318 - 340 Same Torque??

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Topless69

Topless69

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Was just skimming thru old Hamtramck specs & options booklet for 69 Barracudas and noticed something unusual - the factory torque specs for the 318 and 340 are the same(!)
Both engines claim 340 ft lbs... and the 318 at 800 rpm lower with a 2bbl carb!! This can’t be right, can it?
I know factory claims for the 340 were fudged, and it’s possible this is a mistake or misprint, but I’m surprised no one at the factory caught it. Would anybody be able to shed some light on this?
 
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Most likely a misprint. My 1970 Engines manual shows 340 ft lbs for the 340 & 320 for the 318.

And figures for the 340 were far from fudged.....

PHR magazine tested the factory HP rating of the popular small block engines to see if they actually made the advertised HP. Results were published in Feb 69. The 340 was the only engine to do this & in fact made 20 hp more!! 295 hp v 275 adv. No other engine made the adv hp. Here are the numbers, numbers in brackets are the actual hp made.
Olds 350 W-31 325 [ 280 ]
Pont 350 H-O 325 [ 255 ]
Chebby 350 300 [ 240 ]
Ferd 351 290 [ 210 ]

Amen...
 
Bewy said:
Most likely a misprint. My 1970 Engines manual shows 340 ft lbs for the 340 & 320 for the 318.

And figures for the 340 were far from fudged.....

PHR magazine tested the factory HP rating of the popular small block engines to see if they actually made the advertised HP. Results were published in Feb 69. The 340 was the only engine to do this & in fact made 20 hp more!! 295 hp v 275 adv. No other engine made the adv hp. Here are the numbers, numbers in brackets are the actual hp made.
Olds 350 W-31 325 [ 280 ]
Pont 350 H-O 325 [ 255 ]
Chebby 350 300 [ 240 ]
Ferd 351 290 [ 210 ]

Amen...
Click to expand...

Yes, but I assume you’re aware fudging works in both directions - What I meant was Ma fudged the numbers on the LOW side.
You never had someone tell you they had ‘a little’ work done on their engine, only to open the hood and find they’d done major performance mods?
Pretty common, especially if one is challenging the other to a race...
 
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Truth on Fudging. Mopar was always on the low side.At the time insurance companies were charging higher rates for high HP cars.Also if a car was a 4 speed.I bought a new 340 "3" speed manual Duster. The insurance was less than if it was a 4 speed.Mopar made many 3 speed HP cars during the 70's though rare to find today.
 
Darter6 said:
Truth on Fudging. Mopar was always on the low side.At the time insurance companies were charging higher rates for high HP cars.Also if a car was a 4 speed.I bought a new 340 "3" speed manual Duster. The insurance was less than if it was a 4 speed.Mopar made many 3 speed HP cars during the 70's though rare to find today.
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True, I know of a 1970 Road Runner convertible that has a 383 4 bbl, and a 3 speed manual. Apparently it is one of 13 built that way.
 
It may be advantageous for manufacturers to advertise more power for their base engines, 225 and 318 for instance. But advantageous to advertise their performance engines lower to help out the racers, Hemi,440, 340.

Note that a 340 is listed as 275 hp at 5000. Maybe true, but how much at 5500? 295? Same for the 426 Hemi, 425 at 5000.
Note the heading says horsepower, not MAX HP.
 
From Alpar

I could see where the torque numbers could be the same. It comes in at different rpm and the 340 produces more horsepower. Only 22 cubic inches difference between the two.


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It's a misprint because I remember the first time I punched a 318 2bbl from a dead stop and she kicked the back end sideways I was pretty sure they have at least 380 ft lbs of torque.......



:lol:
 
look at a 273-4 and a 318-2 torque was way up on the 318 with more cubes but HP was still tops with the 273 but its where it came it at and where it was measured. You could cherry pick any point on a graph and publish it. That said, the 426 was rated at 425, but IIRC a dyno said the max HP was more like 470. Where do you think the 327/375HP was measured at? probably 6500......@Rustyratrod, Rob, you'd probably know the stats on that 327...?
 
