C2 Inside Wheel Paint & Correct Rad Drain Plug

[Mark Evans]

Could somebody please advise what is the correct Paint Color for the INSIDE of the steel rally wheels on a December 66 built 1967 convertible.

After reading the long thread ,within the archives, I have concluded that I need to install an Aluminum drain cock on my 300 HP small block.
Is this correct? Is the Long Island Corvette a good replacement?

My car has the original aluminum radiator, however it has a Sq Head standard steel drain plug installed. The original owner always had this serviced at a dealer and they could've changed it.

[John H.]

Re: C2 Inside Wheel Paint & Correct Rad Drain Plug

Mark -

The back side of the rally wheel should be semi-gloss black. Your radiator should have an aluminum drain petcock; I haven't seen the one LICS sells, but Tom DeWitt has them.

[Mark Evans]

Thanks for the Quick Response

John,

Thanks for your quick response and help.

Do you have Tom DeWitt's contact information?

Mark

[Joe L.]

Re: Thanks for the Quick Response

Mark-----

You can get contact info for Tom at www.dewitts.com

As far as the plug goes, are you sure that it's STEEL? If it is, then it's definitely non-original. However, if it's actually ALUMINUM then it's likely that it's original. For one thing, having an aluminum plug being later installed on the car by "accident" is very unlikely. Aluminum pipe plugs are rather uncommon in the "automotive world".

Second, 1966 Corvettes did use pipe plugs (and, the aluminum variety for cars with aluminum radiators). This was actually a surprise to me when I confirmed it as part of some checking I did recently. Anyway, it's very possible that early 1967 Corvettes used the plugs, too.

You can easily check the plug with a magnet. If it's steel (or, cast iron), there will be a strong attraction; if it's aluminum, there won't be such an attraction. Of course, if it were brass, there won't be an attraction either, but it should be visually possible to detect a brass plug, even if a little cleaning might be required. A brass plug would not have been originally installed on an aluminum radiator, either, although they were, apparently, used for 1966 with copper/brass radiators.

[William V.]

Re: C2 Inside Wheel Paint & Correct Rad Drain Plug

If the plug is not aluminum I suggest changing it asap. The rad could be subject to bimetal coorision.

[Gary B.]

Correct Rad Drain Plug

Mark,

I don't believe that DeWitt's sells the correct aluminum plug/bolt for '66 SB applications. I think the only game in town is LIC. The LIC plug has no headmark, so in that sense it is correct. I haven't seen an original GM plug next to an LIC plug, so I can't say it's a perfect match or not, but as I said, I don't think there is an alternative.

Gary

[Gerard F.]

Here mine - a plug, late 67 S/B

Looks to be an aluminum hex pipe plug. Original radiator on a June 29, 1967 car (22049). Last time I had the coolant drained the guy told me he drained it from the lower radiator hose as he was afraid to pull the plug.

Guranteed original radiator in car owned 38 years (too cheap to change it and it works just just fine). But not too sure about the plug. Why would someone change a petcock to a plug?

Jerry Fuccillo
#42179

[John Fowler]

[Thomas D.]

It looks gold to me (brass)

The 1966 judging manual calls for this plug, instead of a petcock. I often get asked why we don't install a plug on 66 radiator and sometimes people lose a point or two because of it. Well here's my problem with it. The petcock was not a separate part, it was included in all the parts that made up the bill of material to complete the 3155316. This bill of material remained unchanged for 65-72. If GM changed to a drain plug for 66 (and maybe early 67) why did they do it? What reason could there be to prefer a plug over a valve? Why doesn't the blue print document a change, and then a change back for 67's? If the bill of material changed, then GM's pattern was to change the parent number to something else. A good example of this was the 60-61 top tank. This radiator used 3147536 and then they included a drain assembly with a nipple and petcock, the radiator changed to part number 3151116. The only difference was the drain assembly addition. I don't doubt a few cars may have been delivered with plugs because they ran out of valves, but it probably was really rare and it wasn't what they intended to do. Maybe this was installed at the factory on cars with leaky valves? The plant had to do something to address defective valves. Do you thing they had spare petcock? I think the rule book should be changed to read they MIGHT have plugs but petcocks are normal.

