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Help with 49 Plymouth engine

Discussion in 'The Hokey Ass Message Board' started by plymouthwoodys.com, Mar 28, 2013.

  1. plymouthwoodys.com
    Joined: Oct 21, 2012
    Posts: 10

    plymouthwoodys.com
    Member

    I have a rebuilt Plymouth (Canadian 25" block) that wont pass aircare. It has high hydro carbon readings. It runs so smooth the mechanic never thought it would be a bad cylinder, butI found out the #2 cylinder is low . It is under 100 while the rest are around 120 on a compression test.

    It gets spark, the plugs are OK and seems to run fine.

    Can this just be a valve adjustment? Whats the likely causes and best procedure to take to try and fix it? I cant find anyone that seems to know these engines.
     
  2. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    The possibilities are the same for this engine as for any other : Leaky rings, cracked or worn out piston, leaking valve(s), head gasket, valve adjustment, worn out cam, cracked head or block.
     
  3. Cracked Valve seat?
    usually if that is the case it will have good[same] =COLD=compression as others for a short time,till warmed up then the compression falls as the crack OPENS and allows the valve to leak and lowers the compression after the fact.....
     
  4. plymouthwoodys.com
    Joined: Oct 21, 2012
    Posts: 10

    plymouthwoodys.com
    Member

    Thanks choprods. I'll try that.

    Im hoping its just valve adjustment. Everything was new and built by a well known engine shop here, but unfortunatly he retired before I ever got it installed. Its hardly broken in, so things like worn out anything or cracked block are very unlikely.
     

  5. ottoman
    Joined: May 4, 2008
    Posts: 300

    ottoman
    Member
    from Wisconsin

    Leak down test is always the best way to find out low comp issues
     
  6. Depending on how long it sat before running,A ring could be stuck in that bore.OR.....,end gaps were not staggered appropriately?.Wish you good luck...
     
  7. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,492

    Rusty O'Toole
    Member

    First of all why is a 1949 engine even being tested? There were no pollution laws in 1949, no pollution control devices and no standards. I never heard of laws being retroactively applied.

    What standards are they holding you to? There were no standards when your car was built. A hydrocarbon emission reading that would be off the scale for a 2013 engine could be perfectly normal for yours.

    You could try a valve adjustment. If your engine is newly rebuilt there is a chance that is all that is wrong. Factory specs call for adjusting the valves with the engine hot, so this should be done after installing a rebuilt engine anyway.

    Next, hydrocarbons means unburned gas or possibly oil burning. Is your air filter clean? Carburetor in good condition and properly adjusted? Ignition working correctly and not misfiring?

    Does your engine burn oil? 1 quart in 500 miles was normal for a new engine, or engine in good condition when your car was built.

    Now about the low compression. Do another compression test on the bad cylinder, then squirt some oil down the spark plug hole and test again. If the reading comes up you have bad rings. If not, you have a bad valve. Most likely an exhaust valve but if you want to be sure, put a compressed air hose on the spark plug and listen at the carburetor and at the tailpipe for escaping air. Or at the oil fill pipe for air escaping around the piston (bad rings or bad piston).

    If you have a bad valve it is a simple matter to take the head off and repair or replace it. While the head is off you might want to grind all the other valves. If you really want to do a thorough job, take the pan off, take out the pistons, hone the cylinders and replace the rings. This was known as a ring and valve job and was a normal overhaul procedure when your car was new.
     
  8. beat me to it rusty, i was about to say the exact same thing
     
  9. 48 Chubby
    Joined: Apr 29, 2008
    Posts: 1,014

    48 Chubby
    Member Emeritus

    It could be as simple as a bit of carbon or trash deposited on the valve or seat. I have never heard of 64 year old cars being held to modern emission standards though.
     
  10. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    That basic engine was made for many years. I was thinking, earlier ones had iron pistons. Although they wear well, they tend to fatigue and crack. I don't knoiw at what point the change was made from iron to aluminum. If you have iron pistons, and the engine was run hard or has a lot of miles, that increases the possibility it's a piston problem.
     
  11. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,492

    Rusty O'Toole
    Member

    Chrysler never used iron pistons. They had aluminum pistons, and insert bearings starting in 1934 (first car to use them). They had hardened exhaust valve seat inserts, full pressure oiling, and full flow oil filters (at least on the more expensive models) by 1949 too.

