Why is this on top of my Nailhead?

[Guest 1964 225 Roadster]

After removing the Valve Covers of my '64 401, and stripping them down in preparation to repaint them, I discovered that one of the 1.5" round "flat spots" on top (driver side, toward the front) is a actually a rubber plug. Painted to match the rest of the Valve Cover, at a glance it appeared to be just a part of the metal. I had never focused on that previously, and wasn't expecting to find that!

Is this some sort of access port, rarely used? I don't see it mentioned in the shop manual.

I aslo noticed that both sides are the same raw stamping, and then they made additional passes to punch holes for this rubber plug, for the oil filler cap, PCV, etc, depending on which side of the engine it was ultimately destined for. Clever, those boys in Flint....

[55PackardGuy]

I wouldn't ordinarily post an "I don't know" but since 10 or so people have looked and you don't have an answer yet, I'll tell you that I do know that every one of these I've ever seen is painted over. It would be interesting to know if Buick anticipated using the hole for something, and if they ever did, what it was. Maybe they just made one too many "passes" in the stamping press!

[JohnD1956]

I wonder if it had something to do with upcoming smog contols on California cars?

[variablepitch]

On my '60 Invicta 401, she has an oil filler cap on both banks. I think that the one bank is plugged on later models and only one cap was used on those. The '60s used a road draft tube to evacuate crankcase blow by. It was an open system that didn't burn the blow by in the combustion chamber like a closed crankcase ventilation systems. That's my guess as to why you only have one. I've seen those with the plug as well.

[55PackardGuy]

Excellent! I suppose that second cap was vented too, to improve crankcase breathing. That makes a lot of sense. It could also be used for an attachment to a PCV hose to the carb on later models with a closed system. They were thinkin'!

[Guest 1964 225 Roadster]

I was all set to say - "Yes! That's it!" - but unfortunately it's not.

The rubber cap is on the SAME BANK as the oil filler cap. So the explanation doesn't work. (But it sure sounded good for a minute!)

By the way, the PCV ends up coming off the passenger side, in the middle, opposite the oil filler cap, but a smaller hole, with a rubber grommet.

[55PackardGuy]

OK, I'll curb my enthusiasm and wait for another speculation or "final word." Maybe GM still has the skinny on it in a vault somewhere. But it wouldn't be the first time that a hole leading to nowhere in a stamping or casting got the plug treatment. Take it out and look through it sometime, maybe you can inspect something through it!

[Philippe Racicot]

I'm not sure about 64's but on 65's the hole was used for the closed PCV system on cars with the California emissions. Other cars had the rubber plug you mention. In 66-67 they added a "smog" pump (Air Injection Reactor) to the California emission system but other cars with nailheads and 400-430 engines still had the same rubber grommet and an open PCV system with an oil breather cap.

All 68 Buicks had a closed PCV system and I think that the smog pump was not found on California cars that year probably because they were able to pass the emission tests without the smog pump as they had the new Controlled Combustion System (later called Thermac air cleaner) inspired by the 67 Olds Climatic Combustion Control. It wouldn't be long before the AIR pump returned and it was eventually found on all cars as the emission laws got stricter.

Again, the AIR pump was removed from the non-California cars when they introduced the catalytic converter on 1975 models (but it returned later!).

[55PackardGuy]

So, if I'm reading this right, Philippe, you're saying that somewhere out there are some 1966 California nailheads that use that valve cover hole for a PCV hose? According to the Carnut site, '66 was the last year for the nailhead. It appears that the foresight of Buick putting this hole in the valve cover was useful in some of the engines in one year of model production, and on all others it was plugged. Perhaps the mystery is solved at last--or like many of these questions, maybe not.

[Philippe Racicot]

My last post was a bit confusing, I spoke about 3 different things in it...

What I meant was: The hole was also used in 1965 for the closed PCV system used on California cars. I don't know much about the 1964 models but maybe they also had the closed PCV in California.

The 65 models didn't have the AIR pump however, but that was another thing, I shouldn't have talked about it as it wasn't related to the closed PCV system.

[55PackardGuy]

Ah, so, that would mean TWO years of the nailhead used the valve cover hole for PCV connection in California--1965-66. Thanks for the clarification.

[Philippe Racicot]

And I was thinking maybe 1964 too if there was a rubber plug on the 64 valve cover too... My 65 missed the original air cleaner and I have one from a California car. It has a hole on it's snorkel in which the hose that came from the valve cover connected. I also have the filter and hose but I didn't install them.

You can see it on this picture (don't look at the engine detailing!)

The 66 Nailhead had the same hole in it's driver's side valve cover but it's air cleaner snorkel was moved to the passenger side to accomodate the California models with the AIR pump.

