Mopar 318 'High Performance' vs Chevy 327/250 HP ~ 327/275 HP ~ 350/255 HP

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69 Cuda 440

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Mopar 318 'High Performance'

Takes on the '3' Chevy Mid-Horsepower Small Blocks

327/250 HP ~ 327/275 HP ~ 350/255 HP

Let's see what we've got.
 
From what I've read, the 350/255 was the right setup for stock classes, so I'll go with that.
 
Taking the 318..."because you never take sides against the family"
 
My only question is, "What 318 high performance?".
I have no doubt about 318's abilities, but what the hell are we talking about?
I've had lots of good running 318s, but I also remember a 1970 350 2barrel 250HP Impala in the family that ran real well.
 
The 318 'High Performance', proposed for 1968.

318/240 HP 'Commando'

Almost made it to 'The Dance' for the 1968 Model Year. To be made available
as a 'Junior Performance Engine' for the Valiant and Dart GT 'only'.

Compression ............. 10.0-1 {Flat Top Pistons}
Cylinder Heads .......... #2843675 {Open-Chamber; 60.6 CC's}
Valves ...................... 1.78" Intake ~ 1.50 Exhaust

Camshaft {Hydraulic}
Lift ........................... .420" Intake ~ .435" Exhaust
Duration .................... 254*/260*
Overlap ..................... 38*

Intake Manifold .......... 273 'Single-Plane' Cast Iron
Carburetor ................. Carter AFB #3447 {600 CFM}
Dual-Point Distributor ..
Header Manifold Outlet . 1.875"
Dual-Exhaust

8 3/4" Rear
Heavy-Duty Suspension
 
My girl-friend then, had a 67 Acadian Canso 327/275 hp,, a Canadian Pontiac version of the Chebbie Nova,, or Chebbie II.. ..

She couldn't beat my 340 Dart, but she worried me a few times, and she could stomp my bud's 318 Cuda, along with a lotta other muscle cars of the era.....

We both still own the cars today.. she's no longer my G/Friend,, but we chat often.. lol

Getting them to hook was the problem,, but rolling starts,, Canso/Nova pulled harder..

The Quadrajets huge adjustable secondaries would open way sooner than the un-adjustable AFB secondary that doesn't open till 3k+ rpm unless you drilled half a dozen 1/4 inch holes in the counterweight.. anyway,, those Chebbies were quick..
 
I thought that you were going to compare the 318 4v that Chrysler sold, the E46. The highest HP rating I've seen on it was 175 net. At 8.5-8.6:1 compression, it is a bit of a dog. Even so, I'll bite on the '68 240 hp 318. I'm running something similar except less compression and more cam.

There's also some apples and oranges (Gross vs. SAE net HP) going on. The LT-1 was dual rated in 1971 at 255 net or 330 gross. The 327s mentioned were available in every chebbie, where as the LT-1 was only available in the Camaro Z-28 and the Corvette LT-1.

I think the Commando 318 will take down the 250/327, be close to the 300/327 and will lose to the 255/350 assuming the Mopar is an A-body and the chebbie is an F or X body.
 
1968 Chevrolet 327/250 HP ~ Code 'L-73'

This combination was available in 1968 {only}.

Available in the > Chevelle and 'larger' Cars.

Compression Ratio ............ 8.75-1
Pistons ............................ Flat Top

Cylinder Heads ................. Casting #3917293
Combustion Chamber ........ Factory {75.34 CC} ~ Minimum {68.8 CC}
Valves ............................. 1.75" Intake ~ 1.50" Exhaust

Camshaft {Hydraulic} ....... #3896929
Lift ................................. .390" / .410"
Duration .......................... 253* / 264*
Duration @ .050" .............. 195* / 202*
Overlap ........................... 34.5*
LSA ................................. 112*

Intake ............................. Cast Iron Dual-Plane
Carburetor ....................... Rochester 4-MV 'Quadrajet' {730 CFM}

The Rochester Quadrajet is rated at 730 CFM, but air-flow is adjusted to
630 CFM on a 'low-performance' Small-Block.

Exhaust System ............... Single
Header Outlet Size ........... 2.0"

The 'optional' {N-10} Dual Exhaust System could be ordered with the L-73
Engine.

Generally speaking, lots of the 1968 Chevelle guys did quite well with the 327/250 HP in Stock Class in the NHRA back-in-the-day.
 
