Hello, recently I bought a 1966 Dodge dart 270, with a 225 slant 6 with a A904 transmission. The car revs up to proper RPMs in neutral and park, but when in gear struggles to even get above 100. Not to mention going up hills is a crawl or even a stall. Thats being said, I have had the carb rebuilt, new rotor with strong spark, new pcv and vacuum advance lines, new spark plugs, new transmission filter, etc. This being saidni am curious as to if this car has some sort of vaccum kickdown for the transmission as there is only hard linkages to the transmission. Any help would be appreciated. Thank you.

There is no vacuum line to the transmission; upshift/downshift behaviour is controlled by the solid linkage (which must be adjusted correctly).

As soon as you can, get the three books listed in this thread.

Carb rebuild was wise – are you quite sure it was done correctly? Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

There's more to a tune-up than a good rotor and plugs. Follow tune-up parts and technique suggestions in this post, including the valve adjustment. The base ignition timng must be set properly (spec is 2.5° BTDC; they run better with a small bit more at 5° BTDC) and the centrifugal and vacuum advance mechanisms must be working correctly. The timing mark on the crank pulley must be checked for accuracy; the outer ring part of the crank pulley (with the timing mark on) can slip relative to the inner hub part.

If the engine's definitely running well, you could have a transmission problem. The symptoms you describe could indicate a faulty torque converter or other problem internal to the transmission. Could also be exhaust restriction – is your heat riser valve stuck, or is it free? Is the muffler reasonably new, or is it old enough that it could have collapsed baffles inside?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Wow, is that 100 mph or 100 kph?

If it is mph, then it is highly optimistic for a stock '66 Dart even getting close to that speed. I would start to worry about stuff like front suspension tracking correctly. Good shocks to control the suspension. Decent brakes to slow you down; 9" drums not so much, 10" drums slightly better. Better tires then stock. You would also need a long flat road, preferably downhill, with a strong tail wind.

Dan's suggestions for reading material and tuning procedures is good advice. Follow them, and maybe the car will run correctly at sane speeds.

Good luck.

The way I read it, he probably left off a zero and meant that it struggles to reach 1,000 RPM.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

After some furthur testing on the dart, I think I have diagnosed the issue. Firstly I went over my ignition system, checked for vaccum readings, tested my spark, and found that yes the vaccum advance is frozen but that is not all my problems. After advancing the timing to compensate for the lack of advance, it still would not rev up to 1000RPM in drive or reverse. To furthur test, I lifted the rear of the car and tried my rpm test once again with the car in drive/reverse with the rear wheels off the ground. This test takes all of the load off of the wheels, engine, and transmission to test if the transmission or the torque converter is at fault. With the rear wheels off the ground and the car in drive the car flew threw all gears and reved up to arpund 3000RPM like it should be doing during regular driving with my foot pressed on the accelerator. This leads me to believe that its the torque converter, but I did a few other small tests. Recently before I ran these tests, I changed the transmission filter, so after I ran this test, I smelled the transmission fluid which should be brand new, and it smelt burnt which could mean the torque converter has gone bad. I have a new torque converter arriving Friday and will update when I install and test it in the car. Also I plan on turbocharging the stock slant 6 so let me know if yall want updates on that or a video. Thank you and any feedback is welcomed and appreciated. -Evan

Probably. A formal test for the torque converter is to hook up a tachometer, safely chock all the wheels, apply the handbrake, stand hard on the brake pedal and keep your foot there, start the car and put it in Drive, then see what the tach reaches when you open the throttle. Do the test quickly; prolonged operation like this heats the fluid up hot. Worth doing the test with the old converter and then with the new one.

And yes, keep us up to date on your projects!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Completeing this test just kills the car, sputters and dies out. This is something I meant to put in the last post, but when applying brakes moderatly hard, the car sputters and dies leading me further down the path of a torque converter.

That does indeed sound like a very dead torque converter.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.