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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. MPE426HEMI

    MPE426HEMI Well-Known Member

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    I've heard lots of the 318 "Big block" and "wide block" terms growing up. I've really yet to figure out what they were talking about. The only thing I can figure is the 318A engine built up to 1966, which was the poly. I dunno if that's what they were referring to? Myself, I've only ever known the 318LA engines.
     
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  2. rapidtrans

    rapidtrans Well-Known Member

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    I assume they’re referring to the older poly 318 also.
    The 340 was a light weight powerhouse and combined with the lighter Duster made a great $3k street machine.
    Dad tried a 360 2bbl in a 71 Sport Fury. It was a decent engine in a big car but just didn’t have the ooomph a 383 2bbl had. Plus the 360 used oil for some reason.
     
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  3. Bill Watson 2

    Bill Watson 2 Member

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    The 318 poly was generally referred to as the "wide block 318". In fact, though, the A (poly) and LA (wedge) blocks (less heads and manifolds) were virtually identical in external size. The poly heads, though, were larger which made the complete engine look bigger.

    As for the Chrysler B bodies and GM A bodies, both were in the intermediate market. Generally the Mopar models were on longer wheelbases than their GM opponents, and about 50 pounds lighter as well as a little more money.

    A 1969 Malibu V8 had a 307 as standard, weighed 3,230 pounds and cost $2,690. Plymouth's Malibu competitor was the Satellite with a 318 V8 as standard. Weight came in at 3,156 and sold for $2,883.
     
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  4. voiceofstl

    voiceofstl Well-Known Member

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    wow the satelite was lighter then the malibu.The B body was a bigger car and alot bigger interior....what a deal.
    To bad the you couldn't the 340 in one untill 1971.
     
  5. rapidtrans

    rapidtrans Well-Known Member

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    We had 318s in a 70 Coronet and 71 Satellite. The same years my uncle had a Monte Carlo then a Chevelle with 350 2bbls.
    Being H.S. kids my cousin and i often "compared" acceleration of dads' cars. The 318s could match or beat the 350 off the line then he would pull ahead somewhere in second gear. Don't know what axles were in the cars but dad often ordered 318s with a quicker rear end.
     
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  6. valiant67

    valiant67 Rich Corinthian Leather
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  7. CudaPete

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    318 runs out of steam at about 4K rpm. 340 keeps pulling......
     
  8. voiceofstl

    voiceofstl Well-Known Member

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    I often posted here about the size and comfort of modern cars but even back in my high school days (early 70's) I loved the 68,69 Barracuda and darts. My dream car back the was a 69 barracuda with a 340. not only was it sporty but is was real cormfatable and it had a real trunk.
    Much better car then the camaro or mustang.
     
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  9. RalphP

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    The original 318 was A based; the 67 and newer were LA based. The A was visibly wider due to the heads (the BLOCK was the same width; there's actually folks that have retrofitted A heads to LA motors, either drilling the extra oil return paths in the block or using hoses and dumping the oil return into the oil pan).

    See A series Chrysler small block V8 engines -277, 301, 303, 313, 318, and 326 (at https://www.allpar.com/mopar/a-engines.html ) .

    RwP
     
  10. DC-93

    DC-93 Active Member

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    I had a 68 340 4 speed fastback and it would pull to 6K.
     
  11. Fast Eddie

    Fast Eddie Valued Member
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    We would run power runs to 6000 rpm on the 340" but it peaked at 5600 rpm. We ran power runs to 4800 for the 318" but it peaked at 4400 rpm. We always ran the power runs at 400 rpm increments and would shut down when the power fell off at the next speed after the peak.
     
  12. DC-93

    DC-93 Active Member

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    AHA! So, I was shifting just past peak, and I'm no Ronnie Sox!
     
  13. voiceofstl

    voiceofstl Well-Known Member

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    The 360 never got a good rep mainly because it came out in the smog days.
    If you were on a limited budget and you were hopping up a 70's A body would you go with a expensive 340 or go with the 360.?
     
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  14. CudaPete

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    360. 340's are getting hard to find.
     
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  15. Fast Eddie

    Fast Eddie Valued Member
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    The main issue with the 360 was it had a production cast crank,,,,,,,,,,,,,,,,,,,,
     
  16. voiceofstl

    voiceofstl Well-Known Member

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    Unless your pushing a super hoped up engine 500 horse+ that cast crank is plenty strong enough.
     
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  17. Shane Estabrooks

    Shane Estabrooks Active Member

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    One could always take a 360 or 318 .. work the heads and stroke it to a 340 but with that said my 95 318 with a few aftermarket goodies and on a budget was a very awesome engine.. good enough to paste 340 on the side if wanting too.
     
  18. CudaPete

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    The "problem" with the 318 is its small valves. If you change the heads to get bigger valves you loose compression so you have to change the pistons too which can lead too clearance problems. I left the stock heads on my 318 but ported the heads as well as doing a 3-angle valve job. Compression was bumped up to 9.5:1 so it has plenty of low end power, Also used an Edlebrock cam, Performer intake manifold and 4-bbl carb.
     
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  19. Fast Eddie

    Fast Eddie Valued Member
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    If I remember correctly the 1971 and 1972, 340 and 360 engines were equipped with 3418915 heads, so-called "J" heads, because of the cast-in J in three locations (backwards in one place) on each head. These were either equipped with 1.88 inch/1.60 inch valves, or 2.02 inch/1.60 inch valves, and have "open" chambers with volumes of 65-73 cc.

    Police sedans were equipped with a high performance 318 engine, which was equipped with 360 heads and a 4 barrel carburetor (Thermoquad through 1984, Quadrajet from 1985)??
     
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  20. pt006

    pt006 Active Member

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    Eddie, thanks for your post #31. Peak power at 5600 is impressive. The early 340 [68 to 71] heads were known as 'X' heads. They had the 2.02" intake valves. The 'J' heads came out in 1970. Some with 2.02" , but most with 1.88" valves. Putting 2.02" or even 2.05" valves in the 'J' heads were commonly done back in the day. As you said, the cast crank limits the safe rpm level, so a wild cam is of little benefit. Head porting can give good results. A sensibly built 360 engine makes for a nice street engine.
     
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