Today's Message Index:
----------------------
1. 06:03 AM - Lead Alternative for Valves (lehmansmtl@netzero.com)
2. 04:51 PM - Fuel Pump or Vapor Lock ? (Mike Pierzina)
3. 11:01 PM - Valves and UL GAs (Dean Psiropoulos)
Message 1
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| Subject: | Lead Alternative for Valves |
--> Engines-List message posted by: lehmansmtl@netzero.com
Gentlemen,
Until a few years ago, I endeavored to run either 20% 100LL with mogas (or the
occasional 100LL fill-up when necessary on trips)to protect against the valve
seat to valve face micro-welding (described in a recent posting).
For the last few years, I've used a lower cost alternative called AVP (aviation
valve protectant) obtained from Canadian Aero Petroleum Products. The same company
in the USA is Niagara Airparts. Perhaps Gary can tell us what chemical
additive was used decades ago as a lead scavenger in leaded autogas (in North
America) because I believe that's what AVP actually is. AVP is described as
a vapor phase lubricant, non-toxic and is a added to the aircraft fuel tank in
the ratio 1 ml to 10 liters autogas (1:10,000). I've used AVP with both Continental
and Lycoming engines but don't have enough experience to prove or disprove
its effectiveness (except that to report no valve durability problems, yet).
BTW, my HIO-360-D1A had severe valve stem corrosion and considerable valve seat
recession after about 500 hours of helicopter service (considered severe). Lead
compound deposits are tough on valve stems and guides and, it seems, that
lead is only a partial solution even with hardened seats.
Mike
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Message 2
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| Subject: | Fuel Pump or Vapor Lock ? |
--> Engines-List message posted by: "Mike Pierzina" <planecrazzzy@lycos.com>
Hey Guys,
I fired up my 582 the other day and "top end" was rough....I figured it
was old fuel....I didn't have a decent hose to sipfon the fuel , so I pulled
the fuel line apart and drained most the fuel. I added the new fuel and with
a few primes it was running. I warmed it up to 140 degrees and then started to
raise the RPM's higher until I could test "top end".
It ran great , top end was smooth again.
Next day I loaded it on the trailer , packed all the gear, and while I was doing
my warm-up I couldn't get it to rev up , I noticed the fuel line going to
the rear carb wasn't pushing the fuel. and after the engine would die , I noticed
the fuel in the line would return to the fuel pump....
I'm getting a new rebuild kit for the Mikuni fuel pump.
Do any of you guys think it has anything to do with "Vapor Lock" .....I wouldn't
think so because of the run time the day before 10 - 15 min ......
and wouldn't you know it parts place is closed today...
Well, back to work on my Kolb. I'm still fabracating a 2cycle oil tank....which
was delayed because of the heat & humidity...
Gotta Fly...
Mike in MN FSII 503 w/injection
"B" w/ 3 blade-66" IVO ,EIS,GPL, 90% done 90% to go...
---
Sometimes you just have to take the leap
and build your wings on the way down...
Gotta Fly...
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Message 3
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| Subject: | Valves and UL GAs |
--> Engines-List message posted by: "Dean Psiropoulos" <deanpsir@easystreet.com>
A couple other things that have helped auto engines survive Unleaded gas
are:
Automatic valve rotators and liquid cooling. Automatic valve rotators are
something GM began installing on their engines in the late 70s. From what I
understand they are a fairly simple mechanism that is installed at the top
of the valve stem under the rocker arm. Every time the valve is actuated by
the rocker arm the mechanism turns the valve a set number of degrees before
it closes. This in effect results in a continuous lapping action of the
valve and valve seat. That way when a microscopic piece of the seat welds
itself to the valve face, it doesn't continually contact the same spot on
the seat and exacerbate the problem. This works really well in my
experience, my little 2.8 V6 in my Cheverolet S-10 PU has been run hard for
17 years and 230 thousand miles. After a compression check last year it
showed only 1 cylinder down in compression and that was only 10 PSI less
than the rest. I attribute part of this longevity to religiously changing
my oil and filter EVERY 3000 miles as well. As has been said before, oil
changes are cheap insurance. And while oil does not wear out, the additives
in it do and when they do they quit holding combustion byproducts in
suspension. Then it starts depositing them inside the engine where they turn
into a tarry goo that plugs oil galleries and other important engine parts.
Also a big difference between airplane and car engines is obviously the
cooling systems, car engines run cooler and that's another reason the valves
don't erode like VW beatles or airplane engines. The less differential
between the melting point of metal and the valve temperature, the faster the
metal is going to wear away. Air cooled aircraft engines run almost twice
as hot as most car engines and that is a factor in valve problems, that's
why the rotax can run UL gasoline and last longer, the heads are liquid
cooled (and they use modern engine design techniques, something Lycoming
hasn't bothered to do for 50 years).
Dean Psiropoulos
Tinkerer and RV-6 builder.
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