3919842 no plug, early date code

[Robert W.]

I have been reading up on all the research and stats for the aluminum 3919842 heads and the infamous changing core plug. On my 68 L89, one of the heads has two plugs and the other has no plugs, I always assumed that the no plug head was a later replacement head. Well I just pulled the heads for my first time and what a surprise. The head with NO plugs is dated 7.13.67 and the head with two plugs is dated 11.28.67. Also on the NO PLUG head the p/n has the first digit "3" stamped with the rest of the p/n cast. In the attached pic you will see that the square hole is present yet no plug. Can anyone shed some light on the early date code 842 with no plugs?
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[Joe L.]

Re: 3919842 no plug, early date code

I have been reading up on all the research and stats for the aluminum 3919842 heads and the infamous changing core plug. On my 68 L89, one of the heads has two plugs and the other has no plugs, I always assumed that the no plug head was a later replacement head. Well I just pulled the heads for my first time and what a surprise. The head with NO plugs is dated 7.13.67 and the head with two plugs is dated 11.28.67. Also on the NO PLUG head the p/n has the first 3 stamped with the rest of the p/n cast. In the attached pic you will see that the square hole is present yet no plug. Can anyone shed some light on the early date code 842 with no plugs?
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Robert-----

For the square head drive cavity to be there, there has to be a plug. There is no other reason for the cavity to be present. It may be that the plug periphery was welded over and ground, maybe even at Winters Foundry, but the plug has to be there.

[Robert W.]

Re: 3919842 no plug, early date code

damn, so much for my rare head discovery! went and cleaned head better and took a closer look. you can see the back of BOTH plugs through the water passages. Both plugs have been machined down, one to the point of not having the square port visible. Do you think this was possibly done at the factory? I don't see any reason a person would do this afterwards, but you never know.

[Joe L.]

Re: 3919842 no plug, early date code

damn, so much for my rare head discovery! went and cleaned head better and took a closer look. you can see the back of BOTH plugs through the water passages. Both plugs have been machined down, one to the point of not having the square port visible. Do you think this was possibly done at the factory? I don't see any reason a person would do this afterwards, but you never know.

Robert------


It could have been done at the factory but I don't see why they would have done it, either. In any event and unless somebody knows otherwise, I don't think it could be called "typical of factory production" which is the standard absent other documentation.

[Robert W.]

Re: 3919842 no plug, early date code

It seemed odd to me that the first digit of the p/n was stamped. Is this practice commonly found on these heads?

[Wayne M.]

Re: 3919842 no plug, early date code

It seemed odd to me that the first digit of the p/n was stamped. Is this practice commonly found on these heads?

Haven't seen enough of the early 842 heads to see if there's a trend, but one of mine has a grind and restamp '3'. Can't recall the dates, but one is June and the other is August 1967, IIRC.

Other than yours and mine, there's a 3rd head with a grind that appeared on eBay a couple of years ago.

Don't know what it meant -- maybe it was a letter 'X" (experimental casting) that they converted to the '3' when it was good enough for service or production [long shot].

[Joe L.]

Re: 3919842 no plug, early date code

Haven't seen enough of the early 842 heads to see if there's a trend, but one of mine has a grind and restamp '3'. Can't recall the dates, but one is June and the other is August 1967, IIRC.

Other than yours and mine, there's a 3rd head with a grind that appeared on eBay a couple of years ago.

Don't know what it meant -- maybe it was a letter 'X" (experimental casting) that they converted to the '3' when it was good enough for service or production [long shot].

Wayne-----


The only reason I can think of for the grind-out and stamping would be if the pattern maker made an error when he set the casting number and it was not caught prior to a bunch of castings being manufactured. So, the error was corrected by grinding out and stamping. I just can't imagine that an experimental casting number would have been the same as a released part number casting except for the first digit. Generally, the experimental casting numbers were of a completely different series.

If it were the last one or two digits that would be a completely different story since sequential numbers could be very similar parts and one could be "created" from another by modifying a casting post-pour.