more 340 questions

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    Author Topic: more 340 questions  (Read 6894 times)

    Offline ACE_5150

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    Re: more 340 questions
    « Reply #15 on: May 10, 2005 - 11:18:10 AM »
    Quote from: rnsykes on May 10, 2005 - 07:21:05 AM
    Someone will correct me if I'm wrong, but with the 360 heads, your compression may be lower than you think.  The cylinder head volume I think is slightly higher (around 70cc compared to the 65 cc) which will lower the compression.  Not that it will be a problem to achieve what you are looking for, but it may be around 9-9.5:1 which by some standards would be considered low.  If you are having the head work done, have them cc the heads, and you can get a better idea of what the compression will be.

    Yeah, the 360 heads will definitely lower compression ( more like 76cc) . But like Chryco said, the 340 heads had 360 cast in them.
     Currently I am running a Comp cam and not too happy w/ it. Prolly should've used an engle or mopar. I think comp disregards the difference that the .904 lifter diameter makes on cam grinds, unlike engle and Mopar.
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    Offline Chryco Psycho

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    Re: more 340 questions
    « Reply #16 on: May 10, 2005 - 11:25:18 AM »
    Most Comp grinds are designed fro GM & ground on Mopar blanks , if you look in the Comp catalog 99% of the mopar grinds are listed with exactly the same grind under chev
     The 915 casting 340 head with 360 cast into them are 68 cc , eaxctly the same cc as the X 340 head +or- production tolerances of maybe 2 cc
    « Last Edit: May 10, 2005 - 11:27:25 AM by Chryco Psycho »
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    Offline mrbill426

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    Re: more 340 questions
    « Reply #17 on: July 12, 2005 - 10:40:30 AM »
    Quote from: Chryco Psycho on May 10, 2005 - 11:25:18 AM
    Most Comp grinds are designed fro GM & ground on Mopar blanks , if you look in the Comp catalog 99% of the mopar grinds are listed with exactly the same grind under chev
     The 915 casting 340 head with 360 cast into them are 68 cc , eaxctly the same cc as the X 340 head +or- production tolerances of maybe 2 cc

    So, are the '915 "J" head castings just as good as the "X" heads for flow?  The "J" heads are worth the cash to open up the valves, over seeking out and paying for "X" heads?
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    Offline Chryco Psycho

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    Re: more 340 questions
    « Reply #18 on: July 13, 2005 - 10:32:20 AM »
    if you have either X or J heads the heads are very similar , the only head better is the 308 truck head
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    Offline mrbill426

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    Re: more 340 questions
    « Reply #19 on: July 16, 2005 - 01:30:29 PM »

    Thanks, I'll look into the cost of installing bigger valves in these J heads.  :thumbs:

    I'm still considering the Edelbrock aluminums that are a LOT lighter, already have the larger valves, and supposedly flow better.
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    MOPAR or NO car!

    '72 'Cuda 340, white on white
    '72 Sebring; bracket project
    '64 Imperial Crown black on black
    '66 Imperial Crown; parts car

    dodgetkboy78

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    Re: more 340 questions
    « Reply #20 on: July 16, 2005 - 10:51:21 PM »
    Quote from: rnsykes on May 04, 2005 - 08:00:36 AM
    I think the reason for the 318 balancer is that they are a dime a dozen, and are essentially the same balancer as the 340 balancer.  I have the balancer off of my old 318 on my 340 now.  try calling a junk yard and asking them for a balancer for a 340, and you'll see why searching for a 318 is the better way to go.

    Carefull guys, a 318 balancer is internal, and a forged crank 340 is internal, however, I think it was 72 when auto 340's got cast cranks, and used a 360 balancer.
    Might want to check on what crank you have, unless you are certain it is a internal balancer that came off it.
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    dodgetkboy78

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    Re: more 340 questions
    « Reply #21 on: July 16, 2005 - 10:58:11 PM »
    Quote from: ACE_5150 on May 05, 2005 - 11:59:04 AM
    Since you're not looking for performance and you are wanting good gas mileage I would go w/ stock 318 cam and stay w/ the 360 heads. Dont be mislead, even though the 360 has more CID, the heads were lower performance ( hence the bad rep the 360 always had verse the 340) because the 360 usually came stock w/ a 2 bbl carb. The Intake and Exh. ports are generally smaller on the 360 heads, and Int. valve smaller ( 1.88 ").

    340 and 360 heads have the same port, essentially, there is only two heads With very minor differences), minus the race ones and the newer swirl/magnum heads
    273/318 and 340/360
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    dodgetkboy78

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    Re: more 340 questions
    « Reply #22 on: July 16, 2005 - 11:12:18 PM »
    Quote from: Chryco Psycho on May 10, 2005 - 09:59:10 AM
    the 340 J heads had 360 cast into them , they are the same heads
    Your call on the cam ., But I know the K 54 will work better , you can call Engle & talk to them if you want

    Although I have no experience with Engle cams, I have had good luck with others.
    Some of the m are crane, comp, and mopar, oh, and Isky.
    The 340 cam was a good cam, but, left something to be desired.
    For truck motors, one of my favorites is the Comp 260/260.
    One thing to consider is this, a cam with a longer exaust duration will make more top end power than a cam with the same on both (providing that the intake duration is th same) but, will not make the low end punch that the same/same will.
    The same/same duration cams are meant to keep low end torque on heads that have closer intake/exaust flow, and headers. But, will make more low end on stock heads with manifolds too. Your choice. A same/same cam will help on fuel economy too. :thumbs:
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