340 engine rebuild

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    Author Topic: 340 engine rebuild  (Read 6747 times)

    Offline burnsy26

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    340 engine rebuild
    « on: June 17, 2005 - 12:30:43 AM »
    I have a general question about rebuilding a 340.  I wanted to know if anyone had experience with any of the stroker kits?  What cam, lifters, rods ect. they would put in for mostly street driving? While trying to achieve some more power than original without changing the outward appearance of the engine bay with electronic ignition and that sort of thing.  Basically I have made a mess of the real question which is I want the car to look stock but I want to add some serious punch to the motor.  Any suggestions would be greatly appreciated.
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    Offline Chryco Psycho

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    Re: 340 engine rebuild
    « Reply #1 on: June 17, 2005 - 04:21:06 PM »
    Welcome , I would use at least the stock lenght rods if not longer to maintain rod ratio ,
     cam is determined by the powerband you want to run , due to lifter problems with hydraulic lifters , I like to use a small solid cam & iron rockers liek the 273 rockers for street use
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    Offline mrbill426

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    Re: 340 engine rebuild
    « Reply #2 on: June 25, 2005 - 11:21:04 AM »
    Do those 273 rockers require different shafts than those of the 340??
    Are the hold down assemblies the same?


    Quote from: Chryco Psycho on June 17, 2005 - 04:21:06 PM
    Welcome , I would use at least the stock lenght rods if not longer to maintain rod ratio ,
     cam is determined by the powerband you want to run , due to lifter problems with hydraulic lifters , I like to use a small solid cam & iron rockers liek the 273 rockers for street use
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    Offline Chryco Psycho

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    Re: 340 engine rebuild
    « Reply #3 on: June 25, 2005 - 11:14:17 PM »
    the 273 rockers are a bolt on for the LA heads , the sahfts are the saem , if you use Crane rockers you can buy hte thicker shaft to reduce deflection , you cvan also use stock or billet hold downs
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    Offline mrbill426

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    Re: 340 engine rebuild
    « Reply #4 on: June 29, 2005 - 04:41:44 PM »
    Quote from: Chryco Psycho on June 25, 2005 - 11:14:17 PM
    the 273 rockers are a bolt on for the LA heads , the sahfts are the saem , if you use Crane rockers you can buy hte thicker shaft to reduce deflection , you cvan also use stock or billet hold downs

    Okay, I asked that question because I had "heard" elsewhere that the iron rockers needed different oiling when used with a hyd cam;  something about not ever being "unloaded" to allow oil flow, as they would be with a solid cam.  I am not sure yet if I am going with a hyd or solid cam, but I do intend to use iron rockers either way.

    I have found a set of iron adjustable rocker arms that are supposed to fit a small block (340), but I cannot find a reference anywhere to the casting (or part) numbers that are on the rockers.  All 16 rockers have the same number which appears to be #2465380.  Does anyone have a reference to this number?   These rockers are all "straight", and have the hollow, self-locking (no lock-nuts) adjuster screws.

    Also, I intend to use the open chambered Edelbrock heads on this 340, am I safe to assume this valve train will work with those heads
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    Offline mrbill426

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    Re: 340 engine rebuild
    « Reply #5 on: June 29, 2005 - 05:53:36 PM »
    They look like this

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    '72 Sebring; bracket project
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    Offline bluecuda

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    Re: 340 engine rebuild
    « Reply #6 on: June 29, 2005 - 06:58:50 PM »
    Those are the same rockers on my 1971 340.
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    Offline 1973challenger360

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    Re: 340 engine rebuild
    « Reply #7 on: June 29, 2005 - 08:20:07 PM »
    the 273 and the 340-6 were the only motor to recieve adjust rocker were not they, the 273's had solid cams and the 6 pack used them on the hydrolic cam.
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    Offline mrbill426

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    Re: 340 engine rebuild
    « Reply #8 on: June 29, 2005 - 09:16:29 PM »
    Quote from: bluecuda on June 29, 2005 - 06:58:50 PM
    Those are the same rockers on my 1971 340.

    Okay.  Do they use the same rocker shafts as the stamped steel hydraulic arms do?  I've heard there is an oiling issue with the "solid" rockers.  Not sure if we will run a solid or hydraulic cam yet, but want to be prepared.

    Thanks
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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

    Offline Chryco Psycho

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    Re: 340 engine rebuild
    « Reply #9 on: June 29, 2005 - 09:59:31 PM »
    if you are going to use the Alum heads you need to use a smaller chamber head to compensate for heat loss alone basicallly you need to raise the compression by between .8-1 point of compression so a closed chamber head may be a better choice
     I have never heard of a problem with using iron rockers with hydraulic cams & I really doubt the T/A engine would have used them if there was a problem
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    Offline mrbill426

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    Re: 340 engine rebuild
    « Reply #10 on: June 30, 2005 - 12:09:32 AM »
    Thanks, Chryco,

    We plan to use the Performer RPM heads #60179 with 65cc chambers, which are made for the early high compression 340s, along with Sealed Power forged pistons #LF2316  that according to the manufacture (and Edelbrock), produce 10.06 to 1 compression with those chambers.

    Think we will wait to decide on a cam, until the short block is done and we can check to see what kind of lift space is in there for the valves.
    We may end up using a solid, but not sure.

    Sound reasonable?
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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

    Offline Chryco Psycho

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    Re: 340 engine rebuild
    « Reply #11 on: June 30, 2005 - 12:24:25 AM »
    it will give you a static 10:1 compression ratio but with alum heads you need close to 11:1 to = the same heat / power as an iron head
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    Offline MoparMatt383

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    Re: 340 engine rebuild
    « Reply #12 on: June 30, 2005 - 08:16:25 AM »
    When you guys say 273 does that mean all 273 engines or just the 273 commando?

    Matt
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    Offline mrbill426

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    Re: 340 engine rebuild
    « Reply #13 on: June 30, 2005 - 08:57:04 AM »
    Quote from: Chryco Psycho on June 30, 2005 - 12:24:25 AM
    it will give you a static 10:1 compression ratio but with alum heads you need close to 11:1 to = the same heat / power as an iron head

    Whoa, then the Edelbrocks are not such a good idea unless we want to run 11:1 pistons?  That's a major ($$) shift to our parts gathering  :newsad:  We don't want to have to routinely "feed" an engine with that much compression either.  Think it cheaper and wiser to re-work the stock (small valve) "J" heads by installing larger valves and doing some home porting??   We don't want to blow $1,400.00 on a set of heads to get zero gain  :ack: 

    Was hoping to shave a lot of weight off the front of that car and gain some good HP in the process, now it seems it wouldn't work. :cry:
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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

    Offline Chryco Psycho

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    Re: 340 engine rebuild
    « Reply #14 on: July 01, 2005 - 12:22:05 AM »
    the 11:1 engine with alum heads will run the same as a 10:1 iron head engine so you only need to use pump premium  fuel , it will not detonate at 11:1 seeing as the alum head absorbs the extra heat that will cause detonation 
     I built a 11:1 alum head 440 last year & has minor detonation with 93 octane pump premium fuel 
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