Author Topic: Help Choosing a Radiator  (Read 656 times)

Offline 75gmck25

  • Frequent Member
  • **
  • Posts: 356
  • 1975 GMC K25 Camper Special, 350/TH350/NP203
Re: Help Choosing a Radiator
« Reply #15 on: April 15, 2019, 05:20:45 AM »
GM made changes over the years, but there are really only a few sizes of radiator (2,3,4 rows; 17" vs. 19" core height, etc.).  The simplest is to match the size of the radiator you have (measure the core, not the entire radiator).  My '75 had factory HD cooling, which meant a 3 row radiator with the 350 in that year.  They may have also offered a 4 row, but it was probably with the 454.  My point is that it is a little different for each year.  For best cooling, just look for the best/biggest radiator offered in your year.

The radiator is "clamped" vertically between the radiator support on the bottom and a long bracket on the top.  Inside the brackets there are small molded rubber pieces at each corner, and they are different sizes based the number of cores (thickness).  If you swap from a two core to a three core, you need to use the right rubber piece that will fit exactly over the corners.  Of course you also need to have the same core height and width if you want to use original mounting.

Bruce

Offline 1967KaiserM715

  • Site Supporters
  • Junior Member
  • ******
  • Posts: 914
  • 1985 GMC K1500 w/ 6.5 TD
Re: Help Choosing a Radiator
« Reply #16 on: April 15, 2019, 09:51:14 AM »
Chances are you have the heavy duty brackets, you could get the standard duty brackets, but that means replacing all the shroud, and some other pieces. I would see if you can exchange the radiator for the correct size. It will be the easiest, but probably not the quickest.

Sent from my SM-S920L using Tapatalk

Current Vehicles:1985 GMC K10(Daily) 1991 GMC K2500(Daily) 1975 Beetle(not running) 1985 Mercedes 300D(not running) 1952 M35    1967 M715(not running)
 1986 Chevy K30(under repair)

Offline teamcurtis

  • Newbie
  • Posts: 57
  • dangerous mechanic
Re: Help Choosing a Radiator
« Reply #17 on: April 15, 2019, 11:35:53 AM »
Thanks Bruce

I think this is the info i needed. I have boxed up the radiator I got and will be returning it today. They dont offer a 19" core in the 2.25" thickness, so I will have to go with another brand, but I think I've got a line on one that wont break the bank.

now debating on if i want to pay another 200 bucks to make it an electric fan
1978 C10 Short Bed
350 smogged for CA

Offline teamcurtis

  • Newbie
  • Posts: 57
  • dangerous mechanic
Re: Help Choosing a Radiator
« Reply #18 on: April 15, 2019, 05:55:36 PM »
so the second factory radiator, between the normal radiator and the grill...
is that for oil or an added trans? My truck has one, but its not plumbed
1978 C10 Short Bed
350 smogged for CA

Offline 1967KaiserM715

  • Site Supporters
  • Junior Member
  • ******
  • Posts: 914
  • 1985 GMC K1500 w/ 6.5 TD
Re: Help Choosing a Radiator
« Reply #19 on: April 15, 2019, 06:16:59 PM »
Is it a radiator, or remnants of a condenser for an ac system? If it's is small (less then a foot square) it was likely aftermarket cooling for the transmission or engine. If is thin, but close to the same size as the radiator, it's the AC condenser

Sent from my SM-S920L using Tapatalk

Current Vehicles:1985 GMC K10(Daily) 1991 GMC K2500(Daily) 1975 Beetle(not running) 1985 Mercedes 300D(not running) 1952 M35    1967 M715(not running)
 1986 Chevy K30(under repair)

Offline teamcurtis

  • Newbie
  • Posts: 57
  • dangerous mechanic
Re: Help Choosing a Radiator
« Reply #20 on: April 15, 2019, 10:27:45 PM »
yup, thats what it is... Wonder if i should just take it out...
1978 C10 Short Bed
350 smogged for CA

Offline teamcurtis

  • Newbie
  • Posts: 57
  • dangerous mechanic
Re: Help Choosing a Radiator
« Reply #21 on: April 21, 2019, 10:31:07 PM »
so it seems that all 19" core aluminium radiators are 20.5" tall not 21.  I had to make some lift blocks out of 2"x.5" steel bar. Would have done them in aluminum, but the hardware store was out.
Made a 30 min job a 2 hour job
1978 C10 Short Bed
350 smogged for CA