Next step to increase low end power

Engine, Trans & Driveline

  1. Marco

    Marco Active Member

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    Hello everyone,

    Two years ago I (cheaply, I'm a student and live in the Netherlands zo parts are about 30% more expensive) rebuilt a Mopar 400ci for my daily driver 1966 Plymouth Belvedere. Main parts I replaced/added are:

    Cam: Hydraulic Flat Tappet, Duration @50 212/212, Lift .440/.440
    Carb: Edelbrock AVS 2, 650 cfm
    Exhaust: Added headers-> 1 3/4 primary to a full 2.5inch exhaust system with dynomax race bullets (No crossover)
    Ignition: Mopar Electronic ignition conversion kit with an MSD coil and plug wires.
    Rotating assembly: Stock crank and connecting rods but 030 over pistons raising compression to 9.5-1.
    Valvetrain: all stock rocker arms etc.
    Heads, intake is all stock

    The "problem" is that I want to increase the low-end power a bit but I'm not very sure what would be the best value part/parts to buy.
    Hope someone can educate me!

    Best regards,
    Marco
     
  2. Don Frelier

    Don Frelier FBBO Gold Member FBBO Gold Member

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    1. Intake
    2. Air/Fuel meter - Tune
    3. Heads (and of course tune)
    Double check your cam degree angle consider advancing it slightly and tune.
    Not that this applies to you, but I think many people just put parts together can really leave a bunch of performance untapped.
    Auto or Manual transmission? Converter?
    Gears?
     
  3. Marco

    Marco Active Member

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    Hi don,
    Thank you for your response, i was indeed guessing that the intake would be first.
    About the tune, I already let someone tune the car with an afr meter, as i should have said is that the car is running on lpg, this because the gasoline is on average $7 a gallon in the Netherlands and lpg only about $2.
    I’ve got a tf727 rebuild with a firmer shift kit and new clutches etc, 2200 stall converter and 3.55 rear gears non lockup.
    I’ll start searching for a cheap second hand intake!
    Thank you again for your help!
    Best regards,
    Marco
     
  4. Don Frelier

    Don Frelier FBBO Gold Member FBBO Gold Member

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    The LPG is a surprise, I wouldn't know how to tune that.
    I'm guessing you tune closer to 14.7?
     
  5. steve340

    steve340 Well-Known Member

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    Most engine mods sacrifice low end torque/power generally.
    If the engine is sound leave it as is and bang on a small supercharger and it will probably burn rubber.
    I have fitted 4 of the Holley/Weiand low rise blowers on a few engines and the worked pretty well.
     
  6. Curiousyellow71

    Curiousyellow71 Well-Known Member

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    You can run a LOT more compression then 9.5:1 on lpg. You may consider shaving your heads and running a thinner head gasket or a closed chamber head. With more compression you can run more cam and not just gain on the bottom end you can gain everywhere. Another option is using rhoads lifters. Rhoads lifters will make the cam act smaller and without any loss in top end hp. They do a make a sewing machine sound, but the adjustable vmax rhoads you can adjust however you want. But vmax takes adjustable valvetrain.
    What type of lpg system are you running? Are you trying to run dual fuel?
     
    Last edited: Apr 14, 2020
  7. wyrmrider

    wyrmrider Well-Known Member

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    Whose cam and what is your seat duration at .004 or .006 or?
    We rebuilt a lot of 440 transit bus Propane engines
    our combination was
    first we tried welding up the chambers to make closed chambers like the 67 915 head
    later developed the quench dome piston for the open chamber head tight quench really helps but if you are not going into the short block
    you could flat mill the heads to eliminate that dead area that is detonation site or switch to the wedge heads
    how far down is your piston?away from the plugs and pick up some compression
    second we held the overlap on the cam down otherwise the exhausts glowed cherry red
    intake will save some weight but not pick up much low end
    do post up the rest of your chassis speecs
    not really relevant but on the 413 Industrial motors we ran a 192@.050 cam with 420 intake lift and tried that on the 440's but went to a 202-205 cam on them but with slightly more lift than you have
    you have a single pattern cam which is good what's the lca
    cheers
     
  8. 66 Sat

    66 Sat Well-Known Member

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    Doesn't a H pipe in the exhaust increase low end torque a little bit?
     
  9. wyrmrider

    wyrmrider Well-Known Member

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    Looking at Don's list
    I'd do spark advance curve first
    whaat pistons to get 9.5? gaskets? did you cc the headss as published numbers are less than reality
    post up your cranking compression
    cheers
     
  10. Marco

    Marco Active Member

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    Hello everybody,

    Thank you for all your responses.

    @Don hahaha yes LPG is pretty common on cars here in the Netherlands, with LPG you tune to about 15.5

    @Steve thank you for your input! I will do some investigation on how a supercharger works with an LPG system.

    @Curiousyellow71 Yeah I could indeed run a lot higher compression, but because I eventually want to upgrade my stock heads. I now got the 213 motorhome heads which have a pretty big chamber. Also, I got .042 head gasket which I had laying around from another build so I could indeed gain quite a lot replacing the gasket. About the Rhoads lifters, I never heard about them, will do some research into them right away! I am running a single fuel impco system, with the model e vaporizer and the 425 mixer. Thank you for your help!

    @wyrmrider I've got the comp cams K21-213-4 kit, I don't know what you mean by the seat duration at .004 or .006. I'm not really planning to go into the short block but milling the heads should definitely be possible. hahaha yes, all that for only 9.5, as I said to Curiousyellow I want to one day put some better heads and gaskets on and raising the compression that way. The deck clearance is now about .027.

