True its my guess on how it would play out.
273ci thoughts?
- Thread starter papabear
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True its my guess on how it would play out.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Noise, Vibration, and Harshness
pishta
I know I'm right....
Graphs and data from 1967 Dodge (USA) Dart 270-Custom Hardtop full range specs
Lots of comparisons and metric heavy graphs.
318-2 edges out 273-4 from raw data. 273-4 pulls ahead after 100MPH due to higher revving potential of 273-4 cam profile and solid lifters.
(SORRY, DATA DID NOT SHOW UP IN GRAPHS)
Fun fact, 273-4 had a higher top speed due to camshaft profile and higher solid lifter RPM potential. Simulation says 68 318-2 would beat 67 273-4 by 21 feet at 1/4 mile with a slower MPH but faster ET.
Looks like both 2bbls run out of cam at 4200
Lots of comparisons and metric heavy graphs.
318-2 edges out 273-4 from raw data. 273-4 pulls ahead after 100MPH due to higher revving potential of 273-4 cam profile and solid lifters.
(SORRY, DATA DID NOT SHOW UP IN GRAPHS)
Fun fact, 273-4 had a higher top speed due to camshaft profile and higher solid lifter RPM potential. Simulation says 68 318-2 would beat 67 273-4 by 21 feet at 1/4 mile with a slower MPH but faster ET.
Looks like both 2bbls run out of cam at 4200
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@pista
Oh no! You did it now!
Oh no! You did it now!
JDMopar
Well-Known Member
I suppose someone with some $$$$$ to experiment could always build a stroker 273 with a 4" crank. Wait....where'd I put that pot stirring smiley? 
336 cubic inches. lol a tractor engine lolI suppose someone with some $$$$$ to experiment could always build a stroker 273 with a 4" crank. Wait....where'd I put that pot stirring smiley?
What do you call powerhouse? 12 second quarters? 10 second quarters? 140 mph + in the top end? Ability to burn rubber through 1st and 2nd gear? I have had a High Performance 273 for 45 years. There is a guy down under running one in a vintage road race early Barracuda running about 470 hp. It dynoed at over 500 hp. You guys always assume drag race to the max. I did not get that from the OP. He does not need anything but a cam and valve spring change, a 4 barrel and intake for what he wants. I know more than most of you what drag racing is. Once you start down that road, if you are really serious, it never ends. The OP sounded like he wanted a nice relatively fast car that he could drive and enjoy. Don't worry, he is probably long gone. As for 273's and 360's I have driven both. There is no way a stock HP 360 would take my 273, which was not stock. I looked at buying a new car in the mid 70's with A HP 360. I ended up keeping the 64 Barracuda and 273 since it was faster. Instead I got the seats reupholstered in leather.
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Too bad it does not work out that way in real life.
I have one in my 68 Correct Craft Barracuda. 318 Marine 4 barrel 225 hp.
True! All subjective!
Any basic upgrades (without creating a wacko out of balance combo) are normally a fine addition that will make the engine and owner really happy. I love these kinds of basic upgrades and a simple street machine.
No doubt!
You for surely picked up the right car.
Actually, it does, sort of... driver dependent is the first issue and then there is the possible issue of chassis or traction deficiencies. I say this often, “To bad I’m not a multi millionaire!” Just build stuff just to have fun and test and destroy and rebuild and test again with engine vs engine shoot outs. Like a combo of Richard Holdner, engine masters, road kill, top gear mixed with idiots delight. I guess I better start playing lotto for a change huh?!?! It would make for a awesome you tube channel.
LMAO!!!
pishta
I know I'm right....
Well played. I didn't think of the marine apps. Stump pulling cam with a flat torque curve. Gobs more torque where its needed in a boat, down low.
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Nice and fat through the mid 4,600 rpm, not as low as one would think. Pretty sure they wanted them to run on regular gas also. Still sounds sweet through straight dual 3 in exhaust. It will do over 50 mph on the water and pull up 3 skiers at a time. And do it all day long at that RPM.
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No, I never really had money till later in life. I think you are doing good. Yes, that was pretty much what that 64 Barracuda was. I'd love to have home movies of all the crazy stuff we did. Put the rebuilt shortblock in the car by hand. My buddy Irwin and I. Can't remember how we did it. Then built it up from there. Definitely a test mule. I was a 273 2 barrel for about a month. I bought it after I checked to be sure I could get a bunch of aftermarket goodies for it. Some worked great, others not so much, like one inner fenderwell cut for Kustom headers. When I installed one side, it came right back off and the decision to run manifolds was made. After I had thrown away the originals, of course. Back to the Chrysler Dealer to order new ones. After the last big collision it took a year to strip it and let it go. My brothers 67 Barracuda pretty much the same, to a lesser degree since he drove it anywhere, everywhere, all the time.
The part that has the biggest effect on HP is the cylinder head and because of the small bore, big valve heads will not work. The intakes would contact the block unless you grind relief notches in the deck. Keep the 273 what it is. Any 4 bbl 318, 360, 5.9, or 5.7 will far out perform the 273 and have unlimited parts available.
True but we don't know how much actual effect the bore size will have on flow. Haven't seen anyone do flow numbers a 318 bore nevermind 273. Did see one article on 350 vs 305 bore sizes on some Chevy cylinder heads and there was like a 10 cfm difference. I know 305 has a bigger bore than 273.
To get 400hp out of 318/340/360 the formula seems to be 200-220 cfm heads 10:1 cr and a 285 ish cam. With a 273 probably got to add another 20 cfm. The main problem for some would be at 400 hp you would need to turn the 273 around 7000 rpm.
If I was gonna build a 273 between 250-400hp I'd go with mild ported stock valve size magnum heads on a notched block with some 4.??:1 gears out back.