In 1967, the air cleaner's snorkel moved back to the driver's side the hole was still on the driver's side on the 430's valve cover.

In 1968, the hole in the valve cover was moved to the passenger side and the (then standard) breather tube connected directly to the side of the air cleaner instead of the air cleaner's snorkel as it did in 67.

[Philippe Racicot]

I found a picture of a 64 Nailhead without that rubber plug on the valve cover, maybe your valve covers are from a 65 or 66?

And a 65 with California emissions.

[Guest 1964 225 Roadster]

Well, that is absolutely fascinating to me, especially the photo of the '65 with the California emissions system in place, and actually seeing this (usually plugged) hole being USED. Thank you for taking the time to locate and post those pictures!

You ask is mine is a '64 valve cover for sure. Although I cannot be 100% positive of course, it certainly would seem to be. I am the fourth owner of the car (technically it has been in the hands of 5, although the person prior to me never titled it and only had it about 6 weeks), and I have gone to considerable effort to locate the first three onwers and speak to each of them at length about the car's history. From their information, and from my own detailed study, it appears that the 78,000 miles showing on the car is correct and original. The engine has never been opened, numbers match, etc. I also have a '64 sedan parts car, also pretty unmolested, and it has the absolutely identical set up. Both cars were built in Flint.

This seemingly simple, innocent posting has turned out to be rather interesting. You have to wonder if it was wise of GM to put this hole in all the valve covers for all those years, and then install a rubber plug millions of times. Since the relatively small percentage of cars that actually made use of the hole used other specialized parts, might it not have been more cost effective to have a different valve cover just for those cars that got the California set-up, and install that when those other specific parts were placed on those (relatively) few cars? I spent a brief period working as a classical Industrial Engineer 25 years ago (city bus industry - Flxible) and such a question intrigues me. Seems like the extra cost of manufacturing all those rubber plugs, and installing them, might have been greater than changing out the valve covers on the cars that actually needed the hole. We would need hard numbers to make a truly valid cost comparison, of course.

Also, you have now brought up another subject that I was never certain about: which direction is the air cleaner snorkle supposed to be pointing? I see on your car there is actualy a decal that says "Front," which is no longer present on my car. The mounting of the air cleaner on top of the Rochester does not have any stops or any other way of being certain which way it pointed, it can pretty much be rotated at will. And of course after 40+ years, you see every possible angle under somebody's hood.

I love this hobby!

[55PackardGuy]

As mentioned in the "1960 Electra 225 Convertible R&R" Thread on the "Me and My Buick" Forum, the orientation of the air cleaner can be very important, as the accelerator shaft can bind on the bottom of the air cleaner if it's not installed properly. A shop manual or even an owner's manual might give information on the correct installation.

Also mentioned on that thread is a Buick safety recall relating to motor mounts breaking and allowing the engine to twist, causing the acclerator linkage to move and pull the throttle wide open. A cable "hold-down" for the front driver's side of the engine was installed to prevent this. Check if yours has it.

Regarding the cost/benefit of the "rubber plug" solution, it may well have been more prudent to manufacture all the valve covers with the stamped hole, as the manufacturers would have known that emissions legislation was pending, but did not know how widespread the applications would be. It was probably a safer bet and cheaper to stamp them all the same, and wait to see where and when the modifications would be needed--it wouldn't involve millions of engines, but thousands. I would guess the plug was available off-the-shelf from a supplier. They do make millions of rubber plugs! I'm just guessing on the logic behind it, and your background might give you a differnet perspective. It does seem that manufacturers often have to get out their "crystal ball" to try to anticipate regulations and minimize the resulting costs.

[TxBuicks]

I just purchased a 64 Wildcat that I believe is original and it has the California Emmissions set up exactly like the picture of the 65 above, except my hose connects to the side of the air breather. I can't tell by the picture above where exactly that hose connects.

Roy Faries

[Philippe Racicot]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I just purchased a 64 Wildcat that I believe is original and it has the California Emmissions set up exactly like the picture of the 65 above, except my hose connects to the side of the air breather. I can't tell by the picture above where exactly that hose connects.

Roy Faries </div></div>

That's interesting, this means that in 65 and 67, it connected to the air cleaner snorkel. In 64, 66, 68 and later, it connected directly in the side of the air cleaner. In 68, the hose was relocated on the passenger side but it moved back to the driver's side later. Now I'm guessing that not all 64 Nailheads have the hole in their valve cover as Buick probably used some remaining that didn't the hole in it earlier in the model year on non-California cars...

[55PackardGuy]

There may be no completely consistent rule by model years. As you note, changes on the line could have taken place with some variations during a model run. One source of information for the curious could be "Service Bulletins" which dealers received as updates to service manuals. These can sometimes be found at swap meets or copies obtained from collectors who are interested in such fine points of production data.