[caddor38]

Early 71 Pontiac 455 HO block standard bore for sale. The casting number is 483677 and is a 4 bolt main with caps. Same motor used in the 455 HO GTO Judge. This motor has very light surface rust and easily clean up with 20 to 30 thousandths bore. $2,500

[se428bandit]

Does it have a GTO or a Firebird VIN on it?

[caddor38]

The motor is has YC identification which makes it a GTO according to my research. The motor was assembled in September of 1970.

[Mr_GTO]

Originally Posted by caddor38

The motor is has YC identification which makes it a GTO according to my research. The motor was assembled in September of 1970.

YC is a standard 455, not a HO. Is there a VIN stamped by the balancer?

[caddor38]

The 1970 455’s with the YC designation were placed in GTO’s and some grand prix’s. If you would take the time to review documentation on these “rare” motors I would appreciate that. Here is a link verifying its an HO motor.
http://home.grandecom.net/~desert_bu...tiacblocks.htm

[caddor38]

Here is another link verifying this is a GTO motor HO 455

https://wowmusclecars.com/pontiac-en...des-specs/amp/

[caddor38]

Vin# 68941

[johnta1]

For 1971, the YC was not a HO engine.

Here is a chart for 1971:






What a couple of the guys were asking is that there is a partial VIN on the block down low by timing cover area, passenger side.
This would help determine what it came in.



It would look something like 21R123456
with the last digits of the car VIN

[tom s]

I believe that is a EUN number by the code and not the vin?Tom

['ol Pinion head]

Most common code '71 455 4bbl Dport engine block...
As original assembled engine: 2 bolt main caps, 66 casting press in stud heads, a "2072" single points distrib,, & a "1262" Qjet. Late in '71 model year, unitized distributor became optional distributor.

While the '71 YC was ordered in a few '71 GTO's, A-bodys, & Formulas & model J GrandPrixs, the VAST majority of '71 usage YC coded engines came out of B series cars. '71 Grandvilles came standard with a YC coded 455. Majority of '71 Bonnevilles came with them as well (occasionally will come across a '71 Bonne with a 455 block code YG). When a '71 GP was ordered with the SJ option, the 455 YC engine was standard equipment.

[AG]

Do you have a pic of the main caps?

[caddor38]

Guys I can not find a Vin just the numbers next to the YC code. I have reviewed multiple pontiac sites stating the 70/71 pontiac 455 YC code is indeed an HO motor and the motor has 4 bolt caps. attached is a piture of the main caps.

[caddor38]

This is from a message board:
1970 GTO 455/360HP HO engine, order code L-75- block code for the automatic is YC & YA. Manual trans was code WA. The YC code was found in only 1 book (which is basically a Pontiac "bible") that I have while the YC code is listed as a 1971 455 engine. The 455 is called an HO engine in the GTO where 71 and later had both a "standard" lower HP version or the higher HP "HO" engine with the aluminum intake.

Heads are#64. Full casting number is 9799364.

I have several references to the 455 "ram air", so it may have been a package option.
455 CI Q-jet # for manual trans is 7040267 -non ram air
7040279 -with ram air
automatic trans is 7040268 -non ram air
7040278 -with ram air

Number of GTO's equipped with the 455HO YA/YC engine is listed as 2227 (241 Convertibles).

More investigation is definitely needed and I would get the PHS documents to verify the L-75 455CI option, along with the rest of the info for the car.:thumbsup:

[caddor38]

Ok, I found the Vin. This is getting very interesting.
21P304555.

[tom s]

64 heads were 70 455 HO heads as I remember.Tom

['ol Pinion head]

Originally Posted by caddor38

Ok, I found the Vin. This is getting very interesting.
21P304555.

2= Pontiac division
1 = 1971 model year
P= Pontiac home plant. built B bodies & A-bodies
3004555 is the last 6 digits of the cars VIN

IF the last 6 digits had started with a 1 or a 2, the engine would have come out of a '71 Pontiac A-body built at Pontiac home plant.
As the last 6 digits began with a 3xxxxx, the '71 YC coded block came out of a B series (big car).
The two letter code YC engine was used for near 10 model years straight, 389, 400's, 455's, 350's... ALL of them basic D-port engines with standard log exhaust manifolds.

[grandam1979]

Do you have the heads from this engine? If so what’s the number on center ports and the date codes on them?

[tanksteve]

The casting number says it is an early 1971 455 HO block as the seller claims. The YC code makes one suspect it is a dealer stamped service replacement block even though we cant see the sr on the EUN number. Or somehow the factory ran out of 2 bolt main 455 blocks on that day. Rocky Rotella is probably the best expert on early 455 blocks..

[caddor38]

Hey folks, I just realized its Christmas eve and all you experts are decoding my motor laughs. I hope you all have a merrt Christmas!

To the questions just posted. I posted the vin earlier and dont have the heads. I got the motor as a spare abor 7 years ago. I am working on my 71 Trans am and spent all my money on the motor build. ( 455 30 over edelbrock heads stroked to 4.5, approximately 500 cubic inches now)
Dyno numbers are 556 HP and 650 ft lbs torue goin in 71 firebord/TA conversion.

In regards to the motor I now see its a 325 455 4 bolt main motor and may or may not be an HO depending on the website you pull it up from.
I am not wanting to cheat anyone so the facts are the facts. There is alot of speculation on what the YC motor is? Clearly it would make a great candidate for a replacement 455 for any car and can be argued by many on what car it belongs in.

Thanks for all the feedback, now how about somebody buying it so I can get the additional parts needed to finish my build. Im in Pensacola.

[Tellyshavilli]

Very good 455 block w/4bolt main caps & standard bore and that’s a great price !! it’s just not an HO engine code for 1971 but still a good deal for somebody.🇺🇸👍