It seems that most of the guys out there are using the radiators from companies that specialize in computer cooling. I bought a heater core from pep boys for $22. I figure most just don't want to modify them. Which are more efficient?

I also noticed that guys on forums are very specific about their suggestions, ie. '76 chevy pickup w/out ac. Is there something special about these heater cores, or do they just meet certain specs? I made sure that it is all copper and is 8"x6"x2". Should I have gone bigger?

Well I can tell you this:

Where the heater core is designed to get heat out of the loop it is still fairly restrictive in how much heat it will transmit and how well water flows through it. And they are usually made using brass tubing and fins.

Radiators designed for computers like the ones from Thermochill are designed to perform the best for the amount of space that is available. And the Thermochill ones are made out of high quality copper.

But if you already have a decent radiator core give it a shot. Just remember that you might need a couple decent fans to push air through it.

-ouch1

I have used heatercores in the past and have had great results. To be honest, they are actually quite unrestrictive in my experience. It usually takes almost nothing to even blow air through them.

The main problems most people encounter are these:

Barbs- either they are odd sizes or need to be cut and resoldered/epoxied with the correct ID tubing size...not a big deal, but increases the DIY factor.

Unfinished- they are usually that ugly brass/copper color, spray paint fixes this nicely

Mounting options- they don't have those nice holes for screws for fans and shrouds. You can get creative by using plexiglass and drilling holes for fans and mounts that way. I think they work really well, but their size is often rather oddball compared to 80mm, 92mm, 120mm or even 140mm fans and mounts.

86 Chevette- little bigger than a 1x120mm, but thicker

78 Bonneville- kind of in the neighborhood of 2x120mm

I would say that you might see a little better performance due to increased surface area, but it might be relative to your specific setup and flow. It all depends if the work you are willing to put in is worth the savings and look. Remember, a heater core is cheap to begin with, but you have to pay for additional parts for mounting, barbs, etc. Is it worth the hidden cost by the time its said and done?

http://store.summitracing.com/part [...] toview=sku

You can go with something like this. I have one similar to this mounted as a passive on the side of my case. Just saw off (carefully) the barbs, I think 1/2" tubing fits right over. There are mount holes; just drill and run you some screws through. I have mine offset with 1/4" spacers made from little PVC tubing. Works well.