I am having to replace my heater core again on my 87GT. Because there have been some recent questions and discussions on Pennocks about core replacement, I thought I'd do a small writeup on today's experience
http://gafieroclub.org/pics/pip/S1035316_(Custom).JPG.
We often advise people to clean out their ductwork, especially around the resister that's accessible in the front compartment. I not only pulled material out of the heater core area, but this is what I got out by hand when I removed the resistor. You can see some of the leaves had slipped into the coil of the resistor and had actually started to cook a little.
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There was more that I pulled out with a shop vac, mostly fine stuff that I couldn't pick up with the two fingers I could get into the resister opening. I used a piece of single strand aluminum wire with a bend on the end to get back beyond the reach of my fingers. I'm still not confident that I got everything.
Per the original topic of discussion, the size of the replacement heater cores, this is what I got from Vista-Pro. It's supposed to be a Prorad part, but the paperwork with it says it's a Ready-Aire. I think they also make Spectre.
The dimensions for the core, as stated on their website, is 6.25 x 6.25 x 2 inches. Like all other aftermarket cores, it's far from that. Height and depth are correct, but core length is short.
The replacement core is compared alongside an original Harrison heater core.
Harrison at the top, Prorad/Ready-Aire at the bottom.
You can see that the original Harrison is a true 6.25 inches, while the replacement is only 5.875 inches. A full .375 inches short.
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Also, note the end tanks. They have a large flange on their full perimeter that caps over the core. I've seen none of the aftermarket units that use this manufacturing method. They use a flat seal, like the lower unit, above. The aftermarket core I removed from the 86SE a couple of years ago was leaking at the end tank. When Sims Radiator put pressure on it to see where the leak was, the complete end tank detached. Imagine that happening in the car. They said it couldn't be repaired.