72 LT1 Radiator ID

[Joe S.]

I pulled the radiator out of my 72 LT1 as I am in the process of a body-on resto. The radiator is copper but has no part #'s on it that I could find. Ther eis also suppose to be a tag somewhere on it but could not locate a tag. The only thing I could find is a spring type clip/tag over the passenger side edge of it with an MK9 (Broadcast Code?) on it.

The petcock is an elbow that comes out the bottom with a hex head (maybe 9/16" or 5/8") plug on it. Unfortunately there is a leak/tear at the petcoack where it goes into the radiator. If it is the correct radiator, I'll attempt to fix it. If not, won't bother.

[Mike E.]

Re: 72 LT1 Radiator ID

Joe--
I'm relatively new to the 70-72 cars, but I've had all or parts of 4 of them. All 4, including my 30,000 mile 71 LT-1 convertible (with original plug wires, belts, hoses, etc.) have had copper radiators with a similar tag to the one you described. None have had the part number on it as the Judging Manual indicates. My 80,000 mile 72 LT-1 convert had the identical tag to yours. My somewhat educated call (I bow to those with greater experience than mine) is that you have the original radiator.

[Tom R.]

Re: 72 LT1 Radiator ID

The MK9 is the broadcast code and in later C3 years (1974-82) this code is printed on the build sheet. I would venture to say the MK suggests heavy-duty in early years but I'm not sure. By late model C3 production, MK indicated heavy-duty (78-79). I'm sure others will jump in. This code was used into the 79 production year. The 9 would be the date code for 1969 and perhaps very early 79 but by late 79...the broadcast codes had changed to an FW9 format.

Seems like someone did an article on early C3 radiator broadcast codes...maybe Terry M?

[Joe L.]

Re: 72 LT1 Radiator ID

Joe-----

The 69-72 small block, copper brass radiators did use the broadcast code "MK" . The "MK" code was used for the GM #3018803 radiator which is the one used for most 70-72 LT-1s. This radiator has a core which is 26" wide.

The GM #3018802 is a virtually identical radiator except that it has an integral transmission oil cooler and has provisions on the tank for oil cooler fittings. This radiator was used for all 1969-72 small block applications with THM-400 transmission. However, this radiator replaced the GM #3018803 in June, 1974 for SERVICE of all 69-72 small blocks originally using a copper/brass radiator.

If your radiator does not have the plugged oil cooler provisions, as I expect will be the case, then I'd say it's virtually certain that you have the original radiator or a correct, identical replacement. If it has the oil cooler provisions, which I doubt, then it's a "nearly correct" replacement.

The 3018803 radiator, without oil cooler provisions is quite difficult to locate. So, if you have one, it's well worth it to get it repaired. If it should ever need a new core, DeWitts can fix you up with an excellent reproduction and you can use your original tanks.

[Joe S.]

Re: 72 LT1 Radiator ID - Thanks guys!

No plugged oil cooler lines. Now I'll have to keep my fingers crossed that the petcock can be fixed. My guess is that it can be. It's torn right at the base of the petcock where it comes out of the radiator. Truth is I had a hand in tearing it but it's a long story.

The car ran cool even on a hot day with some spirited driving. I've used the local rad shop before and they have a tank so I'll be dropping it off this week.

Thanks again!

[Joe L.]

Re: 72 LT1 Radiator ID - Thanks guys!

Joe-----

The repair should not be a big problem. I should be able to be soldered. Tank repairs like this are done all of the time.

[Joe S.]

Re: 72 LT1 Radiator ID - Thanks guys!

Got it fixed today. Thanks again!

$25 is much better than $700 especially being it is the correct one. ;-)

[Jim T.]

Re: 72 LT1 Radiator ID - Thanks guys!

Joe my original owner 70 350/300 radiator came with the same elbow drain on the radiator. I learned very early that using a backup wrench on the elbow to remove the bolt plug keeps the radiator from leaking. I don't torgue mine down much, just enough to keep it from leaking and coming out on its own.