Radiator

[lyndon sharpton]

do you guys that have BBs with expanson tanks, fill the radiator through the upper hose after a drain? why did chevrolet use a radiator with out a cap on the side tank?

[Jack H.]

Re: Radiator

Style of radiator (with filler neck & cap on radiator, or tube extention to a remote expansion tank) was dictated by the amount of coolant expansion space within the radiator itself. The silhouette of the radiator support was fixed/limited and some applications taxing the cooling capacity of the radiator needed all of the internal space for heat dissipation dictating the expansion space be remotely located (separate expansion tank).

[Wayne M.]

Re: Radiator

Lyndon -- Chev Service News, March 1965 addresses the procedure for Corvette L78's, because "engine water outlet is located higher than the coolant supply tank.

"Disconnect heater hose from nipple at intake manifold. Add coolant to supply tank until starts to flow from nipple, then re-install heater hose. Completely fill coolant supply tank. Install pressure cap and run engine until engine normal operating temperature is reached, to ensure thermostat has opened. Observing usual precautions, remove pressure cap from supply tank and add coolant as necessary to maintain the tank normal one-half full level. Install pressure cap and tighten securely."

They probably already knew that, for 1966, copper BB radiators would have fill caps on the rad side tank, so no re-design of the 3007436 (396, L88) aluminum rad was not necessary.

[John H.]

Re: Radiator

Big-block cars (except L-88/ZR-2) didn't use expansion tanks - they used conventional copper/brass radiators with side tanks and a fill cap at the top of the passenger side tank. Small-blocks (and L-88/ZR-2) used Harrison stacked-plate aluminum radiators and separate expansion tanks; the Harrison aluminum radiator configuration is all core, with no tanks, so it requires a separate expansion/supply tank, and has no fill cap - that's on the expansion tank. No '63-up Corvette was ever built with an aluminum radiator and no expansion tank; all have either a fill cap on the (copper/brass) radiator side tank or on the expansion/supply tank with an aluminum radiator.

[Warren F.]

Re: Radiator

John:

I'm confused by your first statement of your reply. I believe that LS-5's for '70 to '72 used copper/brass radiator tanks and ALL were used without a radiator cap on the passenger side tank, and using the remote expansion tank, which has the radiator cap.

Am I wrong?

[John H.]

Re: Radiator

Warren -

I'll be the first to admit that I'm not as familiar with C3 cooling systems as I am with C2, and you may well be correct; I guess I just haven't seen a C3 big-block with a copper/brass side-tank radiator with no filler cap and an expansion tank. Gotta look at more C3's, I guess

[Terry M.]

Re: Radiator

1968-1972 (and maybe beyond, I'm not sure of that) Mark IV without C60 (air conditioning) had copper brass radiators with the fill cap on the side tank. Those large motors with C60 had the copper brass expansion tank with the fill cap on the expansion tank.

[Mark #28455]

1969 427's do not have fill cap on radiator

My 1969 BB uses the copper/brass radiator with an aluminum supply tank on the passenger side inner fender (no A/C) and no fill cap on the radiator. 1968 only used the supply tank on L88's (for BB engine). My 1970 has A/C so it uses the copper/brass tank, but that radiator also lacks the fill cap.

Mark

[Terry M.]

Re: 1969 427's do not have fill cap on radiator

Now that you bring it up the 1971 LS6 uses an alluminum expansion tank also. I guess my earlier answer was way too simple.

[Warren F.]

Re: Radiator

Terry:

We may need to revise the TIM&JG on this matter! It shows all '70 - '72 big block cars to use either aluminum or brass expansion tanks. It WOULD NOT make sense to have a radiator with a cap AND and an expansion tank also with cap.

[Terry M.]

[Warren F.]

Re: Radiator

Well Terry, I wasn't absolutely certain you had made a mistake. As a former Team leader and judge for probably more years than I have been a member of NCRS (which is since 1987) you may have forgotten more information than I could have possibly garnered in these last 18 yrs. I certainly admire your dedication, especially to the '70 to '72 years, and hesitate to contradict your opinion without some serious information to back it up!

[Terry M.]

Re: Radiator

Warren,
Those long term watchers on this board know that one of my many failings is to open my mouth (metaphorically speaking) before I engage my brain. I should have learned better by now, but as I get on in years I keep thinking my memory is better than it is.

[Jack H.]

Others have my disease!!!! *NM*

[Joe L.]

Re: Radiator

John, et al-----

Here's the deal:

1) All 1969-72 Corvettes with big block used a radiator supply tank. No exceptions. All 1969-72 big block except L-88/ZL-1/ZR-2 used a copper brass radiator with NO provisions on the integral tanks for a filler cap. This was true for big blocks with or without M-40 and with or without C-60. 1969 L-88/ZL-1 and 1971 ZR-2 used an aluminum radiator (GM #3007436) which also used an external supply tank;

2) 1969 L-88 with THM-400 used the same copper/brass radiator used for all other 1969 big blocks with THM-400 (GM #3019190). 1969 ZL-1 with THM-400 would have used the same radiator if any PRODUCTION examples had been built. 1971 ZR-2 was not available with THM-400, so all ZR-2 used the aluminum GM #3007436 radiator and aluminum external supply tank;

3) All 1969-72 big blocks used an aluminum external supply tank EXCEPT 1969-72 with C-60. C-60 big blocks used a brass supply tank of "cylindrical" configuration. The aluminum supply tank was the same as used for small block cars which used aluminum radiators;

4) After 1972 and through 1982, all Corvettes used radiators with integral filler necks. No external supply tanks were used for Corvettes, big block or small block, after 1972 right through the end of C3 production. However, beginning in 1973 COOLANT RECOVERY tanks were used on Corvettes and were used everafter.

There is one interesting aspect to the 1969-72 big block copper/brass radiators. As you know, all 1963-72 Corvette small block aluminum radiators (used for all 1963-67 small blocks and some 1968-72 small blocks) were a "stacked plate" design and incorporated NO integral tanks, at all. These radiators HAD to use an external tank or they would have had no tanks. The same is true for 1965 L-78, 67-69 L-88/ZL-1, and 1970-72 ZR-1/ZR-2. However, the 1969-72 big block copper/brass radiators DID HAVE integral tanks. So, in the strictest sense, they did not require an external supply tank; they could have been built with a right side tank that included filler provisions. Why GM elected to design this radiator with no provisions for a filler and requiring an external supply tank, I do not know. Certainly, it added a lot of expense to these installations and I can see no significant cooling or other functional advantage.

The only thing that I can surmise is that the external supply tank became sort of a Corvette "signature" piece in the 60s. Perhaps, some of the 66-68 Corvette big block owners complained because they didn't have the external supply tank "like Corvettes" but, instead, had the integral filler cap "like other cars". Consequently, maybe GM decided that they wanted this "signature" item across all Corvette engine options beginning in 1969. After 1972 the "bean counters" might have decided that it was just too expensive and, so, they eliminated it for ALL Corvettes. The feature came back for 1990 and later, though.