273ci--a keeper in my 64 Dart GT 4-speed?

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JACOBI

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Dear all:

I have acquired a 64 Dart (GT) factory 4 speed / 273 ci motor. It is sufficiently rare that my instinct is to not up-size the motor to, e. g., a 318 or 340, but rather keep it as the factory outfitted it. It would probably used as a daily driver, so fuel efficiency is an issue too. Is the 273 (currently not running) inherently able to be rebuilt to upgrade power/efficiency enough to make it worth while and would replacing it with a 318 or 340 be a big step up in terms of power to weight factors and in terms of potential for modest performance upgrades. It is a project car, and one with a factory configuration that is not plentiful. I already have two beautiful slant-six A bodies which I am planning to convert to dual carbs plus exhaust improvements but I am new to the v-8 world. Any wisdom to share? many thanks. JACOBI
 
I'm learning from experience that rebuilding a 273 can get expensive and there are far fewer options available in terms of pistons, head gaskets, and cams. Not that you can't get everything you need, but there are fewer choices and things tend to cost more. That said, I really like original cars so I would do the same thing again.

I recommend the Rebuilder's Choice domed pistons from Kanter Automotive. If you run the numbers you'll find they don't make nearly the advertised compression which is a good thing if you plan on running pump gas.

My tired 273 automatic with a 4 barrel would only get like 15 mpg on the highway. I'm hoping that will improve with a fresh engine, higher compression, and possibly some attention to carb jetting.

If you do swap to a 318/340/360, hold onto your 273 as it will increase the value of your car. You'll probably also want to replace the stock 7 1/4 rear end for anything beyond a stock 318.
 
its hard to wanna build the 273 when it costs the same moeny to build a 318 , 340, 360...EXCEPT that the 273 pistons cost WAY more than the 318,340,360 pistons do...so in reality side by side it costs more to build a 273.

If you build the 273, the best bang for your buck will be porting the heads and running a matched cam, matched for your driving intention, power expectation, and head flow per lift.
There are plenty of really strong running 273's out there, but those are the ones with a good matched cam and some head work done, the rest are just a lil better than stock.

Stay with the 1.78/1.50 valve arrangement, have them ported to flow in the 195-200 cfm int 145 cfm exh, those heads will do that easy and all by .450 lift which is great cause you dont need a big cam with nasty street manners to make such a jump in power and will keep the mpg around where you want them.

fwiw you could up the cid to a 318/34/360 and all the power you want will be more easily attainable by simple means of cid increase/larger bore.

what would be funny is to say throw a 4'' crank in it and have some pistons made, then it would essentially be a 8 cyl 225 slant..lol tiny bore and mountainous stroke.
 
If your bores/pistons are good a 273 can be build with some more hp pretty cheap. I hot tank every motor to make sure it runs cool. Hone the cylinders myself. Zero deck the block. Bearings and gaskets. New cam, lifters, and valve springs. I have $700 into my long block. A little home porting and you got a decent little motor. Only downfall is your heads have smaller/different angle intake bolts so your limited on intake manifolds. I have a 1965 4bbl intake if your interested but shipping may hurt.
 
If your 273 needs to be rebuilt, I would seriously consider replacing it with a 318 out of a late 80's vehicle. The 318 block and heads are virtually identical to the 273, the a 340/360 has slightly different mounts. Such a core 318 should have the closed chamber "302" casting heads, and built with KB167 pistons and a mild cam would be a nice update from the original 235 HP 273. If you plan on keeping the factory exhaust manifolds and single exhaust do go too nuts, they'll only support 250 HP or so, another argument against the 340/360.
 
Best to keep it. They are cool little V-8's that rev high. 4.5L is larger than many current very expensive V-8 Euro cars. Check compression first. If you do take apart the engine, check the pistons and bores to see if a simple re-hone is possible. A new commando piston set is ~$400, so that might be the time for a "push-on vs swap out" decision.
 
Each of these is a much-appreciated, substantive, reply (and quickly made!); hearty thanks, one and all for the time invested. I will mull and have more to report once I have had a closer look at the mill. More thoughts, of course, are welcome. Best, Jacobi
 
nice find,, ide keep the 273, put a 4bbl on it,,nice cam,and hypo pistons if they are available,,273 have floating pins like a 340
 
Of course if you are going to beef up the engine you may want to swap out the clutch for the larger later model also.

And by the way I am swapping out a 273 commando for a 340 in my 64 4 speed dart. But I have had the motor for much longer than the car.

The 273 and 877 was pulled and replaced with the 340 10.5 inch flywheel and a cast iron 877od trans. I already have the 8.75 3.55 limited slip rear.

cant wait to drive it for the first time but that will be a month or 2.
 
a larger clutch will not fit in the factory 273 bell housing,, you would have to go to a different bell housing,fly wheel ,,etc,,,
 
A 273 Commando is a very sweet-revving motor that would be a great combo with a 4-speed -- I wouldn't trade one for any 318. A low-compression 2bbl 273 is a different story, though. Which one are you starting from?
 
My 66 Valiant has a 273 and I once considered changing it to a bigger motor but it has plenty of power-especially for a daily driver-so I would keep the 273 if it were my car.
 
