easyrider
65 droptop
I've read a lot about 318, 340 and 360 motors being stroked. Has anyone ever stroked a 273? I guess you could buy a 360 for less than it would cost to stroke one, right?
Tom
Tom
273 question
- Thread starter easyrider
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Yep! I think a 4" stroke would get you around 327 cubes. The pistons would be the hardest to come by. They would have to be custom made.
Lonewolf3165
Living the Dream!
It wouldn't make sense to do it. 1st it's not cost effective. 2nd the small bore limits putting any kind of head with bigger valves in it that flow worth anything. You'd need more flow to feed the bigger displacement in order to make any kind of power. 3rd there would most likely be clearance issues with the crank journal &/or rods hitting the bottom of the bores. Smaller bore would have less than 340-360 does. 4th it would be so over square(bore dia. vs stroke) that it probably wouldn't rev very well at all.
Sorry to poop on your idea, but thats just the limitations of the motor.
360 would be the way to go. Espescially on a budget.
Sorry to poop on your idea, but thats just the limitations of the motor.
360 would be the way to go. Espescially on a budget.
65Val
Average Length Member
Righty-O...might as well just build a 360 and install all the 273 Hi-Po goodies....easier/cheaper in the long run!
chryslerfat
Well-Known Member
Hey at the least it would make people scratch their heads when you say you have a 350 Mopar.
There's an Australian Holden engine you can get Hypereutectic pistons for that give a pin height that can be used with a 360 crank and be around zero deck. They have Chevy's pins so you have to modify to use Chevy 6.125 rods to work. But a lot of trouble for a 302 mopar.
The Trans Am racers de-stroked 340's to 302's in 1970 and finished 4th.
They finished 2nd with a 273 Barracuda Formula S....
They finished 2nd with a 273 Barracuda Formula S....
The strengths of "64" to "67" 273's are solid cams, forged steel crankshafts, forged steel rods, and good heads for the size motor. They were never smog motors so 9.0:1 motors are pretty easy to get with standard 2 barrel pistons. They were mileage champs in class, won class in SCCA in 66, and can be made to run pretty fast since they are built so strong. To me it makes more sense to replace cranks and pistons in something that wasn't as good to start with, and get a bigger bore and better heads as a bonus.
I didn't know that one. Pretty interesting...
To be fair, in 70 they were running wide, heavy E-bodies against the other guys' pony cars. But the 273 is a great, well-balanced engine design -- it just doesn't scale up. The proof of that is the standard 318 -- more cubes with the same small valves and ports doesn't really do anything. But if you upgrade the heads, then you might as well go for a bigger bore, and so on.
Lonewolf3165
Living the Dream!
318 with 45 more cubes made 50 more horsepower than the 273.
When? Compared to a 273/2 barrel maybe. The HP 273 was rated at 235 horse. The 318 of the same era was rated at 230 horse. The torque was rated the same @ 260
yeah, to be fair, didn't they also run six packs on them e-bodies? Special hood scoops sealed to the hood for fresh air induction. Heads that were capable of being ported more than the 273 head...
It was more competition in 70, but ironic that the special edition Trans Am race cars from Mopar didn't do so hot after all of the special modifications that they did for them.
They were more successful in the early 2nd generation Barracuda Formula S 273 4 bbl cars.
rkite
Well-Known Member
A .03 over 273 with a 4" stroke is 336.67 cubes.
Thanks for the correction. My memory isn't what it used to be I guess. My dyno program won't run on Windows 7 and my old computer is buried in the basement so I can't program in a senario to check the cubes. tmm
I get 335.75 cubic inches for a .030" over 273 stroked 4.000".
B = 3.655 in
S = 4.000 in
Vol = (Pi/4) * (3.655 **2) * 4.000 = .7854 * 13.359 * 4.000 = 41.97 cubic inches per cylinder
41.97 * 8 = 335.75 cubic inches
easyrider
65 droptop
I know this was a silly question, but it did get some interesting answers.
