273/4 -318 debate

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Both in 100% stock form...…. will a 225 slant in a Duster beat a 440 in a motor home??
:D
 
318willrun said:
Both in 100% stock form...…. will a 225 slant in a Duster beat a 440 in a motor home??
:D
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Shortbus type motorhome (built on the 3/4 ton van chassis) or the massive M400/M500 Chassis land battleships (the 40-60’ monsters)?

I’ve driven an M400 Chassis battleship motorhome with a 440 and I can say this... you could take 3 spark plugs out of the 225 Duster and it would still beat the motorhome. Yes the 440 gets up to speed, but granny on her mobile scooter is going to hit 60mph minutes before you do.
 
My Commando wasn't a dog, it was a bone stock 273-4 auto with nothing added. 20 year garaged survivor. Could smoke the tires through an intersection and the power kept coming all the way to the miserable factory tachs 6000 rpm. I spun a rod bearing 3 months after I got it and it was faster for me to move everything over to a $100 68 318 short block from a wrecking yard than to get the crank turned (I didnt know what was wrong with it until I tore it down later). Put all the 4bbl stuff on that 318 (minus the intake I cracked so I put a Performer on it) and it made that still lower compression 318 way quicker than the 273-4 ever was. That got me looking at published numbers and lo and behold in 68, the 318-2 was rated at 230HP (how? because that year they measured it off the crank, no the rear wheels) , 5 shy of the 273-4 and ~25% more torque. WTH? When I see builds of 273-4's with new $$ Egge pistons, E-4 cams, Performer intakes...I gotta ask why and that was the basis for this great debate. There is nothing 4bbl left in these new builds except the stock intake and maybe the #s AFB. Both too small for the motor. For power, Ford guys dont build 260's, Chevy guys dont build 283's because both are simply so much better for 99% of applications in their larger bore higher torque cheaper to build forms. If your going to build a 273/318 for torque, build a 318. If your going to build one for 5 more published horsepower at another 1000 RPM but far less torque in street range, build a 273-4. I know what I will do. Heck, Im building almost a zero deck 273-2 right now because I have one on hand. Fact is a 318 would be better in this app again as it has lower compression for a turbo. Let it ride.....
 
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pishta said:
My Commando wasn't a dog, it was a bone stock 273-4 auto with nothing added. 20 year garaged survivor. Could smoke the tires through an intersection and the power kept coming all the way to the miserable factory tachs 6000 rpm. I spun a rod bearing 3 months after I got it and it was faster for me to move everything over to a $100 68 318 short block from a wrecking yard than to get the crank turned (I didnt know what was wrong with it until I tore it down later). Put all the 4bbl stuff on that 318 (minus the intake I cracked so I put a Performer on it) and it made that still lower compression 318 way quicker than the 273-4 ever was. That got me looking at published numbers and lo and behold in 68, the 318-2 was rated at 230HP (how? because that year they measured it off the crank, no the rear wheels) , 5 shy of the 273-4 and ~25% more torque. WTH? When I see builds of 273-4's with new $$ Egge pistons, E-4 cams, Performer intakes...I gotta ask why and that was the basis for this great debate. There is nothing 4bbl left in these new builds except the stock intake and maybe the #s AFB. Both too small for the motor. For power, Ford guys dont build 260's, Chevy guys dont build 283's because both are simply so much better for 99% of applications in their larger bore higher torque cheaper to build forms. If your going to build a 273/318 for torque, build a 318. If your going to build one for 5 more published horsepower at another 1000 RPM but far less torque in street range, build a 273-4. I know what I will do. Heck, Im building almost a zero deck 273-2 right now because I have one on hand. Fact is a 318 would be better in this app again as it has lower compression for a turbo. Let it ride.....
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That's why we built 273 4 barrels. Had all the good stuff to begin with + higher usable rpm, no good pistons for 318. My 273 was still faster. The 2 barrel 318 engine did not make 230 hp.
 
