Re: knocking sound on spider

[AlfaNeely@domain.elided]

       I am not going to try and diagnose noises over the Internet.  However, 
the cause could be valve clearances.  It is more likely a loose timing chain.
       Checking valve clearance is not hard at all.  In fact, I recommend 
pulling the valve cover about every other oil change to clean out the half 
quart of dirty oil that resides in the cam galleys.  Be careful to not tear 
the valve cover gasket and it should be reusable.  I put anti seize on one 
side of the gasket on assembly to help it come off the next time.
       While you are changing oil (all the dirty oil) it is quite easy to 
check cam chain tightness, and cam timing.  It is a bit more work to check 
valve clearance or lash, but not hard.

       The intake valves should be around 0.017 inches and the exhausts 
should be 0.019 inches.  If the clearances are all below 0.022 or so, there 
should not be any valve noise.  A tight valve should not be noisy, but a 
loose one can be.
       I am running my 84 Alfa spider race car at 0.010 intake and 0.012 
inches exhaust on the stock camshafts.  That is pretty tight, so if your 
valves are all between about 0.008 inches and 0.022 inches, the car should 
run OK.  But ideally they should be 17 and 19 thousandths.
       If the valve clearances are reasonably close, then write down the 
measurements.  Next time you check them, if they have changed, you have 
problems.  It has been my experience that Alfa valve clearances do not change 
unless there are problems like a valve sucking into the seat or excess 
camshaft wear.
       A more likely problem is that someone in the past did not adjust the 
valves carefully.

       Adjusting the valves requires removal of the cam shaft, remove the cam 
follower and the shim underneath of it.  Measure the shim (inside the 
depression that holds it on the valve) and compute how much thicker or 
thinner it needs to be to change the previously measured clearance to the 
desired clearance.  Then go over to Vick in Fort Worth or to your local Alfa 
mechanic and buy the required shims.
       You should have all ready written down the measured clearances.  Now 
write down the measured thickness of the shim for each cylinder beside the 
measured clearance.  The measured lash plus the measured shim thickness less 
the desired lash gives the thickness of the needed shim.  I set this up in a 
spread sheet to do the computations, but then I am an accountant and use 
spreadsheets for everything.
       You may find that you can move shims around to achieve the desired 
clearances for some of the cylinders.  Then you will probably find that you 
only have to buy three or four shims to get everything to spec.  Play with 
Alfas long enough and you will have a pretty good assortment of valve shims.
       You can also grind down the shims to the needed specification.  A 
friend has a surface grinder that allows me to grind the shims perfectly flat 
and to an accuracy of 0.0005 inches.  That works best when you have had the 
valves ground and all the old shims are too thick.
       I do my measurements in inches as my feeler gauge and micrometer are 
both in inches.  I also notice that I used the words valve clearance and 
valve lash interchangeably, which in my understanding is quite correct 
verbiage.
       Good luck.

Ciao,
Russ Neely
Oklahoma City



In a message dated 07/23/2002 1:55:19 PM Central Daylight Time, 
crawfordpat@domain.elided writes:


> 
> To all,
> I have a 79 spider that has developed a "tapping" sound that ios apparent at
> low ipms when I take off, I have heard that it also gets faster but I cannot
> hear it as much, possibly just because the engine sound drowns it out. Do
> you think that I need a valve adjustment, or is there anything else I can
> check? Also, if a valve adjustmewnt is needed, how difficult would this be
> for me to tackle it myself? I have a brooklands alfa spider book and the
> alfa owner's bible, should I take the plunge? My most recent accomplishment
> was swapping out the water pump ( to give you an idea of my technical
> ability).
> As always, I loook forward to your response.
> Pat Crawford
> Dallas
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