# Help! What engine is in my '66 GTO?



## slevin011 (Sep 22, 2012)

Hi everyone, I'm new here, and I come to you with an interesting problem. My dad and I just recently bought a 1966 GTO, but the original owner said he replaced the '66 engine with a '67 400cc because he "blew it up" in high school. The car ran absolutely great when we test drove it, and we couldn't pass it up for the price. Not really being gear heads, we took the owner's word for it when he told us what he replaced the engine with. However, upon doing some research and digging around in the engine bay, I'm not so sure it is a 1967 GTO engine. I've been doing a lot of research lately and I'm stumped. What is in our car?

Numbers I have found so far:

On the front of the engine block toward the passenger side:
Engine casting number? - C382874
Engine code? - YX
Engine VIN? - 21P365691

On the top of the engine block, stamped on the front
L214

Firing order: 
1-8-4-3-6-5-7-2

Pictures, of course:

Engine:









Engine code:









The day we bought it:









...and today, after a wash and wax

















Any help would be greatly appreciated!


----------



## ppurfield001 (Jan 21, 2008)

slevin011 said:


> Hi everyone, I'm new here, and I come to you with an interesting problem. My dad and I just recently bought a 1966 GTO, but the original owner said he replaced the '66 engine with a '67 400cc because he "blew it up" in high school. The car ran absolutely great when we test drove it, and we couldn't pass it up for the price. Not really being gear heads, we took the owner's word for it when he told us what he replaced the engine with. However, upon doing some research and digging around in the engine bay, I'm not so sure it is a 1967 GTO engine. I've been doing a lot of research lately and I'm stumped. What is in our car?
> 
> Numbers I have found so far:
> 
> ...



Check "GTO Alley" website for engine code details, although if the "L214" stamping is correct, it means that the engine was produced at the factory on Dec. 21, 1974. Good luck.


----------



## Icefan71 (Apr 7, 2011)

Try reading up on this Pontiac Power The 3rd paragraph will tell you where to find the casting number. Once you have that you can see exactly what you have. If it is a 67 400 the casting number should be a 7 digit number at the rear of the block next to the distributor. Ppurfield001 is correct about the date code being from 12/21/74, but thats from your intake manifold, not your block. I zoomed in on the 1st pic.


----------



## 68greengoat (Sep 15, 2005)

Your engine vin suggests it's a '71(first 1, you may want to double check that on the motor). If correct, came with a 2 barrel out of an F-body w/automatic. 265hp. 481988 is the block casting # located on the back side of the #8 cylinder next to the firewall.... 2 bolt mains. There's also a date code by the distributor, ex. D231. Last digit being the year.

Nice car!

*YX* F-body	71	400	265	Turbo 400	L-65 1x2	*481988* 2


----------



## slevin011 (Sep 22, 2012)

Icefan71 said:


> Try reading up on this Pontiac Power The 3rd paragraph will tell you where to find the casting number. Once you have that you can see exactly what you have. If it is a 67 400 the casting number should be a 7 digit number at the rear of the block next to the distributor. Ppurfield001 is correct about the date code being from 12/21/74, but thats from your intake manifold, not your block. I zoomed in on the 1st pic.



Ah, thank you. Like I said, I'm not very educated when it comes to engines. I did not realize I was looking at the intake manifold, so I thought the entire engine was from 1974 haha. I did find on a website that the engine code YX can indicate a '67 engine from a "400 fullsize." I googled this, but couldn't come up with anything in particular. Does this refer to a specific car, or is it just a generic engine used in "full sized" vehicles in '67?

Spotts Performance/ Pontiac engine ID


----------



## 68greengoat (Sep 15, 2005)

YX can be a '67, it can also be these:

YX	A-body	73	400	185	Turbo 400	L-65	P	1x2	481988	2 
YX	A-body	72	400	175	Turbo 400	L-65	R	1x2	481988	2 
YX	A-body	71	400	265	Turbo 400	L-65 1x2	481988	2 
YX	B-body	67	400	325	Turbo 400	L-67 1x4	9786133	2 
YX	B-body	73	400	185	Turbo 400	L-65	P	1x2	481988	2 
YX	B-body	72	400	175	Turbo 400	L-65	R	1x2	481988	2 
YX	B-body	74	455	250	Turbo 400	L-75	Y	1x4	485428	2 
YX	B-body	77	301	135	Turbo 350	L-27	Y	1x2	525934	2 
YX	B-body	66	389	325	Turbo 400 1x4	9778789	2 
YX	F-body	73	400	185	Turbo 400	L-65	P	1x2	481988	2 
YX	F-body	72	400	175	Turbo 400	L-65	R	1x2	481988	2 
YX	F-body	71	400	265	Turbo 400	L-65 1x2	481988	2 

Your engines vin indicates a '71. Maybe the engine vin actually starts with a 27 instead of 21? It would be advantageous to verify the year by getting the block date code by the distributor so you know for sure.


----------



## geeteeohguy (Feb 2, 2008)

Nothing wrong with a '71 or '72 block. They're all the same in these years except for the numbers. The late '74 on up blocks are not as strong. No worries with your earlier 400. Nice car!!


----------



## leeklm (Mar 11, 2012)

One nice thing about a non-original motor, is that you can do whatever you like with it, without trying to keep the car "original". 

Welcome to the forum and yes, sharp looking car!


----------



## slevin011 (Sep 22, 2012)

Thanks for the replies so far, everyone. We finally got the chance to put the car up on a lift this morning, and found the casting number. Looks like the engine is a '71. Casting number is 481988 with code YX. Now - time for mods. The guys at the shop we use are big Edelbrock supporters, so we've been looking at a new carb, intake manifold, and air cleaner to start. This may be a dumb question, but are these generally "universal" parts? Edelbrock's website makes no mention of specific carbs for different engines. Another question regarding the carb - the stock carb for the '71 YX engine was a 2 barrel. The Edelbrock (looking at the 600 CFM with electric choke) is a 4 barrel. Are these compatible? What changes will need to be made to accomodate this?


----------

