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Engine diagnosis. Pleas help

Discussion in 'The Hokey Ass Message Board' started by deerejohnb, Jun 22, 2012.

  1. RDAH
    Joined: Mar 23, 2007
    Posts: 465

    from NL, WI

    The Pretronix direction should have mentioned not to use wire wires with there unit.
    Like landseandair said feed back from your wires.
  2. George/Maine
    Joined: Jan 6, 2011
    Posts: 949


    If you have a racing cam your vacuum will be low,and choppie idle.
  3. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    I adjusted the valves by adjusting the intake when the exhaust starts to open. Then I adjusted the exhaust when the intake was almost closed. I put the intakes at .012 and exhaust at .013 cold. The hot spec. is .010.

    In regards to the pertronix. I have the ignitor series 1 and there is no mention of not using solid core in the instructions. I understand the ignitor 2 and 3 say not to. Maybe I am getting EMI feedback.
  4. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    I regards to the cam, I forgot to mention that I had it ground by delta camshaft out of Washington. They cleaned it up and added a little more lift and duration but they told me it wouldn't make it it idle like a dragster.

    The idle issue seems more like a misfire. When I rev it up it runs good, but I still hear the slight popping/pulsing out of the exhaust.

    When I take it out on teh road, there are no misfires under load and it has great power for a flat head 6.
    Last edited: Jun 23, 2012
  5. bluthndr
    Joined: Oct 4, 2004
    Posts: 254


    I like pertronix and similar, but I did get a bad one in the box once. 48 hours of tearing our hair out, we put points back in just to double check. Sure enough, ran perfect with the points. I love electronic ignition, but when they go bad they can do some funky stuff that looks like a lot of other issues (not ignition). I don't think it's fuel, because popping would mean lean, but should get better get better with heat, not worse, especially since you verified no vacuum leaks. Also, something in the ignition system could cause all those symptoms..
  6. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    I have the old distributor with points. I can try that and see if it works. However, I could still have a bad plug wire. I checked each one with an ohmmeter and they tested good, but the ohmmeter test is marginal at best.
  7. redlinetoys
    Joined: May 18, 2004
    Posts: 4,301

    from Midwest

    Before you get too freaked out... I went through a similar issue with an OT 351M in my old Bronco.

    After fighting the problem for months and refusing both professional help and driving of the thing, I finally gave in and consulted with an expert shop owner friend.

    He too was baffled and we chased the problem for days and nights with compression tests, leakdown tests, vacuum tests, infra red video of the cylinders, etc, etc. I was frustrated enough to just throw new parts at it including a new coil, wires, plugs, ignition box, distributor, fuel pump, carburetor, etc.

    Eventually, we discovered we had just one cylinder that was slightly unhappy and it was really only one valve that required loosening by just a few thousandths shim to address the popping, misfire, rough idle issue.

    Sometimes it is the really simple stuff. Keep chasing the valve lash before you get too concerned about a larger problem.

    Good luck, and let us know!
  8. In a regrind to add lift they change the base circle that means your lifters are a little further into the hole than they have ever been. By adding lift, your valves are open a little further than they have ever been. Unless its all been re done, you have many things looking for a new home at the end range of their movement.

    What does the cam grinder say for lash ? You might need more than the factory stated since nothing is the same. Just a thought.
    Last edited: Jun 23, 2012
  9. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    Its funny.. On the cylinder head casting it shows .006" and .008" for the Intake and exhaust valves Hot. The manual shows .010 for each hot. And, some IH guys I know have manuals that say .010 for Intake and .015 Exhaust Hot for severe service.
  10. yruhot
    Joined: Dec 17, 2009
    Posts: 564