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IIRC the 235hp 273 was derated to 210 hp by NHRA.
70-74 Dodge truck.....still legit after net HP ratings took effect?
h-dd268_20180412070407.jpg
 
you plug a 65 "S" 4sp 15.4 ET and 3000 lbs into an ET calculator and you get ~163 HP at the wheels. 904 was 16.0 ET , -25 parasitic HP, whats a water pump and an alternator worth, SG rear end? Where did 70 HP go? Sometimes numbers don't add up if one variable is grossly incorrect. check this article out from a mag that actually did dyno runs on classic muscle cars..
“Rear wheel horsepower was at least 30 percent lower than the reported gross figure, in some cases even more,” Campisano said. Some Super Chevy readers must have been stunned to see that an LS6 Chevelle SS, with 450-hp rating, put down 288 rear wheel hp in the dyno test. That would have put a net hp rating at around 350 hp for that legendary big block...The mighty Chrysler 426 cu. in. Hemi kept its high compression and 425 hp gross rating for 1971 and showed 350 net hp."
Muscle Car Horsepower – How Exaggerated Was It? | Hagerty Articles
 
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AJ/FormS said:
You know it but the page don't say it.
I'm not arguing specs from a different page, I'm calling bs on the page in Post #65. If you never saw any other information than that in #65,you would get a hopelessly wrong picture of Mopar comparative horsepowers.
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It looks to me like some of those ratings are pre 72, and some post 72. In 1972, hp rating went from gross to net. Also, compression ratings were reduced on most high performance engines.
 
pishta said:
My Commando wasn't a dog, it was a bone stock 273-4 auto with nothing added. 20 year garaged survivor. Could smoke the tires through an intersection and the power kept coming all the way to the miserable factory tachs 6000 rpm. I spun a rod bearing 3 months after I got it and it was faster for me to move everything over to a $100 68 318 short block from a wrecking yard than to get the crank turned (I didnt know what was wrong with it until I tore it down later). Put all the 4bbl stuff on that 318 (minus the intake I cracked so I put a Performer on it) and it made that still lower compression 318 way quicker than the 273-4 ever was. That got me looking at published numbers and lo and behold in 68, the 318-2 was rated at 230HP (how? because that year they measured it off the crank, no the rear wheels) , 5 shy of the 273-4 and ~25% more torque. WTH? When I see builds of 273-4's with new $$ Egge pistons, E-4 cams, Performer intakes...I gotta ask why and that was the basis for this great debate. There is nothing 4bbl left in these new builds except the stock intake and maybe the #s AFB. Both too small for the motor. For power, Ford guys dont build 260's, Chevy guys dont build 283's because both are simply so much better for 99% of applications in their larger bore higher torque cheaper to build forms. If your going to build a 273/318 for torque, build a 318. If your going to build one for 5 more published horsepower at another 1000 RPM but far less torque in street range, build a 273-4. I know what I will do. Heck, Im building almost a zero deck 273-2 right now because I have one on hand. Fact is a 318 would be better in this app again as it has lower compression for a turbo. Let it ride.....
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Comparing 2 vastly different displacement is not an apples to apples comparison. Gear ratio has a huge effect on your engines ability most cars are way under geared for max acceleration. And smaller the engine more so. To put a 273 and 318 on the same footing a 273 would need around .5 - .75 to 1 more gear over the 318.

The main problem with the 273 isn't necessarily its small displacement.
Which is only a hindrance if your don't like deep gears high stall and race car idle.
But more so its small bore which limits valve size which limits air flow and limits max ability. 318/360/340 all have bore sizes that can easily make 600 plus hp. 273 bore it would be tricky to do so.

But I do agree most would be miles ahead with a 318 over a 273.
 
Hyup there is so much confusion, deliberate obfuscation, and perhaps outright lies, in the horsepower ratings,wars, and factory dyno's, that IDK, it's enough to make a guy cry.
Like others have said, let the track tell the truth; mph don't lie.
And don't even get started on shipping weights. IMO, the factory wasn't stupid. They knew doggone well the power numbers were out to lunch. And they knew racers weren't stupid either and would figure out real quick what was going on. And so the only way to reconcile the track results to the advertised power was to fudge the shipping weights, and make the insurance companies happy.
I wasn't in the board room so I have no idea what they did or didn't do, but I ain't stupid either, I took just enough physics in highschool to know bs when I see it. I think.lol.
I got "lucky" in 1970. That was the year Manitoba switched from private insurance to a government regulated insurance. I had just purchased a slightly used Swinger 340. Private insurance at the time IIRC wanted well over $1000 to insure it (I seem to remember in the $1200s actually), which for a grade 10 gas-jockey making like a buck-thirty-five an hour, was a lot of cash in 1970. They said with a 340 manual trans,it was racecar, and I was a high-risk teenager. Along comes the new MPIC, (Manitoba Public Insurance Company) and I think it was under $500. Hyup I insured my racecar for sub $500. Screw private insurance I said.
Yeah so I didn't report it when I banged it up a little now and then. I had no idea that 48 years later that car would be worth a fortune. By the time I was done with it, 4 years later it was worth about half of what I paid; Yeah she was beat-up pretty bad. And on; second engine, second trans, second rear gear, third or fourth clutch, and 7 sets of rear tires passed under her; man she was hard on tires!,lol. It came with a flat-black twin-scooped hood and a factory rear wing. FM3/PantherPink too.
 
