Date: Sun, 9 Jan 2000 09:35:09 -0500
Reply-To: Bob Donalds <bostneng@FCL-US.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Bob Donalds <bostneng@FCL-US.NET>
Organization: Boston Engine Exchange
Subject: Re: 6 mils of lash...
Content-Type: text/plain; charset=us-ascii
John wrote:
>
> Hi David,
>
> I've seen all the industry general guide lines about storing
> un-installed lifters in certain positions and pre-filling lifters by
> pumping them in warm oil baths but I can't buy any of it.
>
> I have an '86 Syncro that during a complete powertrain restoration,
> I installed a VW factory exchange motor. I retorqued every fastener on
> the engine prior to installation but I did not even check the valve
> clearance other than making sure the adjuster locknuts were tight.
> Additionally I checked the pre-start engine compression which was an
> acceptable ~170PSI in all cylinders!
>
> When I initially started the engine it sounded like a washing machine
> full of roller skates & siamese cats! The sound was really SCARY!
> However knowing there was adequate oil pressure I let the engine run,
> accelerating to 2,000 RPM at times and you could (almost) hear the
> lifters pumping up and reducing the valve clearance to zero, one by one.
> After about 30 minutes; total silence.
>
> The engine now has now logged 8,000 miles, starts right up, gets ~19 MPG
> @ 70 MPH and has a smooth, stable, idle quality. I'm not a proponent of
> VWoA but their exchange engines must be set up as the Bentley specifies
> since VWoA gave Bentley the procedure. Why then is this basic Bentley
> Hyd lifter set up judged unreliable ?
>
> If Bob Donalds is on-line, I would like his spin on this.
>
> Regards, JP
John and the list
If you think for a moment that the VOA factory follows bentley to the
letter
then I have a bridge for sale I would like to talk to you about
I have taken to many VOA engines apart and can tell you for a fact they
are inconsistant
at best.
Who knows how they get the lifters bled they may do the drill press
thing as bentley discribes but I have had limited luck with that. the
engine will always have atleast one valve open and it over time it bleds
down this may not be a problem if there is for sure no air in the
lifter?
I have said that bentley does not feel that they can pass judgement on
the info and they pass it along unless they have a tech bulliten to
refer to for changes
VOA doesnt care about lifter problems in the vanagons and wouldnt waste
there time on tech bullitens for a ten year old car
the possible explanations I can think of are
1) thought is that hydraulic lifters could be using differant seals than
they once did viton comes to mind and while viton is a great upgrade in
rubber the way it behaves under everyday use may be differant that may
not allow the self bleeding action under some conditions like with
increased oil pressure, oil weight, or engine temps changes
over pumped lifters is not a new thing that happens to only vanagons
2) I am told that there is a racing version of the hydraulic lifter
availible for proformance cams in V8's that acts the same way as some vw
lifters they can take no perload they are made to behave that way so
they dont colapse with the heavy valve springs and higher RPMs I am
looking into whats differant
3) the MBTE additves in the fuel could be reacting with the seals in the
lifters the way it is with the fuel lines sometimes they rot and
sometimes they get hard as a rock
4) the lifters may at times need to be bled like a master cylinder that
needs the full travel of the pedal to take in more brake fliud. half a
pump just doesnt do it
in other words the valve inside the lifter needs the full travel of the
lifters internal piston to get rid of all the air in it. as Dave has
pointed out 0 lash wont do this becomes a small preload when the engine
warms up.
5) the lifter could be air bound and as the engine warms up the air in
the lifters expands creating a vapor lock
before and after compression testing is a good way to tell if the
lifters are letting the valves close all the way after preloading. As
Dave points out the lifter self adjusts over time so preloading the
valve and doing a compression test right away wont tell you if the
lifter has self adjusted. drive the van for a day or 2 then retest the
compression. keep in mind that the lifters over pump when the engine has
warmed up and a cold compression test is meaningless
I need poof that what Im doing works for sure and a compression test
does that. This doesnt happen with every engine or every lifter I have
not been able to see anything that offers a clue to when this will
happen. it's not as important to know why this happens as it is to know
how to deal with it.
Bob Donalds
http://www.bostonengine.com