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By Fastco44 - 13 Years Ago
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I was driving my truck home when the engine suddenly developed a misfire. Under acceleration loads the engine pops and bucks...once up to speed it rolls along with something that sounds like an exhaust leak. At idle you can faintly hear a cylinder not firing right. If you rev the engine yo get the same loud popping in the exhaust. I was told when I bought the truck that the distributor has a bad lobe. I am thinking that the problem is electrical. But I thought I would ask the Y-block experts for their advice.
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By charliemccraney - 13 Years Ago
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I'll guess a broken pushrod.
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By Hoosier Hurricane - 13 Years Ago
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I agree with Charlie, with one addition. Look for a broken valve spring also.
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By GREENBIRD56 - 13 Years Ago
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I can't say that I've ever seen a distributor cam with one bad lobe - 
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By oldcarmark - 13 Years Ago
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Take off rocker covers and check out pushrods and valves.
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By slumlord444 - 13 Years Ago
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I have found most problems like this are electricial. Check dist cap, rotor, points, plug wires, and plugs. Cheap and easy stuff first.
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By jonnireb - 13 Years Ago
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Yeah, usually been my experience too.
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By Riz - 13 Years Ago
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I would agree with looking into the top end first for sunk valve or bent pushrods. The constant backfiring does make it sound like a timing issue-it could be a wiped out cam lobe. Even then you should be able to see the valve hanging etc. If nothing there you may pinpoint a bad piston by checking compression/leak down test. I would not push it until you get a better idea. No sense in putting the entire block in jeopardy.
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By aussiebill - 13 Years Ago
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charliemccraney (3/15/2012)
I'll guess a broken pushrod.I,m with charlie, john and greenbird. we are standing by for results, allways interesting.
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By Pete 55Tbird - 13 Years Ago
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As a strong supporter of the K.I.S.S system of car repair ( keep it simple, stupid ) may I suggest you start by buying a spark tester at Harbor Freight ( $5) that shows a flash if you in fact do get a spark at each and every cylinder. If you do, get a compression tester and use it. With reasonable compression , it is time to remove a valve cover and do a visual inspection and see if all the pushrods are accounted for and the valves move but then if the compression test was OK you did that. Next is burned valve(s) flat cam. BUMMER. Pete
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By Ted - 13 Years Ago
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Normal trouble shooting would include a vacuum reading and a compression check. These would insure that the mechanical parts are doing their job and would help to isolate the problem to ignition or carburetion. An erratic vacuum reading would point you to a leaky intake or carb gasket or something amiss in the valve train. Easy enough on the Y to pull the valve covers and look for anything that’s out of place such as a backed off adjuster, bent or missing push rod, or broken valve spring. The problem could be as simple as a dirty air bleed in the carburetor though.
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By Fastco44 - 13 Years Ago
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Thanks guys for all the suggestions. It will be a little while before I can start trouble shooting the truck. I have too many schedule critical thing to do first...plus the wet weather hasn't helped. I am going to check the electrical things first. Then move on from there.
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By Y block Billy - 13 Years Ago
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I have seen simple items like a bad condenser or the points closing up cause similar reactions, start with the simple things first.
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By ray - 13 Years Ago
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Fastco44 (3/19/2012)
...plus the wet weather hasn't helped. I am going to check the electrical things first. Then move on from there.
Wet weather, old wiring and 'lectrics don't do well together. The wiring is a good place to start. Go out when it is nice and dark and fire her up. Might be real easy to see a lot of 'lectrics jumping all over the place.
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By Fastco44 - 13 Years Ago
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Well, I got some time to check out the 292 in my truck. The electrical and fuel systems were good. Charlie nailed the diganosis...a broken exhaust push rod. If I can get the other half of the push rod out, do I still have to remove the intake manifold and valley cover? Is braking push rods a normal issue with these engines?
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By MoonShadow - 13 Years Ago
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If you cant fish it out don't worry. Lots of Y-blocks have "extra" push rods in them when torn down. They really cant get into anything critical. Chuck
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