[Joe L.]

Re: It looks gold to me (brass)

Tom-----

I agree; the one in Jerry's picture does look like brass. I would not think that the factory would have installed a brass plug in an aluminum radiator. However, brass plugs were in the plant at the time (for the big block copper brass radiators), so I suppose someone could have made a mistake and installed it.

Like you, I always thought that the radiators were supplied with petcocks installed at the source (Harrison-Lockport, NY). However, the 1966 AIM clearly shows the installation at St. Louis of the GM #9424801 drain plug. John Daly has checked and found that this part number is an aluminum, 1/4" NPT, hex head drain plug and I've further confirmed that. The 66 AIM also clearly shows the installation at St. Louis of a GM #444819 drain plug for the big block radiator. The GM #444819 plug was a brass, 1/4" NPT, hex head plug.

For 1967, no plug installation at St. Louis is shown, at all, for the small block aluminum radiator. However, the big block copper brass radiator is shown as having a GM #103647 drain COCK installed at St. Louis. In the revision record, it shows that this was a change from the 444819 plug dated 1/19/67.

For no other model year that the GM #3155316 aluminum radiator was used (1963-72) does the AIM show the St. Louis installation of a drain plug or drain cock. So, presumably, the drain plug or cock was installed at the manufacturing plant, as you say. However, for the 1966 model year, alone, the AIM does specify the St. Louis installation of the plug. While the 67 AIM does not show the installation of a drain cock or plug for the aluminum radiator, it does appear from owner reports of early 67's, that they did, indeed, use the plug. That's also consistent with the fact that the plug changed to drain cock for big blocks about mid-model year.

For the big block copper brass radiator, however, every 66-74 AIM shows the St. Louis installation of a drain plug or cock. So, apparently, the big block copper brass radiators were not supplied with a plug or cock from Lockport. Interestingly, the 66-E67 big block used the plug, the L67 through 1969 used the drain cock, and for 1970-72 it was back to a plug again. However, for 70-72, a 90 degree elbow fitting was added and the plug installed into it. A similar set-up was installed at St. Louis for 71-72 small blocks with copper-brass radiator and may also have been used for 1970, too.

For 1973-74 when all applications used a copper brass radiator, it was back to a St. Louis-installed drain cock.

Why all the "turn-abouts" with respect to the plug and drain cock use? I have no idea.

[Thomas D.]

Is it just me....

or is there something wrong with the term "PET COCK"? I just never liked the sounds of that. From now on the offical term is DRAIN VALVE.
Anyway Joe, thanks for the feedback but I'm still not ready to cave in and start installing the plugs in all 66 aluminum rads. I have found errors to AIM's before and just because they say to install a plug doesn't mean it was done. What if the engineer that put the AIM together didn't realize there was already a DRAIN VALVE installed by the supplier? I could buy into this if anyone could give me the slightest reason why they might have done this. Maybe a new option that interfered with the drain or something. But there isn't one reason.

On the copper BB rads I did pull out the blueprint and that radiator was supplied without anything. So plugs or vavles are both possibilities.

BTW, I think about 90% of the population feels that brass is not compatable with aluminum and that is inncorrect. Brass and Aluminum are non-ferous materials and they do NOT react with each other. Aftermarket aluminum radiators have been using brass drains for over 20 years and nobody has reported any reactions. We've been doing it ourselves for five years without problems.

[Terry M.]

Re: It looks gold to me (brass)

"However, for 70-72, a 90 degree elbow fitting was added and the plug installed into it. A similar set-up was installed at St. Louis for 71-72 small blocks with copper-brass radiator and may also have been used for 1970, too."

FWIW: My early 1970 with copper-brass radiator small block had an elbow with a hex-head plug in it. I could guess, but can not positively identify the material.

[Joe L.]

Re: Is it just me....

Tom-----

I don't like the sound of it, either. However, I was just using the term that GM used in the AIM----COCK, drain.

