340 Mopar Engine

The 340 Mopar Engine is still one of the most popular Mopar Engines from the ’60s and ’70s. Some Mopar Engines were designed for drag racing. They were heavy and bulky, but put-out high horsepower. This made them great for straight line races, but anything that involved curves they struggled. That’s were the quick-and-nimble 340 Mopar Engine found its calling.

The 340 Mopar Engine was developed in the 1960s and found its way to production by the end of 1967. It was close in cubic inches to the 318 Engine, but they differed in a whole lot more than just 22 cubic inches.

The 340 had: high performance heads, special carburetor and cam; New oil pump with a 90 degree adapter; 2.02 inch intake valves and 1.60 inch exhaust valves; Dual Time Chain with windage tray; high-rise dual plane intake.

Even with all of these performance features the top “horsepower rating” that any 340 Mopar Engine was 290 horsepower. This was the 340 Six Pack version debuted in the Dodge Challenger T/A and AAR ‘Cuda. Many believe that many Mopar Engines’ horsepower were underestimated to cut down the costs that buyers would have to pay for their insurance. So the actual horsepower of these 340 engines are most likely more than the rated 290 horsepower.

Stock 340 Mopar Engine Characteristics

Figure 1 show the performance characteristics (power curve) of the stock 340 engine.  The maximums were at 281 hp at 5200 rpm and 328 lbs/ft at 3900 rpm.  These numbers are right on target for the the factory ratings on the 340 high performance which were 275hp at 5000 rpm, and 340 lbs/ft at 3200 rpm.

Share Your 340 High Performance Modifications

How have you built up your High Performance 340 Engine? Share in the comments!

67 Responses to 340 Mopar Engine

  1. Rich Conroy says:

    I just acquired a 1972 340 block(heads not included). The Id pad on the front of the block is blank what does this mean?

  2. andrew says:

    I have a 68 barracuda still 1st owner. Its in need of a little tlc but with its 340 its not that bad im in need of carb and some other parts tail light emblems .ect

  3. Nick says:

    I have an 86 power ram with a 340 in it- love it, am planning on rebuilding it this summer. have gotten into so much trouble with that truck ;P

  4. Loren says:

    I have a 1972 Dodge Charger Rallye with a highly modified 340. All edelbrock top end producing about 400 HP.

  5. jerry6 says:

    I have 2 340 engines , one almost stock with just a cam the other cam pistons and head work .030 over , both 1970 blocks . Stock with cam has 350HP 375 torque , the other 412 HP 391 Torque , these are not guess work but dyno numbers . Factory underrated these engines .
    1972 with no numbers on block means factory replacement block for a blown engine replaced under warranty

  6. Steve Underwood says:

    Hi Jerry6, would you be interested in selling one or both 340 motors.


  7. Robert wade says:

    i have a 1971 plymouth it decodes to having a
    340 4v v8 with a 727 trans this is a 4dr car
    how rare is this car. can any body help.
    thanks rob

  8. jerry6 says:

    @Steve Underwood , no , sorry , using the 400hp and saving the numbers matching stock motor for when and if the car is sold . You could always build up a 360 , can be as good or better , if you’re not looking for an original build car

  9. alain says:

    how many 68 cuda formula S 340 auto was built? thanks

  10. Mike says:

    Hello, I own the domain moparengine.com. Would you be interested in buying it? I only want $30 for it. Thanks.

  11. Terry Foss says:

    I bought a new Cuda TA AAR in June of 1970- $ 7,100. dollars in Walla Walla Washington, it was ‘ HOT PINK ‘, payments were outrageous–$130. a month, ins.- $30. a month. Punched it ounce while going 140 mph–it set me back in the seat-speedo went to 240 if I remember right, 8-to9 miles to the gal. city–9 if I drove it hard-8 if was easy on it-17._ something on the freeway. JUST LOVED IT—TZF

  12. jim says:

    i have a 71 340 motor for sale.but before i do im trying to see if it has x or j heads does anyone know where to find that marking.?

  13. johnny says:

    jim they are on the stamping between the spark plugs a big X or J, or get the casting numbers off the heads and google them.

  14. billy t says:

    I bought an engine and was told it was a 340. The numbers I located on front left….under the head. I can just about make them out…but can only see 10 numbers total. When I do a search on those numbers nothing comes up. Are these the wrong numbers?? thank you

  15. Kevin says:

    I have a 69 10.8:1 .030 over 340 w TRW 2316 forged pistons, lightened 340 rods w/ ARP bolts, and stock forged crank. Ported edelbrock 63cc heads (flow 275 @ 600), Comp XE282S (.520/.540) solid flat tappit cam, Comp roller rockers, PRM air gap w/ 1 in. spacer, and Holley 750DP. Engine just dynoed 440 Hp w/ 425 Tq. Robert Wade, your 71 dr duster is 1 of none. Plymouth NEVER made a 71 4 dr duster. billy t, look on the left side of your block 3/4 of the way back about 1/2 way down the block in front of where starter mounts. Big 1 inch tall #s cast in the block w the cu. Ex: 340-2 Real easy. No #s to decode. This is not a chevy.

  16. Damian says:

    ’73 Vj E55 Valiant Charger (aussie mopar)
    600 holley, chrome box, 1 inch spacer & headers. ran on chassis dyno once. Made 206rwhp. bit of controversy that day. other participants said dyno was showing 30hp less on some of the more wild cars. never the less 300+ hp out crank on a 140,000km original motor.

    Billy T. The first four letter & numbers stamped should be A331, thats what the oz 340s prefix is. if not you’ll find casting numbers behind starter motor also tells you what size engine.

    “Takes a Mopar, to catch a Mopar.”

  17. ralph55 says:

    I have a 70 340 six pak engine that came out of a T/A, it has O heads but the block is not a T/A block, just a std. 340hp, was running great, just pulled it to put a correct T/A engine in the car. No carbs/dist./pulleys/fuel pump, anybody know what it is worth? Thanks

  18. jnm says:

    from what i gathered soo far i have a 1972 340 with j heads..a thermoquad carb.i’m trying to sell it for $800.00.

  19. dd says:

    I may be interested.
    Where are you located?
    I am in


  20. terry says:

    im interested in motor

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