# SoCal newbie - Needs a bit of help with 1970 GTO



## eallenmar (May 6, 2021)

Hi All - First-time GTO owner and browsing through various sites, I believe I have the basics down, but hoping the 'Pro's' on' here can check my work. Any and all input helps-out this newbie!

First the 'Data Plate'
- Believe this represents a 1970-GTO build in Arctic white, from 3rd week in November, number 24237 from.... Arlington, TX?

















Now, for the engine. I snapped a few photos earlier based on the locations I saw from YouTube....

The stamp on the front of the block, just below the heads reads '0147438' on the first line, and 'YC' on the lower. From What I understand, this means it corresponds to a 1970-73' block, 455.


















Finally, on the heads, I found the arrow pointing to N, suggesting the night-shift built them. However, I don't know what the arrow pointing to 3 on the '3 < 6' represents, and I think the four-numbers on the head read 'J139'.













Just for reference, also including a few photos of the car itself.... Thanks!


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## GTOTIGR (May 3, 2020)

Hi,

Great car!

Enclosed is a post from this Forum regarding 1970 455 engine details that you may find helpful.









YC stamped engine in 1970 GTO?


I was looking at a 1970 GTO with automatic tranny, ram air induction & A/C, with a YC stamped 455 in it. The previous owner told current owner that this was the original engine. I could not make out the stamp on the heads due to rust, but I am nearly positive it was not "64" - unless it was...




www.gtoforum.com





The Wallace Racing data may be of assistance with decoding your numbers as well.

In terms of the code J139 code on the head, I believe that’s October 13, 69. That date would synch with your body build of November ‘69. According to Wallace your two number casting code on the center exhaust ports should be 64.



Pontiac V8 Cylinder Heads



What is the date on your intake manifold?


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## eallenmar (May 6, 2021)

GTOTIGR said:


> Hi,
> 
> Great car!
> 
> ...


Thanks for the reply and help! This is altogether confusing to me, as someone familiar with these cars came by to look at it yesterday and left me with the opinion that the 'YC' code was far-off and in no way the stock / original engine. However, briefly reading through this site and others, I'm left with the impression that it may be?

As for the exhaust ports, I can confirm the 6 and 4 on each. Regarding the intake manifold there are two-sets of numbers, the top is '9799068' and the bottom looks to be '18486572'.


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## O52 (Jan 27, 2019)

Top number of your intake is the casting number and is correct for a 70. The bottom number is the firing order but should be 184_3_6572. There is a casting date next to the thermostat. Should be a single letter followed by three numbers. The letter signifies the casting date by month, then day, then the last number is the year. 
For your engine block, look for the date on the back side next to the distributor hole. The block casting number will also be near the distributor.


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## eallenmar (May 6, 2021)

Interesting - Wonder why the visitor I had yesterday said it was altogether different. Then again, maybe it's possible that the block was replaced, and the original equipment used? 

Sounds like I have to dig in further, but so far, all is generally pointing to the correct block. I wonder if I can determine if it's 'numbers matching'?


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## GTOTIGR (May 3, 2020)

Hi eallenmar,

So far it looks correct. The heads are correct for a 70 360 HP 455 as is the YC engine code. The head date corresponds with the (~ four weeks) time span in relation to the body build date.

In terms of numbers matching, most primary components have a part number and date code. The big ones are engine, transmission and differential. Searching the internet you’ll find plenty of sources for that information. A good source is Eric Whites Identification Guide.

He provides the numbers you’ll need for the major and minor components to include carburetor, alternator, etc.

GTOAA Pontiac GTO Eric White GT-37 Illustrated 1964-1971 Identification Guide GTOAA Pontiac GTO Eric White GT-37 Illustrated 1964-1971 Identification Guide | eBay


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## michaelfind (Dec 14, 2018)

Welcome. Nice GTO!


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## O52 (Jan 27, 2019)

Check for the VIN alongside the timing cover. Should match the VIN on the dash. Sometimes hard to see due to dirt and grease.


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## Ols420 (2 mo ago)

GTOTIGR said:


> Hi,
> 
> Great car!
> 
> ...


Hello, sorry to drop in on the gto forum like this but I was curious about the j139 code. Would it be odd to see that same code, even the d>n and 3<6 in a firebird? Thanks


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## PontiacJim (Dec 29, 2012)

Ols420 said:


> Hello, sorry to drop in on the gto forum like this but I was curious about the j139 code. Would it be odd to see that same code, even the d>n and 3<6 in a firebird? Thanks


No. Think of all the heads/engines/parts that are cast in a day/night/shift to keep up with the assembly line production. So it is not odd that numbers of heads would share the same date codes used across all Pontiac body styles..


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## Ols420 (2 mo ago)

Ty, that does make sense but still having problems decoding what engine I have. It was my aunts car and she never got around to restoring it. She left it to me. I remember her saying she didn't think it had the original engine in it. It's a 68 firebird 400 convertible automatic. But the engine in it is a YU 0213637 which the YU doesn't match anything original to the 68. There are alot of YU out there. How can I determine what engine it is? Thanks for any help


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## lust4speed (Jul 5, 2019)

Look back at the photo in post #8 so you know where to look for the date casting code. The number 0213637 near the YU won't help you since it is the Engine Unit Number, and unless you have the PHS for the car or the original owners manual with the Protecto-Plate you can't reference it.


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## Ols420 (2 mo ago)

So the numbers I can find in my pictures are 9799068, just above the firing order number. I was thinking that was for the intake, but probably wrong. Also an A160 a little farther left and behind the belts is 482133 possibly. Thanks again


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## O52 (Jan 27, 2019)

The date and codes are from a '70 engine


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## Ols420 (2 mo ago)

How can I tell what kind of engine? Is it a 350?


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## Ols420 (2 mo ago)

Ok, I think with everyone's help and some more charts I figured it out. I believe it to be a 1970 350, 255hp tempest motor. Yu code, a160 date stamp, 9799916 block cast. Sound correct of have I got it all wrong?


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## PontiacJim (Dec 29, 2012)

Ols420 said:


> Ok, I think with everyone's help and some more charts I figured it out. I believe it to be a 1970 350, 255hp tempest motor. Yu code, a160 date stamp, 9799916 block cast. Sound correct of have I got it all wrong?


Sounds about right.

On blocks produced in 1970 and after, you will find 350, 400, or 455 cast towards the left side of the front of the block vertically on the outside. 

The VIN is located on the passenger’s side front of the block, down where the timing cover and the oil pan meet. the number 2 was added at the beginning to represent Pontiac, followed by a digit that indicated the last number of the model year (such as “9” for 1969) and a letter that represented the originating assembly plant. These digits were followed by the last 6 digits of the VIN.


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