OK. I missed it. The 250/327 was not available in the Chevy II.

In 1965, the Chevy II was available with the 300/327. IIRC, it had dual exhausts. 66 model IIs had a 350/327 option. In 67, the top option was a 275/327. FWIW, the II didn't join the big block party until 1968 (350/396 & 375/396). Yenko built less than 40 427CID "Super Nova"s. But I digress.
 
2 Darts said:
OK. I missed it. The 250/327 was not available in the Chevy II.

In 1965, the Chevy II was available with the 300/327. IIRC, it had dual exhausts. 66 model IIs had a 350/327 option. In 67, the top option was a 275/327. FWIW, the II didn't join the big block party until 1968 (350/396 & 375/396). Yenko built less than 40 427CID "Super Nova"s. But I digress.
Click to expand...

Hold On,

I'm talking about the 1-Year {only} 1968 ~ 327/250 HP {Engine Code 'L-73'}

Only available in the Chevelle series, and large body cars >
{ie; Biscayne, Bel Air, Impala and Caprice}.

1968 > Not Available in the > Camaro, Chevy II Nova, or Corvette.
 
if i remember right the 318 for most of its life was NOT a "HP" engine from chrysler. thats why they had the "HP" 273, and 340. but the later years i not sure. if i remember right.
 
moe7404 said:
if i remember right the 318 for most of its life was NOT a "HP" engine from chrysler. thats why they had the "HP" 273, and 340. but the later years i not sure. if i remember right.
Click to expand...

Correcto El Mundo,

The only factory production 318 'High Performance' was the LM-318 Marine Engine.

A 4-Barrel rated at 240 Horsepower.

But for a while in late-1967. Mopar toyed with the idea of a 318 'Junior Performance' 240 Horsepower engine for the 1968 Model year.

As Chevrolet had the 327/250 HP
And Ford had the 302V/230 HP
And American Motors had the 290/225 HP
 
69 Cuda 440 said:
1968 Chevrolet 327/250 HP ~ Code 'L-73'

This combination was available in 1968 {only}.

Available in the > Chevelle and 'larger' Cars.

Compression Ratio ............ 8.75-1
Pistons ............................ Flat Top

Cylinder Heads ................. Casting #3917293
Combustion Chamber ........ Factory {75.34 CC} ~ Minimum {68.8 CC}
Valves ............................. 1.75" Intake ~ 1.50" Exhaust

Camshaft {Hydraulic} ....... #3896929
Lift ................................. .390" / .410"
Duration .......................... 253* / 264*
Duration @ .050" .............. 195* / 202*
Overlap ........................... 34.5*
LSA ................................. 112*

Intake ............................. Cast Iron Dual-Plane
Carburetor ....................... Rochester 4-MV 'Quadrajet' {730 CFM}

The Rochester Quadrajet is rated at 730 CFM, but air-flow is adjusted to
630 CFM on a 'low-performance' Small-Block.

Exhaust System ............... Single
Header Outlet Size ........... 2.0"
Primary Pipe .................... 2.50"
Tail Pipe .......................... 2.0"

The 'optional' {N-10} Dual Exhaust System could be ordered with the L-73
Engine.

Generally speaking, lots of the 1968 Chevelle guys did quite well with the 327/250 HP in Stock Class in the NHRA back-in-the-day.
Click to expand...

Difference between '1968' 327/250 HP and the 327/275 HP

The 327/275 HP ~ {Code L-30}

* Compression Ratio ......... 10.0-1

* Cylinder Heads ............. #3917291
* Combustion Chamber .... Factory {63.30 CC} ~ Minimum {57.50 CC}
* Valves ......................... 1.94" Intake ~ 1.50" Exhaust

* Exhaust System ............ Single
* Header Outlet ............... 2.0"
* Primary Pipe ................. 2.50"
* Tail Pipe ....................... 2.0"

The 'optional' RPO N10 'Dual-Exhaust' System was offered at a minimal price.

* Same pipe size, just with 'dual piping'.

The Camshaft {Valve Train}, Intake Manifold and Rochester 4-MV Quadrajet Carburetor
were the same components.
 
