<VV> Die! Dieseling Corvair, Die!

[Tony Underwood]

At 01:20 hours 09/10/2006, Charles Lee at Proper Pro Per wrote:
>Isn't it just that part of the combustion chamber (dirt, whatever) 
>gets so hot that it ignites the fuel/air coming in, regardless that 
>there is no electric spark to ignite it ?
>
>Lots of ways for that to happen, right ?


Well, at risk of talking about something besides Corvair tech:

I used to have some problems Back When, with a Mopar performance 
engine (426 with excessive compression) and some rather rich 
carburation, which tended to load up the chambers with carbon and/or 
plain soot when it was granny-driven around town.    I imagine that 
some in here likely have long since gotten bored with my comments as 
regards my streetracing days but I still learned a lot about basic 
engine idiosyncrasies from playing with musclecars.

I learned by default that a blown head gasket which weeps coolant 
into the chamber will not only cause antifreeze loss eventually, but 
it also kept the chamber really clean.   I yanked the head (no small 
feat on an engine like that one) to change the head gasket and the 
chamber in question was almost spotless, while the rest had both soot 
and tan-gray flake deposits on the piston and the chamber, as well as 
the face of the valves.   The non-soot/black stuff was likely 
tetra-ethyl lead, what with having to feed that greedy bastard the 
best gas I could find to keep it from pinging.

In any event, with its aggressive valve timing and duration plus 
rather narrow centerlines, it didn't much like to stop when you cut 
the switch off unless you unclutched it in gear.   I started putting 
a notion to work with a weekly routine of starting the engine, 
running it up to temp and then dragging out the garden hose, 
adjusting it for a small steady stream, and simply spurting water 
down the intake while buzzing the engine at around 4000 rpm.    I 
gave it this sort of treatment for about ten minutes, watching the 
steam come out the tailpipes.   I did notice that when I shut the 
engine off after this treatment, it didn't diesel.

I kept this up weekly, and my diesel issues went away for good, never 
came back.

I stopped doing the water trick when it finally came down to no more 
leaded gasoline being available courtesy of the gubmint's desires to 
remove lead from the environment.


Interestingly enough, the pinging came back when the lead went away, 
had to drop the timing back a bit... which should have caused even 
more of an issue with run-on  but the dieseling didn't come back.


Now:    Finally...  Corvair content.

A while back, I put another engine in my '60 4-door, to sit in good 
stead until I fix the ailing 80hp 140ci engine that came out of the 
car.    The engine that went into the car was something that came out 
of a demolished '66 coupe decades ago and had been sitting in storage 
until I acquired it.   PO said the engine hadn't been run since it 
came out of the car the '70s and only had 30k on it.   From the looks 
of it, the notion of the engine being that fresh is reasonable, 
considering its excellent condition.   It wasn't known how long it 
had sat in the wrecked 'Vair before the PO acquired the car and 
parted it out; said he got it pre-disastered.

It also evidently cut its teeth on leaded gasoline and hadn't seen 
much, if any, low or no-lead fuel by the time it's original vehicle 
had met its demise and the engine sat in storage since the Ford 
administration until the time I dragged it home on a trailer.


First thing I found out about it is that it runs excellently, and it 
diesels when you cut the switch off.   It also pings unless I use at 
least mid-grade or, better, hi-test.    I did pull a plug or two to 
check 'em out, they looked fine although they did have a thin film of 
those brown deposits (lead) on them, and likely the same lead 
deposits are currently coating the chambers, faces of the valves, 
and  piston crowns.

Sometimes I have to leave it in Drive and tap the gas pedal rapidly 
to flood it out, get it to stop so I don't have to walk away from it 
with the engine going chug-chug-chug wheezing and snorting.


I've been putting up with it like this for some time now...  It's 
gonna get a water treatment, see if it helps clean out that stuff 
that's glowing on the edges so the engine will quit when I shut the 
ignition off.

If ever there's a good time to hook up a water injection kit, it's 
when you're having dieseling like this thing diesels.   It could well 
clean out the lead deposits... and help keep soot etc from forming 
which will do the same thing, leave hot spots to glow and fire off a 
fuel-air mixture.    For that matter, the same thing causing the 
dieseling likely isn't much helping the pinging either, same reasons.

For now... I have the idle set so low the car shudders in gear, which 
means it does stop without a lot of fanfare when I switch it off in gear.

Trust me, the water treatment is gonna be a lot easier than yanking 
the heads and chiseling out carbon deposits.    I am not so dedicated 
that I'll yank a 'Vair head that quick, even if it *is* easier than 
pulling a head off a 426.

This post is my opinion and reflection only, and is not to be taken 
as bona fide lawful authorized and approved technique to prevent 
dieseling or pinging in Corvairs or other makes.   Do NOT simply hang 
a garden hose in the carb and pour it full so as to "wash out" the 
chamber like one moron I knew attempted,with the engine sitting there 
not running, couldn't understand why the engine hydrolocked 
afterwards when he tried to start it.    With the engine running at a 
brisk clip, even a trickle of water goes a long way when doing this 
sort of thing.     Don't try it unless you know exactly what you're doing.



tony..