I, too, would be suspicious that the plugs were actually installed as the AIM shows. However, several 66-67 folks have already reported that they found aluminum plugs in their original radiators. Aluminum pipe plugs are not a common sort of thing in the world of automotive replacement parts nor are they common hardware store items. In fact, the aluminum plug specified in the 1966 AIM was never available in SERVICE from GM. They can be obtained, though, if one seeks them out in the world of industrial suppliers. But, who is going to do that for a piece like this? The fact that several were found in what appeared to be original radiators makes it look, to me, very likely that they were originally installed there.

The only reason that I could come up with for the use of the plugs rather than "valves" would be that the plugs would be a more positive means of insuring that the radiator was sealed. A leaky "valve" could slowly drain the cooling system with ensuing problems. After all, unless these valves are tightened down very tight, they usually will leak a bit.

Plus, look at it this way: the engine oil drain is a plug, not a "valve". And, this is for a drain that has to be regularly removed. The radiator drain has exactly the same basic function as the engine oil drain, except that it usually needs to be removed a whole lot less frequently. So, why wouldn't a plug be just as appropriate for the radiator as the engine oil pan?

As far as the issue of the "reactivity" of brass and aluminum, I agree that under most circumstances the brass is not going to cause a problem with corrosion. However, the propensity for 2 dis-similar metals to set up a "galvanic cell" in an aqueous environment is well known. All sorts of problems caused by this phenomenon are known in the world of plumbing. You will note that special (and often expensive) insulated couplings are used in plumbing to prevent damage to plumbing systems caused by galvanic-induced corrosion. The propensity of the galvanic reaction to occur between 2 different metals depends upon the difference in electro-negativity constants between those metals---the greater the difference, the greater the propensity for the propagagtion of galvanic corrosion. I've forgotten the difference in electro-negativity constants between brass and aluminum and I don't have a table handy. However, I'm sure that there is a difference and I'm sure that aluminum will "come out the loser" as far as corrosion goes. Whether that corrosion will become any sort of problem during the life of the part, I couldn't say.

Nevertheless, I have a concern here. GM went through the trouble of obtaining special aluminum plugs for the 1966 model year. We know the plugs existed and we know that they were created in the GM parts system in mid-1965. Plus, we also know that GM created the special aluminum drain "valves" from the very outset of the use of aluminum radiators. We also know that GM took elaborate precautions in the design of the aluminum radiator mounting system to prevent the contact of aluminum with other metals. I've got to figure that they did this for what they considered very important reasons. In fact, I think that the reason that the aluminum radiators were generally supplied with the drain "valve" was to ensure that the correct aluminum drain "valve" was used. As far as I know, every GM aluminum radiator used an aluminum drain valve (or, in the case of 1966-E67) an aluminum drain plug.

Virtually all modern aluminum radiators use plastic tanks and rubber-gasketed plastic drain valves. Still, the mounting systems for these radiators are usually designed to ensure that no portion of the aluminum core directly contacts any steel of the support system. So, the sort of mounting systems that GM pioneered with the early Corvette radiators in order to protect from the affects of galvanic corrosion are still very much in use today.

[Gerard F.]

It looks like brass, but

Tom,

Here's a better picture:


Until I saw this closeup picture, I thought it was brass. But in the picture you can see the white alumininum oxide under the yellow corrosion. It is also non-magnetic.

The part number on the top of the radiator is 3155316 with a date code of 67F.
This is a very late 67 (June 29) in the last weeks of production. My only explanation is "maybe they ran out of the drain valves?". I have a few other anomolies on my car.

About 20 or more years ago I had the radiator flushed at radiator shop (the "Radiator Doc" in my local area). He tried to sell me on a new radiator at that time as he was afraid to pull the plug. He wound up draining and flushing it through the lower outlet, as I couldn't part (and was to cheap to part) with my original radiator. The radiator still works great at 62,000 miles and going on 40 years.

I really believe that the plug is original to the car. I agree with you that the Judging Manual ought to also indicate anomolies of plugs verses drain valves maybe present on both 66's and 67's. Maybe give your customers the choice or option, and let them decide which is right.

Jerry Fuccillo
#42179

[Brian M.]

Re: It looks gold to me (brass)

My original 67 SER# 7471 radiator has a brass plug.