273ci thoughts?

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papabear

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Have a '67 Dart GT 2 door hardtop that my father and I are about to get back to working on. I already added power brakes and power steering and rebuilt the front end. Added Cragar 14" SS wheels and air shocks in the back. I've gathered all new parts to redo the interior and even found all the fender trim pieces to have restored! I pulled the back glass a few months ago in preparation for some seam sealer repair at body shop, hope that happens soon...

Now we're at a crossroads on engine decision. She has a 273ci currently. My Dad's Dart in the 70's was 340 swapped from a Duster. Realizing the price tag on 340's currently, we're weighing our options, which brings me here for help. I've read and read and read and just can't make sense of it all, was hoping for some consolidated info and recommendations on one thread, and I thank you ALL for your valuable advice and wisdom!

Questions;
Is the 273 worth rebuilding and adding some power to? It's a 2 barrel Holley setup now, but otherwise completely original. I know the 4 barrel pistons are a bit of an upgrade, and the 308 swirl (think I got that right) heads? What about cam and intake? Will the Hooker headers bolt right in with no issues with a 727 trans?

Alternately, if I were to go 318 or 360, which car/truck years or applications should I look for for a straight forward swap with 727 trans? Would either be okay with just a rebuild, or should we throw some power at them as well? I know the limitations on stuffing some rubber in the rear, so I'm a little hesitant to have a crazy torque motor to blow the tires loose all the time!

New Hemi swap? After it's all said and done, how much can this be done for?

Suspension - is it necessary to go to a torsion bar eliminating K member and suspension? Could we get by for a while on stock suspension with new components and dics up front?

Thanks for any insight, and I look forward to sharing some pics and progress on the old girl.

IMG_8053.JPG
 
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I would build a mild 360 with aluminum heads and a nice cam. Inexpensive compared to adding power to a 273 and you'd be making more power right from the start.
 
273 is a great engine. Punches above it's weight class. If I were doing a build where the budget is a concern I would keep the 273.

Nothing wrong with torsion bars.
 
I'm partial to the little 273 (favorite childhood book "The Little Engine That Could"). But you are on your own.

65 Valiant5.jpg
 
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For my 65 Dart wagon - now a sedan delivery conversion- I decided to go with what I had on hand - a 66 273/235 Commando in front of a 65 833.
 
It all really depends on your budget. Nothing wrong with a 273 for a cruiser, but probably cheaper/easier to do a 318/360.
 
papabear said:
Have a '67 Dart GT 2 door hardtop.

Looks like a really nice car. sounds like you going for a tight budget build.

Now we're at a crossroads on engine decision. She has a 273ci currently.

Here is the scoop on the engine deal.
1. IF you like /desire an underdog and have money to waste. Rebuild your 273.
2. IF the cost of a 340 vs. a 360 build is a make it or creak it deal, you aren't ready to have an engine built. Your budget just isn't there.

Questions;
Is the 273 worth rebuilding and adding some power to? What about cam and intake? Will the Hooker headers bolt right in with no issues with a 727 trans?

I'll say again, unless you are doing a points resto on a car the 273 is an underdog for a guy who has money to waste. Pistons and/or heads / head work to get your compression and some flow. Cam will be based off your heads, compression, intended usage, car specs, etc. Intake, I'd tel you a performer RPM but as I remember there may be some funny deal with intake fitment on a 273. Any aluminum single 4150 flanged intake will do you fine. You need to look at the specs from the header manufacturer. They are very specific with fitment. I'd be looking at TTI headers.

Alternately, if I were to go 318 or 360, would either be okay with just a rebuild, or should we throw some power at them as well? I know the limitations on stuffing some rubber in the rear.

If you are going to buy another engine to have rebuilt and replace the 273, the 340 and 360 are the desired choices. If you have it rebuilt, you're going to up the stock power level, how much depends on your wallet, choices and engine builders input.

There are no limitations to stuffing enough tire under these cars. It's pretty easy to fit a plenty of tire under them with minimal effort. Crazy torque with a SBM mild rebuild aren't things that go hand in hand considering modern engine outputs.

New Hemi swap? After it's all said and done, how much can this be done for?

You'll need an engine, a controller (or carb conversion), swap mounts and headers at a minimum. No set value can be put on this but I'd plan on spending at least 10,000$ end game.

Suspension - is it necessary to go to a torsion bar eliminating K member and suspension? Could we get by for a while on stock suspension with new components and dics up front?

Necessary? NO, not at all. You can get by with stock front end and discs. As an owner of an AlterKation, I'd never build another without one, but it can easily be done I ran stock stuff for 20+ years.

View attachment 1715406319
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I'm going to tell you as nicely as I can, you need to research your choices more before spending money and you need to grow your budget before making your final choices.
 
