Ferrari Mailing List: Re: Analyzing valve deposits

[Hans E. Hansen (FList]

Nice photos.

Doesn't look too bad to me.  Many, many years ago, I tore apart the
engine in my 1972 Corvette.  Had some deposits on the exhaust, but the
intakes were quite shocking.  The valves were heavily caked, I mean a
LOT, with what looked like hard water deposits. Sort of like a 1/4"
layer of snow.  Don't mean that's what it was, just that's what it
looked like.  Cylinder heads weren't too bad, both combustion chambers
and ports.  I showed several mechanics who seemed to think it was from
oil coming down the valve guides, as it was only on the back of the
valve head.  They reasoned that if it were something in the fuel it
would be more widespread.

Anyway, that was years ago.  Oil and fuel formulations have changed,
so it's hard to tell if any of this has relevance.

Hans.

On 11/15/20, Peter Rychel <dino308gt4 [at] hotmail.com> wrote:
> I’m aware of companies that will analyze used engine oil, but is there any
> facility that can analyze the deposits on valves?
>
> This has been an off-and-on project for me, but my GT4’s engine had not been
> running good and was really down on power. When I stuck my borescope camera
> down the spark plug holes, #7 cylinder showed vertical scratch marks,
> indicating broken rings (oh lovely...). So, I’m pulling the motor out.
>
> I have most of the components off and got a chance recently to pull the
> front exhaust manifold off first. I was quite shocked to see how white the
> tubes were inside. I showed my coworker, but he says that’s a good sign my
> fuel mixture is pretty close to ideal. Now, when I looked into the exhaust
> ports, I was quite alarmed to see how much deposits are on the exhaust
> valves. I’d really like to know what is causing this. Is it the fuel? A
> possibility as I have on occasions run a mix of avgas & pump gas through
> this. Is it engine oil blow-by? Or something else?
>
> I have yet to remove the rear manifold off, so it’ll be interesting to see
> if I see the same conditions.
>
> Peter
>
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