Stock 1972 340 intake and Thermoquad HP limits..?

Discussion in 'Small Block Mopar Engine' started by Woodie, Jun 12, 2018.

  1. Woodie

    Woodie Take-off EH!

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    Any guess what the factory cast iron intake and TQ would be capable of supporting power wise? Lets assume a true 10.5:1 .030 340... Big valve "J" heads and a SFT camshaft... There is a 69 valiant here waiting for a 340 swap from a 72 swinger, the owner plans on making some upgrades but wants to keep the factory iron.
     
  2. abodyjoe

    abodyjoe Well-Known Member

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    friend has a 71 demon that runs well in to the 10's with a cast iron intake and thermoquad on it..


    TD_KenKopecky_ESA-DodgeDemo.jpg
     
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    • rigger3006

      rigger3006 Well-Known Member

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      i wonder if anyone has tried extrude honing on one of these intakes? i read on an article years ago on a bbc and it made quite a difference in hp
       
    • Darter6

      Darter6 FABO Gold Member FABO Gold Member

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      A friend has one done for his stocker. Picked up 3 tenths. Till he got pinched during a tear down.
       
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      • qkcuda

        qkcuda Well-Known Member

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        Those are good flowing manifolds, similar to an LD340 but heavier. I had a buddy that ran well into the 11's with a 340 back in the day. The thermoquad will not be a restriction.
         
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        • furrystump

          furrystump Well-Known Member

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          Extrude hone is not that great. Even if you are required to run the stock casting it’s worth 5-10 hp. Cost is pretty high. There’s so much other low hanging fruit in most combinations.
           
        • Valkman

          Valkman Well-Known Member

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          Yes this a good intake, but any good dual plane intake power would be limited by RPM, that being said I would think that 450+ hp would be possible, and as for the TQ it has the cfm to get you there. For the engine OP was asking about it would be more like 350 hp.
           
        • ir3333

          ir3333 Well-Known Member

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          stock intakes were fine and many are used on 10 second 340's.
          ...there's just no bling.
           
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          • Woodie

            Woodie Take-off EH!

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            Exactly.. Thats what we are shooting for. Bone stock appearance.
             
          • rumblefish360

            rumblefish360 so close yet so far away

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            Been saying for years & years, the factory iron intake is actually not a bad part, very capable. While it is true your giving up power to a nice new shiny modern intake, it can’t be beat for on the cheap and undercover stealth.

            More people loose more time and power in there chassis than the difference in intakes. If you had money for a nice pro porting of the intake that would be crazy awesome.
             
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            • Woodie

              Woodie Take-off EH!

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              I agree. Just business with 45 year old factory iron.
               
            • Wyrmrider

              Wyrmrider Well-Known Member

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              factory 4 bbl manifold and you cannot do better than a tq (well sometimes on a race only deal) unless you have a lot of money in the X or J heads
              if you want to stay stock looking and have not spent money on the J's (guides, hard seats, porting) then start with the Enginequest or 88-92 208 model heads=Magnum heads can also be used with stock manifold with some work and they also flow better- (lots of vendors for the EQ iron heads under several names and various results of work
              get your rockers figured out b4 doing camshaft iron or roller rockers- with any duration or lift you are looking at shimming your stands so be prepared to take the time to do it right if roller rockers think 1.6 (or more)
              use AMC solid lifters and oil through the pushrods, use 3/8 pushrods (pushrod flex is a problem with long pushrod motors)
              once you get the heads figured out (and head flows, and exhaust) fill this out for SFT Street Performance | Jones Cams
              get your owner to be real clear on what rpm range he will be happy with, power brakes, gears, etc
               
            • yellow rose

              yellow rose Doctor of Thinkology.

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              Yes OP...please do fill out the form for Jones cams and if you don't mind, please post the results. I'd bet everything I have that you'll get an .842 lobe.

              At least that's what I always get. Maybe you can get something better.
               
            • Wyrmrider

              Wyrmrider Well-Known Member

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              he's going for a flat tappet- which is a good move for most anyone
               
            • Woodie

              Woodie Take-off EH!

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              Dr Think... Why a .842 lobe???
               
            • Jadaharabi

              Jadaharabi FABO Gold Member FABO Gold Member

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              My guess is those cam Grinders use the Chevy specifications.

              Am I right?
               
            • Wyrmrider

              Wyrmrider Well-Known Member

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              you are so right
              not much market for MOPAR compared to Chevy
              but worse they specify the same timing as for a chevy (long rod vs short rod makes a difference)
               
            • yellow rose

              yellow rose Doctor of Thinkology.

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              You'd have to ask Mike Jones to find that out.

              IIRC he told me (at that time which was 2-3 years ago) that it wasn't needed for what I wanted.

              I disagree.

              But I'd suspect if he didn't spec a .904 lob for me, I'd be hard pressed to believe he would spec one for most anyone else.

              And Jones wasn't the only one. No one would grind a .904 lobe for me but Jim at Racer Brown.
               
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              • Wyrmrider

                Wyrmrider Well-Known Member

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                Bill Jenks at Potvin/ Moon did our ones for the Propane buses
                Crower did the one for the 383 Superbird I put a RB crank in- I still have the spare piston and will see if I can figure out how to post it up
                It had basically Magnum seat duration but lots more lift and lobes for stock rockers
                I've had several .904 profiles from Crower
                Chet Herbert had some non catalog grinds
                Jack Engle actually would recommend .904 grinds- not radical- easy on the valve train
                did you notice how much more intensity the Comp XE 256 has over any of the other 256 Mopar grinds-
                Rick Jones ground me his 440 cam in the early 80's (when Jones Cams was in CA)
                Never dealt with Jim but did run Racer Brown in the Max Wedge
                Also Isky (except for top fuel) only had ONE .904 lifter design- I don't think it's in the catalog anymore but it was amazingly consistent
                The Racer Brown and the Isky both worked but were quite different personality wise
                Racer was way ahead of the game as far as geometry was concerned- First to make a good cam for the OHC Datsun and ran it at Bonneville
                later Ford 4 cylinder had the same challenge- not easy to solve on a hand calculator
                Lunati .904 grinds are easiest to find- or Hughes
                were' talking hyd here
                solids are easier- Ultradyne, Jones several others have a series of .904 solids