    Worth mentioning I just bought a pertronix electronic dist for my big block 55 chevy and they said DO NOT use solid core plug wires. Don't know if the same electronics are involved as you conversion but maybe worth a try. Also dabbling with Model A Fords some of the guys have done the eltronic ignitions with them and chased problems around and came back to installing points and problems went away. Just what I've seen and heard. Good luck, can't wait to see what it was. YRUHOT......Doug
  11. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    The ignitor 2 and 3 say not to use solid core wires, but not on ignitor 1 which is what I have. We have company today so I will have to wait unitl later today to get different plug wires. I like the challenge of diagnosing it, but it is a time monster. The truck is complete restoration and its amost done.
  12. More lift - more fuel
    More fuel - more heat
    More heat - more expansion
    More expansion - more lash

    0.015 hot should be 0.017- 18 cold.
  13. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    Good points 31 vicky with a hemi.
    Would you adjust to .017 on both valves or less for intake.
  14. And, some IH guys I know have manuals that say .010 for Intake and .015 Exhaust Hot for severe service.

    Id start with at least that and see where it takes me.

    Right your adjustments & results down so you don't Chase your tail too much.

    Remember :
    A longer duration cam will run different, and a tighter lash increases duration on top of that.
    Long duration lowers vacuum, increased overlap lowers compression.
  15. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


  16. Why can't you set the valves with the engine being warm?
  17. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    I think I may have narrowed the problem to two issues.

    1. Incorrect valve lash. I got them both set to .019 cold. I may try to adjust them hot, but it’s difficult with the manifold there as it is easy to burn your hands. I have too many burn scars already.

    2. Ignition- I removed the dis. with the pertronix ignition and installed my points distributor. The truck runs a lot better at idle I hear a slight miss every once in a while, but for the most part it is smooth and consistent.

    I plan on getting a new set of suppression plug wires. I have been trying to locate a universal plug wire set for this, but have not had a lot of luck. The only downer is that these are nice looking lacquered colored wires and I like the vintage look. However, I will take the elec. ignition over points
  18. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    My truck is still misfiring and here is what I have completed thus far.
    1. Set valves cold to .019" –Per manual
    2. Replaced Pertronix distributor with point distributor.
    3. Installed new plug wires
    4. Vacuum reading at 15-16. It is steady until the popping occurs. When the pulsing occurs it drops 1 in. hg.
    My concern is now that there is a valve issue. When the truck is idling, the pulsing/popping out of the exhaust is the most noticeable. If I put my hand close to the outlet of the tailpipe with the engine running I can feel inconsistent pulses about a second apart (but it does vary). Right after the pulse occurs my hand gets sucked back towards the exhaust pipe.

    If it were a valve issue, wouldn’t that have shown up on the compression test?

    Here is a link to a video of it running…..740754.mp4
  19. medicinal_marinara
    Joined: Nov 24, 2009
    Posts: 139

    from Oregon

    It sounds like you have a slightly sticky valve or lifter if it's steady until the pop occurs. Does it pop every time a particular cylinder fires or just randomly? I wouldn't expect a slightly sticky valve to show compression issues because you aren't spinning the engine very fast when checking it and the sticky valve has time to seat. I'd try some marvel mystery oil in the crankcase for a while to see if that loosens enough tar to make it stay smooth. 15-16" of vacuum is pretty good if steady, depending on the altitude. You may want to tweak the idle mixture a bit and make sure you don't have a vacuum leak to see if you can peak up the vacuum a bit more. I like my engines to idle slightly on the rich side of peak vacuum.
  20. tractorguy
    Joined: Jan 5, 2008
    Posts: 693


    Could you possibly have an exhaust valve that is sticking in it's guide ?? Did you do valve or guide work ? Do you have carbon build up on exhaust valve stem causing intermittant sticking ?
  21. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    I refinished the valves and seats about 100 miles ago. I replaced the cam recently because of a lifter issue. The problem may very well be worn valve guides because I didn't replace/repair them ( I know….I don't say it/ I shouldn't have taken the shortcut and now I'm paying for it)
    I did another static compression test and I got 70-75 on the first pump for each and 90-100 on all after 5 pumps. The problem with this test is that it doesn’t tell me if the springs are weak or the guides are worn.
  22. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    Its hard to pinpoint the pop to a cylinder. The pop is sometimes consistent and sometimes inconsistent when idling:). It seems the worst at idle.