    @66 Sat first of, a really nice car you got there! Yes indeed, when the car lift is finally not in use by my dad I'll indeed be doing that first.
    Thank you everybody for your responses!!
     
    • Thanks! Thanks! x 1
    • steve340

      steve340 Well-Known Member

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      You may want to investigate the gas flow of that Impco unit as it may not be able to be used for performance?
      There was a car here that had 2 specialist LPG carbs/units with a blower and it was pretty rapid. I don't know anything about his setup other than it was dedicated to LPG and it had special carb things on it.
       
    • Mick56

      Mick56 Well-Known Member

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      Putting in a lower gear ratio rear end may help. Maybe a 4.10?
       
    • wyrmrider

      wyrmrider Well-Known Member

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      Thanks made me look it up it's a traditional

      High energy series 260/ 260 212/212 440/ 440 lift cam duration is 260@.006 IC 56 40 Overlap MI 25.7 (12.3/13.4)
      Extreme Energy 250/260 206/212 432/444 110 Intake close 51 ABDC 35 overlap
      XE 252/252 206/206 .425/.425 110 LCA
      Extreme Energy 256-268 212/218 457/455 110 intake closes 54 ABDC 44 overlap MI 22.9 (11.1/11.8)
      Exreme XFI MI 23.1 (11.2/11.9)
      Purple Plus .904 MI 24.0 (11.6/12.4)
      Extreme Mopar .904 MI 23.1 (11.2/11.9)
      comp does not give the details on your cam
      comp gives you lots of ways to slice the marketing baloney
      you can estimate the intake and overlap for your cam
      note how the XE 256 has more lift from less duration, however all of these vintage grinds are for the .842 chevy lifter
      for example a Lunati Voodoo Voodoo 258 213 ,454 would make more power but not much more low end
      the Howard......,006..,050...200 lift
      HM2063164A 252 206 126 .472 standard .904 is 8 degrees shorter with significantly more lift and area (that's a small block cam number just for reference)
      my favorite cam in this class is the Mike Jones which goes even shorter at .004 and actual seat, is fat where it needs to be yet has a nice big nose for low wear
      256 202 120 .305 .461 50% fatter @.275 than DC 260 (269 @.006) It's going to be WAY fatter than your cam
      Either the jones or the Howard would pump up your dynamic compression and are lots fatter than your "universal" lifter grind
      I do not try and chase the last .015 lift as it usually leads to little pointy noses but Howards profiles are relatively recent, or really recent compared to comps

      comp race hydraulics are MI 25.8 (12.9/12.9)

      NEW NOSTALGIA PLUS™ HYDRAULICS Designed to mimic the sound of the great engines of the past.. designed for chevy lifter
      THUMPR™ HYDRAULICS The Thumpr™ lobe profiles are designed to optimize the character and sound,

       
      Last edited: Apr 16, 2020
    • Mebsuta

      Mebsuta Well-Known Member

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      I think Comp 260 High Energy goes like this for advertised duration (.006 lifter for Comp I think): IVO 24 BTDC, IVC 56 ABDC, EVO 64 BBDC, EVC 16 ATDC. 40 overlap, 110 LSA, ICL 106.
       
    • BSB67

      BSB67 FBBO Gold Member FBBO Gold Member

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      1) does your piston have valve notches?
      2) have you conducted a cylinder pressure test?
      3) what cylinder pressure can you typically get without detonation with lpg?

      Here are my general take aways:
      A) I'm surprised the it does not have good low end now. Which makes me wonder if something else is going on.
      B) if you're looking for meaningful seat of the pants improvement over what you have now, I doubt it will be in the intake or cam.
       
      • Agree Agree x 2
      • Curiousyellow71

        Curiousyellow71 Well-Known Member

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        One thing you have to watch with propane it's a dry fuel and although there is very little cylinder wear and is very clean....it is hard on rings. Moly rings can lose tension after about 10 thousand miles on propane. Cast rings are better for propane seem to handle the dry fuel better and wear better. But often on propane it runs great at first and the slowly loses power over time till it just doesnt feel like it has as much zip. But they can still run ok 100,000 miles later if set up properly. I liked to run as much compression as possible starting out. On the 11:1 engine we ran... it ran pretty good with 120,000+ miles even though it was 30-40 lbs less on compression from when it was fresh. A low compression engine can really run like crap if you start out at 120 psi and after some miles your south of 100. They use to make a upper end cylinder luber that made the rings last great...but I haven't come across one in years.

        Propane octane typically runs 104-112. A lot of the first turbo set ups ran on propane and it is excellent for boost. I was thinking a 425 impco is rated for 300hp or 350hp and it's not uncommon to see 2 set ups in a performance application...or for tractor pulling they run a bigger unit then a 425. They use to have a hp rating on them, but things have probably changed.... we've run propane on trucks, pickups and tractors and power units. Only had one car with a set up. It can be frustrating....been there. LOL
         
        Last edited: Apr 16, 2020
        • Thanks! Thanks! x 1
        • wyrmrider

          wyrmrider Well-Known Member

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          Thanks Mebsuta- I edited my post above your numbers look about right did you have a cam card
          love the way comp switches from advertised to .050 in their cam look up list
           
        • Mebsuta

          Mebsuta Well-Known Member

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          yvw. They used to publish those figures on their old website, and have them in their online cam finder when it was working. I had them saved off in Desktop Dyno.
           
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