68 radiator overflow

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Nov 4, 2010 | 02:02 AM

corvette_newbie

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2nd Gear

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From: WI

68 radiator overflow

I just purchased a 1968 corvette and am currently trying to add a radiator overflow because I did not see that it had one. I located the radiator cap and noticed that it was copper so I figured that the radiator must be copper. I'm looking at an aluminum overflow and was wondering if it was possible to connect the two together since they are of two different materials, and didn't know if that would be an issue or not.

Nov 4, 2010 | 04:42 AM

7T1vette

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From: Crossville TN

I believe that the 'standard' small block model just had an overflow tube from the filler neck on the radiator, and that there was no tank on that model. What engine and options do you have?

Nov 4, 2010 | 09:53 AM

Mike Ward

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There would be no benefit in adding the aluminum tank you call an overflow. That's not what it is and would be redundant in your case.

If your car is puking fluid, you're overfilling it or the cap is weak.

Nov 4, 2010 | 10:16 AM

Easy Mike

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From: Southbound

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The 4 row Harrision copper radiators did not use an overflow tank. No need to add one. Fill your radiator to within an inch of the bottom of the fill hole to allow room for expansion. Do not over fill it.

Small blocks 68s with the TH400 got the Harrison copper radiators.

Last edited by Easy Mike; Nov 4, 2010 at 10:25 AM.

Nov 4, 2010 | 04:16 PM

LB66383

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From: Long Beach CA

Most auto parts stores carry an add-on coolant recovery system -- usally a plastic tank and a hose to connect to the radiator overflow. I'm guessing that is your goal, to have something similar to the coolant recovery systems on newer cars.

Nov 4, 2010 | 05:18 PM

corvette_newbie

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From: WI

Quote:

Originally Posted by 7T1vette

I believe that the 'standard' small block model just had an overflow tube from the filler neck on the radiator, and that there was no tank on that model. What engine and options do you have?

Its a 300 hp 327 4-speed, with no power steering, no power brakes, and no a/c

Nov 4, 2010 | 05:20 PM

PRNDL

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From: Huntersville NC

Yes, the stock configuration has an overflow hose that goes right to the street.

In an ideal world that would be fine because your properly functioning 68 cooling system (that IS an oxymoron!) would never puke antifreeze. In the real world it is a very good idea to install an overflow catchcan of some kind, just in case. I used a plastic autoparts store overflow can, and it gives me peace of mind. I don't think it has caught any overflow in several years.

According to the 68 owners manual, the radiator should be filled only to within THREE inches of the top. Stick a ruler in there; THREE inches is a big space. If you "eyeball" it, 3 inches will look like your radiator is low. That is why it is so common for owners to overfill their radiators which leads to coolant overflow when hot.

oh, and btw, base engine 68 without A/C came originally with an aluminum expansion tank, but if you had the stock expansion tank then your radiator would not have a cap.

Last edited by PRNDL; Nov 4, 2010 at 05:23 PM.