    The enigne has good power, I just wish I could pinpoint the problem before I start the teardown.

    Could a guide be so looses that an exhaust valve does not close properly causing the suction at the exhaust pipe.
  23. coolmilitary
    Joined: Jun 16, 2006
    Posts: 120

    from So Cal

    Just a thought.
    I had it happen to me with a hotter cam on my flathead V8. I had to make thin copper spacers to raise the spark plugs a smidge.
    Remove and look at each spark plug one at a time. Make sure that the gaps have not been closed by valve hitting it. It happens on a flathead 8. Maybe a flathead 6 too.
  24. Could a guide be so looses that an exhaust valve does not close properly causing the suction at the exhaust pipe.

    I'm sure you would have noticed on the reassemble.
    The stem would fit similar to a hot dog in a hallway.

    The valves were all good, not burnt, no checking, no wear on the stems - the seats were the same?

    See the first part of post 38
  25. kye
    Joined: Jul 2, 2012
    Posts: 8


    is the new cam the same rise, overlap and duration as the old one?
  26. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    I ran it again today and when it got hot I bet I could go 10-15 seconds without the exhaust pulse occurring. The pulse is definately inconsistent. I connected a vacuum gauge and the needle fluctuates from 16-15 when the pulse occurs. Otherwise it si steady at 16" hg The vacuum test results I have read say ignition or valve issue, but they say it is usually more than 2 in. hg for valve issues. All my ignition is new and I even swapped distributors.

    The old paper test at the exhaust pipe sucks in the paper when this occurs. This leads me to believe:

    1 I have an exhaust valve intermittenlty not seating
    2. Intermittent sticking exhaust valve.

    What do you guys think.
    Last edited: Jul 4, 2012
  27. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112



    Here is what I have done to the truck recently.

    I bought all new valves and recut all the seats. I then vacuum tested each of the ports to verify they were sealing. I also knurled all the guides to tighten them up. I set the lifters cold to .018".

    I got everything back together and started it up only to have the same problem. I get a slight random popping out of the exhaust at idle which occurs every 1-2 seconds all teh way up to every 5 seconds. it is not very noticeable until I put an exhaust hose on. With a vacuum gauge connected I get about 16 in. Hg at idle. When the pop occurs, the vacuum only drops about .5 in Hg.(This is exactly what happened before I replaced the valves and cut the seats.)

    The funny thing is that when I turn the throttle stop screw to increase the rpm to 1200, the engine runs great and the popping only occurs every 15-20 seconds or longer.

    So my question is.. Could this be a carb idle circuit issue?

    The truck has good power and seems to run very smooth even at idle.

    I am getting pretty frustrated and I just want to get it fixed. Please help.
  28. noboD
    Joined: Jan 29, 2004
    Posts: 7,699


    Have you held your hand over the air intake to make it a little richer at idle? 16 at idle is pretty weak. There's an online vacuum chart that you can read what differant values mean.
  29. FuelRoadster
    Joined: Nov 17, 2005
    Posts: 1,068


    This^^^is some good advice,along with pulling all the plugs & making sure an insulator(or two) didnt accidently get cracked when you put them in.(and there's no anti seize anywhere *near* the buisiness ends)
    Last edited: Jul 31, 2012
  30. deerejohnb
    Joined: Dec 29, 2007
    Posts: 112


    I turned the idle mixture screw all the way in and the popping only occurs about every five seconds or so. When i turn the idle mixture screw out it pops constantly.

    So, I need t to run richer correct? Does the popping mean it is running lean at idle.

    I have a zenith 28 carb an the idle jet has a number on that corresponds with the fuel flow.

    in regards to teh vacuum, I know that 15-16 is low, but according to info I researched they say 15-21 in. is acceptable.
    Last edited: Jul 31, 2012

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