[daduck]

I assumed this was a 1973-1974 engine as it came complete with 4X-1H heads.

Casting on the block is 485428.
Casting on the crankshaft is 8799103

The date code stamped at the distributor pad is K051 which is 1971?

Block code at the valley pan is C or 0...... 223167 YH

partial VIN 22P345292.

It is going to the machine shop for pressure test and crack check but what did it start out as??

[lust4speed]

Cast date of November 5, 1971 which is pretty deep into the 1972 model year. Only thing that doesn't match up with your listing is the 1972 YH 455 should have 7L4 heads. No 1973 or 1974 455 blocks carried the YH as far as I can tell. I don't see any 73 or 74 455 on Wallace Racing either with the YH code.

YH was only offered in the big cars - the B bodies.

[steve25]

The 485 prefix casting code first showed up in early 72 which likely means items where first cast starting late year 71.

Many of these 485428 coded blocks went into inventory for SR blocks and sold much later then 71 or 72 it would seem.

[johnta1]

The block is a 1972 model year 455 engine.
The heads were probably changed on it.

You could send the 22P345292 to PHS and it would tell you exactly what it came from.

Should be a good 455 prospect.

[Gary H]

Check the date code on the heads. Probably were swapped on latter in life of the block.

[jd0n88]

Originally Posted by steve25

The 485 prefix casting code first showed up in early 72 which likely means items where first cast starting late year 71.

I think that chart may be off. I have a 485428 block from 71 model year.

[steve25]

Nothing is fully cut in stone with that chart as production runs ended in Late August of a given year and then the next years production kicked in as I understand it.

[grandam1979]

485428 was used 71-74

[daduck]

Originally Posted by Gary H

Check the date code on the heads. Probably were swapped on latter in life of the block.

the 4X heads were date codes K273 and L063 so I am thinking this block sat in inventory until 1973 model year when they put the heads on and dropped it in a Full Size car.

It really does not matter because I sold the 4X heads and when it goes back together it will have 6X-8 or 6X-4 heads.

[Joe's Garage]

They listed them by application (ie: Pontiac 455 V8 1971-1975, qjet), not by casting numbers.

And they supplied whatever fit the application (again ie: Pontiac heads with 100cc +/- chambers). 4X, 5C, 6X, 66, 7M5 were used interchangeably.

Your engine may well have had a basic 'rebuild' or a 'valve job' where they simply swapped the heads rather than waiting for the original heads to be rebuilt.

Or, as you've speculated it was built from leftovers.

We've also seen the 485428 blocks used from 1971 until 1974. They're good and strong.

[ponyakr]

I bought a '71 455 out of a '71 safari wagon. It had #98 heads & a 2-barrel carb. It was running when pulled & appeared to be original to the car.

So, that block was definitely used in some '71 model cars.