The 273, 318 and 340 all have the same stroke so the torque curves will be near identical. The difference will be from bore size. Cam timing will move the peak around.
 
Topless69 said:
View attachment 1715669102 View attachment 1715669103 Was just skimming thru old Hamtramck specs & options booklet for 69 Barracudas and noticed something unusual - the factory torque specs for the 318 and 340 are the same(!)
Both engines claim 340 ft lbs... and the 318 at 800 rpm lower with a 2bbl carb!! This can’t be right, can it?
I know factory claims for the 340 were fudged, and it’s possible this is a mistake or misprint, but I’m surprised no one at the factory caught it. Would anybody be able to shed some light on this?
Click to expand...
Early 318 truck motors used to say the hp on the air cleaner , 215 or 230hp.

340 rated a hair less than actuality.
318 was spot on imo.
 
318willrun said:
It's a misprint because I remember the first time I punched a 318 2bbl from a dead stop and she kicked the back end sideways I was pretty sure they have at least 380 ft lbs of torque.......



:lol:
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:rofl::rofl:
 
Torque and RPM. 340's were high winders.RPM Teen not so much. The teens never did get credit the deserved.
 
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Darter6 said:
Torque and RPM 340's were high winders.RPM Teen not so much. The teens never did get credit the deserved.
Click to expand...
Like the 360's. Pretty much designed to be workhorses and not performance engines. The teen was pretty utilitarian. They put them in about everything and they just did their job without any complaints. (for hundreds of thousands of miles)
 
pishta said:
look at a 273-4 and a 318-2 torque was way up on the 318 with more cubes but HP was still tops with the 273 but its where it came it at and where it was measured. You could cherry pick any point on a graph and publish it. That said, the 426 was rated at 425, but IIRC a dyno said the max HP was more like 470. Where do you think the 327/375HP was measured at? probably 6500......@Rustyratrod, Rob, you'd probably know the stats on that 327...?
Click to expand...

I had a 1968 Barracuda with a 318-2, and I transplanted a 273-4 from my 1966 Barracuda into it. I ran the car at the drags with both combinations and they ran pretty much identical times. The 318 had more low end and the 273 had more top end.
 
Low rpm torque is directly related to TRAPPED pressure and SWEPT volume.
So yes it is totally possible for the EARLY 318 to make 340 at 2400 and the EARLY 340 to make 340 at 3200.
But there is no way for us to know if the 340 made more torque later in the powerband. Maybe Ma just pulled the 3200 number and knew the buyers would figure it out.

If you plug the appropriate stock-cam and Scr numbers into the Wallace calculator, you will find that a 9.2 318 actually compares very nicely to a 10.5 Scr 340 in the lower rpms. Engines with the same VP index will perform similarly below 3000-ish rpm . Keep your eyes on the Dcr numbers.
Here are the Wallace results;

First the 318
Static compression ratio of 9.2:1.
Ica of 48*
Effective stroke is 2.89 inches.
Your dynamic compression ratio is 8.15:1 .
Your dynamic cranking pressure is 167.57 PSI.
V/P (Volume to Pressure Index) is ........................ 140

Then the 340
Static compression ratio of 10.5:1.
Ica of 64*
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 8.37:1 .
Your dynamic cranking pressure is 173.49 PSI.
V/P (Volume to Pressure Index) is ............................. 137

Then the 360
Static compression ratio of 8.0:1.
Scr of 52*
Effective stroke is 3.02 inches.
Your dynamic compression ratio is 6.91:1 .
Your dynamic cranking pressure is 134.82 PSI.
V/P (Volume to Pressure Index) is ............................. 123

the smog 318
Static compression ratio of 8.0:1.
Ica of 48*
Effective stroke is 3.02 inches.
Your dynamic compression ratio is 6.91:1 .
Your dynamic cranking pressure is 134.82 PSI.
V/P (Volume to Pressure Index) is ............................. 123

