1966 389 numbers - Pontiac GTO Forum
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post #1 of 8 (permalink) Old 12-21-2009, 02:49 PM Thread Starter
 
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1966 389 numbers

Ok - I'm new to the Forum, but look forward to learning and sharing knowledge. I've been a British car guy for a while (MGA, MGBGT, TR3, Jaguar(350engine), AH Sprite - for autocrossing and it's time for a change. Been a while since I played with real American muscle and can't wait to dig in. Fact is I used to be a Ford fan (I know...) 1966 Mustang, '69 Cobra Jet.

The wife said - let's build a real car - so..picked up a 1966 LeMans convertible as the next project. Not sure how the Forum feels about GTO clones (may have an idea though), but my wife wants it, so that's where this project will go.

Hence, my question.
I picked up a 389 engine #9778789 that according to my research is a 1966 - right for the year of the car.
It has 092 heads (correct fro the GTO)
There is a number stamped on the right front - looks like 576488 YC
I believe the YC is a 290hp engine for an automatic-Is the difference between the 290 and 325/333hp the cam or cam and carburation? Or is there some other variable? Any idea what the 567488 might mean?

For now I plan to stay with the 2 speed automatic, as archaic as it sounds. Anybody have any experience with the 2 speed/389 combo? I would prefer a 4 speed, but I'm not ready to hang new pedals, etc.

I hope to make it a frame off (or close) project. Stay tuned for updates.
Thanks for any comments back.
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post #2 of 8 (permalink) Old 12-21-2009, 10:49 PM
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The YC is an automatic block. The only difference between that and a real GTO engine (you already have the good heads) is the camshaft. Put in an "068" grind Pontiac cam....that's the one used for the tripower car in '65 and '66, and the HO cars '67 up. The carter AFB is the same as on the GTO that year. Decent and reliable carb. I'd leave it alone. I had a '65 back in 1980 with the 389 4bbl and the stock 2 speed auto, and it was an excellent driver, and no slouch in the performance dept. Those super turbine 300 2 speeds are just about indestructable. Good luck with your project.
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post #3 of 8 (permalink) Old 12-22-2009, 07:35 AM Thread Starter
 
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Originally Posted by geeteeohguy View Post
The YC is an automatic block. The only difference between that and a real GTO engine (you already have the good heads) is the camshaft. Put in an "068" grind Pontiac cam....that's the one used for the tripower car in '65 and '66, and the HO cars '67 up. The carter AFB is the same as on the GTO that year. Decent and reliable carb. I'd leave it alone. I had a '65 back in 1980 with the 389 4bbl and the stock 2 speed auto, and it was an excellent driver, and no slouch in the performance dept. Those super turbine 300 2 speeds are just about indestructable. Good luck with your project.
Thanks for the reply. I'm glad to hear the 300 2 speed works well - It'll save a few dollars and time that can be used elsewhere to accelerate completion of the project. I'm taking the engine to my builder today. I plan to flow the heads with a 3 angle grind on the valves. I will keep the stock 10.5:1 compression ratio as close as I can after cleaning up the deck and heads. I appreciate the heads up on a good cam. I wasn't sure where to go with that.

I plan to run long tube headers on the exhaust side to get the sound I want and to let the car breath a bit better. I haven't researched options for those yet. I also have access to a tri-power set up, but am not sure if it is numbers correct for the year. As much as I'd like to go that route, I'm assuming (I know - shouldn't do that) a good 4 bbl set up would be fine for the street cruising I'm planning. But the tri-power sure looks nice and sounds relatively trouble free after intial tuning. Dollar-wise the Carter with a good intake may be the best bang for the buck.

While the engines being developed, I'll be starting the body stripdown and inspection. Always fun to explore the life of a car layer at a time.
Thanks again for the feedback.
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post #4 of 8 (permalink) Old 12-22-2009, 07:55 AM
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For what it's worth~ in the 16+ yrs I've owned my GTO, not 1 person has checked the #s on my Tri-Power.
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post #5 of 8 (permalink) Old 12-22-2009, 08:39 AM
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For what it's worth~ in the 16+ yrs I've owned my GTO, not 1 person has checked the #s on my Tri-Power.
Building a numbers matching clone is a futile effort since the 23767 VIN is a dead giveaway that the car is a LeMans. If you want the tri-power, get one. I wouldn't worry about if it is "correct".
Welcome to the forum and look forward to pics of the tear down and hidden issues......you know they're lurking in there....

Mitch
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post #6 of 8 (permalink) Old 12-22-2009, 11:03 AM Thread Starter
 
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Building a numbers matching clone is a futile effort since the 23767 VIN is a dead giveaway that the car is a LeMans. If you want the tri-power, get one. I wouldn't worry about if it is "correct".
Welcome to the forum and look forward to pics of the tear down and hidden issues......you know they're lurking in there....
If I have someone looking numbers on my carbs, I don't want them looking at my car anyway! The plan isn't to pass it off as anything but a great looking, great running car. It'll never be a 242 car but I can bask in the history and performance of one. I'm not in the habit of selling completed cars anyway - The VIN won't matter. If circumstances require selling the car, it will stand on it's own merits.

Any pitfalls I should look for in finding/setting up a tri-power? I haven't had a chance to lok at the one I hear is available. Anything I should look for - especially key parts that may be missing and made of unobtanium?

I'll get some picture up as soon as I figure out better how to do so on the forum site. I'm pretty impressed I got this far!
Thanks for sharing your experience.
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post #7 of 8 (permalink) Old 12-22-2009, 12:12 PM
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Great stuff, Y2k. I think you have an excellent grasp of your project and direction. I would recommend a '66 Tripower set-up due to the bigger center carb. (all three carbs are the same size) . It produces more power than the '65 set up. Only the middle carb is a regular Rocester 2jet, with choke and idle circuits. The two outer carbs are power only, so no synchronization problems, no fussy adjustments, etc. It's a bulletproof, powerhouse system. Good luck on your project. Look at the AMES catolog and on the 'net for the correct linkage, fuel lines, etc. Also, be prepaired to run octane booster in your 389. You'll ping on less than about 96-98 octane.
Jeff
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post #8 of 8 (permalink) Old 12-22-2009, 12:49 PM Thread Starter
 
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Thanks Jeff. Just the type of advice/reassurance I was looking for. Octane booster? dang - was hoping to avoid that...Ah, what price power.
Mark
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Data Plate, Vin Tag and Drive Train Numbers

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