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i just purchased a 69 GTO automatic and im not impressed with the 400 engine and its performance, does anyone know anything i could do to change this?
 

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i just purchased a 69 GTO automatic and im not impressed with the 400 engine and its performance, does anyone know anything i could do to change this?
I think we need a little more details JP.

What about this engine do you not like? Is it original? Is it wore out? What kind of rear is in the car?

I have the same 350hp 400 w/AT in my 70. Granted, it put out closer to 365 becase of the mild street cam and 3" exhaust. But, it has the stock Q-jet carb and no mods have been done to the tranny, and this thing will snap your neck!

Give us a little more info and we'll try and set you in the right direction.

Russ
 

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what! a chevy in a pontiac! i dont think so. It all depends on what your looking at as far as budget, and direction your wanting to go. If the engine is old and tired then you can get it rebuilt, put a cam in it, mabey some heads an intake and a carb. Or possibly if you want some more horsepower options go to this website. jbp-pontiac.com every engine i believe on overhaulin they had something to do with. but we are going to need some more info about your car to really tell you anything.
 

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Discussion Starter #5
the car has a 400 4 barrel with no mods and a three speed automatic transmission, the car runs smooth and consistent but just doesn't have the power of other 400 engines and the acceleration isn't the greatest
 

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the car has a 400 4 barrel with no mods and a three speed automatic transmission, the car runs smooth and consistent but just doesn't have the power of other 400 engines and the acceleration isn't the greatest
Well JP, a properly running stock 400 should have plenty of power, power you can feel. You may want to have the engine looked over. You might want to start with just a tune up. You may look into a carb rebuild, and have the distibutor tuned. Or, it may just be worn and need a rebuild.

The other possibility could be that your tranny is not operating properly.

Look at the simple stuff first, then move on from there.

Russ
 

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I think it's also important to ask, compared to what?

If you're a young guy (or an older one with a bad memory), you may be expecting more than there really is.

A standard 400 CID GTO with an automatic and 3.08 or 3.23 gearing isn't going to be all that fast to someone used to the magic of today's fuel injected, computerized hot cars. Remember, back then, a 14.8 or so in the quarter mile was quite respectable. Today there are stock Honda Accords that can do it that fast.

Fast is a relative thing. Compared with all the other cars in 1969, that wasn't bad. Compared with a new GTO, it's not in the same league.

I'd suggest a dyno to find out what you're really pulling. A stock, 350 hp 400 probably put out around 300-310 net, then by the time it got back to the rear wheels with an automatic, we're probably looking at around 250-260 hp.

Find a club with a free dyno night and get a few pulls. That'll tell you if you've really got a problem or not.
 

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First thing I'd do if I suspected a weak engine would be to check the compression, especially if it's never been rebuilt. Engines get tired when they're nearly 40 years old, they want a mid-afternoon nap just like I do.
 

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JP11,

You got some good suggestions from the others. Here's a few more. Check the heads to see if someone has slipped you a set of low compression ones that like pump gas. The 'good ones' for your YS 400 have 62 at the center exhaust connection. Run a compression check to see if all eight are working together. Read the posts from Lars regarding ignition and carburetion. If your 400 isn't pushing you back in the seat and leaving rubber when it hits second, your 400 needs some work. I'm running 390 gears and a RA III cam in mine and it will keep up with my 04 LS1 under 5500 rpm. After that, the newer Goat is gone....
 

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My 69 is a neck stretcher with a 8.5 comp engine on pump gas with the stock 3.55 gear. Are the secondaries opening? It won't downshift to 2nd over 60 mph stock. Is that it? Just guessing
 

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I think it's also important to ask, compared to what?

If you're a young guy (or an older one with a bad memory), you may be expecting more than there really is.

A standard 400 CID GTO with an automatic and 3.08 or 3.23 gearing isn't going to be all that fast to someone used to the magic of today's fuel injected, computerized hot cars. Remember, back then, a 14.8 or so in the quarter mile was quite respectable. Today there are stock Honda Accords that can do it that fast.

Fast is a relative thing. Compared with all the other cars in 1969, that wasn't bad. Compared with a new GTO, it's not in the same league.

I'd suggest a dyno to find out what you're really pulling. A stock, 350 hp 400 probably put out around 300-310 net, then by the time it got back to the rear wheels with an automatic, we're probably looking at around 250-260 hp.

Find a club with a free dyno night and get a few pulls. That'll tell you if you've really got a problem or not.
Jackolope said it best. I would have asked how old are you? When I was a teenager these were considered fast cars in 1980. Now normal cars are pretty fast. I have a 1970 GTO 455 HO all original. It's fun , sounds great,pulls hard but I would bet in the 14 sec range believe it or not. Do a compression test and make sure it's all good then start w/ the other stuff. Good luck Jim
 
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