1974 casting numbers - Pontiac GTO Forum
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post #1 of 16 (permalink) Old 11-11-2015, 11:37 AM Thread Starter
 
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1974 casting numbers

Hi folks, I'll try not to waste to much of your time.
I'm helping a friend work on his '74 GTO. It was built in California. We have pulled the engine and ran the casting numbers 488986= 400ci, The numbers stamped in the front right of the block are 186905 ys = 400ci. Pulled the heads, measured the bore, 3.875 = 350ci. Obviously the bore is boss but why is there a difference of external info? The car was built in September. Is this a 400 block cast with 350 internal moulds? Anyone shed any light on this anomaly?
Thanks in advance.
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post #2 of 16 (permalink) Old 11-11-2015, 11:52 AM
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Your first bit of code translation was incorrect. Casting number 488986 indicates a 1973 or 1974 350.
To nail the year, you need the 4 character date code from the top center of the block near the distributor hole.

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post #3 of 16 (permalink) Old 11-11-2015, 07:24 PM
 
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The '74 only came with the 350CI. The head casting numbers on the center port should be #46 and the heads will have screw-in studs. Check this out 1974 Pontiac GTO | Hemmings Motor News
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post #4 of 16 (permalink) Old 11-12-2015, 05:00 PM
 
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So my book says a block cast code of 488986 is a 350ci motor that was made for model years 1973, 1974, 1975, 1976 and 1977.

But the ys stamp
in 1973 does not exist for a 350ci engine...
in 1974 exists for 350ci in a 170HP version and a 200HP version
in 1975 does not exist for a 350ci engine
in 1976 does not exist for a 350ci engine
in 1977 does not exist for a 350ci engine

So that engine cast code of 488986 is for a 350 cubic inch motor for model year 1974, that either had 170HP or 200HP. The horse power is probably derived from different heads installed.

An online resource says the same thing but has an additional entry that says for GTO a ys stamp on a cast code of 4888986 is 200 ponies.

the 186905 is or should be part of the VIN of the vehicle.
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post #5 of 16 (permalink) Old 11-12-2015, 05:22 PM
 
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"...the 186905 is or should be part of the VIN of the vehicle."


I think the numbers he posted are those found just above the YS code.

The numbers which will match the last numbers of the VIN, are located down by the lower part of the timing cover, on the passenger side.

Here's what the Wallace site says about the partial VIN:

"Pontiac stamped the VIN numbers next to the timing cover about even with the timing marks on cover.This will start with a 2 (for Pontiac) then the last digit of the year then the car serial number starting with the plant letter.These are usually covered with oil and crud, and probably hard to see.This will tell you if this is an original motor."
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Last edited by oldskool; 11-12-2015 at 05:37 PM.
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post #6 of 16 (permalink) Old 11-12-2015, 06:41 PM
 
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For 1974, there were 3 offerings of the 350CI. The base 155HP engine, the 170HP engine, and the 200HP GTO engine having block codes WP, YP, YS, ZP. Compression was 7.6 to 1 on all engines. The GTO used the #46 head with screw-in studs, although I read that some early engines still had the #46 press-in studs which were also used on the 170HP engine. The heads would have all had the same chamber volume to make the 7.6 compression -so no difference in the heads other than screw-in studs. The GTO engine used the Q-jet and the hotter 066 factory cam while the lesser HP engines were 2-Bbl and milder cams. Do a search for "1973 Ventura" as I posted a magazine article on super tuning the 350CI. The 350CI and light weight of the Ventura body gave the GTO similar performance of the earlier GTO bodies with the 400CI. The 350CI has a lot of potential like any Pontiac engine
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post #7 of 16 (permalink) Old 11-13-2015, 10:54 AM
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..still need that date code to get a positive ID on the model year

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post #8 of 16 (permalink) Old 11-13-2015, 12:31 PM
 
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Quote:
Originally Posted by BearGFR View Post
..still need that date code to get a positive ID on the model year

Bear


As Pinion head has pointed out many times, lots of online Pontiac info is wrong.

But, just going on the online info I can find, there was only one 350 engine which had a YS code. It was a '74 200hp GTO engine, with an auto trans. In both '73 and '75, the YS code shows to have been used on 400 engines.

"...So that engine cast code of 488986 is for a 350 cubic inch motor for model year 1974..."

AS ALWAYS, the info could be wrong.

Wallace Racing's Pontiac Engine Search

Classical Pontiac Engine Codes

Pontiac Power Net – Engine Codes

While we're talkin about 350's, I'd like to ask a question. Some sites show that the late '75's and the '76 350's used block #500810. And, I have been told, on another forum, that these 500810 blocks had the same thin main webs as the 400 "557" blocks. Is this true ???

Last edited by oldskool; 11-13-2015 at 12:56 PM.
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post #9 of 16 (permalink) Old 11-13-2015, 05:31 PM
 
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When did they stop casting the cubic inch size on the block that identifies the engine?
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post #10 of 16 (permalink) Old 11-13-2015, 07:30 PM
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Quote:
Originally Posted by PontiacJim View Post
Do a search for "1973 Ventura" as I posted a magazine article on super tuning the 350CI.
Forget what year it was but my late wife had an early `70s Ventura, it had an Old's 260 CI V8 engine. Worthless!! Hit passing gear at highway speeds and it actually slowed down!!
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