "Hole Cutting" was just a factory service short cut as it was all about time and money.
JM2C

Cheers

GTO Jr. - A.K.A. SPRINT 6
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post #4 of 4 (permalink) Old 05-16-2018, 08:03 PM
 
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Originally Posted by GTOJUNIOR View Post
FWIW
If you get a long handled ratchet wrench set you can accomplish this without cutting anything.
My 66 has AC and I was able to swap out my Heater core in under 3 hours.
The nut can be accessed somewhat blindly but accessed none the less.
The "Hole Cutting" was just a factory service short cut as it was all about time and money.
JM2C

Cheers
Jeff is dead on. Have R&R'ed half a dozen early heater cores and have never cut ahoese in the inner fender for access. '64-67 A-body's are relatively easy to access the nuts in comparison to several later 60's GM models.
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