340 Production Numbers

1968

Barracuda 340........................................ 3,917

Dart GTS 340........................................... 5,828

Swiss Barracuda 340****......................      40

                                                     Total      9,775

1969

Barracuda 340.......................................  6,018

Swinger 340...........................................16,637 

Dart GTS 340..........................................  3,645

Swiss Barracuda 340****......................      90

Savage Barracuda 340***.....................        8

                                                    Total     26,398

1970

Duster 340............................................. 24,875

Swinger 340........................................... 13,785

‘Cuda 340................................................. 6,256

‘Cuda AAR 340......................................... 2,724

Challenger 340........................................ 6,633

Challenger T/A 340................................. 2,399

                                                    Total     56,672

1971

Duster 340............................................. 12,866

Demon 340............................................ 10,098

Road Runner 340.................................... 1,681

Charger SuperBee...................................   320

‘Cuda 340................................................. 3,440

Challenger 340........................................ 2,344

Challenger T/A 340..................................        1

Cdn Swinger 340 Specials*....................      85

                                                    Total     30,835

1972

Duster 340............................................. 15,681

Demon 340.............................................. 8,773

Road Runner 340.................................... 2,360

Charger Rallye 340.................................  1,527

‘Cuda 340................................................. 7,363

Challenger 340........................................ 6,279

Cdn Swinger 340 Special*.......................     30

Australian VH Charger 5.5L**.................   124

Swiss Demon 340****.............................     40

                                                     Total    42,171

1973

Duster 340............................................. 15,731

Dart Sport 340....................................... 11,315

Road Runner 340.................................... 5,384

Charger Rallye 340.................................. 2,780

(hard top #’s only)

‘Cuda 340................................................. 7,209

Challenger 340........................................ 8,435

Australian VJ Charger 5.5L**.................... 212

                                                      Total   51,067

 

Totals: 1968-1973................................216,924

 

* Canadian Swinger 340 Specials '71/ '72 Western Canada

**Australian order '72 / '73 - Bathhurst Racing Series

***AutoCraft Savage GT US - 280hp

****Schinznach hand built for Swiss Mrkt (approximate #s)

 

All numbers courtesy: Galen V. Govier / Consumer Guide / Valiant.com / Dart pg

The Little Giant Killer!

1968 340's

• engines painted red w/black accessories

• 275 hp at 5,000 rpm & 340 lb-ft torque at 3,200

• 4.040" bore and 3.310" stroke

• forged crank w/shot peened rods

• 10.5:1 compression ratio

• ‘206’ hydraulic cam - 268 in. dur. - 276 ex. dur. 44 overlap (in 1968, only the

   4 speed cars got a more aggressive cam, automatic versions got a cam

   that become the standard in these hi-performance engines)

• a dual timing chain and a windage tray

• big X heads - 2.02 inch intake valves and 1.60 inch exhaust valves (894’s)

• free flowing dual plane 4 bbl intake

• Carter 650cfm AVS Carburetor w/1.44" primaries and

   1.69" secondaries

1969 340's

• virtually unchanged from 1968 other than:

• most engines painted turquoise

• both automatic & manual engines shared same cam

• Carter 650cfm AVS Carburetor re-used

1970 340's

• engines were painted street Hemi orange

• valve covers change slightly - breather/valve

• fresh air openings in air cleaner

• Carter 650cfm AVS Carburetor re-used

• 340 gets Six-Pak for AAR Cuda & T/A Challengers only

   T/A blocks had thicker webs for 4 bolt mains

• 360 J-head saw first limited use in the 1970 340

   Six-Pack AAR/TA, which had 2.20/1.60 machined 

   heads & revised pushrod holes for more meat in the

   intake runners (598’s)

Bogus Numbers

There was no escaping the truth when it came to the horsepower ratings during the 340's run. The two clips below help put the record straight. The 1st one is from an article from Hot Rod magazine back in 1968. 

 

 

 

 

 

 

 

An article from Hot Rod Magazine from '71 states that the NHRA refactored the 340 up at 325hp. So, was it the new 800cfm TQ?

