Weber 32/36DGV verses the Weber 38DGES

(pooh bah)
Sat Apr 16 2005
03:03 AM
Sarge
(carpal tunnel)
Sat Apr 16 2005
02:38 PM
yodta
(pooh bah)
Mon Apr 18 2005
11:25 PM
Re: Weber 32/36DGV verses the Weber 38DGES
Ok, that explains the jetting then completely. You have to compensate for the delay quite a bit with those split runner designs, the
MG guys have used those for years. It's also going to make it hard to guage F tube changes but should produce some good
results anyway.
Sarge
Re: Weber 32/36DGV verses the Weber 38DGES
I had a pretty frustrating weekend with this thing. seems I'm trying to do too many things at once. for me, there is a cloud
surrounding Weber perfection. I'm fine all around the cloud; it's sooo close to being dialed I can taste it! BUT, as soon as I dip
into that cloud surrounding perfection, I get SO! FRIGGIN'! LOST! again!!!!
anyway, here's a little correspondence from Sarge this weekend...
Quote:
A lot of guys get the mix screws set wrong and consequently the idle jet size as well. Remember, these settings
must be done with the throttle valves closed completely so you are tuning ONLY the idle circuits. The base idle is
just set until it's as smooth as possible. That split runner design manifold is going to show a delay in your setttings,
take your time and allow the engine to stabilize, sometimes up to 8-10 seconds. If it is correct and vacuum/timing is
correct you should be able to idle that motor down to 400 revs or less. I can drop this 1600 as low as 200rpms with
the 36DCNF easily. You should see how touchy these idle circuits are in this thing , one 1/32 of a turn is too much. I
do like though only using 45's for idles
Once the base idle mix is set, try this :
Slowly, very slowly raise the idle speed until you hit 2000 revs. If there is no hesitation or flat area , return the idle to
750 or so and try a driving test. Remember, the main circuit also affects timing as the blend between the two circuits
changes. If the main is too large, a smaller idle jet is indicated although tuning doesn't seem to come out right. Too
small a main jet results in an oversize idle jet and the same tuning problems as well as overall crispness disappears.
There is a reason those old Ferrari and Porsche mechanics are paid so well ......lol.
okay, so I took a little time away and went back to the basics and followed these instructions thinking I've got to be missing
something...
my results:
sure enough, I was able to get it to idle at just above 400rpm. according to Pierce, 2 is the magic number on the mixture screw,
so that's what I shot for.
I disconnected the advance hoses so there was no advance running on the engine (not sure if that was the right thing to do,
though. help me out here...). I connected my handheld tach and a vacuum pump to the manifold vacuum hose that normally goes
to the idle advance on the distributor to see what kind of vacuum I was getting, and also as a tuning guide -- smoothest idle &
highest vacuum, right? at 400rpm, I was getting around 21-23" vacuum. it was bouncing around a little bit indicating a vacuum
leak? (probably through the throttle shaft, I think). at this point, I proceeded to adjust the mixture screw. I was very surprised to
find that the smoothest, fastest idle here required a different mixture screw setting than when it's idling at 800-850rpm or so, but it
makes sense now that I think about it; at 850rpm, the throttle plates are open drawing in more air, hence the need for more fuel
for smooth idle -- different mixture screw setting. I was at under 1.5 turns with a 65 jet, so I went down to a 60 and did the whole
thing over again and ended up with just under 2 turns. it would probably be equivalent to 5 or 10 minutes on a clock if that makes
sense.
next test, the slow throttle advance to 2000rpm listening for flat spots or stumble. I still wasn't sure what to do here as far
as the distributor hoses, but I went ahead and reconnected both advance hoses. figured that this is how it's gonna be when I'm
driving it, so...
as I turned in the idle speed screw, what I found was that the whole range below 1200rpm was very unstable. it didn't seem to
react much to the screw and then came in in a bit of a rush. at around 700rpm, I got a pretty bad stumble, then again not much of
a reaction to screwing in the speed screw. things stabilized at around 1200rpm and then it was smooth sailing up to 2000rpm.
so what does this mean?
seems to me that it's making a poor transition. in the past, I would increase the size of the idle jet, but perhaps I need to stand
firm on the idle circuit and look at the main circuit and reduce the main jet size? not sure what to do at this point.
current jetting is:
idle: 60/65
main: 140/140
air: 170/180
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