69 chevelle L78 HEADS 3919840 MARKING - Chevelle Tech
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post #1 of 11 (permalink) Old Mar 13th, 20, 7:36 AM Thread Starter
 
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69 chevelle L78 HEADS 3919840 MARKING

I have some markings on the inside of the passenger and driverside head that im not sure what they are , can i get someone to help me on this one? Thanks in advance.
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post #2 of 11 (permalink) Old Mar 13th, 20, 8:28 AM
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Re: 69 chevelle L78 HEADS 3919840 MARKING

3919840 is the casting number as you probably know. Casting dates are as follows: L-4-8 L=December, 4th 1968. A-29-9 A=January 29th 1969. I don't know what is typical for 1969 L78's but a two month spread in casting dates seems like a bit excessive. What is the stamped engine assembly date and code from the front passenger side deck and the block casting date on the passenger side bell housing flange?

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post #3 of 11 (permalink) Old Mar 13th, 20, 8:39 AM Thread Starter
 
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Re: 69 chevelle L78 HEADS 3919840 MARKING

Ok so the heads are 2 different mfg castings? The. Engine numbers behind the alternator are not present, sometime in its life it has been torn down and the block has been decked but the cast number on the back of the block is as follows 395272
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post #4 of 11 (permalink) Old Mar 13th, 20, 10:21 AM
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Re: 69 chevelle L78 HEADS 3919840 MARKING

I've seen these 840 heads 3 months before the build date so it's not impossible for the spread between the dates to be wide. Are these heads original to your car and if so, what's the trim tag date?
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post #5 of 11 (permalink) Old Mar 13th, 20, 10:49 AM
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Re: 69 chevelle L78 HEADS 3919840 MARKING

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Originally Posted by Dave Deluca View Post
Ok so the heads are 2 different mfg castings? The. Engine numbers behind the alternator are not present, sometime in its life it has been torn down and the block has been decked but the cast number on the back of the block is as follows 395272
As long as they both have 3919840 on them they're the same casting just different date codes.

Also I believe you're missing one 5 in the block casting number. It should be 3955272. The 3955272 block can have either 2 or 4 bolt mains. The 396/375hp used the 4 bolt main blocks which would be appropriate for the 840 heads. You need to look above the oil filter to see if it has the two plugs to determine if it has 2 or 4 bolt mains. Take a look at the 2 vs 4 bolt section (https://www.chevellestuff.net/qd/blo...ar.htm#3955272).

Also look for the casting date on the block. It's either on the side of the block by the freeze plug or passenger side of the bellhousing flange. The article show format which is the same as the heads (1st position alpha = Month A=Jan, B=Feb, C=March; 2nd position is numeric = day of month; third postion is numeric = year

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post #6 of 11 (permalink) Old Mar 13th, 20, 5:04 PM Thread Starter
 
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Cool Re: 69 chevelle L78 HEADS 3919840 MARKING

Here is my trim tag plate
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post #7 of 11 (permalink) Old Mar 13th, 20, 5:09 PM Thread Starter
 
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Re: 69 chevelle L78 HEADS 3919840 MARKING

Yes it's a 4 bolt it has the 1/2"npt plug on above the oil filter there is the brass 45 degree high performance fitting in it for my oil pressure , there are 2 kinds apparently
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post #8 of 11 (permalink) Old Mar 14th, 20, 12:54 AM
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Re: 69 chevelle L78 HEADS 3919840 MARKING

The trim tag says it's a 3rd week of April built car (04=April, C=3rd week). The heads seem a little early for the car. Typically the casting codes are within 60 days of the car build date and the casting dates of the heads and block are usually fairly close together.

On the block, I'm not sure what you mean by "there are 2 kinds apparently". A 4 bolt block has 2 plugs above the oil filter. A large plug (3/4" NPT) centered above the oil filter and a smaller (1/2" NPT) in front of it. Can you post a picture of that area of the block? Also do you have a casting date for the block?

For Reference from the Camaro Research Group:

Block casting date must always be before engine assembly date.
Block casting date is usually very close to engine assembly date.
Engine assembly date must always be before vehicle (not body) assembly date.
Engine assembly date is almost always before the Fisher Body cowl tag date.
Engine assembly date most often less than 30 days before vehicle build.
Engine assembly date less often 30-90 days before vehicle build.
Odd exceptions of older blocks can occur.

FWIW - NCRS (National Corvette Restorers Society) does accept casting dates up to 6 months prior to car build date.

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post #9 of 11 (permalink) Old Mar 14th, 20, 9:35 AM Thread Starter
 
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Re: 69 chevelle L78 HEADS 3919840 MARKING

Ok thanks i will check it out .
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post #10 of 11 (permalink) Old Mar 14th, 20, 11:12 AM
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Re: 69 chevelle L78 HEADS 3919840 MARKING

Again, I've got a '69 L78 Chevelle that hasn't been on the road since '74. All numbers matching, original bore block, and the water pump is dated 4/69, the heads C28/C29 and the trim tag is 7B. That's all I can remember, but will look for the block date when I get a chance. It's one thing to gather dated parts and adhere to accepted dates, but don't ever be discouraged when you find parts that you presume to be original to the car and they preceed what others seem to accept. Most of the opinions on dates are based on what is read, not what has been witnessed.
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post #11 of 11 (permalink) Old Mar 14th, 20, 11:33 AM
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Re: 69 chevelle L78 HEADS 3919840 MARKING

Is that a crack around the back of that intake bolt in your photo?
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