 

This 2nd clip was pulled from the January 2009 issue of Muscle Car Review magazine where it gives examples of what other bogus numbers the NHRA was calling the factory out on.

1971 340's

• engines started Hemi Orange but changed to

   corporate blue in April '71 when they changed plants

   from Windsor to Mound Road, MI. Stream-lining was

   a large part to this move with all engines now blue.

• Carter 800cfm ThermoQuad spread bore carburetor

   introduced - offering more throttle response & better low to mid range

   transition and helped lower emission readings with smaller 1.38"

   primaries and huge 2.25" secondaries

•  valve covers now had wire harness tabs, not the tray/trough 

   version the '70 and early '71's had

•  compression dropped to 10.3:1 due to new emission laws and upcoming

   changes in gasoline lead content

•  with introduction of blue engines, the new white with blue 'Parts' air filter

   service decal replaced previous yellow version

•  late year – partial introduction of Electronic Ignition (May 14th), first on

   manual shift 340's then a little later automatic versions

• introduction of ‘360 style’ J head (915’s) – a.k.a the ‘O’ and ‘U’ heads.

•  All the  J heads received the 2.02’s

•  All heads now received hardened seats for new unleaded gas

With this website built for the ultra rare Canadian order '71 & '72 Swinger 340 Specials, this page hi-lights the peppy 340 that powered these cars...

One of the most popular performance engines in the '60's and '70's... the all new for ’68 340 was based on the standard LA-series lightweight block and was designed from the outset as a performance engine. Look at the stats – high compression (10.5 until '71), big valves (2.02 intake, 1.60 exhaust until '72), bumpy cams, double-roller timing chain, forged and shot-peened crank and rods, windage tray, free flowing dual exhaust, dual plane intake manifolds and large 4 barrel carburetors. These engines were built to perform, and stay together at upwards of 6,500rpm!

Horsepower stayed consistent throughout it's life, from '68 to '73, but not without a couple blips along the way. Coming off the starting blocks in the Dart GTS and Formula S Barracuda's, the 340 made everyone stand up and pay attention. The horsepower rating was set by Chrysler at 275bhp thru to '71, but with the '72's being detuned slightly to 240 net bhp. Those initial numbers were instantly challenged, with the NHRA raising the stock index to 310bhp and all the magazines stating 'underrated' 275 horsepower. Even the net rated 240hp 340's from '72 & '73 would have still been pushing 285bhp at the crank. As well, remember, the new for '71 800cfm ThermoQuad was still bolted to the dual plane intake, which made them healthier than the 650cfm AVS carb from earlier models. With that said - anyway you look at this feisty little small block, it performed. Here's a look at the year-by-year chronology of the 340. 

 

1972 340's

• painted corporate blue w/black accessories

• detuned, ostensibly for emissions and insurance

   reasons with compression ratio dropping

   to 8.5:1 – producing 240hp (now net rated), see

   side bar for actual horsepower output

• new larger orange un-silenced air cleaner with plumbing

   on snorkel to drivers side exhaust manifold, and underside warm air

   flap to accommodated warming of carb for cold weather starts

• exhaust manifolds changed on drivers side to accommodate ducting from

   attached heat stove which was then plumbed to air cleaner

• cast crank replaces steel forged crankshaft on April 11, ‘72 with engine

   #HM340R-3911-8000. Damper now stamped ‘use with 340 cast crank only’.

