273, or 318?

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66fs said:
Not at all, I milled the J heads .040" so the chambers were at 64.7 cc and I started with 10.5 TRW forged pistons. Does not really matter since the better heads are where it's at. Before the 340 top end, I could run with a 383 Road Runner. After the 340 top end it went to another level of power.
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Notch the bores for valve clearance or were they the small valve heads?
 
I would think a 273 commando in an early Dart Valiant or Barracuda would be a nice stout performer. A 65 Barracuda came in at just under 3000 pounds.
 
Just remember. Dodge=Charger 273 Plymouth=Commando 273
 
Except for the air cleaner sticker, there is no difference. Probably just ran out of the Charger 273 sticker that day, or grabbed the wrong one off the shelf.
 
cudamark said:
Except for the air cleaner sticker, there is no difference. Probably just ran out of the Charger 273 sticker that day, or grabbed the wrong one off the shelf.
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There was a lot of that that went on. You wouldn't stop an assembly line or send a incomplete car out just because of a incorrect sticker.
 
DartGuy67 said:
I plan on running 3.73 gears and putting in an A500 overdrive. Try to stay with like the Isky E4 cam. I want to make an all around good driver, not just a drag car! All opinions welcome.
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If you're really gonna cut up the tunnel to fit the A500, then numbers matching originality is gone . and
If you are installing that A500 in a bid for fuel-economy, then a short-period cam, high-pressure 273, is a natural.
But;
if you're idea with the A500 is to reduce the engine rpm that comes with hi-performance gears, then the hi-pressure-318, with a modest solid-lifter cam is a natural.
But if yur going that route, a cheaper alternative is the 360 or a Magnum with a regular automatic and compromise rear-gears.
There are so many ways to skin this cat, that it can takes months to finalize your decision.
-----------------------------
>IMO, for this Combo, you need to make your transmission decision the very first one, cuz it can/will make or break the rest of the combo.
>As for originality, the only guy that cares, is the one-in-a bazillion guy; and if you can supply the "numbers matching" parts, at the time of sale, it's all good, regardless of what's under the hood .
>Besides all that, we seem to be living on the Eve of Destruction, so ....... build whatever you want while you can, and drive it while you can, cuz there's a really good chance that, you'll never be able to sell it anyway....
>If it was me;
and overdrive not available; then
I'd go with more than a 273, cuz bigger will have more pulling power as the Torque-Multiplication wanes in each successive gear. Bigger will allow you to run less hiway gear. But
>If it was me:
and the A500 is for sure; then
your rear gears are unlimited, up to about 4.30s. This makes the lo-torque273 a natural...... in a streeter, and let the track results be whatever.
>No matter what;
the smaller the engine, the more important the flash-stall will be.
The TC in the A500 may not be available, in the stall that you may need, for a small engine. Or, if it is, it may be very expensive.
However, as the installed engine puts out more low-rpm torque, the flash-stall will be higher, increasing take off performance, and so, requiring less torque-Multiplication out the back-door.
>As for me, the smallest cid I would run in your dual/triple-purpose combo would be a very small-cammed, tight LSA, 340 with headers.
If fuel economy is somewhat important, than a high pressure 318.
If fuel economy is very important, than a high-pressure 273.
If fuel economy AND performance is desired, then you need a longer stroke with a cam that has a longer power-extraction cycle and less overlap.
>With log manifolds, forget any long period cam.The overlap provided by long period cams is totally stifled, and with it goes the power........ so the long-period does nothing but kill cylinder pressure, reducing low-rpm torque. All-in-all a disappointing situation.
> but here's the thing, with 3.73s and .69overdrive, the Final-drive becomes 2.57 and 65=2080 with 27" tires. This is too low for the stock-type distributor to meet the engine's cruise-timing requirement with even the stock cam, never mind any performance cam. So you kindof shot yourself in the foot. But, you can get a stand-alone timing computer to fix that, but fuel-economy will depend on the chosen cam.
The minimum rpm that the modified stock-type distributor can provide adequate timing, for fuel-economy purposes is ~2400, and that would require 4.30s@6500. and a cam to support that cruise-rpm.
Or you could cruise the 3.73s up to 2400, which would get you 75mph.
 
