[dreamingmuscle]

Like the title says any information on this block would be helpful.

[F ROCK]

Copy/pasted from Wallace's website:
8 Matches Found (displaying 1 to 8)
Year Engine HP Engine code Trans CR Cam Head Code BBL Carb No. Misc
1967 400 350 HP XH A 10.5 066 670 1-4 4242S GP Block Casting # 9786133
1968 400 350 HP XH A 10.5 066 16 1-4 7028262 GP Block Casting # 9790071
1969 400 350 HP XH A 10.5 066 62 1-4 7029268 GP Block Casting # 9790071
1970 400 350 HP XH A 10.25 066 13 1-4 7040264 GP Block Casting 9799914
1973 400 170/185 HP XH A 8.0 555 4X 1-2 7043060/61 Block Casting # 481988
1977 400 180 HP XH A 7.6 793 6X 1-4 17057274 Block Casting # 500557
1978 301 150 HP XH A 8.2 464 02 1-4 17058272 Block Casting # 525934
1979 301 135 HP PXH XH A 8.2 424 01 1-2 17059160 Block Casting # 525934

What year is your block? the answer will be cast near the distributer hole.
The displacement might be cast on the driver side of the block.

[dreamingmuscle]

Thanks that's what I was forgetting. The block casting. I'll look that up in the morning.

[turbo69bird]

Probably want the casting number and date code

[unruhjonny]

casting date would corroborate with the casting number;
The model year of the casting date would dictate which XH that is.

I believe Rocky and maybe a few others have a list that makes the EUN useful, but for the most part, it's gibberish to most of us.

[Matt Meaney]

if there is a vin number stamped on the front, it isn't a '67 casting. the second digit will be the model year it was designated for.
example:
2= pontiac
0- model year (0- for '70. 1- for '71 etc.)
P- plant it was built
1- last six of the vin for the car used.
2
3
4
5
6
you can also use this number to get a phs.

[John V.]

PMD did not start stamping the 7 digit EUN until very early in the '69 Model Year. Up til that point the EUN was 6 digit.

In '69, PMD thought they might hit 1 million units so they added the 7th digit. But they never hit 1M so the first digit was always a 0.

Circa the '73 Model Year, it appears that the stamp for the 1st character 0 had become chipped.

This leads to the leading 0 looking like, and often reported as, a C rather than a 0.

So you can eliminate the possibility of this XH stamped block having been original to a '67, '68, or '73 Engine Assembly.

Assuming you can distinguish between a 400 and a 301, I'm betting it isn't a '78 or '79 and in any event I'm not sure if the Manifest Codes were still being stamped in '78 and '79 or had been reduced to a decal sticker.

So I believe it is most likely a '69 or '70 out of a Grand Prix.

The casting p/n should leave little doubt and the partial VIN stamp would seal the deal.

That said, hardly matters as far as the block is concerned unless it happens to have been factory drilled and tapped for 4 bolt caps.

If it turns out to be a '77 XH, a bit of a bummer. The 500557 casting isn't as well thought of. The XH was used in the B Body that year, my suspicion is that it was a lot less common than the '69 or '70 XH.

['ol Pinion head]

My bet is its '69, 70, or a 77 XH 557 400 block. Reason... not enough room between block/ timing cover water mating holes to be a short deck (301) block.

John, def understand how you eliminated '73 model XH coded 400.

Used the below obscure detail in history for many years in my engine core program & when looking at supposed original cars. To clarify, the ( was the first character in the engine production number from sometime in June of 1970 through 1974 model blocks. Will need to ck cores, but believe it was also used on early '75 model 400 blocks before the first "557" castings 400's arrived. Also, the ( was never the first character of a '73 or 74 455SD block, & since I prev mentioned "sometime in June of '70", any late assembled '70 WW or XP shortblock continued with its non gangstamped somewhat sloppy style of RA4 block stamping

Amazing what one will commit to memory... One of my favorite amusing moments from ck'ing out a purported original numbers match local '69 M40 Judge, & few years later, a '70 GTO convert made up as a "Judge". In both I observed the YZ coded 400 blocks with the hyphen in the middle of the Z. Not something one will observe til the worst of the smog era 400's. No reason to try and have the owner pull the RA aircleaner & try and see a casting date.

[android 211]

The commonest 'XH' was a 400 Grand Prix motor with 62 heads in 69 and 13 heads in 70.

[johnta1]

5 Motor mounts bosses on the side of block would make it 1970 and up.
1977 seem to have only 3 mounting bosses.
Casting code on block would help.

[bigger=better]

I may be an idiot but couldn't he just look by the distributor hole?

Sent from my SM-S906U using Tapatalk

[John V.]

Originally Posted by bigger=better

I may be an idiot but couldn't he just look by the distributor hole?

Depends on what you need to know. If you mean the cast date code, they are notoriously hard to read and often misread.

The block p/n is cast on a ledge behind the no. 8 cyl (starting early in the '67 Model Year, was on the pad by the distributor hole prior to that change), usually more reliable but some block p/ns were used multiple years.

The stamped manifest code can help identify the other pieces and parts that would be part of the complete engine assembly if it hasn't already been mix and matched since original vehicle final assembly.

In the case of a block casting having been used for multiple Model Years, the EUN can help distinguish between a late Engine Assembly from a particular Model Year build versus one originally installed early in the next Model Year.

The stamped VIN ('68 and up) will identify the specific build that the Engine Assembly was original to if you are checking for "matching nos.".

Assumes no restamps or creative use of brazing rod to create a "new" cast date which some restorers have resorted to.

Personally, I would rely more on the cast p/n rather than the cast date code tag for a quick ID of a block. But usually I would be interested in knowing more about the block than either of those nos. alone can provide.