273 or NOT 273?
- Thread starter 67_Slimer
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I've definitely been up staged
The 273-4 puts out 5 more horsepower than a 318 but at 800 more rpm. Now, the 318-2 put's out 80 more ft/lb of torque at only 2400 rpm. The 273-4 put's out it's max. torque at 4000 rpm.
| 1967 283 V8 | 2 barrel | 4 barrel |
|---|---|---|
| Gross hp (Valiant) | 180 @ 4,200 | 235 @ 5,200 |
| Torque (Valiant) | 260 @ 1,600 | 260 @ 4,000 |
| Bore and Stroke | 3.63 x 3.31 | 3.63 x 3.31 |
| Compression Ratio :1 | 8.8 | 10.5 |
| USA specifications | 273 V8 | 318 V8 (LA) | 340 V8 |
|---|---|---|---|
| Gross horsepower, 1968 (1962 for 318-A) | 190 @ 4400 | 230 @ 4400 | 275 @ 5000 |
| Torque, lbs.-ft. , 1968 | 260 @ 2000 | 340 @ 2400 | 340 @ 3200 |
| Compression ratio, 1968 | 9.0 to 1 | 9.2 to 1 | 10.5 to 1 |
| Bore, inches | 3.63 | 3.91 | 4.04 |
| Stroke, inches | 3.312 | 3.312 | 3.312 |
| Carburetor type (1968-73) | 2-bbl. | 2-bbl. | 4-bbl. |
| Fuel | Regular | Regular | Premium |
I think most think those factory numbers are kind of out there some.... 340 vs 318... 22 more cubes, 4bbl vs 2bbl ?, better compression, hotter cam, better heads, and only 45 hp?
Beams
Well-Known Member
@67_Slimer I’ll trade you my 273 for your 340. It’s a 1967, so very proper.
340 being a preformance engine, when the insurance companies were jabbin people driving those cars, Mopar downrated the power. Like the 426 Hemi, what was it rated, 425 horsepower? Ya, right. That was at low rpm too.I think most think those factory numbers are kind of out there some.... 340 vs 318... 22 more cubes, 4bbl vs 2bbl ?, better compression, hotter cam, better heads, and only 45 hp?
I have to be honest. When I read "street", "12:1 compression", and "4.56 gears" I had to laugh. There is nothing street about either of them, let alone both. You would be building a race car to drive on the street. The good thing is there are no rules on the street. I, like you, do love high winding small blocks better than anything, and I have anything in the shop except for a /6 or a 2nd gen Hemi. To me the "street" limiting factors are the valve train at 6,500 to 7,000 rpm, compression ratio about 9.0:1 to run pump gas, factory exhaust manifolds, and gears to run 75 to 80 mph all day long. I'll be building a "cheapie" 273 build to replace the 273 Commando in the 66 so I can run 91 to 93 octane gas. But that is me. Good luck and keep us posted.
Newbomb Turk
Well-Known Member
Amazingly enough I had 4.56’s and 11.75:1 and my engine was very streetable.
This time it’s 12:1 or a skosh more (I have to measure it) and 4.88’s.
My wife could drive the former and I’m betting she can drive it with this iteration. And she’s not into cars like that.
Oh yeah, this engine will have a tunnel ram.
And it’s a STREET car.
Don't put "Street Car" in a box. Anything goes whether it's practical or not.
Sure it's a street car! It's driving on the street asd it's not on the trailer.
67_Slimer
Real Hot Rods don't shift themselves.
No , I'm sorry but my 340 is special to me.
67_Slimer
Real Hot Rods don't shift themselves.
Call it whatever you want but it's registered , insured , lights work , directionals work , wipers work , full interior. I drive it to every show , cruise night , we take it out on our date nights. runs on pump gas (11/1) . So I rev a little with 4.56s , big deal. It's a street car. I also take it to work.
LOL, I have no doubt. My friends parents drove a SS Ford Galaxy with a 427 side oiler, 4 speed, factory fiberglass fenders, teardrop hood and trunk lid. It was their only car, and his, 110 lb, mother drove it all the time, and she could make it go... But that was the 60's. They drove it on the street, but lets face it, it was not a street car. 1964 Ford Galaxie 500 Fastback Lightweight I've also seen SS cars trailered in a few blocks away and street raced like they were street cars also. What fuel are you running? Believe me, I don't doubt you, but I think you are out of a lot of our league with parts, experience and money. I'm also sure that your car was not cheap to build. It matters not to me if you run your car on the street, it is nowhere near what I would consider a street car.
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Well then, you will have no problem building a 12/11 second 273. I had 4.10's in my 64 Barracuda for about a month. Not my cup of tea, no traction and not fast enough at the top end.
The hp numbers for the 318 are inflated, my 318 marine 4 barrel with a bigger cam is only 225 hp. My cousin thought the same, until we raced. The 318 got the jump, but my 273 passed him like he was standing still. Horse Power is in the heads, all things being equal. Cubic inch dictates what rpm it takes to get that horsepower. Engines have an rpm limit they can safely run. The only difference in price building a 273 and a 318 is pistons. What is the big deal? At least you can get decent 318 pistons now.
Dan the man
Well-Known Member
A 4 barrel was added to the 318 as you stated. The 4 barrel 273 has more compression than the 318 does, also the 273 4 barrel has a bigger cam. If the 373 and the 318 you spoke of both had the same compression ratio and cam, I'm sure that the out come would've been very different.
Dan the man
Well-Known Member
I over looked the part about your 318 also having a bigger cam. Horsepower is in the heads, if your 318 doesn't have anything done to the heads then that's why you are not getting the full benefit of the 4 barrel and the cam.
Digging another hole, turning another thread into a DTM thread, He already explained it to you.
How does this help the OP in anyway?
Dan the man
Well-Known Member
If he wants to build the 273 as a challenge, I don't see anything wrong with that. But in my opinion I think that he would be money ahead by going with a 318. The 318 has 45 more cubic inches, better bore to stroke ratio and the bigger bore of the 318 will make for better breathing and rpm's
Dan the man
Well-Known Member
The OP choice is between a 340 he has or a 273, so your 318 recommendation is counterproductive unless you think it’s a better option to a 340 ?
No doubt about it displacement has it's advantages, but if you don't overly care about those advantages then they don't really matter. I wouldn't fault the OP in the end to decide to build the 340 or even a stroker. But the 273 is capable to reach his goals if he does choose to go that way no need for some to over sale the 273 short comings.
Dan the man
Well-Known Member
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