New life for an old 340 (stock stroke)

Discussion in 'Small Block Mopar Engine' started by RAMM, Jun 22, 2018.

  1. RAMM

    RAMM Well-Known Member

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    Picked this pretty nice '70 340 block up to build. Some of you know that I'm not the biggest advocate of long arm crank throws and this build will uphold that. I believe the stock stroke 340 WAS an excellent engine design back in the day and want to see what can be done with one now. The plan: Build a 340 with X heads and solid lifter cam for some high rpm fun. Target 450-475 HP @ 6000+ rpm
    The package:
    ' 70 340 block 4.100" bore 10.5-10.6 comp target
    stock steel forged crankshaft
    Scat I beams 6.123"
    SRP 4.100" flat tops 1.804" cht (before anyone asks, yes they are making them for me)
    Custom Comp Cam (see photo)
    X casting heads w/Ferrea 2.02/1.60 hollow stem valves
    Torker II intake
    Rockers (undecided as of yet) Hughes 1.6 or Crane 1.6 or possible 273 iron

    Really looking forward to this one. J.Rob

    340 block.jpg

    340 steel crank.jpg

    340 cam.jpg

    Torker II.jpg
     
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    • RAMM

      RAMM Well-Known Member

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      Couple of head shots before and after a trip to the shotblaster. Seats look really nice, after installing 11/32" guides. J.Rob

      X heads before.jpg

      X heads after.jpg

      Xheads.jpg
       
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      • yellow rose

        yellow rose Doctor of Thinkology.

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        Hey Rob...I can't tell from the cam card what series of lobes those are. Do you have any idea which lobes they are?

        This is an interesting build as this is damn near exactly what I built.
         
      • 67autocross

        67autocross A new iron curtain drawn across the 49th parallel

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        I another 340 I had used that single plane torker intake, I seem to recall it don't really do the car any good after I switch over from the stock 70 iron intake. Looking forward to seeing what kind of power you make with that cam.
         
      • MoparMike1974

        MoparMike1974 Well-Known Member

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        I would spend the extra money on some H beam rods.
         
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        • 273

          273 Well-Known Member

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          Glad to see, to me one of the best features of Chrysler motors besides valve angle was there bore to stroke and rod ratios.

          Instead of stroking, spin and gear it.
           
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          • perfacar

            perfacar Well-Known Member

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            that engine should have the 496 rod, those are very good rods, we ran a set, for 18 seasons, every 4 years, new mopar race bolts and resized. they are way lighter versus H beam rods. we turned our 340 7000 RPM in the traps, we have a customer, runs a340 dart, with same heads, cam is 254/267 .545 , 108 lca, runs 11. 20's 117 /118 MPH.
             
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            • rumblefish360

              rumblefish360 so close yet so far away

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              Nice! I’m doing something similar now. A 340 refreshing. TRW forged 10.5-1 slugs in a .030/340 with a Hughes solid HEV 239/245 w/.546/.582 lift. It may get the 1.6 rockers I was saving for another build. IDK.....
              I got it from 340Doc. It should make for a solid street driver IMO.

              Looking forward to to your builds as always!
               
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              • Wyrmrider

                Wyrmrider Well-Known Member

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                unless your heads are professionally ported you only need the 1.6 on the intake the ex likes the extra exhaust which you have
                do you have any flow data
                 
              • rumblefish360

                rumblefish360 so close yet so far away

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                I don't know who that was directed at by that is the plan of attack.
                 
              • RAMM

                RAMM Well-Known Member

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                The lobe numbers are right at the top. You will need Comp's Master Lobe Reference Catalog in order to look them up. J.Rob
                 
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                • RAMM

                  RAMM Well-Known Member

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                  Why? The Scat I-beams are rated for somewhere north of 600+ hp and 7000 rpm. Why would I want a much heavier more expensive rod rated for 800-1000+hp when I clearly stated a target of 450-475 hp @ 6000+ rpm? J.Rob
                   
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                  • RAMM

                    RAMM Well-Known Member

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                    Totally agree ^^^^^^^^^. J.Rob
                     
                  • RAMM

                    RAMM Well-Known Member

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                    I didn't receive the rods with this core and probably wouldn't have used them anyways. No way of telling how close they are to the end of their fatigue cycle. J.Rob
                     
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                    • RAMM

                      RAMM Well-Known Member

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                      Get it done and thanks! J.Rob
                       
                    • RAMM

                      RAMM Well-Known Member

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                      The heads are not ported yet , but will be comparable to a "stage 2" type job. Not going crazy on these. No flow data yet but I do know a stock X head will flow 195-205 cfm on my bench. Targeting a modest flow rate with a nice tight port--245-255 cfm is all that is needed here--maybe less. J.Rob
                       
                    • 67autocross

                      67autocross A new iron curtain drawn across the 49th parallel

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                      Did you orders the Pistons yet?
                       
                    • RAMM

                      RAMM Well-Known Member

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                      Yes, pistons are on the way. If you look around for a stock stroke 340 replacement piston in a 4.100" bore, you will quickly see that only one (DSS Racing) offers one. MAhle Motorsports only offers a 4.07" pistons. JE/SRP offers a nice piston but only up to a 4.08" bore size.
                      I was extremely fortunate to have a great contact at RWB (Race Winning Brands) who own JE/Wiseco/K1 etc........ that was willing to do me a SRP piston at a SRP price in a 4.100" size without the expense of a full custom route. << This was really the cornerstone of this whole project. J.Rob
                       
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                      • rumblefish360

                        rumblefish360 so close yet so far away

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                        Thanks man, I will!
                         
                      • Wyrmrider

                        Wyrmrider Well-Known Member

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                        your It may get 1.6 rockers post
                         
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                        • 67autocross

                          67autocross A new iron curtain drawn across the 49th parallel

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                          I’m interested in putting pistons that 340 with the gap less rings I ran last summer, I was looking at forged flat tops just in .30 over as the bore on my block is good.
                          My J heads flow around 250 and l have the same rods and crank as you are using.... it makes me want to buy the same cam you have and see how close our engines are on the dyno...
                           
                        • crackedback

                          crackedback FABO Gold Member FABO Gold Member

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                          That's a 550+ hp build on some dyno's... :lol:

                          It should make 450ish maybe a bit more. Saw a 340 with xs282s and ootb ede's make 455 or so. Should be at least equivalent to that.

                          At least it's a torker II and not the doorstop torker 340.
                           
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                          • moper

                            moper FABO Gold Member FABO Gold Member

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                            About 15 years ago I did a top end on an existing 340+.030 short that made those figures. X heads with 2.05/1.65, Serdi 5 angle valve job, my "Stage 2" porting, shelf grind Comp hydraulic, small tube headers, M1 intake. By weight & MPH it was around 460hp. Very fun package with a loose convertor and 4.30s on a 28" tire. But by the GenX & Millenial definitions not as streetable as the 4" combos. It's old-school fast.
                             
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                            • mderoy340

                              mderoy340 Well-Known Member

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                              Thanks for sharing. I need to upgrade the cam in my 340 and always enjoy reading your posts.
                               
                            • RAMM

                              RAMM Well-Known Member

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                              ^^^^^^^^This is exactly the idea. Any idea on the RPM characteristics? J.Rob
                               
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