    You are thinking of inferior makes that had iron pistons, poured babbitt bearings, low pressure "spit and hope" oiling and no oil filters as late as the early fifties.
     
  12. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,492

    Rusty O'Toole
    Member

    I would like to know what pollution standards we are talking about and how badly it failed?

    If it is close to passing there are a few gimmicks that will help. Add methyl hydrate (alcohol) to the gas. Take it out for a long drive and get it thoroughly warmed up before the test (like a 20 mile drive). There are additives that "guarantee" a passing grade.

    I still have no clear idea what the problem is. It seems a newly rebuilt, 1949 engine was tested for pollutants and failed the hydrocarbon part of the test. There are still a few unanswered questions.
     
  13. plymouthwoodys.com
    Joined: Oct 21, 2012
    Posts: 10

    plymouthwoodys.com
    Member

    They didnt even have a record at air care for my car, so they just made one up. It passed everything but hydro carbon readings. They say old flatheads should read under 900, and mine was 1700. Adjusting the carb and timing wont get it any lower than 1350. The air filter was converted to hold a modern filter.

    It did sit for three years before being installed, but it runs so nice you would never know there was anything wrong. It doesnt smoke or seem to burn oil, but I havnt gone 500 miles yet, so hard to tell how much its using.

    If valves are supposed to be adjusted while the engine is hot, that might be the problem because that was never done after the engine was installed.
     
    Last edited: Mar 29, 2013
  14. As mentioned above, a setting engine is a prime candidate for the old "chunk of carbon stuck in valve.seat"....this happens when driven after a long hibernation....it pops off the piston in a big chunk and usually lands in the exhaust valve and seat letting it leak compression....usually if this is the case it will miss a little or run really lame....
    an easy fix is this-
    take an old windex spray bottle filled with water.
    rev up the engine and spray the water in the carb till it dies down, repeat repeat till it dislodges the chunk....It does work.
     
  15. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,492

    Rusty O'Toole
    Member

    To adjust valves you are supposed to drive around and warm up the car. Then jack it up and remove the right front wheel and remove the access plate in the fender and finally remove the valve covers. I guess the fender plate should be removed beforehand.
    Finally adjust the valves. I really don't know if it makes any difference, hot or cold, but that is the way the factory did it so I guess they had their reasons.

    I don't like this making stuff up. Why does your car even need to be tested if there are no standards that far back?

    Have you taken a good blast up the highway? Or is that out of the question till you get your test approval?

    You could also try the additive, mentioned earlier.

    It is also possible your car won't pass because it is not broken in. Old engines that have been rebuilt, typically burn a little oil until they are broken in. Even then a small amount of oil burning is normal.
     
  16. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,492

    Rusty O'Toole
    Member

    I think I would adjust the one valve that is not sealing then take a blast up the highway, come back and adjust them hot. Then put some alcohol or additive in, go for a long drive and have it retested.
     
  17. Are they doing the hydrocarbon test at idle or at criusing RPM? It might be something as simple as increasing idle speed a bit or dropping the float level a tad. Maybe the float is leaking and has taken on some fuel.

    As far as a bit of oil getting past the rings into the combustion chamber, would that increase HC or CO readings? :confused:
     
  18. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    When I was a kid my family had a '54 Plymouth. When they sold the car around 1964 it was on it's third engine. The first failure was a broken crankshaft. The replacement engine ran until some pistons failed. I was only nine or ten years old at the time but I remember seeing broken pieces of iron piston. And, I remember the discussion about the pistons in that engine being iron, and the ones in the rebuilt replacement engine being aluminum. That engine was a used replacement so I can't say where it had been or what had been done to it. So, I guess I can't say that Chrysler is the one who put iron pistons in that engine, but I can say that it had them.
     
  19. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,492

    Rusty O'Toole
    Member

    Are you sure it wasn't a Chev? They were the last to use iron pistons. I think even they had moved on to aluminum by 54. Last year for iron pistons 1953.
     
