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.

I'll guess a broken pushrod.


Lawrenceville, GA

I agree with Charlie, with one addition.   Look for a broken valve spring also.

John - "The Hoosier Hurricane"

I can't say that I've ever seen a distributor cam with one bad lobe -

 
 Steve Metzger       Tucson, Arizona

Take off  rocker covers and check out pushrods and valves.

  

I have found most problems like this are electricial. Check dist cap, rotor, points, plug wires, and plugs. Cheap and easy stuff first.

Yeah, usually been my experience too.

55f100

West Monroe,La.

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.

Mike Rizzo

1963 F100 "Rudy"

Daniel Island, SC

I,m with charlie, john and greenbird. we are standing by for results, allways interesting.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

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