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Tapping and scratching

Discussion in 'Engine & Transmission' started by Farnakl, Jul 11, 2013.

  1. Farnakl

    Farnakl Member

    Messages:
    144
    Location:
    Gisborne, Vic
    Hi all,

    i have two noises coming from the back, and my mechanic hasn't been able to track them down.
    firstly though, I just had an engine rebuild, full box and dice, about 500 k ago.

    first noise is a tapping sound seems to be on drivers side of motor. I asked what clearances were set, he said "hard 7" which is too much I think, so my question is would this cause the tapping. The tapping is worse in the morning, very cold here, and gets less obvious when the motor is hot, and goes away when the revs go past about half way. Should I get the clearances down to 5.5 or 6 thou and would it make a difference?

    second noise is maybe worse, I drove into Melbourne and back yesterday, 100 km round trip. On the way home and going up the escarpment towards Bendigo I hear this sound, sort of crackling noise or like sand flicking up against glass. Even maybe a bit like a crackling grass fire. I heard this before the rebuild and like this time it came with a loss of power, as I had to drop gear on a hill, that doesn't usually happen.

    I think this might be about the motor overheating. I had been cruising along at about 110 for 10 minutes or so, and the air coming through the heater was pretty hot.

    anybody got any insights?

    dennis

    P.S. - Just took it to the mechanic who reckons this crackly noise is probably pre-ignition. This would explain also the new oil leaks if the engine was overheated - the leaks are from the rocker cover and might have been due to overpressure.
     
    Last edited: Jul 11, 2013
  2. VanAime

    VanAime Active Member

    Messages:
    2,349
    Location:
    Primate Gully Vic.
    Pre-ignition or "pinging" is usually a high pitched, metallic sound. A bit hard to describe, but maybe like someone slowly pouring a handful of bird shot onto the bottom of a Milo tin.
     
  3. sclarke7171

    sclarke7171 Member

    My kombi did that. Was the relay for the relay fan chattering over bumps. Cleaned contacts. All good :)
     
    Last edited: Jul 11, 2013
  4. 1500king

    1500king Well-Known Member

    Messages:
    1,550
    Location:
    Adelaide, SA
    Did you get the carbs done? correct spec for the engine? What distributor is in it? Has the dizzy been rebuilt?..Detonation is very serious... It BREAKS piston rings, melts pistons and does bad things to the heads.. Super hot heaters on a cool day suggests the engine is running lean too...in which case it will also be overheating.

    Have the exhaust studs been re-torqued? They should be done @ 500km. Overheating the engine will cause loosening of the heater boxes as the copper rings anneal and deform from the heat.

    I'd suggest that your mechanic investigates the mixtures and timing...Who knows, you might even have 1800 carbs on a 2L engine and could have killed the last motor.
     
  5. Farnakl

    Farnakl Member

    Messages:
    144
    Location:
    Gisborne, Vic
    OK, thanks everybody. The3 tapping is the valve clearances - too big a 7 thou - so they'll get adjusted next week.

    The other scratchy noise is indeed pinging - the timing was advanced too far. I've put back to 10 BTDC (from 12.5) but the book says 7.5! However the car runs like a dog at that setting, and even with 10, it has a big flat spot - however seems to do a lot better at highway speed.

    The engine is an AD serial - 1600 but bored out to 1800. Petronix dizzy, alternator, electric fuel pump, 34 Pict 1(?) carby which is the wrong one for the AD motor but I needed a new one and you can't get the Pict 4 new.

    I'll pass on all of your comments King when I drop it in on Tuesday
     
  6. cbus

    cbus Well-Known Member

    Messages:
    12,358
    Location:
    sunshine coast
    sounds like youre trying to kill the new engine :(
     
  7. Kai

    Kai Well-Known Member

    Messages:
    4,752
    Location:
    Sydney, NSW
    12.5 would give it around 33/34 max advance. should be around 28 with no vac connected to can
     
  8. Farnakl

    Farnakl Member

    Messages:
    144
    Location:
    Gisborne, Vic
    I shall check that max advance. Not trying to kill the engine, it's doing nothing right now.

    anybody know if the electronic dizzy has any effect here?
     
  9. 1500king

    1500king Well-Known Member

    Messages:
    1,550
    Location:
    Adelaide, SA
    That is too much initial advance you have... 7.5BTDC is it..with a VW 043905205B (1600 kombi) distributor. You need to make sure the dizzy is functioning correctly with BOTH vac and mechanical advance. The 34 Pict 3 needs to be correctly calibrated for the vac advance to kick in at the right spot...A major cause of flat spots... The 34Pict 3 is also a 1600 carb... Mixtures need to be set for idle, progression, main circuit, power circuit and high speed circuit...They will most definitely be wrong for the high speed circuit(under power and load...the highest risk for hurting the motor).

    What cam is in it?

    What is the static comp ratio?
     