    Last edited: Mar 29, 2013
  20. plymouthwoodys.com
    Joined: Oct 21, 2012
    Posts: 10

    plymouthwoodys.com
    Member

    I dont like it either, but its the government, and they make up whatever they want. Have been on two 30 mile highway runs, Have about 200 miles on it and it runs fine. Doesnt make a difference in the readings though. Have also had another old mechanic tell me it could be its just not broken in.

    Thanks for telling me about the plate to remove. (Didnt even know it was there.) Now that I know I dont need a hoist, I have a friend that can look at the valve adjustments. Will just do the #2 first as you suggested.

    ClayMart: They only make me take an idle test.
     
    Last edited: Mar 29, 2013
  21. pdq67
    Joined: Feb 12, 2007
    Posts: 787

    pdq67
    Member

    Please look up your Vehicle Inspection/Maintenance (Air Pollution Control Program) Rule and just see how they can test a car that old??

    A while back I helped on amending this I/M Rule for the St. Louis Nonattainment Area. 10 CSR 10-5.381. Look it up and you will see what I'm talking about.

    Oh, and btw, my old $80, '48, Dodge 5-pass. coupe's engine had several cracked seats in it, but still ran fine, altho not as strong as the old 6-banger 3-speed stick Hy-Drive should have!!

    pdq67
     
  22. If it's got a Carter B+B carb maybe some of this info will help, even though it's for a '48. It could have a plugged idle air or emulsion tube. If they're checking at idle you may want to get it to idle as slowly as possible without missing. Look down in the carb at idle with the choke open at operating temperature. Do you see any fuel dripping from the main nozzle onto the throttle plate? That would raise hydrocarbons.

    http://old-carburetors.com/Plymouth/pages/Plymouth-001.htm

    http://old-carburetors.com/Plymouth/pages/Plymouth-002.htm
     
  23. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    No, it was definitely a '54 Plymouth Savoy. The second or third replacement was a truck engine. If it was the second maybe that had something to do wth it? Do you think the engine might have been rebuilt at one time with iron pistons? If someone was offering iron service replacements that would explain it.

    Iron pistons aren't all bad. That's what steam engines had. Where the application allows, iron has some advantages over aluminum in gas engines too. It tolerates more heat, it wears better, and it can be fit to the cylinder tighter. Some heavy duty diesels have pistons with an aluminum lower and alloy iron upper. Some of those are articulated rather than just a crown insert. The puts the iron where it provides the most benefit while minimizing piston weight.
     
  24. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,492

    Rusty O'Toole
    Member

    Some Dodge truck engines and heavy duty engines had reinforced upper ring lands with a steel insert. I never heard of any Chrysler built engine that had anything but aluminum pistons. Certainly not from the mid 30s onward.

    Iron pistons have some advantages especially where long life, silence, and low cost are valued over speed and power.
     
  25. 36tudordeluxe
    Joined: Oct 2, 2008
    Posts: 496

    36tudordeluxe
    Member

    If you have an air compressor and a compression gauge remove the rubber tip from the compression gauge and put it on the end of an air nozzle. Put #2 cylinder at TDC and hold air nozzle firmly in #2 spark plug hole; if you hear air coming up through the carb... bad intake, air coming out the exhaust, bad exhaust valve.
     
  26. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    Wouldn't a 50+ year old memory of what a 10 year old understood be more credible than whatever experience you have with these engines?:D
     
  27. 1948plymouth
    Joined: Feb 22, 2011
    Posts: 109

    1948plymouth
    Member
    from Minnesota

    So I found this http://www.aircare.ca/aboutus-qa.php

    It says "Collector vehicles are required to pass an AirCare inspection as a one-time condition of application for collector's designation."

    I did not find any specific specs on that website. It did state that there is supposed to be a running test and an idle test.

    Try this http://www.aircare.ca/inspinfo-standards.php . It is an Aircare standards calculator. I tried your vehicle with rough numbers and came up with 469 ppm HC.

    I think these should be exempt
     
    Last edited: Mar 29, 2013
  28. plymouthwoodys.com
    Joined: Oct 21, 2012
    Posts: 10

    plymouthwoodys.com
    Member

    I know what your talking about. I tried another carb and you can see the raw gas dripping. Still had the same readings. Its a rebuilt carb on it now, but I will have a another look to be sure thats not the problem.

    Will try everything that has been suggested here and will post the results. Thanks for the help.
     

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