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What is the truth behind the 340

Discussion in 'A Body: Duster, Valiant, Dart, etc' started by voiceofstl, Nov 8, 2017.

  1. Locomotion

    Locomotion Active Member

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    The cast 360 cranks will take a lot of abuse. Their main journals are bigger than the 340, 318, etc. cranks (forged & cast). In fact late '72-'73, the 340's had cast cranks, which required external balance weights on the damper/balancer and converter. But it was less weight than the longer stroke cast 360 required. When the 340 was discontinued at the end of 1973, the hi-po parts - intake, carb (bit bigger TQ), cam, springs, etc. were put on the 360. I don't have any performance comparisons, but the factory rated the 360-4bbl 5 more HP than the '73 340-4bbl. With 20 more cubic inches, I'm sure it was faster, even if they hadn't gone to the bigger Thermoquad.

    The 915 castings were also used on the T/A and AAR 340 6 packs in 1970. Same head as was cast for the new-for-1971 model year 360 2 bbl. But all they did was use better springs and machined the intake pushrod hole further away from the intake port, which allowed more porting but required the offset intake rocker arms.

    As for the 318, using later model 302 casting heads with closed chambers and upgrading the valve size to the 360 spec 1.88"/1.60" is suppose to be a good performance upgrade.
     
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  2. Tin Man 2

    Tin Man 2 Active Member

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    I had a 71 340 4 speed Demon that was plenty quick, but as I understand it the 68,69 340's were ever hotter. Years later I picked up a 72 340 auto Dart that was decent but nothing to write home about. The 71 Demon was Black and it had the hood scoop and chrome metal "Demon" badging that was a bit rare. Wish I had it today.
     
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  3. Fast Eddie

    Fast Eddie Valued Member
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  4. AHBGuru

    AHBGuru Active Member

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    The '78-'83 E48 318 HP was available in the Aspen, Volare, St Regis, '79 Newport, Gran Fury, and '81-'83 Diplomat A38 police vehicles. It did use the E58 Police 360 heads, intake, and 850 TQ. Sometime in 1983, the J head was changed to improve coolant flow, resulting in the 587 head.

    There was also a light duty 318 -4 used in retail cars through 1983.

    In '84, the engine was relabeled the ELE, and used in M body Diplomat/Fury squads. While the police car books make much noise about the '84 squads, the harsh reality is that year they came with probably the very worst emissions package ever used in a Chrysler. An ultra-lean TQ equipped with an altitude compensator, 8.0 (at best) compression, and no provision for vapor-lock resulted in cars that were very difficult to keep in tune.

    When Carter discontinued carburetor production in late 1984, Chrysler had to scramble to supply a fuel system for the '85 cars. At that time, the M body was more or less grudgingly produced, and they likely did not originally intend to continue production beyond '84. Sales, however, were increasing enough to justify another model year, and the TBI system on the drawing board would not be ready until '86 at the earliest, so they were able to use AC Delco and Holley as the vendors. Thus, the Rochester 17085433 and Holley 6280 replaced the TQ and BBD. And again, while the police car books poo-poo the Qjet, they actually provided excellent service in the squads. Emissions were simplified, it used a much better electric choke, they held their tune far longer, and also proved particularly amenable to the new Anti-Vaporlock package that Fleet offered, starting in 1986.

    The ELE itself didn't really change much through 1989. They remained a lower compression, hydraulic flat tappet, heavy duty beast of burden. The '86 cars had a slightly different intake, without the well for the electric choke. All other changes were in calibrations within the EFC/ESC systems.

    The ELE was the last police-specific V8 produced until the EZH 5.7 Eagle from 2009+.
     
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  5. Bearhawke

    Bearhawke Things happen for a reason

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    I drove a few 318-4V cars from around the 1978-81 era while still living in Calif............a bone stock 318-2V in a 1973 or similar Dart would blow the newer cars' doors off. They were that bad.
     
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  6. AHBGuru

    AHBGuru Active Member

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    That's where the 360 E58 really shined. Putting the same heads and intake on the 318 killed bottom end torque. This is why so many guys who try to "build" a 318 wind up wasting their money. Unless you bore it and stroke it within a mm of its life, you need 3.90's out back just to get it moving. Then you have no top speed. This is why the '80 CHP St Regis was so terrible. 2.94 gears (probably the best overall ratio, otherwise), full emissions package, with cold air intake capped or flapped in 3 places, "tamper-proof" mixture screws and choke, non-lockup close-ratio 727, all in a 4200 lb barge. They'd top out around 105 on the flat. One year later, the Diplomat with a virtually identical powertrain and drivetrain ran 115. The '80 Plymouth Fury R-body used here in Wisconsin had the 360, and the unmarked units would run close to 130.

    When they went to the QJet, they were maybe a half-second slower than the 81-84 cars, but far more consistent. When they put the good 921 computer in for '86 - '89, they were much better most of our State Patrol Mopars were running 120+ (sans light bars).
     
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  7. A-Body

    A-Body New Member

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    "Wide blocks" were the first 318's (mid 60's) while the later ones were called the "LA" small blocks.
     
  8. rapidtrans

    rapidtrans Well-Known Member

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    Correct, but not offered in A bodies. 318 LA and later small blocks were based on the 273.
     
  9. Scrounge

    Scrounge Got parts?
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    The "wide block" 318 was also called waffle-head. It was introduced during the late 1950s, and was a high-performance engine for a few years.
     
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