A 360 with a little more compression
Static compression ratio of 8.7:1.
Ica of 54*
Effective stroke is 3.02 inches.
Your dynamic compression ratio is 7.50:1 .
Your dynamic cranking pressure is 150.26 PSI.
V/P (Volume to Pressure Index) is ............................ 137

the Commando 273; I don't recall the 273 cam specs, but here it is with a 52* Ica
Static compression ratio of 10.5:1
Ica of 52*
Effective stroke is 2.82 inches.
Your dynamic compression ratio is 9.08:1 .
Your dynamic cranking pressure is 192.80 PSI.
V/P (Volume to Pressure Index) is ............................ 135


Here is the 440 Magnum of 1968:
Static compression ratio of 10.5:1.
Ica of 72*
Effective stroke is 2.69 inches.
Your dynamic compression ratio is 7.81:1 .
Your dynamic cranking pressure is 158.48 PSI.
V/P (Volume to Pressure Index) is ............................. 150

Just for kicks, Here's my alloy headed 367;
Static compression ratio of 10.95:1.
Ica of 62* @ sealevel, like the others
Effective stroke is 2.84 inches.
Your dynamic compression ratio is 8.89:1 .
Your dynamic cranking pressure is 187.60 PSI.
V/P (Volume to Pressure Index) is .............................. 164
She burns E87 full-time, this, with a cam of
276/286/110+2 advertised; 230/237@.050

Some people say pressure is not a big deal for a streeter
here is the 340 cam in a smog teener
Static compression ratio of 7.8:1. A more true number with a composition headgasket
Ica of 64*
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 6.27:1 .
Your dynamic cranking pressure is 118.36 PSI.
V/P (Volume to Pressure Index) is ................................ 88
This VP is what a 225 slanty makes............ Do you really want that under your bonnet? Just try driving that with a stock 318 TC and 3.23s,
or worse, with a regular A833

Here's my opinion on VPs
123 is a Reasonable grocery-getter type number
135 is where Performance begins
140/145 are getting to be Tire-friers and Heap-Big-Fun
150 or more is overkill on the street, but it lets you run hiway gears and lo-stalls.
164 in my combo is batchit crazy; but it pulls nice controllable second gear slides without much rpm. (A833). If you combine this with a 224 *or less cam, it's pretty amazing what you can do with gearing; like run 65=1580rpm (overdrive and tall tires), and get phenomenal fuel-mileage. My Barracuda went 106@12.9 with a 223Cam, on it's one and only run with that cam, on street tires, spinning for a long long long ways out.

 
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qkcuda said:
I had a 1968 Barracuda with a 318-2, and I transplanted a 273-4 from my 1966 Barracuda into it. I ran the car at the drags with both combinations and they ran pretty much identical times. The 318 had more low end and the 273 had more top end.
Click to expand...
Been preaching that for years.....
 
318willrun said:
It's a misprint because I remember the first time I punched a 318 2bbl from a dead stop and she kicked the back end sideways I was pretty sure they have at least 380 ft lbs of torque.......



:lol:
Click to expand...

And prolly another 50-75 with a 318willrun sticker on the air cleaner right? LOL
 
A deadstock smogger-teen long-block, is a killer with a 4bbl, a 2800 and 3.91s or better. I ran one with 4.30s for a while,lol, and a 4-speed/GVod, of course.
IIRC those engines were like 150 RWHP..... But you know, when you multiply the torque by
3.09x4.30, or 2.45x3.91 x1.8 to 1.2, well, she perks right up.
 
318willrun said:
It's a misprint because I remember the first time I punched a 318 2bbl from a dead stop and she kicked the back end sideways I was pretty sure they have at least 380 ft lbs of torque.......



:lol:
Click to expand...
First off, now we know 318s will run, lol. Secondly, I believe ma mopar absolutely new what they were doing with those numbers. First off they manipulated ratings for the cars, say 69 and older for racing purposes. Then they manipulated rating for cars 70 or newer for insurance purposes. Insurance was a real killer back then. The car prices were out of reach for most kids and if insurance companies saw 300 hp ratings and if you were under 25 years old you were doomed. Hence the beginning of the lower hp ratings, again. And guess what, they're doing it again. Everyone wants the highest hp ratings again. And the factories are obliging.
 
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