My 1968 318 marine is rated at 225 hp, with a 4 barrel, cam, mechanical advance Distributor, and low compression pistons. I will never believe the 230 hp 2 barrel numbers. Besides, I have actually raced a 318 2 barrel in an A Body with a 66 Barracuda 4 speed, stock 273 Commando and know who won. If you want to race benches or computers, I’m not interested.
 
66fs said:
My 1968 318 marine is rated at 225 hp, with a 4 barrel, cam, mechanical advance Distributor, and low compression pistons. I will never believe the 230 hp 2 barrel numbers. Besides, I have actually raced a 318 2 barrel in an A Body with a 66 Barracuda 4 speed, stock 273 Commando and know who won. If you want to race benches or computers, I’m not interested.
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You lost me; at what rpm is your 225-Marine rated at?
 
Gross hp numbers are worthless. 318 specs didn't change much over the years until the magnum. Theres a dyno of a stock 70's 318 with headers and it only dyno a gross 175 hp. They added a 4bbl and xe262h and got 282hp showing the 318 responds well to a cam. Since a 67 2bbl 318 and 273 are identical besides pistons and bore. Imagine there real hp numbers are fairly identical. And the commado has more cr carb cam and probably gear can't see it being the losser between the two.
 
pishta said:
I spun a rod bearing 3 months after I got it and it was faster for me to move everything over to a $100 68 318 short block from a wrecking yard than to get the crank turned (I didnt know what was wrong with it until I tore it down later). Put all the 4bbl stuff on that 318 (minus the intake I cracked so I put a Performer on it) and it made that still lower compression 318 way quicker than the 273-4 ever was. That got me looking at published numbers and lo and behold in 68, the 318-2 was rated at 230HP (how? because that year they measured it off the crank, no the rear wheels) , 5 shy of the 273-4 and ~25% more torque. WTH? When I see builds of 273-4's with new $$ Egge pistons, E-4 cams, Performer intakes...I gotta ask why and that was the basis for this great debate. There is nothing 4bbl left in these new builds except the stock intake and maybe the #s AFB. Both too small for the motor. For power, Ford guys dont build 260's, Chevy guys dont build 283's because both are simply so much better for 99% of applications in their larger bore higher torque cheaper to build forms. If your going to build a 273/318 for torque, build a 318. If your going to build one for 5 more published horsepower at another 1000 RPM but far less torque in street range, build a 273-4. I know what I will do. Heck, Im building almost a zero deck 273-2 right now because I have one on hand. Fact is a 318 would be better in this app again as it has lower compression for a turbo. Let it ride.....
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Just one thing to throw into this Pishta, if it has not been mentioned...I have not followed this thread much ...

Per a direct report on this forum of compression height measurements of some factory pistons from an early 318..... the CH in the early 318's was a lot higher than for a post '71 or '72 318. Those early 318 pistons reportedly were nearly zero deck. So that is a big reason for what you experienced and may be part of the early HP/torque numbers.... those early 318's apparently were higher CR. When you swapped your 273 4BBL parts onto a '68 318, you were putting them on a higher CR block than the smog era 318's (post 1971).

After seeing that thread post, I went and measured CH on my '68 2 BBL 273 pistons, and low and behold.... those pistons were also near or zero deck. CH is 1.828" on those lowly 2BBL 273 pistons.

