Re: [T3] Push rods breaking

[Marlin Viss <mrlnvss@dordt.edu>]

oops!  Forgot to copy the list...

-------- Original Message --------
Subject: Re: [T3] Push rods breaking
Date: Tue, 25 May 1999 09:40:10 -0700
From: Marlin Viss <mrlnvss@dordt.edu>
To: jadney@vwtype3.org
References: <199905250240.VAA43260@mail1.doit.wisc.edu>



> Is there
> any chance that you are doing extra high RPMs or have heavy duty
> valve springs in there?
>

...The valve springs are stock, and I drive like my grandma

>
> BTW, the classic sign of an over-revved engine is that you can see
> bright bands around the middles of the pushrods where they have been
> flexing and rubbing. Do you see this?

...no

>
>
> If your clearances all seem to be opening up then this is a sign that
> something is wrong. A valve clearance that is too large puts the
> valve train under a lot of stress every time the clearance is
> suddenly taken up and the valve must be instantaneously accelerated.
>

...Is 0.006" about right?  The valve in question had too much clearance,
but
only after it had compressed the pushrod.

>
> What are the two kinds of push rods in your engine?

Both kinds are the same length/diameter.  The two that broke (and
there's a
few more like this) are aluminum tubes with a steel end on both ends. 
The
steel end is about 1.5-2.0 cm long.  These ends attach by wrapping
around the
aluminu'vÄind of like a pipe fitting on a pipe.  The breaks occured
right where the steel ends and the aluminum begins.

The ones that seem to work better are also an aluminum rod, but have
smaller
(as looked on from the outside) steel ends.  These ends attach to the
aluminum via a 1 cm steel extension that sticks into the hollow aluminum
rod.  These seem to be more common, since they are all I see at the VW
Parts
House.

If it was just a matter of the strange pushrods breaking, I would just
pass
them off as a poor design and replace them.  But since it's screwing up
the
good ones now, something must be wrong.  Is there a way I can test the
pressure required to open the valve?  Could it be binding in the head
somewhere?

Thanks,

Marlin
'65 1500S

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