• ‘915’ 2.02 J heads quickly replaced with ‘875’ J castings with 1.88 intake

   valves to comply with newly introduced emission laws

• 800cfm ThermoQuad reworked slightly with fuel metering, instead of being

   air metered as in '71 versions

1973 340's

• last year for 340, virtually unchanged from ‘72

• Warm air flap under air cleaner discontinued

• white & blue 'Mopar' air filter service decal replaces

  'Parts' version

• new version of emissions canister utilized

Carburetor & Intake

Ever since the 340 was introduced in 67 for 68 cars, they always carried the Carter line of carburetors. Prior to ’71, the 340 came standard with the Carter AVS, rated at 650 cfm. Carter brought out its resin-bodied ThermoQuad in the late ‘60’s and soon found a home in 340’s starting in ’71. The AVS did not pass the new emission tests for ’71, while the 800cfm ThermoQuad - with its 1 3/8” primaries - passed. Even with a slight drop in compression in ’71 and with the help of the new ThermoQuad, NHRA quickly realized the carb was a big plus, and ’71 340’s got a 30hp bump over previous index’s. It was fun while it lasted – in ’72, the tightening noose on performance found compression down to just 8.5:1 and more restrictive 360-type J heads - the 340, in ’73 came to an end - though the ThermoQuad remained in place, perking up the smog laden HP 360 4bbl in ’74 and ‘75. The stock dual plane 4 bbl intake manifold on the 340 engine was very good incorporating large passages and raised over an inch to get a hi-riser effect.

 

Cylinder Heads

Chrysler engineers always seemed to have the knack of using just the right valve and port sizes for a given displacement size. The ’68-’71 340 ‘894’ casting X heads have slightly larger intake valves – 2.02 as apposed to the ’72-’74 J heads, with 1.88/1.60 inch valves. In ’71 - after the factory used up the X heads, 340’s received the ‘915’ casing J heads, retaining the 2.02 valves - for only that year. In 72, both 340’s and 360’s received the 1.88 versions but a few large valve heads made it into a few early production ’72 340’s. The J head carried on after ’74 but were modified in ’75 to reduce emissions even further. The J head (casting # 3418915) actually saw first limited use in the 1970 340 Six-Pack AAR and TA’s, which had 2.02/1.60 machined heads. They also had relocated pushrod holes for the offset intake rockers. These were only used on 1970 T/A Challengers and AAR Cuda’s

 

*Thanks to Kori Alexander for additional knowledge, information and nuances that make up the Dodge and Plymouth 340. 

Cut-away illustration of the new for '68 340 from the Chrysler archives

Back in the day:

According to CAR LIFE Magazine, “Rated at 275 bhp, Mopar’s 340 may have had 325 or more” and that it was “as cleverly engineered as the 426 Hemi, just not so fussy."

In the '72 Engine Annual from Popular Hot Rodding Magazine, they stated:

"Besides the renowned Hemi engines for which Chrysler has been so famous, probably the best engine, is the 340 Small Block."

CAR and DRIVER called its '68 340 Dart GTS

(4 speed, 3.91:1 gears, 14.4 ET @ 99 mph) “a giant killer.

In a 1969 test, HOT ROD Magazine got its 340,

4 speed Formula S ‘Cuda with 3.91:1gears to turn high-13’s. It is stated – the 340 should be considered the ‘Hemi of the small block family’. Why? Simply because the 340 was designed from the outset as a performance engine.

In May of 1970, CAR CRAFT Magazine ran an article titled 'Econo Racer Test' which pitted the 4 strongest and cheapest performance cars against each other - here's the results:

#1  Duster 340 4sp w/3:91's = 14.22@99.88

#2  Swinger 340 3sp w/3:91's = 14.70@96.84

#3  Nova SS 350 4sp w/4:10's = 14.91@94.04

#4  Mach 1 351 4sp w/3:50's = 15.23@94.33

Then in April of  '71, CAR CRAFT ran an article titled 'Drag Comparison' where it put the Demon 340 with the new 850cfm ThermoQuad up against a Hornet 360 and this is what it ran:

Stock form:  14.41@98.69mph

W/Headers:  13.61@104.52mph

The quickest a stock 340 ran was with Ronnie Sox at the helm of '70 Duster 340 4sp w/3:91s. He ran 10 times with the average of all being 14.07@100.09mph. BAM! BAM! BAM! BAM!

Steve Magnante wrote this article for Hot Rod Magazine where they look back and recreate findings from back in the day:

 

 

 

 

 

 

Performance Numbers

Hope you enjoyed this info I put together on the 340, now, get out there and put yours thru the gears! Cliff Guinand

Researched*, written & designed by

Guinand & Co. / Cliff Guinand
 

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