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After reading all this I was thinking why not just find a junkyard 5.9 and o.d. trans. all together. Couldn't be that much cash and you would have the bigger, torquier motor gets decent fuel economy and still run a 3.73 or 4.10, best of all worlds. So guys what would a junkyard 5.9 and trans cost? My guess $700.00? Cheap deal.
 
AJ/FormS said:
If you're really gonna cut up the tunnel to fit the A500, then numbers matching originality is gone . and
If you are installing that A500 in a bid for fuel-economy, then a short-period cam, high-pressure 273, is a natural.
But;
if you're idea with the A500 is to reduce the engine rpm that comes with hi-performance gears, then the hi-pressure-318, with a modest solid-lifter cam is a natural.
But if yur going that route, a cheaper alternative is the 360 or a Magnum with a regular automatic and compromise rear-gears.
There are so many ways to skin this cat, that it can takes months to finalize your decision.
-----------------------------
>IMO, for this Combo, you need to make your transmission decision the very first one, cuz it can/will make or break the rest of the combo.
>As for originality, the only guy that cares, is the one-in-a bazillion guy; and if you can supply the "numbers matching" parts, at the time of sale, it's all good, regardless of what's under the hood .
>Besides all that, we seem to be living on the Eve of Destruction, so ....... build whatever you want while you can, and drive it while you can, cuz there's a really good chance that, you'll never be able to sell it anyway....
>If it was me;
and overdrive not available; then
I'd go with more than a 273, cuz bigger will have more pulling power as the Torque-Multiplication wanes in each successive gear. Bigger will allow you to run less hiway gear. But
>If it was me:
and the A500 is for sure; then
your rear gears are unlimited, up to about 4.30s. This makes the lo-torque273 a natural...... in a streeter, and let the track results be whatever.
>No matter what;
the smaller the engine, the more important the flash-stall will be.
The TC in the A500 may not be available, in the stall that you may need, for a small engine. Or, if it is, it may be very expensive.
However, as the installed engine puts out more low-rpm torque, the flash-stall will be higher, increasing take off performance, and so, requiring less torque-Multiplication out the back-door.
>As for me, the smallest cid I would run in your dual/triple-purpose combo would be a very small-cammed, tight LSA, 340 with headers.
If fuel economy is somewhat important, than a high pressure 318.
If fuel economy is very important, than a high-pressure 273.
If fuel economy AND performance is desired, then you need a longer stroke with a cam that has a longer power-extraction cycle and less overlap.
>With log manifolds, forget any long period cam.The overlap provided by long period cams is totally stifled, and with it goes the power........ so the long-period does nothing but kill cylinder pressure, reducing low-rpm torque. All-in-all a disappointing situation.
> but here's the thing, with 3.73s and .69overdrive, the Final-drive becomes 2.57 and 65=2080 with 27" tires. This is too low for the stock-type distributor to meet the engine's cruise-timing requirement with even the stock cam, never mind any performance cam. So you kindof shot yourself in the foot. But, you can get a stand-alone timing computer to fix that, but fuel-economy will depend on the chosen cam.
The minimum rpm that the modified stock-type distributor can provide adequate timing, for fuel-economy purposes is ~2400, and that would require 4.30s@6500. and a cam to support that cruise-rpm.
Or you could cruise the 3.73s up to 2400, which would get you 75mph.
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I like your thinking. Adding ac to the car, I am thinking more along the lines of the 318. I’m thinking the 273 will not be turning enough rpm to keep it in the power band. I plan on locking out the overdrive on the a500, until interstate speeds. Which should be around 24-2500 rpm. 3.73’s and a 2000 stall. With the 920 heads, it should be around 9 1/2:1 compression. Then pick a cam to bring it all together. Something with a power range of 1800- 4500 or so?
Mileage is somewhat important, but not everything. I just wanted to get good all around performance from it. Mostly local driving(poker runs, cruise nights, and occasional 100-200 mile runs, with a once annual long trip)
 
I advanced the E4 a couple degrees on my 273 and it has plenty of low rpm torque. It runs out at about 4800 but I can start out in 1st and skip second, start out in second and skip 3rd or what ever and it still puts pretty hard for a small cube engine. It will pull almost 20 mpg on the highway.
 