  10. 1500king

    1500king Well-Known Member

    Messages:
    1,550
    Location:
    Adelaide, SA
    Your Valve clearances should be 0.004"(inlet and exhaust) for a standard 1600.
     
  11. syncro

    syncro Well-Known Member

    Messages:
    9,640
    Location:
    Southern Highlands
    Shouldn't it be .006"?
     
  12. Farnakl

    Farnakl Member

    Messages:
    144
    Location:
    Gisborne, Vic
    I've seen both in the various places. One dude says 4thou if you check them regularly, reckons the 6 thou thing is there because most people are lazy about maintaining their engines. Certainly the 7 thou that I've got is too much and giving me the engine noise. Probably ok to be on the safe side while running the engine in.

    ive set the timing to 7.5, but will leave the carby setup to the mechanic
     
  13. splitbus

    splitbus Well-Known Member

    Messages:
    3,315
    Location:
    Brisbane
    Tapping noise isn't you electric fuel pump is it ?
     
  14. Farnakl

    Farnakl Member

    Messages:
    144
    Location:
    Gisborne, Vic
    No, it's different, definitely mechacical
     
  15. 1500king

    1500king Well-Known Member

    Messages:
    1,550
    Location:
    Adelaide, SA
    For 1600 type 1 motors, it was 0.004" up to 1974 model year, then went to 0.006" with 9mm exhaust valve stems, hotter running engines(smogging and higher temp thermostats, leaner burning engines, sodium filled exhaust valves to carry heat away). You will have no issues with 0.004". Nearly all new cams come with 0.004" for a clearance spec too.
     
  16. 1500king

    1500king Well-Known Member

    Messages:
    1,550
    Location:
    Adelaide, SA
    You can at least synchronise the carb with the distributor...by doing the following;

    The throttle stop screw on the end of the throttle lever can be backed off so that the throttle valve in the carb is completely shut. Then screw in slowly until it JUST makes contact with the fast idle stepped cam, then screw in 1/4 turn. People use this screw to adjust the idle speed, but that is not what it is for, it is a THROTTLE STOP and sets the throttle valve internally so that it just covers the vacuum port for the distributor vac advance. Therefore, if you crack the throttle under light loads(with good manifold vacuum), the vacuum advance on the distributor responds at the right moment. If it is just a little bit off position, you engine will carry on like a pork chop and give you flat spots.

    There are TWO brass screws on the left side of the carb, a big one and a little one. Set the little one at 2.5 turns out(from fully screwed in) as a start-this is the idle mixture screw and is fairly likely that the idle jet is too small anyway, they normally like 1.5-2 turns(with throttle shafts that are not flogged out), so we are going a little rich. The fat brass screw is your IDLE SPEED screw, set it initially at 2 turns out from fully seated and start the car. let it warm up and once war, tweak it to you desired idle speed.

    The above will at least get the distributor responding when it should and get idle mixture a little richer to help fuel cool it. The rest needs a gas analyser and road testing.

    Make sure you have the Kombi distributor as it has a flatter mechanical advance curve than a beetle one. 043905205 B.
     
  17. Farnakl

    Farnakl Member

    Messages:
    144
    Location:
    Gisborne, Vic
    thanks king,

    i did these things and set the timing to 7.5 btdc, and its going a lot better. Still a bit of a flat spot tho nothing like before. Mdrove into Melbourne and back yesterday and car didn't overheat or ping.

    the dizzy is a petronix job, and does not have a vacuum advance.

    Is the fact that the engine has been built out to 1800 likely to require bigger jets? It seems to be running well on the highway, I had to back it off on the pedal to keep it at 100. It felt like it had another 20 k in it. On the long downhill,run anyway. It pulled up the big hill in top at 80 k - better than last time when I got down to second gear.

    oil leak (rocker covers) seems to be mostly gone, will get fixed when valve clearances are reset. I'll leave them to the mechanic.

    so thanks everybody in continuing my kombi education.

    next stop is to get all the electrics sorted.

    cheers,

    Dennis
     
  18. 1500king

    1500king Well-Known Member

    Messages:
    1,550
    Location:
    Adelaide, SA

    You WILL get a flat spot with that distributor that you have as it is a "009" with electronic pickup.. Has the wrong advance curve and no provision for "light cruise" . The timing on that one needs to be set at TDC but with engine OFF.

    We don't call them "engine killers" for nothing.

    The other problem is that it gives too much advance too soon... Find yourself a VW 043905205B distributor and have it rebuilt... All the parts are available for them, PM me if you are having trouble with auto sparkies being lazy.....

    Yes, your carb will be running LEAN...DON'T push the motor...It needs rejetting. The distributor will contribute to hotter head temps due to the lack of advance at cruise... The Mechanic who built the motor should have known this. What exactly did you ask for when it was built to 1800? I see warranty issues if it fails from abnormal combustion...
     
  19. Farnakl

    Farnakl Member

    Messages:
    144
    Location:
    Gisborne, Vic
    I got the engine like that, 1800 I mean. So when it was rebuilt, it was done the same.
     

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