1985 K10 Radiator Core 19" vs 17", which do I need?

[AZ-Jason]

I need a radiator for my 85 K10 (305) truck. I didn't notice this the last time I put a radiator in it 6+ years ago, but the mounting is homemade. The original upper brackets are missing and the radiator was bolted directly to the core support. There are homemade brackets holding the shroud to the core support, basically where the factory brackets should be. I want to mount the new radiator correctly so I can get the brackets and the rubber isolator pads no problem. What I have no idea of is whether I should order a 17" or 19" core radiator. Since the original mounting is gone, and the radiator that just failed is an aluminum job I got from Amazon 6+ years ago so I have no idea what size should go in there. FWIW, the one that is in there now is a 17" core. I'm sure I measured whatever I took out when I ordered the Amazon one but I don't know that I trust the 17" will work with the new brackets. If I order new brackets, can I expect they are designed specifically for one of the 2 sizes? Or how can I figure out which size I need?

 

[cadillac_al]

I was surprised that my K20 came with a 17" radiator. I think the majority use that one. I'll see if I can double check that tomorrow

 

[Broken85]

I have a 1985 K10 that came with a 305 originally. It came stock with the 19” radiator, and I don’t think you can go wrong with putting a 19” in now. Mine is a Silverado so it has AC which “may” be the deciding factor between 17” or 19”. The brackets are on LMC for about $10 for each side and your radiator support is probably already drilled and tapped with captured nuts for those brackets. You can get a set of upper and lower grommets from Amazon or LMC also. Probably have it back to stock for like $50 in hardware.

If you think your truck originally came with two brackets that went on to the top of the radiator support, it was a 19”. If it looks like there was some kind of fab’ed sheet metal that went from the radiator support and sloped down to meet the radiator, you had a 17”.

 

[AZ-Jason]

I have a 1985 K10 that came with a 305 originally. It came stock with the 19” radiator, and I don’t think you can go wrong with putting a 19” in now. Mine is a Silverado so it has AC which “may” be the deciding factor between 17” or 19”. The brackets are on LMC for about $10 for each side and your radiator support is probably already drilled and tapped with captured nuts for those brackets. You can get a set of upper and lower grommets from Amazon or LMC also. Probably have it back to stock for like $50 in hardware.

If you think your truck originally came with two brackets that went on to the top of the radiator support, it was a 19”. If it looks like there was some kind of fab’ed sheet metal that went from the radiator support and sloped down to meet the radiator, you had a 17”.

So I ended up ordering a 19” 4 core. Another Amazon one which I was on the fence about but this one lasted 6 years. I thought it would last “forever” but…. The Summit branded ones look like Amazon ones too.

I do have the 2 tapped mounts. I have more than enough space for the 2 extra inches and my shroud looks like it won’t be a problem. I will figure out the mounting when I get it and I would like to put the 2 top mounted brackets back on there. Also I live in AZ and the truck has some kind of aftermarket AC.

Lotsa space

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You can see how it’s mounted and how it should mount.

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Fan shroud measurement

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[bucket]

I don't believe that any post '80 trucks got the shorter 17" core.