Expansion tank on my 68 L36

[Mark J.]

My car has the correct numbered part (3016340) and it is even correctly dated for my car, J 67 would be October 67 which is consistent with my Nov 67 build date. The only problem is the expansion tank was not used on the 1968 L36 engines. My radiator has a pressurized cap. The expansion tank also has a pressurized cap (RC-36, but is supposed to be RC-26), so the entire system cannot be working properly. I can't believe this correct numbered/dated part was installed during a misguided restoration. Were these expansion tanks put in by dealers perhaps to address early overheating problems in the 68s? Any thoughts? Thanks, Mark Jackson

[Dennis Trayes]

Re: Expansion tank on my 68 L36

Mark, when I purchased our 68 in 1982 it had a burglar alarm siren mounted where i thought the tank should be. I thought someone had removed it. I had seen pictures in restoation books showing a tank on an L36 car. I found a correctly dated tank at Carlisle and when I removed the siren I found that the holes for the tank mounting bracket had never been drilled. I later found out that the L36(copper radiator) didn't have and aluminum expansion tank (dis-simular metals). I never had any over heating problems. My car is auto without air and a very late car.

[Joe L.]

Re: Expansion tank on my 68 L36

Mark-----

Which radiator does your car have? The 1968 radiator, GM #3008566, is a "brass" radiator with a radiator fill cap. It has no provisions for an external tank, although such provisions can be added.

The 1969 radiator for all big block applications(except L-88/ZL-1)was GM #3019190. This is also a "brass" radiator of somewhat similar configuration to the 68 model. However, it has NO filler cap. It does have a nipple connector located on the upper right portion of the radiator for connection to the required external tank.

I suppose it's possible that very late 68s used the 69-style radiator system, but I've never heard of it before. Also, 68s used a different radiator support than 69s and the two are NOT interchangeable, so a 69 support could not have been used in your 68 without major modifications to the car and support. The 69 radiator will fit in the 68 support, but modifications to the support would be required.

[Gene M.]

Re: Expansion tank on my 68 L36

Mark, Take a close look at your right side inner fender. See if the aluminum rivets that secure the bracket that mounts the H2O tank are the original wide head type installed from the out side in. If correct the pieces may have been grafted on from a small block car due to some small fender bender. The rivet heads if original at GM assembly will NOT have undercoating under the heads. The coating and black out were applied after the rivet operation.