69 Cuda 440 said:
Difference between '1968' 327/250 HP and the 327/275 HP

The 327/275 HP ~ {Code L-30}

* Compression Ratio ......... 10.0-1

* Cylinder Heads ............. #3917291
* Combustion Chamber .... Factory {63.30 CC} ~ Minimum {57.50 CC}
* Valves ......................... 1.94" Intake ~ 1.50" Exhaust

* Exhaust System ............ Dual
* Header Outlet ............... 2.0"

The Camshaft {Valve Train}, Intake Manifold and Rochester 4-MV Quadrajet Carburetor
were the same components.
Click to expand...
The one good Chev small block mill...350/327 refactored to 275/327 with bad manifolding..
Where Chevy's high performance division, & aftermarket made major moohla... Sell a sexy body style,with a turd for a mill. The kids bought the base line body models, threw cams ,heads,pistons ,headers at a good looking body style. Mopar always tried to do more complete hot rods,for the money( my soapbox opine..)
The 240 318, would be a great NHRA stock class option. On the street ,too much stuff is modified, without thought on the whole package.. ( Includes myself...)
 
1968

The 1968 Valiant with a 318/240 HP would have fell 'perfectly'
into the {12.00 to 12.49 Wt/HP} Weight Class.

#2880 lbs. ~ 240 HP = 12.00 Wt/HP

'Dial Me In'
 
69 Cuda 440 said:
Correcto El Mundo,

The only factory production 318 'High Performance' was the LM-318 Marine Engine.

A 4-Barrel rated at 240 Horsepower.

But for a while in late-1967. Mopar toyed with the idea of a 318 'Junior Performance' 240 Horsepower engine for the 1968 Model year.

As Chevrolet had the 327/250 HP
And Ford had the 302V/230 HP
And American Motors had the 290/225 HP
Click to expand...

There was even a more potent 318 c.i. factory engine:

In Mexico they had in the Valiant Super Bees a 318 c.i. 4 bbl rated with 270 HP for some years.

View attachment superbeeqd02.jpg
 
Chevrolet 1969 ~ 350/255 HP {Code; LM-1}

Was an early-year only Engine combination for Chevrolet.

Compression Ratio ............ 9.0-1
Pistons ............................ Flat Top w/notches

Cylinder Heads ................ #3932441
Combustion Chamber ....... Factory {76.33 CC} ~ Minimum {73.26 CC}
Valves ............................ 1.94" Intake ~ 1.50" Exhaust

Camshaft ........................ #3896929
Lift ................................ .390" / .410"
Duration ......................... 253* / 264*
Duration @ .050" ............. 195* / 202*
Overlap ........................... 34.5*

Intake Manifold ............... #3927184 ~ Cast Iron Dual-Plane
Carburetor ...................... Rochester 4-MV Quadrajet {730 CFM}

Exhaust Pipe .................... 2.50" {Single-Exhaust}
Exhaust Pipe .................... 2.00" {Optional Dual-Exhaust}
 
I'm always amazed at how small the factory cams were on some of these engines. I run a Comp 252H with 206* @.050 in my 289 Mustang, and it idles stock with 18.5" of vacuum. That 350 had an even smaller cam, yet that engine combo ran great!
 
Aaron65 said:
I'm always amazed at how small the factory cams were on some of these engines. I run a Comp 252H with 206* @.050 in my 289 Mustang, and it idles stock with 18.5" of vacuum. That 350 had an even smaller cam, yet that engine combo ran great!
Click to expand...

The Chevrolet 1969 350/255 HP {LM-1}

Just a flat-out 'Killer Combination" for NHRA Stock Class back-in-the-day.

1969 Camaro ......................... #3141 lbs. ~ 255 HP = 12.31 Wt/HP
1969 Camaro 'Convertible' ....... #3260 lbs. ~ 255 HP = 12.78 Wt/HP
1969 Nova ............................. #3035 lbs. ~ 255 HP = 11.90 Wt/HP
1969 Chevelle '300' 2-Door ...... #3200 lbs. ~ 255 HP = 12.50 Wt/HP
1969 Biscayne 2-Door Sedan .... #3623 lbs. ~ 255 HP = 14.23 Wt/HP

You can't beat '350' Cubic Inches and a throaty Rochester Quadrajet {730 CFM} with 1.94" Intake Valves.

The #3932441 Cylinder Heads had big Combustion Chambers, but they
had decent sized Ports {Intake = 155 CC} and {Exhaust = 62 CC}.

Of course, it didn't hurt that Chevrolet under-rated the 'LM-1' Horsepower by {25 HP}.
 
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