<VV> Re: main jet vs idle

[djtcz at comcast.net]

Top posted - 

In order for the main jet to be the slightest bit important at idle I think the throttles are too far open when on the idle stop. That is something that can be measured directly using wire or thin feeler gages for comparison against someone's good running auto.  The implication is some dead or weak cylinders, requiring more throttle to get the remainders to produce the required power to idle.

First I'd do a 6 cylinder balance test shorting (not open circuiting with a wire yank) 1 plug at at time.  I sort of recall some of The Heathkit Analyzers had some cylinder balance capabilities.  Sounds like you already had at least one dead one, without a particularly rough idle, with incomplete closure as to whether it was plug/wire/? .  I'd confirm IF all 6 new plugs fire strongly, AND all 6 positions can jump a wide-gapped test plug, AND all 6 fire at the right time (3 TDCs on damper via tape or other method) . 

If the ignition tested strong and consistent I'd question if the idle circuit(s) are operative (long term gunk, short term water drop).


--
Dan Timberlake

-------------- Original message -------------- 
Message: 3
Date: Fri, 18 Nov 2005 23:27:38 -0500
From: Padgett <pp2 at 6007.us>
Subject: <VV> Got Idle
To: virtualvairs at corvair.org
Message-ID: <5.2.0.9.2.20051118231811.01c8cb00 at mail.bellsouth.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At last an idle. Some time ago Ed mentioned that it might run better with 
52 jets instead of 50s and today I wanted to check the float levels anyway 
so swapped them out.

Carbs were very clean inside and were running what I thought was pretty 
good but with the 52s the only word is "nice". 800 rpm in N and 650 rpm in 
D warmed up and stable.

Stable until the #4 plug (W8AC) stops firing that is, then idle drops to 
400 rpm but is still stable and will stay there as long as desired. Rev it 
a bit and #4 starts firing again  for a while but will eventually quit 
again. May be a bad plug or may have gapped wrong but will replace and see 
what happens. Important thing is that still was idling at 400 & other than 
the miss, felt smooth. (earlier I had checked the compression in #4 and was 
155 psi)

Testing was limited by rattling idle pulley bearing & not going to drive 
that way but feel much more confident now.

Had previously opened the idle mixture to 2.5 turns which helped but did 
not think at closed plate idle the main jet would have that much of an 
effect. Was rong. Sometimes too much thinking hurts.

Padgett