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Discussion Starter #1
According to this website:

http://www.supercars.net/cars/435.html

"Dodge's normally aspired high performance 273 was rated at 235hp. The extra 40hp the D/Dart produced was basic hotrodding. Off the speedshop shelf bolt on's included Racer Brown valve springs, a Camcraft 284-degree .500" lift cam, Doug's Headers, and a Holley 4160 bolted to the stock intake. All were equipped with the A-833 4 Speed and a Hurst shifter, Weber clutch components, and an 8 3/4 Suregrip with 4.86 gears. Unavailable for this car were air conditioning and a warranty. There were no external badging or markings to note the D/Dart package over a regular Dart GT."


The way to make a stock 273cu engine into this wonderful creation is to add the following items:

1) Racer Brown valve springs
2) The .500" ift, 284-degree Cam (also Racer Brown)
3) The Holley 4160 4bbl carb (and 4bbl intake since I have the 2bbl now).
4) Doug Thorsley headers tube headers
5) Low restriction air cleaner


Sounds easy enough. Can you still get these, or similar, parts?
Since 1966, is there a better way to turn a stock 1966 273 into a nice sleeper? I mean, who expects a 4 door family sedan to haul it when you stomp it?

I don't need/want a 500hp monster, just something that has more ummph when I rebuild it at some future point in time. That's why I was facinated when I read about this 50 car special Dart production in 1966. I wish Dodge had done more of this.

Also, I have a Sure-Grip 7.25" differential, any more umph, and I may blow out the rear end. I'd love to up that to the 8.75", but who can even find one these days without paying out the yin-yang?
 

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Sure you can buy today's cams with that lift/duration and drive around with a 4:86 gear but it ain't fun. 273 is a little motor and I think piston are expensive, better off building a 408 stroker and smash 'em.
 

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A 408 stroker... fitting that under the hood of a car not even designed for the 273...?

There's that guy (name eludes me, he's posted here often enough) who put 2.2 turbochargers onto slant sixes. Could try the same on a 273, a light pressure turbo with the carb... mechanical wastegate control... probably easier, and I don't think it'll boost power to the point where the crank would be clobbered. Yeah, it's a risk, but it would very likely gain you that same 40+ horsepower, and you could control it via the wastegate.
 

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The stroker crank adds no size to the block! I'd for sure do the usual hot rod stuff, go to a 4.10 gear, put on an Airgap manifold and have some fun. 742 or 489 axles are not that hard to find, but you'll have to narrow the housing for the Dart. Finding an 8.25 might be difficult, but should hold the power well.
 

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It's just a 360 LA with a 4" cast crank all from Mopar, Wouldn't need a tall gear to drive around and a .500 lift cam might even idle decent. Nothing beats cubic inches as they say.
 

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Even if you don't stroke it, I'd exchange the 273 for a 360 and dress the 360 with vintage parts like the air cleaner and maybe valve covers.
Dollar for doillar you'll get way more from the 360 and no one will need to know it's a 360.
 

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I believe it had a mechanical cam with adjustable valve train to help with higher RPM's. The 7-1/4 sure grip is a pretty stout unit and should stand up fine to a 273. It's actually a rare bird. I would keep it.
 

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Aftermarket can take care of the third member for the 7.25 these days as noted, the 8.75s for the A bodies are not too difficult to find, small bolt pattern is usually why they are easier to find, but that can be changed if you like, just keep your eyes open for one. Simply opening the stock heads with 1.88 stock 360 valves is a biggie, and the bore can handle them, porting is definitely a positive for more than 40hp even if the rest of it is stock. Just don't drop 360 or 340 heads on her, drop in compression is too great. Crank should have no problem holding up to a turbo if you go that route, it is a steel crank, same as the 318 actually, (even though there are some early 273 years that have a different bolt pattern for the flywheel if not mistaken), so not a difficult item to find, replace or get bearings for. I believe the cams were solid with adjustable rockers, which is a positive, and I think you could change that over to a hydraulic cam and different pushrods to have better adjustment. Make sure the Air grabber intake is for a 318, not a 360, port size is different and messes up flow if they don't leak.
 

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Discussion Starter #9
I believe it had a mechanical cam with adjustable valve train to help with higher RPM's. The 7-1/4 sure grip is a pretty stout unit and should stand up fine to a 273. It's actually a rare bird. I would keep it.
Just to make it clearer (I was a little vague), I have the 1966 Valiant with the 273cu engine and the 7.25 sure-grip differential, not a Dodge Dart. I just wondered if I could modify MY engine to be like the 1966 Dodge D engine - which after reading even more about them, there never was a run of 50, 50 was planned, and by most accounts, only about 25 were ever actually built.

I am keeping the 273cu engine for the very reason Cudapete states - they are rare birds. My car even has the factory AC, which I find is even rarer. The only real mod I would love to do is to put the 8.75 sure grip differential into this car to make sure that any extra torque I may add to the car, the rear end can handle. I have read all over the web that the 7.25 rear end has a problem even with /6's, so adding anywhere between 40 to 60 more horses to the LA engine with even simple mods may be too much, and I would end up wishing I had.

