# 1966 389 "xs" motor



## gto-pete (Oct 31, 2004)

I need info. on how or if i can accurately build a 1966 gto as a factory built ram air gto with the "xs" package. The motor is stamped "xs", with the 744 cam and all associated parts. The question is if i drop this motor into a 1966
that has a 4-spd m21, (need 4.33:1 rear) can I state a bone-stock ram-air car yet not-original car? I have the "xs" motor, not just the dealer installed parts. Did the gtos that were factory-built (possibly 40-50 cars) have a different fire-wall code number? I am extremely particular on all original gto's, but this item has me perplexed on the right thing to do. If anyone has a knowledge or history on this very rare option please help me. Thanks.

pete


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## 05GTO (Oct 6, 2004)

gto-pete said:


> I need info. on how or if i can accurately build a 1966 gto as a factory built ram air gto with the "xs" package. The motor is stamped "xs", with the 744 cam and all associated parts. The question is if i drop this motor into a 1966
> that has a 4-spd m21, (need 4.33:1 rear) can I state a bone-stock ram-air car yet not-original car? I have the "xs" motor, not just the dealer installed parts. Did the gtos that were factory-built (possibly 40-50 cars) have a different fire-wall code number? I am extremely particular on all original gto's, but this item has me perplexed on the right thing to do. If anyone has a knowledge or history on this very rare option please help me. Thanks.
> 
> pete


I doubt (my opinion) they had an accessory code on the data plate for the Ram Air Modification since the cold air components were shipped in each car's trunk and it was up to the dealer or owner to modify the hood scoop to be functional. Here is the web site of Pontiac-Oakland Club International, they have a library which includes an Accessories Catalog for 66 pontiacs. You will have to join POCI to have access to the library.
The car with the ram air installed was rumored to produce 380 to 400 hp, but was only rated at 360 hp. Shortly after the XS engine GM stopped offering cars with the 3x2 carbs except for vettes.
Good luck, I will continue to search for accessory code information on the 66.


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## gto-pete (Oct 31, 2004)

Thanks for your reply. I believe in order to put a ram-air '66 back to its original or stock form, i believe i need the following: heavy duty fan, 4spd close-ratio, 4.33:1 gearing, metallic-lined brakes, not to mention if there is any info on the color of these 50 cars that came from the factory! If an A/C package was available. I guess my goal, (which maybe impossible) is to put a car back to exactly like it was in '66. Its been 21 yrs. since i owned a gto, ('67 335hp car), and i have a chance to get back into this wonderful world of gto cars. Now if this car is to be done, i wouldn't build it for myself, (to much power for me and to many rare parts). I'm looking for a nice crusier '65, or '66 335hp car). I would think there is a collector out there who would be interested, thus the importance of the above list of items. The only problem would be once finished i don't know if my wife has enough strength to pry my hands from it! Thanks.

pete


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## 05GTO (Oct 6, 2004)

I believe the XS option did not include A/C. Here is a link showing if air was available with certain transmissions and it does not show being available with the close 4 speed on the Tri-power car. Also, it shows the standard rear end is a 3.90

1966 GTO Drivetrain Options

Another rare car is the 67 XS and XP which were also Ram Air cars, Around 700 produced and only 100 or so were automatics (XP).


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## Roscoroo (Dec 9, 2004)

As a of owner of a '66 RA 1 GTO , I can tell you quite abit about them .

1st most of them were done at Royal Pontiac , were they had the xs engine installed/doctored along with the 4 speed . they did not all come w/ muncie's as for the muncie would spit its countershaft to easy .
None of them had A/C . Some of them were also done at Central Pontiac ( They did alot of the 421 trophy cars there .) 
They were none insulated and most of them were Sport coupe's .
I believe there was 51-53 cars produced total in '66 . These were dealer built only (remember Gm didnt sanction any racing at this time)

I have seen 13 of them over the years . one hardtop and all the rest were coupes . I'm not sure if the hardtop was a real one but it did have the xs eng code and the tell tail punch in the build tag .(but you wont see any different code/s in the tag ) I also had a '66 Lemans in this same config but its eng was long gone when I got it .

the Engine was hand picked Night casting w/ thin copper head gaskets .022 ,different valve springs ,and didn't always have the 744 cam . (I think this depended on the dealer ) the Heat riser on the tri power was blocked off , and the tri power was rejetted along w/a dist kit and curve,Hi-volumne fuel pump, and larger fuel lines. You should see an arma steel crank , and if it hasnt been raced to death and changed theres a good chance it will still have steel rods also. (remember these were built as out the back door special order superstock cars ) Some of the RA1 cars also had 421's in them and very few kept there 4.33 to 1 rear end in them if any (mine blew up at the starting line ) 


A few Quirks that they have is an A/C core support and the large desert cooler radiator , anouther item that i believe all of them have is the 6 cyl Frame in them (these cars Weighed 3100-3150 lbs in full dress ) 

now remember to try to get one back to how they came stock, it would be near impossiable as for they had alot of aftermarket parts tossed at them and were sold to the serious race crowd only . I dont think any of them kept the stock height pyramid valve covers for instance . 

