Engine puffing

[Deleted User]
[Deleted User]
edited November -1 in HUDSON
I have a 54 308 with dual carbs. I had them rebuilt by Daytona Parts. They look great. Since putting them on I have a slight puff out of the exhaust at idle and a constant puff while reving the engine. I have set the mixture from 1/12 to over 2 turns with only a slight difference (better) at around 2 turns. It has gotten progressively worse. I have changed plugs, plug wires, replaced the vacuum advance, checked the vacuum, done a compression check. The cap and rotor look new. I now think it might be the timing or a carb issue. Any ideas out there someone might suggest me trying?

Comments

  • Unknown
    Unknown
    Long distance diagnosis is a shot in the dark...but based on what you have listed I will offer the following. If you have not done so already you should do a vacuum check. This check will isolate the source of your problem without doing any mechanical changes. If you do not have a handbook on how to use the vacuum gauge go to this site... http://autorepair.about.com/cs/troubleshooting/a/aa112401a.htm

    Carefully use the gauge and the information that is available at the website listed to ID the source of your problem.

    You have not indicated where the timing is set or if it was changed after the carburetors were installed. To properly set a twin H there is a specific process one goes through to balance the carburetors and match their performance to your engine. This process is listed here: http://members.aol.com/stepdown53/TWINHADJUSTMENT10001.htm

    Once the balancing adjustments are made the vacuum testing and subsequent trouble shooting should commence.

    Above all... I would not change anything until a complete vacuum check is done. Then use a process of elimination to accomplish more precise tests to ID the specific problem(s).

    Good Luck
  • [Deleted User]
    [Deleted User]
    I cannot see any vapor. If I had a cracked block, a blown head, piston or valve issues would that not show up in the compression test?
  • SuperDave
    SuperDave Senior Contributor
    If by "puff" you mean a different "sound" from the tail pipe..And you say it changes with RPM makes me believe it's not a carb problem. perhaps it is a cylinder not fireing every time it should. Try this... Loosen each plug wire from all six plugs. Just let them rest on the plug so as to make a connection. Start the car and let it idle. remove each plug wire one at a time. each time you remove a plug wire,then replace it. the idle should drop slightly and the exhaust should sound different as that cylinder stops fireing. It should pick back up when you put it back on.if you find a plug wire that makes no difference or very little difference, you have narrowed the problem to that cylinder. If your compression readings were good, we can assume the problem is in the cap,wire or plug. If you don't have spare wires or plugs to substitute, swap them to another cylinder. if the problem, moves to that cylinder you have narrowed it even more. If you find that by removing the wire a little distance from the plug and the spark jumps to the plug and the engine runs smoother, you probably have a fouled plug.The fact that you say it's getting worse leads me to think it's a simple ignition problem.. Crack or carbon trail in the cap, leaky wire or fouled plug (my guess). Hope this helps..
  • rambos_ride
    rambos_ride Senior Contributor
    52Hudson wrote:
    I have a 54 308 with dual carbs. I had them rebuilt by Daytona Parts. They look great. Since putting them on I have a slight puff out of the exhaust at idle and a constant puff while reving the engine. I have set the mixture from 1/12 to over 2 turns with only a slight difference (better) at around 2 turns. It has gotten progressively worse. I have changed plugs, plug wires, replaced the vacuum advance, checked the vacuum, done a compression check. The cap and rotor look new. I now think it might be the timing or a carb issue. Any ideas out there someone might suggest me trying?



    You probably already checked this but how about the oil and anti-freeze do they look good?



    What were the results of your compression check? How long did the car sit before rebuilding the carbs - sometime valves will stick or piston rings can actually break causing problems?



    I think someone else asked this question but what color is the puff of smoke coming out?