When considering transmission change remember that the 273 crankshaft pilot is smaller than the other LA engine series. I built my original 273 as I wanted with a built 904. The 904 has less parasitic loss than the 727.
You really can’t go wrong with the 318 motor though. Plentiful and lots of bang for the buck.
 
Thanks for the thoughts, guys. I truly appreciate it. I know there's more research to be done, which is why I'm here after all. I made this post in hopes of clearing some things up on one post. The more I read the more I'm confused with options.

As far as budget, there isn't one in mind yet, we just don't like wasting money that could be used elsewhere.

Can anyone suggest a better place for more comprehensive facts in one place so I don't have to spend hours and hours reading on this forum and going in circles?

Thank You all
 
Keep the 273 for now... drive it. Don’t tear it apart making the car undriveable for too long. You can get a nice 318 or a 360 from nearly any vehicle up to the 90’s before going Magnum or you can go beyond the 90’s and get a Magnum 318/360. There are subtle differences between the two.

Get this book: “How to hot rod the small block Mopar”

https://www.amazon.com/dp/1557884056/?tag=joeychgo-20

Stock style suspension is cheap and effective. You don’t need a coil over front end.

I also agree with staying with a 904. They are a little bit lighter, and take a little less power to operate. They can be built to be plenty strong.
 
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I can elaborate more later, but if you are going hp/dollar or per cube the 273 can be very pricey. We did the 273 2 bl conversion and disappointed.
 
The car has been sitting in my garage for 3 years and driven monthly while waiting on parts to do the body/interior all at once. Plan is to start engine when the car leaves for body, so that it's ready when the body/interior is done, or shortly thereafter.
 
I just went through this decision myself for my 66 Barracuda. My 273 Commando is tired and needed to be rebuilt.

I decided to swap to a 5.9 (360) Magnum. It's not quite a straight forward swap as there are some differences. For example, to run a carburetor you have to swap intakes, the 5.9 is externally balanced so you need a new harmonic balancer to run the V-belts. Need a car oil pan, and I'm going with headers to avoid any clearance issues. An electric fuel pump helps too.

Here's some of the parts I've collected so far.

IMG_20191004_203408.jpg


IMG_20191004_134444.jpg
 
@papabear

I'd get everything with the car situated and ready for the engine you plan to put in there, especially because it already runs.,
 
papabear said:
The car has been sitting in my garage for 3 years and driven monthly while waiting on parts to do the body/interior all at once. Plan is to start engine when the car leaves for body, so that it's ready when the body/interior is done, or shortly thereafter.
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If it's the original engine you shouldn't have any regrets freshening that. 273's are fun little powerplants. They do have their limits if you are looking for big performance. Here's some Builders Choice HP pistons.

52A56A73-D6D1-4894-AA63-BE93331BE67C.jpeg


430045CF-DC8D-4B16-B463-B072829A7F79.jpeg
 
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A hi-compression LA318 or a regular Magnum 5.2 come out of the gate at about the same power as a hopped up 4bbl Commando 235hp, but has the added advantage of a boatload more torque throughout the rpm band, allowing you to run a rear gear that is a one or even two sizes smaller.
And even a low-compression 360-2bbl annihilates them both, with the advantage of running even less rear gear.
Depending on the direction of your project, a 5.2/5.9 Magnum with an A500/518overdrive and 4.30s to 3.91s is gonna be a dynomite combo. The od ratio is .69, so even say 4.10s, are the equivalent of 2.83 cruising gear, so 65= about 2250rpm,
and the starter can be 2.74x3.91=10.71 with the 904based unit; or 2.45x4.30=10.54 with the 727 based unit.
With that much Torque Multiplication, you don't need a lot of power in a streeter, and you can run the factory TC.
The nice thing about these steep street gears is the shifts come early and closer together. Second with the either combo is gonna get you 60mph@~4900/5000 just as the cam is done, so perfect; the engine has run thru the power-peak twice on the way to the speed limit. Put some power in the heads and yur done.

But HO273S or HO273ST (Hi-Output;supercharged or Staged Turbos) has a nice ring to it. All that lil engine needs is some form of supercharging, and then you can run something like 2.94 rear gears for 65=2400. Ima thinking staged turbos; 400 on turbos should be easy on the mini-Mopar;
but a belt-driven side-mount is probably easier and cheaper.
 
