My aluminum expansion tank (1968 L36) has a cap with "RC-36" on it. The correct cap is supposed to be "RC-26". I asked the folks at AC Delco who told me they have no record of a part numbered RC-36. They suggested I either had a mis-stamped cap or the part was discontinued long ago and they had no record of it. Anybody seen, heard or have an RC-36 cap? (I know I am not supposed to have the tank at all) thanks, Mark Jackson
-
-
Re: RC-36 expansion tank cap
Mark-----
Yes, the RC-36 was a radiator or supply tank pressure cap used on much later GM cars. Included are 1984 and 1991-96 Corvettes. It was, originally, GM #6410785. Later, it was known as an RC-27 under GM #10283897 and, currently, GM #10409635. It has a 15 PSI relief pressure which is the same as the RC-26.
Bear in mind, however, that for 63-72 aluminum supply tanks, ONLY the RC-26 cap should be used. The RC-26 cap is specially insulated to prevent dissimilar metal (galvanic) corrosion from occuring as a result of the direct contact of the steel cap with the aluminum supply tank neck. RC-26(or whatever) is the Delco parts sytem designation for a radiator cap. These numbers generally(but NOT always) remain constant although the GM "long number" of the part may change. The original RC-26 cap circe 1969, GM #6410203, had a galvanized steel outer cap with large "ears" and a black, plastic insulator inside the cap. The current day RC-26, GM #6410206, uses a stainless steel outer cap with small "ears" and a black plastic insulator inside the cap.
The RC-36 or RC-27 caps are designed for use with plastic or brass radiator/ supply tanks and do not have the insulation necessary for aluminum radiators/supply tanks.
By the way, the fact that your 68 L-36 has an aluminum radiator supply tank is probably a "vestigial artifact" of the small block or L-88 that may once have resided in your engine compartment. It could have been either: a small block or an L-88 and, based upon the information which you provided, I can't tell which.In Appreciation of John Hinckley -
Re: RC-36 expansion tank cap
Joe, thank you very much for that great information! Why did I expect the people at AC Delco to know that? My immediate concern is getting a cap that will not leak. I had the old one (RC-36) tested and it is shot. I continue to get some coolant overflow and I thought maybe the RC26 fit slightly differently from the other one.
You raise an interesting question: Was the expansion tank incorrectly added to an L36, or was the expansion tank left behind when the original engine was swapped out? Someday I may have the car judged just to get some expert opinion. All I can say is, if the L36 engine is not original to my car somebody went to a lot of trouble to match numbers and create a small piece of tank sticker with very little monetary payback! I mean, it's a 68! If you are going to convert a small block to a bigblock and restamp the engine wouldn't you do a 67? Originally an L-88? I don't think so....Thanks again, Mark
Comment
-
Re: RC-36 expansion tank cap
Mark-----
The original expansion tank bracket was rivetted to the front right fender well with 4 rivets with a small, flat head on the inside and the "flattened", set end seen on the outside. If your bracket is original, chances are it will have these characteristics. If it was added later, the chances are that the fastners will have some other characteristics. Someone adding a non-original tank to a 68 probably wouldn't have gone to the effort of obtaining and SETTING correct rivets. So, check them and let us know what you find.
As far as an original L-88 goes, I agree with you; it's very doubtful that's what you have. Actually, I was being a bit facetious with my earlier comment.In Appreciation of John HinckleyComment
Comment