    Not completely related but a good story...A Long time ago... In High School I rebuilt a 350 chev and dropped it into my 68 Chevelle. About 1 mile into the first break in drive huge white smoke started pouring out of the exhaust - it looked like I was roasting the tires off at a stand-still while driving down the road. People behind me couldn't see and had to turn their lights on and slow down! :eek:



    I wasn't overheating, oil pressure was good and I immediately pulled over to check the fluid levels - all ok. It continued to smoke like that all the way back to the school - by which time I had been pulled over by the po-po and given a warning.



    Let it sit overnight - re-checked everything again and started her up - no problem!



    I drove the heck out of that engine for 5 years - 1/4 mile racing for 2 summers in a row and didn't burn one drop of oil or use any water - go figure!?



    *



    Good Luck - I hope you get things figured out!
  • [Deleted User]
    [Deleted User]
    I will just hazard a guess here as you say it happened after you put the rebuilt carbs on. Your engine is running in a condition of too rich a mixture. When the carbs were rebuilt you can have any number of issues. First to check is that the accelerator pump intake check ball is installed and is the correct size. If wrong size it can stick and draw extra fuel into the motor. Could be in one carb or both. Also the choker shaft on the choke circuit may be binding.



    How does the motor sound when it is just idling? then when you rev quickly. Is the exhaust note constant?



    Be nice if you could swap out carbs to isolate the problem.
  • [Deleted User]
    [Deleted User]
    No smoke from exhaust. The car sat for 6 weeks. All plugs and wires are new.
  • Unknown
    Unknown
    LI cant bellieve all you guys never came up with PULL THE PLUGS AND CHECK THE COMPRESSION WITH A GAUGE, SOUNDS LIKE A BURNT VALVE TO ME AND A LOW COMPRESSION ON THAT CYLINDER. ALWLAYS THE FIRST THING I DO TO CHECK A PUFF lol
  • [Deleted User]
    [Deleted User]
    We didn't have to, if you read the original post he said he did a compression test, a vacuum test and they did not show a problem.
  • SuperDave
    SuperDave Senior Contributor
    We may have to define "Puff". My wife told me her car "wanted to keep going when she tried to stop". I did a brake job only to find out the ENGINE was dieseling when shut off hot! and then there was the lady that told me her car was "skipping" after I did a valve job and a tuneup(which it needed). Then after a test drive with HER driving found out the front tires needed balancing.. so just what is a puff? I interpret that as a slight misfire? But what do I know? Grinnn, LOL
  • [Deleted User]
    [Deleted User]
    A puff could also be the , (what I call a hiccup) little change in exhaust note cause when the distributor gear gets a little worn and lets the timing vary by a degree or so. Many of the Hudsons I have heard have it. Especially if there are a few miles on the engine. When you rev the engine, the thrust on the gear keeps it from moving, so no hiccup.

    Bob Hickson
  • [Deleted User]
    [Deleted User]
    It also puffs when reved.
  • Geoff
    Geoff Senior Contributor
    Have you tried a vacuum gauge? If compressions are equal, a vacuum gauge will usually sort out what's wrong. For instance, if the problem only happened since you fitted the twin carbs, it could be a break in the inlet gasket. This will allow air into that particular cylinder. If it is a regular misfire then it has to be either a burnt valve, bad plug, or as I have explained. Good luck. What were the compression readings?

    Geoff.
  • rambos_ride
    rambos_ride Senior Contributor
    Geoff C., N.Z. wrote:
    Have you tried a vacuum gauge? If compressions are equal, a vacuum gauge will usually sort out what's wrong. For instance, if the problem only happened since you fitted the twin carbs, it could be a break in the inlet gasket. This will allow air into that particular cylinder. If it is a regular misfire then it has to be either a burnt valve, bad plug, or as I have explained. Good luck. What were the compression readings?

    Geoff.





    I think he said in an earlier post that they had used a vacuum guage - but did they check for a vacuum leak?



    2 physical ways I know of 1)Spray soapy water around the base of the carbs and look for bubbles being created or 2) spray starting fluid around the base of the carbs while running - if the RPM changes there is a leak...
  • [Deleted User]
    [Deleted User]
    Compression was 95-105. Could it be an exhaust manifold leak?
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