So I guess this thread has to start all over now LOL
 
273 said:
Gross hp numbers are worthless. 318 specs didn't change much over the years until the magnum. Theres a dyno of a stock 70's 318 with headers and it only dyno a gross 175 hp. They added a 4bbl and xe262h and got 282hp showing the 318 responds well to a cam. Since a 67 2bbl 318 and 273 are identical besides pistons and bore. Imagine there real hp numbers are fairly identical. And the commado has more cr carb cam and probably gear can't see it being the losser between the two.
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I agree with you there. The factories numbers can't be trusted so until someone has dyno numbers for both engines off the same dyno with both original stock engines, there's no definitive answer. I wouldn't trust drag strip time slips much. Unless you could run one engine in a car and swap it out the same day for the other and run that. Then it would be fairly accurate. Unless the weather changes. :BangHead::BangHead:
 
nm9stheham said:
I went and measured CH on my '68 2 BBL 273 pistons, and low and behold.... those pistons were also near or zero deck. CH is 1.828" on those lowly 2BBL 273 pistons..
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The 64 2bbl I have is almost zero deck itself. I chose a 67 318 (it was a 67, as I remembered the snout size issue) as it had the same snout bore as the 273. My mistake back in the original post.
 
My 273 with a .400 lift cam has gone 12.20s and its slow for my class, 4 bbl much faster than 2 even given the extra cubic inches.
 
ValiantRacing said:
My 273 with a .400 lift cam has gone 12.20s and its slow for my class, 4 bbl much faster than 2 even given the extra cubic inches.
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is it quicker to 60? Thinking Chrysler was making a street car motor instead of a 1/4 miler. Look where the torque peaks. Were still talking stock motors here with an emphasis on what you could build with similar 'hop up' variables.
 
you know; we can always fall back on the NHRA factors. They give us a horsepower factor, and the blueprint to get there.
They give us;
67.... 273 2bbl@180hp with ; 9.5Scr, 57.3cc heads, -.011 decks, .028 gasket
67.... 273 4bbl@235hp with; 11.5Scr, 57.3cc heads, +.129decks, .028 gasket
67/69 318s not spec'd with. ; 9.5Scr, 57.3cc heads, close to zero decks.......
78/80 318 4bbl@230hp with; 9.0Scr, 65.5cc heads,, -.041 decks, .030 gasket
71.... 340 4bbl@330hp with; 11.0Scr, 63.3cc heads, +.045decks, .028 gasket
72/73 340 4bbl@275hp with; 9.3Scr, 64.7cc heads,, -.054 decks, .036 gasket
74/76 360 4bbl@300hp with; 9.0Scr, 64.7cc heads,, -.067 decks, .032 gasket
78/80 360-4bbl@250/265 w/; 8.6Scr,68.4cc heads,, -.067 decks, .030 gasket
My Bulletin Book does not show the early Hi-compression 318s
 
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AJ/FormS said:
you know; we can always fall back on the NHRA factors. They give us a horsepower factor, and the blueprint to get there.
They give us;
67.... 273 2bbl@180hp with; 9.5Scr, 57.3cc heads, -.011 decks, and .028 gaskets
67.... 273 4bbl@235hp with; 11.5Scr, 57.3cc heads, +.129decks, and .028 gaskets
67/69 318s not spec'd with. ; 9.5Scr, 57.3cc heads, close to zero decks.................
78/80 318 4bbl@230hp with; 9.0Scr, 65.5cc heads,, -.041 decks, and .030 gaskets
71.... 340 4bbl@330hp with; 11.0Scr, 63.3cc heads, +.045decks, and .028 gaskets
72/73 340 4bbl@275hp with; 9.3Scr, 64.7cc heads,, -.054 decks, and .036 gaskets
74/76 360 4bbl@300hp with; 9.0Scr, 64.7cc heads,, -.067 decks, and .032 gaskets
78/80 360-4bbl@250/265 w/; 8.6Scr,68.4cc heads,, -.067 decks, and .030 gaskets
My Bulletin Book does not show the early Hi-compression 318s
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Saturday morning laugh. Those specs are a bigger lie than the factory specs. Those maximum allowed compression specs?
 
67/69 318s not spec'd with. ; 9.5Scr, 57.3cc heads, close to zero decks.................
78/80 318 4bbl@230hp with; 9.0Scr, 65.5cc heads,, -.041 decks, and .030 gaskets
How did the Scr go down only .5 with a 15% larger cc and a lower piston?
Are those NHRA ratings or just specs? I thought they derated the 273-4 to 210
Man, that looks uh..... Drop a Performer and AFB on it and go.

EDIT>>> I think 66fs said those NHRA specs were max dimensions you could mill to and still be legal. No where close to what came off the line in an old thread. Goes back to foundation of thread of the claims of published 235 and 230 HPs.
 
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