Thanks FABO. I'm looking for a 360 that I can afford. Will let you know when it happens.
Tom
Thanks FABO. I'm looking for a 360 that I can afford. Will let you know when it happens.
Tom
Ok, so im gonna tag along if I may and ask 273 head questions....
Im thinking future plans, but with Dads 67 cuda. Heads are stock with new Comp springs.
New solid 270-s Comp cam
New dbl roller timing chain.
Std bore block I believe and stock pistons.
New Eddy 600 carb
I am thinking of doing my own porting/polishing/gasket matching. Is there anything else that I can do to them, or would/should they have to be sent out to be machined??
Im planning on doing the port/polish/gasket match myself.
Ideas??
Oh yeah low budget too....I dont want to get into the lower end....yet..
Thanks
Im thinking future plans, but with Dads 67 cuda. Heads are stock with new Comp springs.
New solid 270-s Comp cam
New dbl roller timing chain.
Std bore block I believe and stock pistons.
New Eddy 600 carb
I am thinking of doing my own porting/polishing/gasket matching. Is there anything else that I can do to them, or would/should they have to be sent out to be machined??
Im planning on doing the port/polish/gasket match myself.
Ideas??
Oh yeah low budget too....I dont want to get into the lower end....yet..
Thanks
rkite
Well-Known Member
Standard bore = 3.63 = Diameter
3.63 + .03 = 3.66 overbore = Diameter
Radius = Diameter / 2
Radius = 3.66 / 2 = 1.83
(Radius**2) * pi * height = volume of a cylinder
(1.83**2) * pi * 4 = 42.0835
42.0822 * 8 cylinders = 336.6681
That is the way I do it. Something I learned in math class eons ago.
It varies a little depending how far out you take pi etc.
3.63 + .03 = 3.66 overbore = Diameter
Radius = Diameter / 2
Radius = 3.66 / 2 = 1.83
(Radius**2) * pi * height = volume of a cylinder
(1.83**2) * pi * 4 = 42.0835
42.0822 * 8 cylinders = 336.6681
That is the way I do it. Something I learned in math class eons ago.
It varies a little depending how far out you take pi etc.
Our difference is in the bore.
I used the book at 3.655" and you used 3.660". There is where the difference dame from.
I take pi to 3.1416
Have the heads been milled? Do they hardened exhaust seats? Have you done a valve job? What Intake are you running?
Ok, I musta had a brain fart again last night, the cam is not an Eddy it is Comp 270-s
We went with complete cam lifter springs, from Comp
springs are 901-16, cam is 270-s solid, timing chain dbl roller from Comp, the carb is eddy.
When we installed all the new goodies, we didnt measure the bore, but pretty sure its std bore 2bbl pistons
heads are stock from a commando engine, (not sure if there is a difference) and I dont think any work at all has been done to them other than new springs. I believe this engine has approx 50 thousand miles.
Intake is stock 4bbl iron commando intake. Im still thinking of going LD4B, but that intake has no provision to mount the coil.
904 with I believe 2800 stall. Not sure how to tell.
Im not looking to go crazy with it, but just stuff that I could do in my shop to make it a little "healthier"
Thanks
Yep!
not a maybe, a fact. Apples to Apples: 273 2bbl vs 318 2bbl = 50 horse diff, and drive cars of equal weight and you will feel it in the seat of your pants, or the black mark laid on the highway.... Most 273 2bbl cars ran 17's, while my 318 2bbl auto and 2.94's in a b-body went 15.9's.
Head castings are the same between 2 barrel and Commando. If you are pulling the heads you may want to consider hard exhaust seats and milling the heads with a fresh valve job. I get different opinions on the hardened seats, still debating with myself on that one. If the Commando Intake is not modified, the secondaries will not open with the Edelbrock carb since they are larger than the stock Commando intake secondary bores. So I guess you should go with the LD4B, Performer, or Weiand. The Holley Street Dominator looks close to the Original Commando... Sounds like a nice build.
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