It's all up to you. Really the easiest way to go would to rebuild what you have to Hi po specs (or what ever combo you choose) Hop it up too much and everything but the trans and driveshaft will need changed to take the power.
Check out my 273 build thread (link below) to give you a idea what is involved. Keep us posted on your progress. tmm
 
I would keep the 273. These motors rev!!! Here's what I run in my 66 barracuda original 273 4bbl.Me and my late son went through it. The block .30 over 0 decked all arp studs and bolts. Milodon pan, pump 10 1/2 comp lunati bracket 2 cam crane gold aluminum rollers rockers, lots of head work eddy air gap 650 double pumper Mallory ing.A883 trans 83/4 with 3:55 sure grip. This thing hauls some serious ***. This summer were gonna take it to the local track and get some numbers. Most people think I'm not being honest when I tell them it's a 273.LoL just my thoughts
 
I love 273s! The two barrel 273 is just a nice running motor. But it would be a bit more affordable to put in a nice 318 and the extra displacement gets more torque at low rpms where it's noticeable. If you go for even more torque & power with say a 360 then you'll start getting into upgrading other items like the rear axle.
So I say 318.
 
If your only shooting for 200-300hp the 273 will be fine
Not that a 273 can't make more but it will at a fairly high rpm, I wouldn't assume 273 will be better on gas cause a 273 needs more gear to get the performance out of it.
 
Here's an analytical route. Disassemble it,find out what you have to work with. A 64 Dart GT ,with a 273 is rare these days. Maybe the piston/walls are good. I'm expecting low oil level,bad crank journal.
 
Abodybomber said:
Here's an analytical route. Disassemble it,find out what you have to work with.
Click to expand...

I agree with this route. See what you have to work with first.

My opinion is moth ball the 273 if its the original motor and build a 318 or 360. But it all depends on what you want out of the motor, intended use and budget and in this case the budget. 318's are a drop in with the 273 accessories and pan, abundant, cheap, and you can get a Magnum block and go hydraulic roller, and you can still say "I have the original motor".
 
ProStocker273 said:
... Only downfall is your heads have smaller/different angle intake bolts so your limited on intake manifolds. I have a 1965 4bbl intake if your interested but shipping may hurt.
Click to expand...

First I'd do a compression check on all the cylinders to get an idea of where you are. If all is good, early 273's have decent compression so your stock pistons should be good. I'd swap in a cam, lifters, and matching springs. Use the newer Viton positive valve stem seals while the springs are off. Exhaust manifolds are all the same on 64 - 66 A bodies. Get custom duals with turbo mufflers or the original Performance exhaust was 2.50" single with two straight through mufflers in line. Get a 4 barrel manifold, see above, an original Carter AFB, or a 500 cfm Edelbrock with an adapter plate. The best milage Carb would be a TQ, ThermoQuad, and an adapter plate. People will tell you that it is too big, but we used to run them all the time on 273's. Get the earliest you can lay your hands on. They have the least smog complications and have a ported vacuum for your vacuum advance. You just adjust the secondary air valve till it does not bog when you floor it. Last I'd add a performance electronic distributer. Set your timing at 35 degrees total without the vacuum advance. Make sure the fuel system is clean and replace fuel filters. Now in short order you will need to get a 10" performance clutch, pressure plate and throw out bearing , from somewhere like Brewers Performance, since your stock one will not last long. Get your brakes and suspension up to snuff. Stock is fine but you will probably enjoy a front sway bar and 15" x 6" wheels and sticky low profile tires. You can go bigger but it is hard to beat the efficiency of a 273. A Performance 273 with a 4 speed is pretty sweet "all around" A body. Enjoy.
 
66fs said:
First I'd do a compression check on all the cylinders to get an idea of where you are. If all is good, early 273's have decent compression so your stock pistons should be good. I'd swap in a cam, lifters, and matching springs. Use the newer Viton positive valve stem seals while the springs are off. Exhaust manifolds are all the same on 64 - 66 A bodies. Get custom duals with turbo mufflers or the original Performance exhaust was 2.50" single with two straight through mufflers in line. Get a 4 barrel manifold, see above, an original Carter AFB, or a 500 cfm Edelbrock with an adapter plate. The best milage Carb would be a TQ, ThermoQuad, and an adapter plate. People will tell you that it is too big, but we used to run them all the time on 273's. Get the earliest you can lay your hands on. They have the least smog complications and have a ported vacuum for your vacuum advance. You just adjust the secondary air valve till it does not bog when you floor it. Last I'd add a performance electronic distributer. Set your timing at 35 degrees total without the vacuum advance. Make sure the fuel system is clean and replace fuel filters. Now in short order you will need to get a 10" performance clutch, pressure plate and throw out bearing , from somewhere like Brewers Performance, since your stock one will not last long. Get your brakes and suspension up to snuff. Stock is fine but you will probably enjoy a front sway bar and 15" x 6" wheels and sticky low profile tires. You can go bigger but it is hard to beat the efficiency of a 273. A Performance 273 with a 4 speed is pretty sweet "all around" A body. Enjoy.
Click to expand...

Worth repeating, well said my friend!
 
To all of you, who have given such detailed and informed advice, I am grateful. I will take delivery soon, and begin assessing what I have. Other things being equal, I tend to favor keeping, but upgrading, the 273--but then, depending on what I find, all the other options suggested above are still in play.

I'd like to be able to say when asked "it is the original engine", but that may prove a bridge too far. I read this thread several times a day, and am encouraged by all the high-quality support there is among the members/contributors here.

The only down side to this new project is that I should probably sell my Honda S2000 (read: "go-kart on steroids") to make room and generate a budget--not to mention to head off divorce papers!
 
Thanks, ToolmanMike. Hope you are surviving the weather. We are to get record cold tonight. Not so bad compared to Iowa and South Dakota temps though. I'm in hibernation mode here anyway. I did forget the true roller timing chain above. Happy New Year!
 
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