Ugh! You just reminded me in the head flow numbers I forgot to post up on with the flow rates from two different bore sizes. Bore size has a direct impact on HP.
Think your calculations on a 400HP 318/340/360 are good though a bit general however broadly covering the bases. Less cam and head flow can do it but I wouldn’t cut to much out of ether.
Now let me go find those flow numbers dam it!
66f’s was who I told I get them for and I’m sure someone still remembers that and is waiting just to see.
Bighead440
Well-Known Member
I suppose someone with some $$$$$ to experiment could always build a stroker 273 with a 4" crank. Wait....where'd I put that pot stirring smiley?
I know (Chevy) guy that built a stroker 305 (400 crank, 3.75" stroke), I kid you not. I asked him why and he said "gas mileage." Had to buy crazy $$$ dished pistons to keep the compression pump gas with the tiny chamber 305 heads. If I'm not mistaken he used some hind of "305 Torquer" World Product heads from the '80s. A good deal on those heads probably was the catalyst for the whole build. I would have just built a 307 (3.25" stroke, basically Chevy's 318).
ir3333
Well-Known Member
NVH.....Noise, Vibration, and Harshness
that's why the 2.94 gear set is so wonderful..no harmonicss, vibration, noise or harshness at hwy speeds
and why the increased torque from a 360 works well with them
that's why the 2.94 gear set is so wonderful..no harmonicss, vibration, noise or harshness at hwy speeds
and why the increased torque from a 360 works well with them
Seems to me a over use of theory, I never get the over focus on fuel mileage especially on a summer toy, you almost never recoup the cost, it's almost always cheaper to dump the extra $$$ into the gas tank.
JDMopar
Well-Known Member
LOL.....spending a dollar to save a Nickle!
Won't agree on the giving up on the 273, the reality is flow through the heads. When I first got the Barracuda I was at the local Chrysler Plymouth Dealer and they had a Petty Enterprises list of available motors and their specs. I remembered that there was little difference in horsepower between 273, 318, and 340. The only thing that changed was the rpm level they ran. Super Stock guys flow heads and carbs especially back in the day. That will give you a clue. Money is no object for them compared to most of us. They just have to live at that rpm. That is where the decisions are made. Valve train becomes critical. All the rest is adjusted to maximize 1/4 mile time. That is where the 273 becomes more costly, but it is the higher rpm that makes it great for me. In real life, the 1.88 J heads, early A body exhaust, manifolds and 7,000 rpm are as far as I will go on a 273 or any motor in my 66 Formula S. Since I'm running a small motor, I don't need as big a cam with those heads, so it is very streetable. And the top end is faster than I would run anymore, except in the midwest where you can see for miles. Nothing will perform any better until you go past what my 1.88 J heads will flow no matter how big your engine is. That was what "273" was trying to say, I believe. Hemi's are a totally different ball game for more reasons and should not be compared to wedge heads. I have run and still have 340's and 383's why would I stay with a 273??? I still have to laugh that you guys are still talking drag racing... You keep answering a question that was never asked...
What year was that Petty Enterprises motor list in ? 273-318-340 ? All the same year ?
Bighead440
Well-Known Member
Sounds like 1968-up. Weren't they all offered 1968 and 9? 1969 was the last 273, right? I think those even had hydraulic lifters and the 318-2bbl cam.
papabear
Mopar Noob
Well, that was fun to read...now back to where this topic has morphed - building this 318.
I have a 318 with 675 casting heads. I tore it down and the block seems good, no bore taper, only one questionable area on cylinder 3. Mains are 10 over, but rods seem to all be stock size and measured consistently and not out of round.
I also have a running 273 that I pulled on Saturday. Ideally, I leave this thing complete and stash it away to remain untouched for the car in the future.
From these parts, what is my optimal build here?
Desires:
318 street build - fun driver
Plan:
Vat/clean block - remove ring ridge and hone cylinders
Disassemble/clean/inspect heads for damage
Port 675 heads at home
Valve job at home
Edelbrock 2176 dual plane
Hughes Whiplash Cam and supporting parts from Hughes
New bearings/gaskets
Unknowns/Still left to decide:
Compression ratio - which pistons to use? Which head gasket to use?
Carb - Thinking we gonna be around 650 cfm?
Exhaust - car currently has 2" true duals...going headers I would imagine, which ones for 67 Dart?
Thanks
I have a 318 with 675 casting heads. I tore it down and the block seems good, no bore taper, only one questionable area on cylinder 3. Mains are 10 over, but rods seem to all be stock size and measured consistently and not out of round.
I also have a running 273 that I pulled on Saturday. Ideally, I leave this thing complete and stash it away to remain untouched for the car in the future.
From these parts, what is my optimal build here?
Desires:
318 street build - fun driver
Plan:
Vat/clean block - remove ring ridge and hone cylinders
Disassemble/clean/inspect heads for damage
Port 675 heads at home
Valve job at home
Edelbrock 2176 dual plane
Hughes Whiplash Cam and supporting parts from Hughes
New bearings/gaskets
Unknowns/Still left to decide:
Compression ratio - which pistons to use? Which head gasket to use?
Carb - Thinking we gonna be around 650 cfm?
Exhaust - car currently has 2" true duals...going headers I would imagine, which ones for 67 Dart?
Thanks
I would narrow down cam choice and go with a compression ratio thats suits that cam, pick 3 or 4 cams to start and get peoples feed back.
plus what rear gears and stall level are you willing to run?
I know this ain't a drag car but it helps to know what level of performance your shooting for eg like 90's 5.0l mustang/ 73 340 duster 15 flat ish or like 70-71 340 4 speed duster etc..
plus have you read 318willrun low dollar 318 build, probably something similar to your wants.
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