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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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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.

Bear
 

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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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"...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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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 :thumbsup:
 

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..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 ???
 

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When did they stop casting the cubic inch size on the block that identifies the engine?
I know the last 400's still had 400 cast on the side. They were cast in '77 and used right on thru the '79 XX481988 W72 engines. And the 80 & 81 301 blocks had 301T on the side. So, I assume that all the 350 blocks had 350 cast on the side, right up to the last block cast. :)
 

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That's what I thought. The block size can be identify by the casting as a 350CI which was the original question. Y'all missed that one.
 

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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.
"... The block size can be identify by the casting as a 350CI which was the original question. Y'all missed that one."

I'm sorry. I'm an old country boy. Maybe my reading skills are not that great. But I just re-read the OP twice. I do not see the OP asking if the cubic inch size is cast on the outside of the block.

I can see 3 questions that were ask:

(1) "... why is there a difference of external info?..." He was referring to the block casting number & the YS code conflicting with the 350 bore size. But, what we pointed out to him was that his info about the block casting number being for a 400 block, was incorrect. It was actually the casting number of a 350 block. And, that a YS code 350 block came in a '74 GTO.

(2) "...Is this a 400 block cast with 350 internal moulds?..." Again, we answered this question with a "no", by giving him the correct ID according to the casting number and YS code.

(3) "...Anyone shed any light on this anomaly?..." I even posted links to sites which show that casting number and code block to be a '74 350.

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

Wallace Racing's Pontiac Engine Search

Classical Pontiac Engine Codes

Pontiac Power Net – Engine Codes"

So, EXACTLY what is it about the original post that we missed ???

Although 350 is cast into the sides, and there is a 5 0 in the lifter valley, this info is not needed, to ID the block as a 350, if you have the block casting number--which he did.

Hey, as always, I could be wrong. But in this particular case, I don't think I am. If so, then I stand corrected, and apologize to all concerned. :eek:
 

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maybe of interest...

-The 350 blocks had a small pyramid, aka transfer lug, not quite a big as those on a 428 or 455. Helps spotting them when looking for 400 blocks.

-Nearly 20 years ago, a machinist friend and I experimented in boring a '71 350 block. Our goal was to find out if a known great shape std bore Pontiac 350 block could be bored to an oversize and if the cyl walls would be able to support a 400 piston. We ended up breaking through in two cylinders at aprox .120 over bore. th block would not even support a 389 piston.

What we dreived: Pontiac Central Foundry wasn't giving away a thicker cyl block with the 350's. I personally would not bore/hone one over .040 without sonic testing for core shift..

Of interest, the 350 block used came out of one of the last 71 1/2 GT-37's out of the Fremont plant, a white/blue stripe parts car built July of '71 bought from Tim Dye.
 

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"... The block size can be identify by the casting as a 350CI which was the original question. Y'all missed that one."

I'm sorry. I'm an old country boy. Maybe my reading skills are not that great. But I just re-read the OP twice. I do not see the OP asking if the cubic inch size is cast on the outside of the block.

I can see 3 questions that were ask:

(1) "... why is there a difference of external info?..." He was referring to the block casting number & the YS code conflicting with the 350 bore size. But, what we pointed out to him was that his info about the block casting number being for a 400 block, was incorrect. It was actually the casting number of a 350 block. And, that a YS code 350 block came in a '74 GTO.

(2) "...Is this a 400 block cast with 350 internal moulds?..." Again, we answered this question with a "no", by giving him the correct ID according to the casting number and YS code.

(3) "...Anyone shed any light on this anomaly?..." I even posted links to sites which show that casting number and code block to be a '74 350.

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

Wallace Racing's Pontiac Engine Search

Classical Pontiac Engine Codes

Pontiac Power Net – Engine Codes"

So, EXACTLY what is it about the original post that we missed ???

Although 350 is cast into the sides, and there is a 5 0 in the lifter valley, this info is not needed, to ID the block as a 350, if you have the block casting number--which he did.

Hey, as always, I could be wrong. But in this particular case, I don't think I am. If so, then I stand corrected, and apologize to all concerned. :eek:

Original post asking what the block was: "Is this a 400 block cast with 350 internal moulds?" He did not specifically ask if the cubic inch size was cast on the side of the block - undoubtably he was not aware of the casting or he would not have asked if he had some kind of hybrid block - and this may be confusing you by creating a question to which was never asked.

The casting "350" on the side of the block would clarify this as a quick reference in about 30 seconds and have answered the question about his hybrid block regardless of the block casting ID numbers. The original poster was confused due in part to the misinformation he had found researching the block casting number and engine codes. The engine codes can be the most confusing form of ID as Pontiac used the same engine codes on different blocks over the years.

Taking into account that there is INDEED much disinformation as there is information, the quickest ID would have been the block casting "350" found on the block while disregarding the engine code which only added to the ID confusion. Once confirmed as a "350", then the subsequent identifying engine code of "YS" would have been a match for that car for that year and the only thing in question would have been the block casting number. Evidently, the original poster was not aware of this as he is probably new to Pontiac type engines/autos. AND, if you have been around Pontiacs for a while, you know that nothing is carved in stone as Pontiac did things that not always fit the mold of what should be and what is.

Everything else offered to ID the block as being original to the car was in addition to first ID'ing the block as a "350" or "400." :thumbsup:
 
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