Aftermarket can take care of the third member for the 7.25 these days as noted, the 8.75s for the A bodies are not too difficult to find, small bolt pattern is usually why they are easier to find, but that can be changed if you like, just keep your eyes open for one.
If you have ANY idea where a 8.75" Sure grip differential (read this as the entire rear-end including housing, axles, etc) with the small bolt pattern can be bought, I would LOVE that information. There are absolutely NONE anywhere near North Alabama (200 mile radius range), that I can find.
 

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The 7.25 with sure grip is substantially different and more robust than an open 7.25 rear end. It should be able to handle your 273. I have the origininal open 7.25 behind behind my 318 with 300 HP. Haven't broke it in 11 years. They are not as weak as made out to be. All stock 8.75 A-body axles are small bolt pattern. I have one in my garage for when the 7.25 finally gives up the ghost...........
 

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The 8.75 found in a Dart, Duster, Demon, actually all the A bodies through what, 1975 (help me out on the end date), gives you a lot of room to look for one. Most of the time it is the fact the A body rear end is the smaller bolt pattern allows them to sit around a lot longer than the few/rare large bolt pattern. They are out there, they are fairly available, just keep looking. As a good side note, the third member 8.75 is the same for all 8.75 rear ends, housing and axles are specific due to the width.
 

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Discussion Starter #12
The 8.75 found in a Dart, Duster, Demon, actually all the A bodies through what, 1975 (help me out on the end date), gives you a lot of room to look for one. Most of the time it is the fact the A body rear end is the smaller bolt pattern allows them to sit around a lot longer than the few/rare large bolt pattern. They are out there, they are fairly available, just keep looking. As a good side note, the third member 8.75 is the same for all 8.75 rear ends, housing and axles are specific due to the width.
I think one of the JY's near me has a national used parts search capability that I think I need to tap into. Let them do the dirty work of finding me one.

Now, back to the engine. I know that there are lots and lots of 318, 340 and 360 aftermarket mods I can find/buy out there, but not so much when it comes to the 273. Does anyone know of a good source for 273 aftermarket mods? Maybe I do need to jump into the bigger is better bandwagon and move upward.

There is a 1976 Plymouth Valiant in my local JY that has a v8. What is the most likely size of that engine? What all would I have to swap out in order to go from a 273 to (for lack of better information) the 318 or 340 (360?) engine from that Valiant? Cross members?, Steering components?< Suspension components?, Hood?, Radiator?, etc. etc. etc. Not sure I really want to go that route, but as someone above stated, nothing really beats having more cubic inches.....

Ha! Like most men, we just want bigger......whatever....... :w00t:
 

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1976 Valiant is almost certainly a 318 if it's a V8. The 340 was long gone by 1976 and the 360 was pretty rare (though there were Valiant 360 powered cop cars).

If you swap to a 318, you need to address two issues:
  • The front of the motor is probably set up for a radiator with at least on of the outlets swapped to the other side. You either need a late model radiator or to transplant the front cover and accessories from the 273 to the 318.
  • The pilot hole on the torque converter will be wrong. I can't recall if the 1967 was larger or smaller than the 1968 up.
If you swap to a 340 then you add one more issue:
  • One motor mount is different, believe it's the left side one.
If you swap to a 360 then there is still one more issue:
  • The 360 requires a weighted torque converter since the 360 is externally balanced. (or a weighted flex plate)
It's not a true bolt in for any of these, but pretty easy as swaps go. All engines (273, 318, 340 and 360) have the same external dimensions and are close in weight.
 

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You also have to re-use the 273 exhaust manifolds for clearance.
 

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The 273 will take any 318 and a lot of 360 bolt-ons. Cam is not a big deal, but a little extra lift is always a good power builder. Windage tray is always nice and an easy modification/addition, high volume oil pump, a 318 performance intake, not a 360 manifold, is good for more breathing, good rings and bearings, one thing that works every single time to gain easy pep, power, and mileage, is porting the heads (but don't polish them for street driving).
 

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Discussion Starter #17
That 1976 Valiant is a very rare bird as well -- they made darned few 1976 Valiants and few of those were 318s.

If it's still there, I would appreciate the driving light lenses ... they were only amber in 1976 ...

(Is it white perchance?)
It is indeed White, 4 door, and last time I was there, it still had the driving lenses. I will try to go by this weekend and check again. I remember that I was going to do this for you awhile ago, and as usual "stuff happens" and I did not get a chance. The engine and rear end was still there as well as all of the brake components. The drive axle was gone, and the body is pure crap - rusted out completely. Most of the glass was intact, put the interior is farily well gone. If I can, I will take pics.
 

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Discussion Starter #18
Darn! The 1976 Valiant is gone! The junkyard got rid of it! It was there a month ago! Either someone finally stripped that sucker clean, or they decided it had sat long enough and scrapped it. Darn! I hope it was the former and not the latter! I know they have to sell parts to make it worthwhile, but sometimes ya gotta let things stew for awhile.... That really breaks my heart....especially now that I was planning on stripping some parts off of it.....
 
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