heads #s game

[robert leazenby]

My 70 LT-1 has head casting numbers of 3973414, correct for the 350/370. Cast date for one is 5/25/70 and the other is 6/5/70. Both fit for a body build date of 6/30/70. Engine block cast date is 5/3/70. The problem I have is the engine assembly date of 06/03/70. It seems it doesn't match the one head with the 6/5/70 date. Is the assembly date stamped on after the heads were installed?

[Joe L.]

Re: heads #s game

robert-----

The engine pads are stamped with the assembly and date code at the time that the engines are assembled. I don't recall, at the moment, if this is done before or after the cylinder heads are actually installed. However, it's a moot point since whichever way it was and considering the way that the engines were assembled, the timing difference would only be a matter of a few minutes. Certainly, not 2 or more days. My guess would be that the cylinder head was a VERY early warranty replacement. It is also possible that the engine was repaired via replacement of the cylinder head before the car was delivered to the dealer. This could have happened at the engine plant subsequent to the hot test or it could have happened at "heavy repair" in St. Louis subsequent to the car's build and prior to shipment. Unfortunately, it would be difficult, if not impossible, to document either of the latter 2 possibilities.

[Patrick H.]

Re: heads #s game

Joe,

I suspect you could document it, so to speak, if the engine has original paint on it, all the internals appear original, and you remove an original style head gasket from underneath the head. This would make the case for these being replaced in heavy repair as you mention. This would DEFINITELY be a process to photograph.

The chance of 1) someone going through the trouble to find dated castings that are so close yet so far from being "correct" seems minimal, and 2) who else but the factory would have had the correct heads available a few days after the engine was built?

For small blocks, the code was stamped onto the final assembly AFTER the heads were on.

Patrick

[Joe L.]

Re: heads #s game

Patrick------

The "closeness" of the cylinder head dates is why I suggested the possibility of a VERY early warranty replacement cylinder head. The SERVICE parts system inventory during the period of 1 month to, say, 12 months after delivery of the car could have had cylinder heads dated around the time in question. The fact that a cylinder head had a date 2 days subsequent to the assembly date of the engine could just have been a coincidence of what SERVICE head was actually used on the car.

Of course, it's also very possible that the engine was repaired at Flint or at St. Louis. However, regardless of where repaired, including the dealership under warranty, I would expect that the same PRODUCTION-type steel shim head gasket would have been used. Also, since the repair and replacement of the cylinder head would have taken place subsequent to the original painting of the engine, I would expect that the replacement cylinder head would have had to be painted off or on the engine. In any event, I would not expect the paint to precisely match the original paint. Even if the repair had been done at Flint, I would not expect that the engine would have been taken back to the line and re-painted. The Flint repair scenario probably would have resulted in the closest paint "match", though.

[robert leazenby]

Re: heads #s game

thanks for the input. I have since removed both heads and observed original type gaskets. the paint all looks the same but who knows, that could have been done by previous owner. At least it is the same casting number as the other.

[Joe L.]

Re: heads #s game

robert-----

Another possibility is that an incorrect date was set into the mold the day that your head was cast. We tend to think of the dates as being "absolutes" but they had to be changed by someone every day of production. That "someone" was, undoubtedly, not infallible and could have simply entered an incorrect numeral. That would have resulted in the whole day's castings from that mold being incorrectly dated. I'm sure that if and when the error was caught they would not have scrapped all the castings as a result.

[John C.]

Re: heads #s game

Robert, you may know this already but these dates are not judged. It'll just be a little quirk that makes your car that much more interesting!

[John H.]

Re: heads #s game - Trivia

Major engine repairs were not done at St. Louis - any repair of that nature resulted in pulling the engine and returning it to Flint or Tonawanda, and running another new engine (with the correct VIN stamp) down the engine dress line to replace it. Field warranty on engines was charged to the engine plants, and they didn't want anyone else "inside" their engines that could result in field problems.

[Joe L.]

Re: heads #s game - Trivia

John------

That's what I always understood, too. In fact, for many years I had friends who, during the 60s and 70s, worked in various positions at the GM Fremont, CA assembly plant. They had told me that "unit replace" was the only way that the did any repairs. If a carburetor was bad, the repair would only be to replace the carburetor. Likewise, if an engine failed in any way, the "fix" was to replace the engine.

However, several years ago I was at a restoration workshop at Bloomington regarding St. Louis procedures. The presenters were George Barlos, Phil Hawkins, and another fellow by the name of "Jim", as I recall. All had worked at St. Louis Corvette for many years and "Jim" had worked in the repair section for a good part of his time there. He stated that they did do internal repairs to engines in what he described as "heavy repair". I recall that this stimulated quite a bit of discussion and Phil, who had also worked in repair at times, and George chimed in and further discussed the fact that heavy engine repairs were performed. Quite frankly, I was stunned.

[John H.]

Re: heads #s game - Trivia

I'm sure occasional "internal" repairs (head or manifold changes, etc.) were made when there was no other alternative due to shipping deadlines for "hot jobs", correct replacement engine not in stock at the moment, etc., but parts had to be "robbed" from production engines to do so, as assembly plants didn't stock "internal" parts (engine plants wouldn't supply them). "Heavy Repair" was off-line in a hoist stall, for mechanical repairs that couldn't be done on a moving flat-top "Light Repair" floor conveyor (engine/transmission/axle changes, wrong springs, etc.). I knew George, Phil, John Evans, and the rest of the St. Louis crowd from Ed Teske on down - great bunch of manufacturing guys that did more with less than you can imagine.