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Discussion Topic:
239 c.i.d. missing on 2 cyls.
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roymech |
05-11-2010 @ 5:53 PM
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Member
Posts: 3
Joined: May 2010
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i have a 53 ford pickup with a newly rebuilt .030 over 239 in it. i have 85 pnds. comp. cranking on all cyls. spark on all cyls., its got new pistons,rings,valves,springs,heads,timing,10/10 crank, like new cam, new distributor,cap,rotor. and it still misses on #3 and #5 cyls. ive swapped out the intake and gone thru the valves twice changed plugs and wires and still no change. any advice or thoughts would be greatly appreciated. thank you.
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ford38v8 |
05-11-2010 @ 8:40 PM
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Senior
Posts: 2735
Joined: Oct 2009
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Roy, If the miss is constant, you may have swapped plug wires between 3&5. If it is intermittent, check for carbon tracking inside the distributor cap. Any backfiring through the carburetor can also indicate cross firing.
Alan
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roymech |
05-12-2010 @ 3:58 AM
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Member
Posts: 3
Joined: May 2010
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i have checked and rechecked the firing order ,swapped plug wires and even put a different cap on. same results its always #3 nd #5 could the carb be the problem?
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supereal |
05-12-2010 @ 8:44 AM
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Senior
Posts: 6819
Joined: Oct 2009
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How did you determine that only #3 and #5 are misfiring? As the other cylinders fed from the carb seem to be OK, it is doubtful that the carb is at fault. Check all plug wires with an ohmmeter. They should all register within a few ohms of each other. If they are carbon filament wires, flex them as you check, particularly at the end connectors. At idle sped, pull the plug wires and test to ground at the cylinder head. The suspect cylinders should be as "hot" as the rest, with a strong, blue spark. You have covered most of the "usual suspects", but the problem you state is almost always found in the secondary (high voltage) side of the system.
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37RAGTOPMAN |
05-13-2010 @ 7:15 AM
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Senior
Posts: 1940
Joined: Oct 2009
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this is along shot., but how are the distributer cam lobes ? does the points open and close for every cylinder? is there a wrobble in the shaft ? check your dwell, new dist does not mean it is ok, is it China or FORD U.S.A.? just for ho ho's try a leak down test in those 2 cylinders, and also check the ignition wires, like superreal said, are they running through a loom of some sort shorting out, you can spray the wire with a mist of water while running, does the spark jump ? and just swap the 2 spark plugs with 2 others, let hear how you made out, It has to be something you overlooked KEEP ON TRUCKIN 37RAGTOPMAN
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roymech |
05-13-2010 @ 11:39 AM
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Member
Posts: 3
Joined: May 2010
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i will try everything you guys suggested all good suggestions i`ll let you guys know how it goes
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Reds34 |
06-01-2010 @ 6:24 PM
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Member
Posts: 16
Joined: Jun 2010
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I actually have a similar problem, although it is a '34 with a 221 c.i. It only runs on 4 cylinders though. I changed wires, distributor, taken the carb apart 2 or 3 times and still have no idea. It skips on 1,4,6 and 7 if i believe correctly. Sorry to hijack the thread. Thanks in advance for your help. Red
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tgs40ford |
06-01-2010 @ 7:25 PM
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Member
Posts: 12
Joined: May 2010
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Roy, Were you able to find the solution to your problem? I had a similar problem many years ago on a newly rebuilt motor. This may not be the same problem you are having but i hope it helps. My problem was mainly at idle. Rebuild shop had left the valve guide seals off. Allowing exhaust gases to mix with the intake fuel air mixture. Everything checked out with normal mechanical testing. Its been so long ago i forget how i finally figured it out. The seals fixed it. I pulled them all in the end and found three seals missing. Its still running great 35 years later. Good luck. Let us know how you made out.
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supereal |
06-02-2010 @ 9:53 AM
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Senior
Posts: 6819
Joined: Oct 2009
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If your engine skips or doesn't run on cylinders 1-4-6-7, they are not getting fuel, as the right (passenger) side of the intake manifold feeds those, while the left (driver) side feeds 2-3-5-8. That eliminates the ignition, as the distributor caps and rotors and wires are separate for each side. Be sure that you have the missing cylinders correctly by pulling the plugs wires to see what effect it has on each. I believe something is blocking the right side of the carb, possibly the main jet, or a passage feeding that jet is clogged. If you didn't boil out the carb and check it with compressed air thru the passages, it is easy to miss a blockage. If you have access to a spare carb, try it to confirm the problem. When diagnosing a V8 problem, always remember you are really dealing with TWO four cylinder engines joined at the crankcase.
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supereal |
06-02-2010 @ 10:09 AM
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Senior
Posts: 6819
Joined: Oct 2009
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I need to clarify my post. Looking from the FRONT of the car, the driver's side carb throat feeds cylinders 1-4-6-7, while the passenger side feeds 2-3-5-8. When I read my post, I think it could have caused confusion by saying "right and left".
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