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AJ/FormS said:
A hi-compression LA318 or a regular Magnum 5.2 come out of the gate at about the same power as a hopped up 4bbl Commando 235hp, but has the added advantage of a boatload more torque throughout the rpm band, allowing you to run a rear gear that is a one or even two sizes smaller.
And even a low-compression 360-2bbl annihilates them both, with the advantage of running even less rear gear.
Depending on the direction of your project, a 5.2/5.9 Magnum with an A500/518overdrive and 4.30s to 3.91s is gonna be a dynomite combo. The od ratio is .69, so even say 4.10s, are the equivalent of 2.83 cruising gear, so 65= about 2250rpm,
and the starter can be 2.74x3.91=10.71 with the 904based unit; or 2.45x4.30=10.54 with the 727 based unit.
With that much Torque Multiplication, you don't need a lot of power in a streeter, and you can run the factory TC.
The nice thing about these steep street gears is the shifts come early and closer together. Second with the either combo is gonna get you 60mph@~4900/5000 just as the cam is done, so perfect; the engine has run thru the power-peak twice on the way to the speed limit. Put some power in the heads and yur done.

But HO273S or HO273ST (Hi-Output;supercharged or Staged Turbos) has a nice ring to it. All that lil engine needs is some form of supercharging, and then you can run something like 2.94 rear gears for 65=2400. Ima thinking staged turbos; 400 on turbos should be easy on the mini-Mopar;
but a belt-driven side-mount is probably easier and cheaper.
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I wondered about that...we just got done building a turbo LS3 in a Caprice PPV recently with a friend, and had a lot of fun with the turbo. Surely the freshened up little 273 could hold a few pounds of boost....not to mention how cool it would be!
 
You really need to state what you intend to do with this car.
Sure I run my cars down a dragstrip occasionally but the percentage of the total miles is far less than 1%.

My observations...
Adding power brakes wasn't necessary, adds weight and introduces more potential reliability issues.
The Mopar torsion bar suspensions were superior to the Ford and GM stuff. Upgrade the t-bar diameter, etc. There's a reason those others get replaced because of bad geometry and inferior parts.
Of your engine options, the G3 Hemi is the most complex and expensive on your list.
A good 904 is fine with a small block and less parasitic than a 727.
Check out your 273 and if not needing a complete rebuild, run it for awhile with a good tune. After a year or so, you'll know if you want more power.
A later 5.2 or 5.9 Magnum is easy and pretty cheap to do. They were made with non electronic OD trannies for a few years in trucks and vans. 3.91 rear with OD should do it.
Radical engines sound good but is the price of gas going to go down?
 
KosmicKuda said:
You really need to state what you intend to do with this car.
Sure I run my cars down a dragstrip occasionally but the percentage of the total miles is far less than 1%.

My observations...
Adding power brakes wasn't necessary, adds weight and introduces more potential reliability issues.
The Mopar torsion bar suspensions were superior to the Ford and GM stuff. Upgrade the t-bar diameter, etc. There's a reason those others get replaced because of bad geometry and inferior parts.
Of your engine options, the G3 Hemi is the most complex and expensive on your list.
A good 904 is fine with a small block and less parasitic than a 727.
Check out your 273 and if not needing a complete rebuild, run it for awhile with a good tune. After a year or so, you'll know if you want more power.
A later 5.2 or 5.9 Magnum is easy and pretty cheap to do. They were made with non electronic OD trannies for a few years in trucks and vans. 3.91 rear with OD should do it.
Radical engines sound good but is the price of gas going to go down?
Click to expand...

Great ideas and suggestions, I didn't think to list intentions. Basically we want the car to be reliable, quick, able to stop and steer safely, and have more power than the 273. Not looking for a drag car, or a street racing car, but a fun street car with the balls to tote the mail if needed.

Power brakes were added so my mom can drive the car, same with steering.

The 273 has been driven on for 5 years now, but only a few thousand miles. Has some issues already like a leaking freeze plug and exh mani gaskets, so it's gonna come out for sure, even if just for a refresh.

And for what it's worth, the price of gas is not important to me, really.
 
I love 273's. The Piston is at the top of the bore. No need for 4 barrel pistons. If yours is the original 67 273 you should have closed chambers, forged crank and bushed forged rods, solid lifters and adjustable rocker arms. About the only things I'd add would be a small solid cam, Isky or Racer Brown, with valve springs to match, double roller timing chain, windage tray, high pressure oil pump spring, 4 barrel intake, and small Edelbrock AFB or AVS. Your 904 will live forever, change fluid and filter, adjust the bands, and adjust the pressure higher. It is also mated the small pilot forged crank perfectly. My brother put 400,000 miles on his 904 in a 67 Barracuda. Accidently shifted into reverse at 40mph, Topped his 273, 2 barrel converted to 4 barrel as above, at 140 mph and cruised all day long at 100 mph out west. It does not have the torque of a 360, but he never had a problem going fast either.

Any small block Mopar will make power, It's what do you want and what are the plusses each has to start with.
 
non electronic OD 92-95
so 360 93-95 no 360 magnum in 92
I have built several so ask if interested
 
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