help upgrading my 340

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    Author Topic: help upgrading my 340  (Read 3401 times)

    Offline tvanlant

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    help upgrading my 340
    « on: August 02, 2005 - 10:11:32 PM »
    Hi, new to these forums.  I have a 73 Cuda 340 4-speed.  The best run I have made in the car is a 13.34 @ 105 mph, and I would like to go maybe 12.70s.  Not all at once though.  Here is what the car has done to it so far:

    bored .030
    forged 9.5 CR JE pistons
    MP purple cam (284 duration, 484 lift)
    Edelbrock Performer RPM Intake
    Long tube headers
    J heads with 2.02 valves, but not ported
    finely tuned thermoquad
    Chrome ignition box
    Accel Distributor
    3.55 posi
    BFG Comp TAs for at the track

    First off, I have a set of forged JE pistons that will bump compression to 10.5.  How much power/time would these help.  Other than that, I would be very appreciative of any other advice to help make my car faster. 

    Also, it is in perfect condition and numbers matching, so I don't want to reduce weight or put in a bigger motor.


    Thanks, Tyler
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    Offline 4Cruizn

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    Re: help upgrading my 340
    « Reply #1 on: August 02, 2005 - 10:17:51 PM »
    Welcome to cc.com Tyler!!  That sound like a great car!!  Do you have any pics you can share with us . . . we are picture junkies!!   :dogpile:
    « Last Edit: August 04, 2005 - 08:36:31 PM by 4cruzin »
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    dodgetkboy78

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    Re: help upgrading my 340
    « Reply #2 on: August 02, 2005 - 10:22:40 PM »
    I would think you should work on traction, more than launch. Also, wich cam is it? the 114 center? or the 108 center cam? (or was it 110?)
    Raising the compression a point might not do as much as you might think.
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    Offline Chryco Psycho

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    Re: help upgrading my 340
    « Reply #3 on: August 02, 2005 - 10:49:40 PM »
    I would leave the compression a lone especially if you are using it on the street , the 2 flaws I see in the package are the heads & cam , the cam is decent but it is a 30 year old design , a newer Engle or Ultradyne fast ramp cam will  pick up the power & we just did a swap from J heads to newer 308 castings & gained 41 hp & 45 ft lbs with no other changes
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    Offline tvanlant

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    Re: help upgrading my 340
    « Reply #4 on: August 04, 2005 - 06:53:53 PM »
    so if raising compression isn't all its cracked up to be, then what should I do next? 
    What did the 308 heads come on?  What makes them better than Js?   
    Here is a pic of the car before I put the new springs in the back, you can see it sags a little.

    [attachment deleted by admin]
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    Offline Chryco Psycho

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    Re: help upgrading my 340
    « Reply #5 on: August 04, 2005 - 10:09:42 PM »
    308 castings are used on 360 engine from 87 -91 , the exhaust port is far better
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    Offline tvanlant

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    Re: help upgrading my 340
    « Reply #6 on: August 04, 2005 - 10:33:07 PM »
    what other modifications are required to run those heads?
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    dodgetkboy78

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    Re: help upgrading my 340
    « Reply #7 on: August 05, 2005 - 12:13:42 AM »
    Not a thing, ther are a bolt on! I would cc your engine, to figure out exactly what compression you have withg the 308's, and then choose your cam. :thumbs:
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    Offline Chryco Psycho

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    Re: help upgrading my 340
    « Reply #8 on: August 06, 2005 - 12:31:12 AM »
     :iagree:
     the 308 heads use Shaft rockers , the last heads to do so & literally bolt on , Porting is highly recommended , you can also enlarge the intake to 2.02   
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    dodgetkboy78

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    Re: help upgrading my 340
    « Reply #9 on: August 06, 2005 - 11:04:23 AM »
    308 heads really that great Chryco?

    oh, and................ :worthless:
    got any porting tips on th e302/308's?
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    Offline Chryco Psycho

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    Re: help upgrading my 340
    « Reply #10 on: August 06, 2005 - 11:25:40 AM »
    pix to follow , the heads seem to be that good , we dynoed a 340 with J heads & swapped the ported 308 heads on & gained 41 hp & 45 ft lbs with no other mods
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    dodgetkboy78

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    Re: help upgrading my 340
    « Reply #11 on: August 07, 2005 - 01:29:26 AM »
    looking at mine, (302's) the ports look pretty good, a lil smooth in places, and need some clean up, should work great, however, the bowl looks as if it needs some help.

    (am installing 2.02's, I think.)
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    Offline Chryco Psycho

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    Re: help upgrading my 340
    « Reply #12 on: August 07, 2005 - 01:33:20 AM »
    shaping the valve guide is where the big gains are , think wing , curved on the leading edge & knife sharp on the trailing edge
     I doubt 2.02 will help in the small port head
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    dodgetkboy78

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    Re: help upgrading my 340
    « Reply #13 on: August 07, 2005 - 01:37:38 AM »
    supposidly, the 2.02's help in the 450 and up lift department, Ive never put 2.02's in a small port, but was gonna give it a shot, ut, after you said that, I think I'll stick with what I got. :thumbs:

    sounds like the same need as the older heads. :thumbs:
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    Offline tvanlant

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    Re: help upgrading my 340
    « Reply #14 on: August 08, 2005 - 05:12:39 PM »
    What is the combustion chamber size of the 308?  Is it larger or smaller than the J head?
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