<VV> Re: main jet vs idle

[djtcz at comcast.net]

I still think the reported carburetor situation/response is highly suspicious.

Have you measured the cam lift at all 12 valves ?  Maybe the hydraulics are hiding a jaked lobe.  Since so many of a Corvairs lobes are shared, 1 = 2.  http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=2313308&PMT4NO=2829269

http://www.jlindustrial.com/catalog/product.jsp?id=BAK-17000B&spec=JK&origin=SALES:WEB_SALE

If I was too frustrated to deal with the troubleshooting process right now, I might set the valves at zero lash (barely quiet, no turns in). Then I Might even take a fuel sample (pre-cleaner) in a clean glass jar for evaluation with small amounts of isopropyl.  Then drain the fuel for lawn mower use, put in a full tank of the good stuff. And buy and install one can (each) of premium fuel cleaner and thin oil treatment, and put on some more test miles.  LUCAS and Seafoam and Valvoline synthetics are my favorite snake oils right now.  I would definitely drain the fuel before accepting a kind hearted V-Varian offered me a fresh set of known good running loaner carbs. 

Also suspiciousto me is the otherwise commendable use of any Ultra plugs in times of trouble...........shooting.
And ignition components subjected to multiple full power hi-pot tests with plug lead yank-offs.  I provide Genuine grounding, Especially on fragile vintage European electronic ignitions, but even on points ignitions, using 6 pieces of wire cut from a straightened paper clip with heart still beating, one piece slid deep into each cylinder's dist cap tower after the plastic boot is gently pulled up revealnig the base of the wire.  Then a cheap-oh test lead attached to ground kills the cylinder nicely by shorting without subjecting coil, cap, and leads to attack by a desperate angry pent up spark.

It might be fun to see your Heathkit's opinion of what happens during a plug lead yank-off, although the instrument is probably off-warrantee by now.

re- valve adjustment - at any rpm below float a  hydraulic lifter simply assumes the correct length for zero lash. 1/4 turn in, 1 turn in, 1.5 turns in, as long the lifter is in in its lengthy operating range the valve action is the same.  But gunky or damaged lifters have a limited range, aometimes zero. If 1/4 turn in >just happened< to be the end of the range in the shortening direction,  and the engine warmed up further, that valve would be too tight.  Oughta see it as pulses in the vac gage, if the old troubleshooting books are to be believed.


--
Dan Timberlake

-------------- Original message -------------- 
Subject: Re: <VV> Re: main jet vs idle

>   As for the #4 plug intermittently not firing, REPLACE it!  Splurge the 
> $0.99 for a spare plug.  LOL.  It is very conceivable that you might have 
> a marginal plug.

Well the good feeling was shortlived. Am almost beginning to think that 
there is something else going on.

Replaced the odd #4 with a good spare and am now able to identify some 
really odd things going on.
First, it revs nicely but at steady 2000 rpm can feel just a bit of a 
flutter in the exhaust, not a lot more like twice a second.

Second it starts out with a nice 650 rpm idle in D but the longer it runs 
the more often and quicker it just drops to 400 rpm. Smooths out if I open 
the throttle just a bit and then returns to smooth 650 rpm. Idle in N is 
steady at 800 rpm.

Have checked timing often and is rock steady at 14 degrees below 900 rpm.

Pulling plug wires at 800 rpm in N produces a similar minor (under 100 rpm) 
drop from each cyl. Think I really have it well balanced.

When it drops to 400 rpm the engine seems relatively smooth but can pull #3 
and #4 plug (center cyls) wires with no apparent effect.  When #1, #2, or 
#5 are pulled engine stalls. Pull #6 and engine seems to run a little 
better for just a second as if #4 were firing again. Does same when 
reattached. Verified plug wires are in right order.

Have had ignition analyzer in parade mode and is no apparent difference 
between when at 650 rpm and at 400 rpm. But am not entirely sure what I am 
looking at. Assume the bright spot in the spike is where the plug fires.

Right now valves are adjusted while warm running to 1/4 turn from clack. Is 
there any chance this is not enough ? Now that I have separated the bad 
idler noise engine is pretty quiet while running. When covers were off was 
evident the engine is pretty clean with no sludge apparent.

Know the engine is somewhat worn, is some blowby evident and appears to be 
using some oil though excess idling may be a factor. Suspect it is a 74,000 
mile original but compression on all cyl is above 150.

Have learned that just taking apart to see is really not a good idea, at 
least not while the vehicle is still mobile so want to exhaust all 
possibilities before pulling more than the valve covers.

Thanks for listening,

Padgett 



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