LO23M8B said:
After reading all this I was thinking why not just find a junkyard 5.9 and o.d. trans. all together. Couldn't be that much cash and you would have the bigger, torquier motor gets decent fuel economy and still run a 3.73 or 4.10, best of all worlds. So guys what would a junkyard 5.9 and trans cost? My guess $700.00? Cheap deal.
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pull your own locally is about 650 for a motor minus the accessories, which they'll nickle and dime you to death on and a transmission w/ a converter is 400-ish.

so you're at a smooth G just to get into the game.

from there, figure all the ticky-tacky bits n' bobs to do a swap plus all the nonsense for a standard r&r and you're rapidly approaching a few hundy more.

oh, and don't forget the motor and trans are completely unknown entities.
 
DartGuy67 said:
I’m thinking the 273 will not be turning enough rpm to keep it in the power band.
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I'm not understanding this statement;
If you're talking at cruising speed, w/3.73s and 27s, 65=3020 in Drive/2080 in overdrive. So that's plenty of power there to cruise with.
The thing is, it takes a specific amount of power to cruise at any given speed, in terms of pounds of fuel per horsepower. So then you can gear any of the small-blocks and with a bit of tuning, get about the same mpgs.
The problem without an overdrive, comes with the take-off power and Second gear performance, with that hiway gearing. This is where the bigger engine comes in handy.
But with the overdrive, which works well with 3.91s to 4.30s, this punches the take-off power back up.
You have to scrutinize this, by converting your various Torque multipliers to Roadgears. If you are willing to purchase a stand-alone timing computer, and program it yourself, then mpgs are just a matter of reducing the cruise rpm until it takes WOT to maintain your cruising rpm, lol. No but I mean
the keys to getting great fuel economy are a tiny engine, operating in a high efficiency mode, at a low rpm, with the exact right amount of cruise-timing.
To cruise at 65mph, usually requires about 35hp. At 2400rpm that requires 77ftlbs. But at 1600 rpm, it requires 115 ftlbs. I think any SBM can spit out these numbers. The trick is to achieve the other parameters, and still have reasonable performance under other driving circumstances, without running a nasty camshaft.
Cruising at under 2400rpm, it gets harder and harder with a stock type distributor, to achieve optimum ignition timing..... which is essential for fuel-economy. And thus the reason for a Lean-Burn Computer for cars that ran the 2.45 and under rear gears.
Your 3.73/.69od comes to a Final Drive of 2.57 and 65mph=2080 with 27" tires. That's a really good cruise-number, but will require computer-timing to be fuel-efficient. And you cannot run any old hi-performance cam with it either, cuz that type of cam is NOT fuel-efficient at cruise-rpm, unless you build it absolutely just right. To operate at 2080, the cam can NOT have any significant overlap, nor any late closing intake valve. and the Power-stroke has got to be long enough to extract as much energy from the expanding gasses as possible, without asking the pistons to actually pump those gasses out. This is very torque-limiting, which usually leads to installing a bigger engine for reserve-power.
However, in your case, gearing and stall can overcome that with a Lock-up Convertor.
Let's look at your gearing in terms of Roadgears, which is simply the transmission gear multiplication times the rear gear. So, the A500 has ratios of 2.74-1.54-1.00-.69od. with 3.73 rear gears, the Roadgears are
10.22-5.74-3.73-2.57
Now;
The 10.22 is plenty of TM with which to get rolling
The 5.74 is a bit long for a Second, but doable
The 3.73 Third is just a gear to get to overdrive, in most cases or a cruising gear in the City, so almost any roadgear will work.
Lets look at the range from 30>50mph, which can make or break any combo.
In Second gear with a Roadgear of 5.74, the rpm window is 2140 to 3570@ zero-slip, say 2320>3880 thru the TC @WOT So then, whatever engine you install, this is gonna be it's life-long handicap, so it's gonna need to have a natural propensity to produce torque in that Second gear range, else you will forever be downshifting to get some.
Say you have one each of the LAs, and each one is able to output an average of .90 ftlbs at WOT, in the range of 2320 to 3880. The horsepowers would range from:
108>182 for the 273 to
126>212 for a 318, to
135>226 for a 340, to
143>239 for a 360.
Now remember, these are theoretical average WOT numbers.
So then you can imagine that the 360 will NOT need WOT to match the 273 performance. This is always a welcome situation.
However, each bigger engine will have a larger power loss due to internal friction; but, each bigger engine will tend to produce more torque than the percentage of incremental increase in size. That is to say, with all engines built identically, and the 273 at .9 ftlbs per cube, each bigger engine will have the potential to produce incrementally more than .9ftlbs per cube. Say, by the time you get to a 360 it is up to 1.05ftlbs per cube; now the WOT power in the window is up to 167>279 horsepower, outstanding!
Ok so now, you can see, how a specific Roadgear affects the combo.
and if you are happy with the modest WOT performance of the 273, in a Roadgear of 5.74, then build it. If it turns out Not to be enough, well just install more rear gear until it is. But that will mess up your fuel-economy a bit and you can't get it back. Whereas, a bigger small-block engine will hardly affect the economy yet instantly jump up the WOT performance, and you know, you don't have to step on the gas as hard or as long, to achieve the same rate of acceleration.
With a given Cruising Roadgear, the downsides of a bigger engine are; a slight loss of efficiency at cruising speed, and a slight loss of power to friction. However, those losses can be overcome, by cruising at a lower rpm........ and the bigger engine will still maintain it's comfortable power edge over a 273.

