Expansion Tank, do I need this?
Thread Starter
Racer
Joined: Nov 2004
Posts: 261
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From: Appleton WI
Expansion Tank, do I need this?
I have a 1972 350 AC without an expansion tank. The engine is not origional numbers so was this an option at time of purchase or am I missing this. If it was an option should I put this in the car?
Race Director
Joined: Oct 2002
Posts: 12,065
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From: Smalltownville Michigan
Cruise-In 5, 6 & 10 Veteran
St. Jude Donor '09
IMHO, its supposed to be a semi closed system. when i biught mine, it didnt have one and i was eating antifreze. I put one on and the issue went away.
Race Director
Joined: Jul 2001
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Originally Posted by Fevre
Does the rad have a rad cap? If so you do not need a exp tank but you should have a recovery tank so the system will suck coolant back in instead of air when it purges.
Team Owner
Joined: Jul 1999
Posts: 26,545
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From: Huntersville NC
Originally Posted by Mike Ward
Corvettes did not come with recovery tanks prior to the 1973 model year.
true, but when he said, " but you should have a recovery tank so the system will suck coolant back in instead of air when it purges." I think he meant, "you should install a recovery tank...", not, "the factory configuration would include a recovery tank"
I think adding a recovery tank to a pre 73 vette makes for less messes when the engine gets a bit hot, less pollution, and less worry! Worked for me.
Le Mans Master
Joined: Sep 2002
Posts: 5,236
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From: Myrtle Beach SC
Originally Posted by pmurray
I have a 1972 350 AC without an expansion tank. The engine is not origional numbers so was this an option at time of purchase or am I missing this. If it was an option should I put this in the car?
Your 72 350 AC would have come equipped with a brass radiator and therefore no external supply tank or more popularly called surge tank. For a pre 73, C3, the use of "surge" to describe the tank is a misnomer and more accurately describes a post-C3 coolant recovery tank. Assembly instruction manuals for this period (68-72) described these tanks as "radiator supply tanks." Here's why...
A pre 73 tank was used as a supplemental tank due to the size limitation of the aluminum radiator on Base motors and special high-performance motors. These radiators had no integral tanks configured with the radiator to pour coolant into so GM used the external supply tank or "radiator supply tank." Therefore the radiators had no radiator cap...but used the supply tank as the receptacle for coolant.
In 73, the coolant recovery system was introduced that incorporated the plastic recovery tank in conjunction with a brass radiator with integral tanks. The tanks served as a resevior for coolant and also included a radiator cap to receive coolant.
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Originally Posted by hunt4cleanair
In 73, the coolant recovery system was introduced that incorporated the plastic recovery tank in conjunction with a brass radiator with integral tanks. The tanks served as a resevior for coolant and also included a radiator cap to receive coolant.
Pre-73 Corvettes (and all other cars) needed a tank on the pressurized side of the system to allow normal expansion of the coolant, avoiding spill overs. This was accomplished by leaving 'space' inside the radiator or the aluminum expansion tank as the case may be.
These cars had no coolant recovery tank, and did not need one if the system was kept in good shape and was not overfilled. Many owners today mistakenly overfill the system and then complain about the ensuing 'boil over' thinking that the car is overheating.
In 1973, the coolant recovery tank was introduced, and is located on the non-pressurized side of the system. This means that the radiator can (and is designed) to be filled completely without need for any room for expansion. The radiator cap, filler neck and tank plumbing are designed to capture any overflow when the engine reaches operating temperature, and to allow return of the fluid as required when the engine cools.
Mixing the two types of systems is not necessary and can lead to additional problems if carried out incorrectly.
