Good morning. I have a 1970 SX. I am needing to replace the radiator. I notice that many of the replacements have a 1.5 outlet in the bottom position. I know the hose is 1.75. I have seen people use a spacer to make them 1.75. My question is, does the smaller diameter opening effect cooling? Thank you

 

I had always wondered about that, too. The smaller size is for the 1971-newer applications. The 1968-1970 used the larger size. But as the later engines cooling was sufficient, I would guess the smaller hose sizes wasn’t an issue.

 

Kenneth's observation is correct; however, many people use a rubber adaptor bushing to allow the larger, existing hose to fit the smaller outlet.

Butler Performance sells one: https://www.butlerbuiltperformance.c...p/all30240.htm
Others are currently on eBay.

If you don't use the adapter, you may have trouble at the water pump end trying to use a smaller hose.

 

There are a few ways to do this, Gates, Jegs, Allstar... to name a few that slip over the radiator port. This is what I have on mine and it's been good since 2009.




You can also go with a coupler hose and a 1.75 hose barb coupling



or a 1.75 to 1.5 hose barb reducer and a straight piece of 1.5 hose.

 

Thank you guys. I appreciate your input

 

Does your car have the original radiator in it now? If so, is it a 4 core? If it is the original 4 core it is very much worth having it re-cored. If it is a 4 core, it is likely a very valuable radiator and I would keep it in the car with the new core. If you go that route be sure they reuse the top and bottom rail instead of the replacement rails that can come on a new core.

 

What Eric said. If you have the correct original radiator, have it recored. As for the aftermarket replacements, vendors try to save money by consolidating parts. Since the 1.5" outlet works on early cars with the bushing, that's what vendors stock - one part number instead of two. The smaller diameter isn't a problem - that outlet isn't the smallest restriction in the system as far as flow is concerned. By the way, I also have seen aftermarket radiators where the outlet port is stepped so it can accommodate both hose diameters.

 

By the way, if you have the stepped outlet port (the upper one) and are using the bigger part, I recommend cutting off the smaller end. Otherwise the pressure can blow off the hose, even if the clamp is very tight-- spraying hot coolant everywhere--ask me how I know!