AS for me:
1) I would be willing to give the 273/A500 a chance, but maybe Not with 3.73 gears. I would be prepared to install a lil more gear to satisfy my need for acceleration in Second gear, and/or less gear for fuel-economy.
2) I have already built a hi-compression, low-performance 340, which I know is a stinking blast to drive, and so
3) my feeling is that a hi-pressure 318 would be a reasonable compromise, and if it turns out that with 3.73s it more than satisfies your need for acceleration, then there is no good reason to Not give some up, by decreasing the cruise rpm with less gear.
4) I know I could be happy with a 318/A500/3.73s, maybe even with 3.55s;
but not sure I could be happy, with a 273/A500/3.73s. I know the 273 would be just fine in First gear. But I think for me, that 5.74 Second Roadgear would be a tad disappointing at 30mph/"hammer-time". And the downshift into First @30mph is going to 4200, so can't be in First very long until it's time to shift.
But I might be happy with a 273/A500/4.10s. That would make 65=2290 which is now on the lower limit of timing for a stock-type distributor, so yeah, for me, I can see 4.10s being a good compromise. And 30 is now, mathematically ~2600/2700 in Second at WOT..... which is considerably better than 2320.
5) Aw, who am I kidding; that 273 is getting moth-balled, in favor of a high-efficiency, high-pressure, modest-power, 318/A500/3.23s tuned to cruise at about 65=1800, and the timing computer is pretty much a must-have. I'd be running a step-piston, tight-Q, with closed chamber alloy heads, headers, an aluminum 180*intake, a spreadbore carb, fresh air, and a Tight-LSA , all tied together with a very modest solid-lifter cam. Badaboom!
Hey waitasec, I bought this Dual-Port a few years ago; hmmmmmmmm.
 
toolmanmike said:
I advanced the E4 a couple degrees on my 273 and it has plenty of low rpm torque. It runs out at about 4800 but I can start out in 1st and skip second, start out in second and skip 3rd or what ever and it still puts pretty hard for a small cube engine. It will pull almost 20 mpg on the highway.
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I guess, these guys have never had a high performance 273 that gives you the best of both worlds with just a set of 3.23 gears. Not sure why your Charger 273 only revs to 4,800 rpm. Mine does not hit it's stride till 3,000 and pulls to 6,000+ and mine is stock, including original AFB carb intake and exhaust manifolds, other than the Isky E-4 and a set of 340 valve springs. Good luck to the OP with all that cobbling.
 
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66fs said:
I guess, these guys have never had a high performance 273 that gives you the best of both worlds with just a set of 3.23 gears. Not sure why yours only revs to 4,800 rpm. Mine does not hit it's stride till 3,000 and pulls to 6,000+. Good luck to the OP with all that.
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Valve springs I think.
 
Rug_Trucker said:
920's? Is that the closed chambered truck head with no exhaust crossover? If so I have a set of those in the shop.

One thing I would think would be good on this motor would be the 302 heads.
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Nope. 920's are a 66-67 273 head. CLosed chamber 1.78/1.50 valve
 
DartGuy67 said:
It’s a’67 4barrel
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There are no numbers to match in a 67 car. Numbering the block with the cars VIN didn’t start until the middle of 68, and across the board in 69. That being said, if the cylinders need to be bored to correct one cylinder, you will have no choice but to use aftermarket pistons for a 273 with an overbore. You can however, have the offending cylinder sleeved and use the stock pistons if the other cylinders check out as ok. That’s what I would probably do, I have a few cars running 273’s, and they’re a great little motor.
 
