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11-03-2015, 12:07 PM | #1 |
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Irregular miss under load😫
'49 Engine, oversize valves, 3/4 cam Holley 94 electronic dist. no vacuum adv.
Started with engine irregular missing losing power under load above 2500 rpm. Been keeping up with several similar threads. Changed 12v coil, checked voltage out of ballast resistor - 3.5v. Engine smooth and runs great revving beyond 3000 rpm and at idle under no load. Starts immediately hot or cold. Plugs light brown? What am I missing?
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Nomad Last edited by AnthonyG; 11-03-2015 at 01:37 PM. |
11-03-2015, 12:18 PM | #2 |
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Re: Irregular miss under load😫
Stick valves?? G.M.
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11-03-2015, 12:42 PM | #3 |
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Re: Irregular miss under load😫
GM engine has under 2500 mile, what do you think would cause sticking valves? Can't ever hear at idle or revving up while sitting no load. If it were valves wouldn't it happen then as well as on the road. That's why I was leaning towards something electrical. Timing / distributor maybe? Ran fine for a couple thousand miles? No pinging and seems like plenty of power up to that breakup point?
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11-03-2015, 12:52 PM | #4 |
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Re: Irregular miss under load😫
fuel starvation?
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11-03-2015, 01:04 PM | #5 |
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Re: Irregular miss under load😫
As part of the elimination procedure I tore down the 94, which was rebuilt a couple of years ago & cleaned checked it & replaced Power valve. Tried another 94 with similar engine performance during process.
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Nomad Last edited by AnthonyG; 11-03-2015 at 01:38 PM. |
11-03-2015, 01:43 PM | #6 |
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Re: Irregular miss under load😫
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Martin. |
11-03-2015, 01:57 PM | #7 |
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Re: Irregular miss under load😫
Yes I would say too ,to low to run a 12 volt coil on 3,5 volts change the coil or resistor .Ted
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11-03-2015, 02:04 PM | #8 |
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Re: Irregular miss under load😫
Hi Martin, yes to all.
Ted, what ballast R. should I go for? Ho high is too high. From reading some threads on points or in my case electronic dist. too much can cause premature wear on both?
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11-03-2015, 02:15 PM | #9 |
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Re: Irregular miss under load😫
I had that sort of thing early on. have you tried chocking it while the power loss is happening? Mine perked up when I choked it and one of the experts here had me check for a vacuum leak, which I found between the carb and the manifold.
bill
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11-03-2015, 02:16 PM | #10 |
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Re: Irregular miss under load😫
The electronic distributor specs should determine the coil and ballast resistance. I have a Pertronix that wants full voltage to a 1.5 ohm coil.
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11-03-2015, 02:26 PM | #11 |
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Re: Irregular miss under load😫
What system Malory or pertronix Check with the suppler ,the module can fail with the wrong set up,. 40Cpe is correct 1.5 volts for pertronix .Ted
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11-03-2015, 02:50 PM | #12 |
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Re: Irregular miss under load😫
Tony,
That 3.5 volts to a 12 volt coil is, as you can tell from above posts, is way to low. The right resistor is what the manufacturer of that electronic ignition says. What make is it? Martin. |
11-03-2015, 03:00 PM | #13 |
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Re: Irregular miss under load😫
Also while your checking what resistor they want, double check on what spec coil. Some of them like a standard points type coil, some want a specific electronic ignition type coil.
Martin. |
11-03-2015, 03:02 PM | #14 |
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Re: Irregular miss under load😫
You may be able to run your coil without the resister but check the resistance of the coil ,Ted
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11-03-2015, 03:05 PM | #15 | |
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Re: Irregular miss under load😫
Quote:
Looking at your profile pics the distributor is a mallory and you are using a ballast resistor. Can't tell what coil it is ??? Mallory makes two coils and its pretty common to see someone use the .6 ohm coil . This coil is too low of resistance!!! You need 1.5 ohm coil. Also i would question the wiring , make sure you have battery voltage going to the module. They need at the very least 8-9 volts . Install a 1.5 ohm coil and bypass the resistor for a test drive . Let us know what that does.... |
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11-03-2015, 03:14 PM | #16 |
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Re: Irregular miss under load😫
http://www.speedwaymotors.com/Mallor...Ohm,27571.html
Mallory, and it calls for a 1.5 Ohm resistor which should read .75 cold and 1.5 hot. Doesn't give voltage out just says 200 watts?
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11-03-2015, 03:15 PM | #17 |
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Re: Irregular miss under load😫
I know long time use without a resistor will cause premature wear, will a short test run without to see if the problem goes away hurt?
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11-03-2015, 03:19 PM | #18 |
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Re: Irregular miss under load😫
What is the stock resistor under the dash rated at on a '35 ford? I have mine jumped beings I was using the ballast resistor the engine builder supplied when I received my engine with the ignition installed already.
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11-03-2015, 03:38 PM | #19 |
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Re: Irregular miss under load
Don't know what you are using for plug wires but Pertronix and possibly Mallory recommend suppression wire (with electronic ignition) such as spiro-wound to eliminate radio interference that causes problems like skipping.
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DON'T RECALL DOING SOMETHING FOR MYSELF BASED ON SOMEONE ELSE'S LIKES OR DISLIKES Last edited by 51 MERC-CT; 11-03-2015 at 03:58 PM. |
11-03-2015, 03:43 PM | #20 |
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Re: Irregular miss under load😫
i had some skipping under load. voltage but lower than it should be at coil. it turned out my ezwire system coil fuse was corroded. eventually it wouldn't start at all. biggest help in diagnosis was running a wire directly from batter to coil, by-passing ignition circuit. started right up. indicating ignition prob.
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