[Formulabruce]

There is a 455 listed on eBay , owner has it as a '71. It is missing one of the casting numbers, the "year"
Date Should read J203 . This is a 250hp YA block from late '73 . The heads are 1971 it seems , # 191 castings though.
https://www.ebay.com/itm/1971-PONTIA...75.c100623.m-1

[jwcfbd]

yeah the J20? is a poor casting but I can see why he would say J20 is Oct. 2 1970 but no YA blocks for 70. Block number 485428 is for 73.
Here they say date codes could be a letter and 2 or three numbers. http://www.teufert.net/pontiac/bloccast.htm

[Bermuda Blue]

looks like a reproduction intake

[tom s]

Its Joe from the Parts pPace!Tom

[tom s]

PLACE!

[NeighborsComplaint]

Not to obvious that the last number of the casting was knocked off leaving a crater where it used to be. I guess PP was making aluminum repro intakes 18 years ago too. Wow.

[johnta1]

owner has it as a '71. It is missing one of the casting numbers, the "year"
Date Should read J203 . This is a 250hp YA block from late '73

No, it's a 1971 YA 455 block.
The cast date is correct also.
Oct 2, 1970 (J 2 1970 basically)

YA code was used every year from 1965 to 1978.
1970 to 1973 it was for a 455 engine. The other years it could be some other displacement.

Engine Codes

[Formulabruce]

Originally Posted by johnta1

No, it's a 1971 YA 455 block.
The cast date is correct also.
Oct 2, 1970 (J 2 1970 basically)

YA code was used every year from 1965 to 1978.
1970 to 1973 it was for a 455 engine. The other years it could be some other displacement.

Engine Codes

You contradict Wallace Racing?? :P :P ?? IF what you say is true, that should be a 4 bolt block? 2 bolt?, what is the application?

[John Milner]

Originally Posted by Formulabruce

You contradict Wallace Racing?? :P :P ?? IF what you say is true, that should be a 4 bolt block? 2 bolt?, what is the application?

I think a '71 YA would have come with 66 heads originally and probably would have been in a Grand Prix and maybe a full size. If it's a '71, it stands a good chance to be a 4 bolt block. The block should have a big 71 casted by the distributor hole but it looks like that area is covered with tape. Date code does look a little strange.

[johnta1]

Use the link I provided.

That pic of the page is an old one from 20 years ago.
I probably need to update it?



I use the linked page and its database for everything now (plus more info in it).

[johnta1]

Or another page that may be OK if you don't want to search:

Engine Codes



But it may have some codes not updated also.
(it's almost as old as the pic)

['ol Pinion head]

Originally Posted by johnta1

No, it's a 1971 YA 455 block.
The cast date is correct also.
Oct 2, 1970 (J 2 1970 basically)

YA code was used every year from 1965 to 1978.
1970 to 1973 it was for a 455 engine. The other years it could be some other displacement.

Engine Codes

the 455 block in question was NOT cast October 2nd 1970, VERY simple to deduce, NO Pontiac engine block castings were being poured between aprox Sept 10th & near the end of Nov of '70 as all GM UAW workers were on strike.
Earliast cast pieces I've ever ran across that were cast by Pontiac Central Foundry after the 67 day strike were Service Replacement 614 heads. It's been over 25 years since had a pair, but they were late K of '70 dated, the first RA4 heads with external date codes.

The YA block in question is a nothing special 455 block from a later model year, obviously someone has obliterated the last digit. For correct market pricing range of this engine, take a pair of 197's, a repop Joe intake & crossover, then drop them on a nothing special 455 big car shortblock that was rebuilt many years ago. 3500, maybe, on a good day.

['ol Pinion head]

Originally Posted by John Milner

I think a '71 YA would have come with 66 heads originally and probably would have been in a Grand Prix and maybe a full size. If it's a '71, it stands a good chance to be a 4 bolt block. The block should have a big 71 casted by the distributor hole but it looks like that area is covered with tape. Date code does look a little strange.

YC coded 455's were installed in 71 SJ GP's, a low number of A-body's & Formulas, 534 455 Dport GTO's, & tons of 71 big cars; mainly GrandVilles & Bonnes.

[johnta1]

One way to see what year it is would be to see what the partial VIN on the block is.

But the front of the block looks like it is possibly 'milled', so the VIN may not be there.
The date code does look like there could be another digit there.
(didn't look at pic before, just went by the posted J20)

Seems to be a lot of work though since this would not be a 455 HO or anything real special.

BTW, I think the YA in 72/73 would have had the Unitized distributor.

[NeighborsComplaint]

Date code has been altered. There is an obvious divot where the last digit was removed. Looks like someone tried to chip it away and the breakout went too deep.

[Bermuda Blue]

Great detective work by old pinion head.

If block was really cast in October 2nd 1970 the casting date would read J020 not J20. Hope no one gets burned by this dishonorable seller. Crap like this really takes the enjoyment out of the hobby.

[johnta1]

I have a few data info on blocks with a letter and only 2 digits, no leading zero for day. Probably not the J20 though. So, that is not a sign of deceptive work.

[John Milner]

There is an example of a block with a date that is a month, followed by two numbers. They are out there. However, I agree that the date does look strange on the block in the ebay add.

['ol Pinion head]

The H31 dated 483677 casting 455 block is the only 455 block casting I've ever ran across that the year designator was mistakenly left off. Have owned a 71 YE engine that the block was cast that date. Also have info on several other 455 HO coded blocks cast that date.

Odd enough, the 483677 casting block was only cast from early G of 1970 til I100, then the strike hit. After the strike, the 485428 casting 455 block appeared. The early G dated 483677 blocks tend to be coded for 455 D port applications, have never ran across an original '71 YE or WC or WL coded block cast in G.

Another oddity, the EARLIAST casting date 455 block that ive examined that was not drilled for outer main cap bolts was cast A082. Years ago, pulled an A082 cast 455 block & later that year examined another cast the exact same date while at Len's, both were not drilled for outer cap bolts.