Engine Performance Mysteries?

Engine, Trans & Driveline

  1. Ron H

    Ron H FBBO Gold Member FBBO Gold Member

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    I thought I’d ask about what I think is some untapped or missing giddy-up with my poly after an extensive and expensive overhaul. My car is a ’63 Fury with the PB 727. Among the mods as I can recall offhand:

    Eddy 4bbl, solid lifters, cam (262 deg, lift .450), bored .60 over, headers, 3” exhaust with X pipe, flow masters, 340 rods. I had changed the rear from 3:23 to 3:55. An issue is the distributor I’m still futzing with. I’m running full mechanical as so far the vac advance adjustments get engine missing at various RPM’s; but runs smooth without vac advance. I’m now aware that the 3” pipes were a mistake for this motor and build. I’m looking at a quieter exhaust reducing the mufflers to 2.5”. The TC was changed out to a later era mopar with I think around a 2500 stall (got to double check this). I installed a mopar electronic ignition 15 years ago that’s unchanged. (Before this build I had put on a 4bbl and dual exhaust).

    The rough estimate is around 325 HP setup. Anyway, my ride seems lethargic off the line; but more power at higher speed. In fact, as I recall the giddy-up off the line, it doesn’t seem better than before all this chit. Hope this offers enough info…in case anyone has thoughts on garnering some better performance. Thanks!
     
  2. pnora

    pnora FBBO Gold Member FBBO Gold Member

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    Usually with a miss with the vacuum advance is one of two things. The gap on the pickup is wrong or something with it is a possibility. Or over advanced base timing. Was the cam properly degreed when assembled?
     
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    • 451Mopar

      451Mopar Well-Known Member

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      I don't put much faith in the Mopar electronic ignition boxes and ballast resistor setup.
      In the Motor Trend Engines Masters video, they had issues with an engine, and then found the orange ECU box was going bad. I don't recall the power difference when it was changed. I run the MSD 6AL, or Crane HI-6, or EFI (or combination EFI triggering CD box.)
      Ran those since the 1990's and they still work fine. I did have an issue with the MSD when I got water in the wiring loom once, but once I unwrapped the loom and got the water out it worked as normal.

      For the cost of a MSD all-in-one, I would get the Holley Hyperspark ignition system with CD box and ignition coil. Now these are made for the Sniper EFI, which is where I was going......
       
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      • 66 Sat

        66 Sat Well-Known Member

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        Ron, I think you've lived with this issue for long enough. I'd try to find a local tuning guru who can take a look at it for you and sort it out once and for all. Get the exact cam specs from the engine builder if you can, and then get the cam degreed. Sort out the ignition issue. Think about changing the exhaust to 2.5". Maybe you can then sell the 3" system to offset the cost. What compression ratio have you got?

        As you know I have a similar spec engine with 3.23 rear, 727, stock converter, manifolds not headers. The car weighs 3,640 lbs. Without qtr mile times to compare, performance is subjective, but I think my car goes hard off the line (for a 318 in a big car) and runs strong right throughout the rev range (to just under 6,000 rpm). The only time I am disappointed with the performance is accelerating say from 30 mph in 2nd, when I'm going a bit too fast to drop to 1st gear, but 2nd is too high. Acceleration in this situation seems a bit lame, until the revs get to 3,000 rpm. 3.55 gears and a higher stall converter would probably fix this, but you've already done that.

        I'd love to catch up and do some testing with you but the distance is a bit of an issue...
         
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        • Babyblue66

          Babyblue66 Well-Known Member

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          What is your initial, and total timing? I'd start at 15 at idle, and 35 total. Also what is the actual compression ratio? Have you done a cylinder cranking pressure check? You say you think 2500 stall. At what rpm does it flash when you hold the brakes. If you nail the gas and the tires don't spin, you should be able to see the approximate stall speed if you have a tach. Is it a 600cfm edelbrock? There's a lot to tuning. And guessing 325 means nothing unless it's actually put on the dyno. I recently built a 67 400 buick. 8.9 to 1. Good machine work, balanced, ta performance cam 216 226 @50, 110 lca, stock intake and Quadra jet, pertronix distributor curved right, That motor runs strong, it made 331 hp on the dyno. Getting 325hp out of an old 318 may not be as easy as you think. I'm now doing a 401 nailhead for the same guy. Ported the heads, bigger cam than the 400, and more compression. Its old technology. If I get 350 out of this I'll be happy.
           