As this is a mild street applicaiton and drivability will be a concern, building a 318, or even a 360, would be best. The 273 is nice and it is original, but it lacks torque and the small diameter bore has impacts on air flow into the cylinder. This limits HP to some extent. I built my 340 in 1974 with a 318 cam and a small manifold as the energy crisis then made fuel economy paramount. This combo with a 4-row radiator and electric cooling fan ran 14.50's @95 and got 25-26 MPG and was able to drive in Tucson in 117°F heat and not run over 190°F. Ideal combo that can be duplicated with a 318 or 360. The OD Trans makes me think torque qill be most important, so displacement needs to be considered along with overall project costs. That may argue for the 318. I would mildly port the heads especially port matching and valve bowl area to clean up any casting issues. Some of these heads need some TLC to perform well.
 
I am with Dan on this, a numbers match car is worth more. The 273 engines run well, so I would be inclined to rebuild it. Either get David Vizard's How to Port and Flow Test Cylinder Heads, and his Build HP books, or watch his Youtube videos; David Vizard Powertec 10. Most is Chev or Ford discussion, but the principles apply. He is involved with Andy Wood of Unity Motorsports Garage and Uncle Tony of UTG, on a project called Mission Impossible. Another porter, Charlie Servido, might bbe misspelled is doing head and port work. A number of Mopar oriented videos to pick up little bits of wisdom.
For valves DV is starting with the stock LA 318 valves and is then going to test a set of used Chev LS valves to get larger valves with lighter weight. LA engines have 3/8" valve stems while the LS use 8mm stems. The Mopar Magnum also have 8mm stems. It would be interesting to compare valve weights between the LA, Magnum and LS along with installed heights.
With regard, for an example, the SBF and Chev use 11/32" valve stems. Before the LS Ford guys were installing Chev 1.94/1.5 or 1.6 valves. The Chev valves are a bit shorter but the keeper groove is at about the right height. The LS valves are about the same length and the keeper groove is at about the same height. A 1.9" LS Intake valve is about 20g lighter than the 1.78" Ford Intake valve. The 221 and 260 Fords used 5/16" valve stems but small valve heads. These two engines suffer the same situation as the 273, short number of production years, so parts are harder to find at reasonable costs. I would consider putting 5/16" bronze guides in the 273 heads which can then be honed the 0.0015" to 0.002" to fit the LS or Magnum valves.
Back to the Ford heads, 63 to 67 289 HiPo heads and 68 and on SBF had 1.78" spring installed height. LS valve springs with their 1.8" installed height work. The 2V 289 had an installed height of 1.64" or 1.66" which posed a bit of a problem in spring choice. A call to PAC Racing Springs solved the part number problem and ordered through Summit. Jegs or another supplier can likely get them.
For your one bad cylinder, you can have the machine shop sleeve it and finish the bore to match the other seven.
Just some ideas to think about. Compare the difference in cost and fit between the Magnum and LS valves along with the springs, retainers and keepers required. Also consider that the out of pocket today will be spread over 20 years of happy, snappy and reliable driving.

Dan the man said:
Since it's a all original number matching car, I would go with the 273 as originality is worth more money.
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Dan the man said:
No, FYI, I'm tired of looking at junk. It's unreal people who don't understand the difference between a project car and one that doesn't need any body work. Seen one awhile back the owner said it was rust free, he should have said that it was metal free.
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Then there is the other end of the spectrum, people that see some rust as not repairable. I know a guy that sold the interior out of a Firebird Turbo coupe because of a bit of rust. Then he saw what someone else was restoring, way worse. When I asked if hhe was going to do the body work and get a new interior, I got a big truck you. :) Same guy had a 1940 Olds Coupe and a tree fell on it. Cut it up and hauled it to the scrap dealer. Only about 10,000 Olds coupes were built in '40 which would be a rare car today. I talked to another guy that knew the car and damage and he said it was pretty bad, but I know his thoughts on bad also. If a person knows how to work metal it could be jacked and hammered into shape. Check into what Fitzees Fabrications does on his videos.
RustyRatRod said:
Put a LS in it.
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