Hi All, I am replacing my old small block radiator with a 4 core NOS big block unit on a 73. will I need special hoses or is the inlet & outlet in the same location? Thank you all in advance

 

It should still work

 

Thank You!

 

Welcome to The Corvette Forum Jim DE!

This is the right place to ask a question like yours as there are a lot of 1973 Corvette owners amongst the Corvette Forum.

I took a look at the ZIP catalog and the 1968-72's are one shape and the 1973 on up use a different hose shape. Take a look at their on-line catalog and the hose shapes that are shown. You might be able to identify the upper and lower hoses by their shape alone. I don't remember if there was a difference when I had a small block (350 c.i.) in my C3 while building the 427 again. I used the 1970 LT-1 engine while I was tearing up the 427 engine. I used as many of the same parts on the LT-1 install as I recall. My C3 was able to break 20 mpg with the LT-1 engine which is something you can forget about in the BB world.

My BB uses a Hose #3947868 for the lower and a #3947866 for the upper on my 1968 427-4 speed car. If you are not sure I would call ZIP and ask them to check it for you. Good Luck and I hope the Corvette is back on the road again soon!

If you have a warm or hot running engine you might want to try REDLINE's Water Wetter. It is a great help as it changes the way the engine gets rid of the heat more effectively. It is also cheap...

If you live someplace warm you might want to use a 70/30 water/anti freeze versus the 50/50 that many use. Where I live we Rarely see anywhere near 0* (F) so I use the 70/30 with 70% Water and 30% anti-freeze. Believe it or not Water cools more efficiently than anti-freeze. If you are seeing boil overs or water bubbling out then you probably need a new 15 lb radiator cap as that provides the protection up to about ~260*. I like to replace the radiator cap and thermostat on a schedule as to not get bitten by one of them failing. These parts do wear out over time like everything else.

Even if you are using the large expansion tank on the right front fender you still need a good pressure radiator cap.

 

I replaced the small bock in my '69 with a 502 and kept the small block radiator. It was about 18 years ago but I think the top hose worked and I had to shorten the bottom hose a bit.

 

Thank You!

 

a big block radiator and a small block radiator with an automatic are the same radiator

 

My car has a manual transmission and radiator, if that matters.

 

All 73 Corvettes used the same 4 core copper radiator, there was no "big block" or "small block" radiator in 73. The only difference in any radiators used in 73 was radiators for cars with an automatic had fittings for the internal trans cooler, that aren't in manual trans radiators. All 73 radiators had a core that was 27 1/2" wide, 17" tall and 2 5/8" thick, the same radiator was also used from 74 till around January 76.

 

The big is a wider and longer block so shortening hoses would be a good solution. No reason t change unless they were going to hit a rotating assembly

 

In 69-72 there were three different radiators. There was the 19" aluminum one that came in small block cars with manual trans and without AC, the 26" copper one used in small blocks with automatic and/or air conditioning and the 27" used with all big blocks. This all changed starting in 73 as there was only one basic radiator for 73-76, the 27 1/2" wide core. There were 4 variations of the 73-76 radiator, automatic & no AC, automatic with AC, manual trans no AC & manual trans with AC, but they were all the same size, all used the same core support and were all used with both the 350 and 454.

Looking at the Corvette Parts Book it appears by the late 70's the GM parts system only carried two service replacement radiators for 73-76, part number 3030199 the manual trans AC one and 3030201 the automatic AC version. The difference between the no AC and air conditioning versions may be 3 verse 4 row core, but none of my Parts Books include a core count.

 

good luck changing the bottom hose .😩

 

I change mine from underneath