        • Ron H

          Ron H FBBO Gold Member FBBO Gold Member

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          I greatly appreciate the replies gents - all helpful. I had jotted down some notes on some of the issues brought up; I bought a fancy timing light in the hunt with more features than I need; but my 45 year old light crapped out anyway. Right now as i recall from my checking last year I have around 12 initial and around 33 total. BUT, I have no functioning vac advance. As the timing is set, after some adjusting, is the only range where I have no missing occurring throughout low to high rpm's. Some adjustments here more or less would garner miss-firing from 2000 to 3500 rpm's. Wasn't aware my ECU in my old ride could be 'mapped'. Been looking this up. I tuned the eddy following my old school lessons (vac/rpm) but understand there are extra tricks with this carb. As for the exhaust, my next move is going to a more restrictive muffler to cut some of the noise downsizing it to 2.5" on the 3" system. Changing the entire system is too painful to think about and will live with it.
           
        • Don Frelier

          Don Frelier FBBO Gold Member FBBO Gold Member

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          My thoughts are possibly two problems:
          1. Was the cam degreed properly? Sounds like it's retarded or you advance is too slow.
          2. It also sounds like a rotor phasing problem. I would drill a hole in the cap adjacent to #1 towars #8 and put a timing light on it.
          If you have a mopar electronic distributor Rick Ehrenberg sells a reluctor with multiple phasing positions to move the rotor back towards #1 when the plug is fired.
          It could also be the ECU if its the Mopar Orange box style, I had that happen one summer and it was very difficult to troubleshoot.
           
        • Babyblue66

          Babyblue66 Well-Known Member

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          Advancing the timing usually doesn't cause a missfire. 33 isn't enough in my opinion. The vacuum advance is probably adjustable with a small Allen wrench through the vacuum port. I was able to dial mine in this way. Although that won't give you more power, just better mileage and cooler running at cruise. I'd verify that the timing marks are correct on thd balancer too. Sometimes the outer ring can move a little.
           
        • Ron H

          Ron H FBBO Gold Member FBBO Gold Member

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          The timing mark was set with the rebuild, my evident-current gremlin is the canister adjuster screw isn't functional so getting another. Motor runs great; but damn...something seems 'off' with giddy-up off the line - like something isn't mating well as it could be. Ok, could be full a chit; but considering ALL that was done to this motor and gearing, I only notice better get go at higher speed and squat difference off the line from what it was before. Yep, could be I'm thinking this is a pipe dream with this here motor redo and I got what I got...but don't want to rule out some possible fixes either. Dang, was soooo close to getting me a crate 360 and was talked out of it...
           
        • Babyblue66

          Babyblue66 Well-Known Member

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          Those symptoms sound like too much cam, or a retarded cam. Or not enough stall speed.
           
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          • 66 Sat

            66 Sat Well-Known Member

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            Ron you need to work out what's going on with your engine before feeling more regret on not getting a crate 360. The poly is a much cooler looking engine and when it's running right you'll feel different I'm sure.
            If you had done the same upgrades to a 318 LA it would have some decent power, and the poly heads are supposedly better.
             
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            • Ron H

              Ron H FBBO Gold Member FBBO Gold Member

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              Thanks - that's something I haven't heard of before (adj reluctor). I had the orange ECU crap out once a few years ago and got another. I keep a spare one and a ballast in my trunk. I bought a mopar one from halifax couple months ago and haven't put it on yet. I was going to look into those iridium plugs I've heard good things about and better wires along the hunt.
               
            • Don Frelier

              Don Frelier FBBO Gold Member FBBO Gold Member

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              Thinking more about it the rotor may be closer to #2 when it misfires.
              You shouldn't need any high end plugs to get it to run properly.
               
            • Ron H

              Ron H FBBO Gold Member FBBO Gold Member

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              Yeah - was chatting with a few car bud's this morning at our weekly breakfast get together...vast opinions on plugs, lol.
               
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