So there ya Go, good luck w/ your '66 
Please dont hound me w/ emails or any of that ,We would like to keep some of the mystery in our Factory Race cars . I will tell you that the last one I know that was sold in the mid 80's and brought top dollar for being a worn out race car. so who knows I may stop in and anser a few more questions sometime again .


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## rustytinman (Jul 14, 2018)

for what it is worth I have a 66 xs gto would love to find an xs block etc built before 3rd week of june 66


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## Jerry H. (Mar 19, 2020)

If this 'xs' engine was mine, I would find someone with a documented 'xs' car that needed an engine and sell it for what it is worth and find a good dated WT or WS to put back in the car. If you are wanted to build a 'tribute' 'xs' car, you can always build up a regular big car engine and restamp it.

You have a very valuable engine that needs to go back with a very valuable car.


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## PontiacJim (Dec 29, 2012)

Jerry H. said:


> If this 'xs' engine was mine, I would find someone with a documented 'xs' car that needed an engine and sell it for what it is worth and find a good dated WT or WS to put back in the car. If you are wanted to build a 'tribute' 'xs' car, you can always build up a regular big car engine and restamp it.
> 
> You have a very valuable engine that needs to go back with a very valuable car.


I believe he has a documented "XS" GTO, but is looking for an original "XS" engine dated for his car.

Very few "XS" GTO's made, so I too would simply rebuild a 389CI to the "XS" specs and call it a day.


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## Jerry H. (Mar 19, 2020)

"I need info. on how or if i can accurately build a 1966 gto as a factory built ram air gto with the "xs" package. The motor is stamped "xs", with the 744 cam and all associated parts. The question is if i drop this motor into a 1966 "

I may be wrong, but I read this to say he already has the engine, just trying to find out what else he needs to make a 66 into a 'xs' car.


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## PontiacJim (Dec 29, 2012)

Jerry H. said:


> "I need info. on how or if i can accurately build a 1966 gto as a factory built ram air gto with the "xs" package. The motor is stamped "xs", with the 744 cam and all associated parts. The question is if i drop this motor into a 1966 "
> 
> I may be wrong, but I read this to say he already has the engine, just trying to find out what else he needs to make a 66 into a 'xs' car.



OK, I see what is happening. You are answering to an Oct, 31, 2004 post - 16 year ago. I was answering to the recent post, post #6, 2 days ago.


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## Danny Goat (Dec 9, 2020)

I recently purchased my 2nd 1966 GTO ( Got my first one when I got out of the service in 1971). If I could get one car back of all I've owned, it was that one. 50 years later, i got another one. It's very unique. Frame off total restoration, with all rubber mounts, stops, etc. Everything you would expect in a top restoration. I got all the documentation for it from PHS, and I'm waiting on a copy of the original window price sheet. The car was originally a WS (Tri-Power) 4 speed car, built on Feb.17th,1966, and all options are original and intact. It does however have in it a true XS engine, stamped and date coded. The car, and engine has just turned over 3000 miles on it. I've researched the engine as far as I can, and now I'm waiting for the window sticker, to determine the original dealer. I have all the receipts from the restoration, including all parts used to rebuild the engine. Some parts were remanufactured, but dimensions, part numbers, stampings are like the original. As this was a WS engined car from the factory, the XS engine either came from the parts department, or from a wrecked or caniblized Ram Air car. I had no idea what an XS engine was, and the previous owner kept pointing to the block, showing me the XS stamp. All I know, is that I was finally able to buy another 1966 GTO, and trilled how the car is. But the XS engine, with the rarity of it, makes it more special. One last thing, the car is absolutely wicked.


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## nick rice (Nov 10, 2014)

Thats sounds like a great and worth while project. I had no idea these were mostly post cars or all that went into the factory engine and accessories on these late year and rare builds. I'd sure love to see one. Good luck if you go forward.

Sent from my SM-G970U using Tapatalk


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## TLehn (6 mo ago)

gto-pete said:


> I need info. on how or if i can accurately build a 1966 gto as a factory built ram air gto with the "xs" package. The motor is stamped "xs", with the 744 cam and all associated parts. The question is if i drop this motor into a 1966
> that has a 4-spd m21, (need 4.33:1 rear) can I state a bone-stock ram-air car yet not-original car? I have the "xs" motor, not just the dealer installed parts. Did the gtos that were factory-built (possibly 40-50 cars) have a different fire-wall code number? I am extremely particular on all original gto's, but this item has me perplexed on the right thing to do. If anyone has a knowledge or history on this very rare option please help me. Thanks.
> 
> pete


Pete, are you still on here? Do you still have this engine? I have an xs car that I need an XS block for. I know looking for a needle in a haystack.


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## geeteeohguy (Feb 2, 2008)

TLehn said:


> Pete, are you still on here? Do you still have this engine? I have an xs car that I need an XS block for. I know looking for a needle in a haystack.


Pete joined October 2004 and last visited the site January 2005..almost 18 years ago. Maybe you can get his contact info from the mods, who knows? For sure worth pursuing, considering what is at stake here. Good luck!!!


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