Date: Thu, 24 Oct 2013 08:08:52 -0700
Reply-To: Tom Carchrae <tom@CARCHRAE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Tom Carchrae <tom@CARCHRAE.NET>
Subject: Re: off with her heads
In-Reply-To: <BAY403-EAS23E6975D135E72005E425FA00C0@phx.gbl>
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@Scott:
Thanks for confirming about the valves. I'm not entirely sure which ring
it is, I'll go and have a closer look today. Btw, I didn't adjust anything
with a bar - bar was meant as a synonym for 'except'. I am pretty sure it
is cylinder #1 (it is the closest to the passenger seat).
@Dennis;
On Wed, Oct 23, 2013 at 10:50 PM, Dennis Haynes <d23haynes57@hotmail.com>wrote:
> Please take this as training.
I do take it that way - mistakes are the best teacher, so they say?.... but
still enjoying learning and working on it.
I also very much appreciative of all the time and insight you, and others,
on the list are so generous with.
> At the point that compression test was taken
> that engine should have been taken out of service and further evaluated.
> All
> the cylinders are down and the one with 60 psi indicates a failure. If you
> had an emissions test program it should have failed. The catalyst is most
> likely shot. More concerning is while that cylinder was down the remaining
> three had to work harder to compensate.
That is the strange part - it passed the emissions test fine, not even
close to failing. The mechanic who did the compression test also thought
it would be a problem. So, I don't understand how that works, except
perhaps that Vancouver's AirCare is a farce - one that they are ceasing to
operate next year.
> This often translate to increased
> wear on the rod bearings. The oil contamination from unburned fuel doesn't
> help things. Before taking the engine a part a leak down test would help to
> diagnose if you had a valve or a ring problem.
>
This is was my most expensive lesson. I took it to a mechanic, and asked
him to do a leak down test, and to look at the compression problem. He
reported back that he had got the compression back up by adding racing lash
caps. I recall asking him about the leak down, and got back 'fine', and
'it holds pressure', and so on. It is clear from what you're saying that I
should replace the valve adjusting screws, not just pad them with lash caps.
Shortly after that, he changed the expansion cap, and I started to get a
really expensive series of coolant explosions. Then I drove the van across
western canada, with a few incidents, although after I changed the pressure
cap to another one I didn't have any more explosions - just coolant backup
behind the plate, and it was fine for an entire leg of the journey home.
Each experience made me want to fix it myself more - the last incident was
taken care of while we stopped for lunch (the first involved a tow truck,
waiting around for a day, and a crappy patch on a hose).
Anyway, all that is now water under the... no, coolant under the van? har
har. sorry, sorry... groan-worthy.
> Now that the heads are off there are some easy checks you can make. Put the
> spark plugs in and set the heads with the combustion chambers facing up.
> Fill the chambers with some light liquid like WD-40 or even carb cleaner.
> You will find leaking valves real fast.
Thanks. I'll give that a shot before I dig further into the valves. I saw
a video of someone doing that, but it was on a different type of engine.
> The exhausts should not be ground.
> If the seat are cut or the valves ground the stems should be shortened and
> the springs shimmed to compensate. This is to maintain spring pressure and
> rocker geometry. Adjusting screws should always be replaced. If the valve
> guides are worn it is likely time for new heads. These are a heat the head
> to 400 and cool the guides in liquid nitrogen fit. Otherwise they tend to
> go
> in off center and the seats will need a lot of cutting to compensate.
...and I though the spring tool was going to be fiddly.
They are newish AMC heads, no pitting (aside from some crowbar scratches).
I think they were done 5-10 years ago according to the receipts log, but
I'm not sure both sides were done at the same time. I've read the bit
about the AMC valves being terrible. I'll do some more reading up on how
to check those (aside from WD-40 test)
Back
> when VW rebuilt these heads they almost always ended up drilled out and
> fitted with oversized guides. A lot of labor. Make sure the intakes get the
> oil seals. ETKA does not show them but they should be there. I have a bunch
> in stock. They will keep oil from getting sucked down the intake guides.
>
and that would help prevent the valves and cylinder getting filthier?
You need to remove that carbon ridge at the top of the cylinder. The new top
> ring can get broken hitting it. If honing the cylinders remove as little
> material as possible. A few more thousandths and you will have an engine
> with piston slap noises. With the cylinders out at least measure the rods
> for play and bearing wear. The rods and bearings can be replaced without
> splitting the case, (this sucks but do-able).
>
I've been reluctant to pull any more cylinders out until I try getting one
back on.
Good luck,
> Dennis
Thanks Dennis - very much appreciated.
Tom
