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Discussion Starter #1
Few months ago I bought a VIN242 GTO.It had a stock 350 verified by PHS.I replaced it with a 400 that coincidentally had block and head #'s
were within a month of the assembly date of the car.For value,should I have kept the #'s matching
350?Checked various 68 GTO spec sites and never found specs or info for this engine..thanx
 

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No 1968 GTO came with a 350 cubic inch engine. It came with a stock 350 HORSEPOWER 400 cubic inch engine. The first GTO to get a 350 engine was the 1974 GTO, followed by the 2004 model year. The only factory installed displacement engine for the GTO for 1967, 1968, and 1969 was 400 cubic inches. Period.
 

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No 1968 GTO came with a 350 cubic inch engine. It came with a stock 350 HORSEPOWER 400 cubic inch engine. The first GTO to get a 350 engine was the 1974 GTO, followed by the 2004 model year. The only factory installed displacement engine for the GTO for 1967, 1968, and 1969 was 400 cubic inches. Period.
X2 on that one. No '68 GTO would have had a 350CI. Now if it did have a 350CI, then someone slipped it in as a replacement.

So I hope you did not misunderstand the PHS documents and ditched your numbers matching 400CI for the engine currently in it because you will have dropped the car's value quite a bit. :banghead:
 

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Discussion Starter #4
Thanx guys,I'll recheck the PHS documentation.I still have the original engine,manifolds,rear and drum brakes
 

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Discussion Starter #5 (Edited)
Ok,the PHS doesn't really help.I checked engine block#....386602YN,I think what kinda confused me was it had a 2 barrel...vin# 242678B123701
Checked a few engine code sites and it got really confusing saying some codes overlapped.Pretty obvious I ain't the sharpest knife in the drawer
.....this morning found #9790347 next to timing marks
 

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In '67 and '68, an 'economy' 2bbl 400 engine was offered. It had lower compression (8.2:1) heads, TH400 auto, and usually a 2.56 rear gear. Not many made, but they are out there. And they are usually cream-puffs, as they were never driven in anger like the higher HP 4 speed cars were.
 

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Ok,the PHS doesn't really help.I checked engine block#....386602YN,I think what kinda confused me was it had a 2 barrel...vin# 242678B123701
Checked a few engine code sites and it got really confusing saying some codes overlapped.Pretty obvious I ain't the sharpest knife in the drawer
.....this morning found #9790347 next to timing marks

Pretty simple to ID. Assume you jammed block number with the 2-numeral engine ID code. YN is for a 1968 265HP 350CI.

Next form of ID is to look at the center exhaust port on each head. You will find a 2-digit number. 1968 350CI will be "17".

That is basically all you will need to ID the engine unless someone had swapped parts around and done a mix & match.
 

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Discussion Starter #8
Ok,so my last question,can since this is a same year car/ motor can this be a freak one of a kind mistake bye the assembly line?
 

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Ok,so my last question,can since this is a same year car/ motor can this be a freak one of a kind mistake bye the assembly line?
NO. It could actually be a Lemans/Tempest and someone swapped a GTO VIN and/or firewall Data Tag onto the car - which happens with the prices these cars fetch as GTO's.

You might want to verify the partial VIN which is also stamped on the driver side frame rail just after the axle arch. It may be on the side of the rail like my Lemans or on top of the rail - depends on which factory it was built at. It will take some cleaning to find it. I recall it is about 4" back from the arch there-abouts.

You did not say what transmission. 1968 would have been a 2-speed automatic, 3-speed Dearborn (Ford) manual, or 4-speed for a Lemans/Tempest. GTO would be a TH-400 or 3-speed Dearborn or 4-speed Muncie. Your transmission will also have matching VIN numbers.
 

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The block casting number for the 68 and 69 400 should be 9790071, this number is located on the back of the block on the passenger side on a ledge next to the head, the number you posted near the timing marks is for a 68 timing chain cover. Can you post pictures of every number you find on the engine?
 

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I'll say it again: with a 2bbl carb, TH400 with dual gate shifter, and 2.93 rear gears, your car is probably one of the few 'economy' model GTO's that were available in '67 and '68. The up-side is that most of these economy versions were seldom beat on and tend to be in better shape years later.
 

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The engine geeteeohguy is speaking of is the economy 400CI/265HP with 2 Bbl carb and 8.6 compression.

Engine code is XM, not YN. You may be reading it wrong or it is lightly stamped and needs to be thoroughly cleaned up to be seen.

You still have not provided the 2-digit head casting found on the center exhaust ports of each head. The correct number for the 265HP engine is "14". The date codes you provided for the block and heads are within a time frame that would indicate the engine parts match.

The TH-400 with the His/Hers shifter is correct for a GTO.

If the engine is the correct 265HP economy engine, they did not install many, BUT, it does not increase value nor is it desireable. The economy engine was for a buyer who opted for the GTO looks/package but did not want/need the bigger HP engine. :thumbsup:

You can also see if the engine has the partial VIN number stamped along side the timing cover. This began in 1968 due to federal regulations. It may also be under the timing cover at the same location. Check out this website and look at the last photo showing were to look on the passenger side front block- http://www.teufert.net/identify/identify.htm
 
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