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New 32/36 DGEV jetting


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Adjusting new 32/36 DGEV per Redline instructions and with the supplied size 60 idle jet, I had the mixture out 2-1/2 turns to get Lean Best Idle.

Redline says more than 2 turns out would need larger idle jets

I purchased 65 and 70 idle jets and here are the results:

65 - 3/4 turns in on idle screw to maintain 800 rpm - 2-1/4 turns out on mixture screw to Lean Best Idle

70 - 5/8 turn on idle screw to maintain 800 rpm and 2 turns out on mixture screw

 

I'm thinking of trying a 75 jet to see if I can get the amount of turns less than the max recommended.

Does this seem like a good idea?

If I do, how do I know if I overcorrected?

 

I'm wondering if this lean condition is indicative of another problem or if it is not unusual to do this change.

 

I checked for vacuum leaks by spraying sh*tloads of starting fluid, carb cleaner and brake cleaner around all of the parts of the engine that I disturbed and I'm confident that there are no leaks.

Timing is at 3 degrees BTDC

Z24 engine has 68000 original miles and compression is 175 in all 4 cylinders

We have E10 gas in Oregon

All smog stuff aside from carbon canister has been removed

We live at 400 feet above sea level

Edited by matrophy
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Sea level is denser air so more fuel usually needed. Over 2,500 foot and you will run richer than needed and need smaller jets.

On a Weber the idle jet is also the main jet? correct?

 

 

If two turns out is the tipping point then 70 sounds about right however you certainly could try the 75 but I would fill the tank right to the top of the filler pipe and drive it say a hundred miles and record miles and how much to fill it back up the same. Later put the 75 jets in and do the same over the same course. I would expect the leaner jets to give better mileage. It may not change enough to really matter.

 

 

 

 

 

My 710 is from Nevada average elevation 5,000 feet. I'm right at sea level. Car ran great but on holiday trips I noticed mountain driving gave better mileage. This makes no sense to me at all but I pulled the jet from the stock Hitachi and it was #99. I had an engine from a local Datsun and it was a #112. I swapped the #112 jet in and it ran better, better ass dyno results and the mileage went up. With all the air at sea level I was leaner than I needed to be. Running more gas produced more power so I didn't need as much throttle so my mileage went up... go figure.  

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Main jet and idle jet in DGEV are separate. I'm going with the recommendation to adjust idle jet size. Main jets weren't mentioned in Redline instructions. I will swap in the 75 jet and see what happens. Seems odd to go with a 25% jet size increase over what's recommended on a stock motor though.

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The idle jet sets your mixture all the way across the transition circuit. The idle screw only adjusts the amount of fuel flowing behind the butterfly when it's closed. As the butterfly opens, it uncovers the transition holes. If you run a very rich idle jet, your whole transition is going to be fat. Believe it or not, a lot of your cruising mixture comes from the transition circuit alone, so if you notice sooty plugs, you might want to step back a few sizes and just open the screw a little farther. 70 seems large to me, but 2 turns out was the sweet spot I thought? (I'm used to much smaller L engines that normally run between 50-60.)

 

If the throttle stop screws are set in too far, it'll crack the butterflies open, uncovering the first transition hole. This will screw up the idle mixture. You may need to go back and forth a few times to get it right. 

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8 minutes ago, mainer311 said:

The idle jet sets your mixture all the way across the transition circuit. The idle screw only adjusts the amount of fuel flowing behind the butterfly when it's closed. As the butterfly opens, it uncovers the transition holes. If you run a very rich idle jet, your whole transition is going to be fat. Believe it or not, a lot of your cruising mixture comes from the transition circuit alone, so if you notice sooty plugs, you might want to step back a few sizes and just open the screw a little farther. 70 seems large to me, but 2 turns out was the sweet spot I thought? (I'm used to much smaller L engines that normally run between 50-60.)

 

If the throttle stop screws are set in too far, it'll crack the butterflies open, uncovering the first transition hole. This will screw up the idle mixture. You may need to go back and forth a few times to get it right. 

 

Thanks. This is not something I know a whole lot about so maybe I'm being overly cautious in adhering to the 2 turns out recommendation but as I understand it, lean is worse than rich for an engine. 2 turns out is max and from what I've gathered, a lot of guys are running more in the 1-1/2 to 1-3/4 turn area so I'm wondering if I shouldn't go up a jet size to stay off of the ragged edge of the recommendation. The idle speed adjustment is between 1/2 and 3/4 turn which is well in the guidelines of no more than 1-1/2 turns in. 

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I will tear my 86 720 K646 Weber apart tomorrow and will note the jet sizes and emulsion tubes sizes.

 

I live in the Phoenix AZ area that is around 1100 feet in elevation.  I installed and drove this carb while I lived in Battlemountain Nevada elevation 4,500 feet.  I did not re-jet carb when I moved back to Phoenix.

Edited by Charlie69
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2.5 turns seems close enought   I think I have a 55 or maybe a 60 but its all L16/18s

but they are cheap if you get the right jets depending on holder size as there are 2 versions  I know the DGV 5A use the smaller versions. The E and EV-IC ue the bigger holders.

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Life got in the way of tearing my Weber apart I will not be able to get to it until Saturday now.

 

Here are the specs I have on my other Webers.  I will fill in the other 2 carb specs as I get time to tear down the carbs.

 
           
           
           
           
           
           
           
           
           
           
           
           

 

 

 

Charlie69s Weber DGEV 32 36 Jets E Tubes Venturies-1.jpg

Edited by Charlie69
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3 hours ago, DIY 1985 said:

1/2 to 3/4 turns-in on the speed screw is 3/4 to 1 turn less than mine is set.  I'm at the max 1.5 turns in.  I'm probably far less than 800 rpm.  Where is the air coming from?  Is this a used carb?

 

I'm at 6,800'

Brand new K662 kit from Carbs Unlimited with 60 primary idle jet. The 75 jet I installed lowered the amount of turns out of the idle mixture screw to 1-1/2 so well within the recommended 2 turns out max. It bothers me that I had to go so large on the jet though. The truck runs better than it did with the 60 jet but I am not sure that I didn't overcorrect.

 
I ordered a wideband AFR gauge, etc  - partly because it was either pay for a gauge or pay a shop to analyze my exhaust and partly because it seems like a cool gadget.

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Oops, I forgot, I have a 1mm hole in the throttle plate, opposite the progression holes, as per Pierce Manifold's video.  I have achieved as high as 32mpg with the Weber on my Z24.  I've also hacked harness so that both coils fire regardless of the computer.  I'm a bit advanced for static timing at idle, but I'm not running ported vac advance.

 

The AFR readout is a nice thing, apparently, it is just a super fine reading of voltage.  It works with repeatable results on the Nissan exhaust, with original O2 sensor.

 

Are all the vac sources in good shape, PCV system, brake booster, adapter plate, gaskets, etc?  Have you taken a vacuum reading at idle?

 

 

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3 hours ago, Charlie69 said:

Does your Weber have cast in the metal made in Spain on it.

 

Weber notes that over 4,000' elevation needs to be re-jetted because of the altitude.

 

 

I'll have to look. It's a Redline kit so I assume it's legit. I'm at 400 feet and occasionally go over a mtn pass of 1200 feet but mostly stay at around 400 feet. Do you think it might be the float? I hadn't checked it when I installed the carb. I order a gasket so I can have a spare if I need one and then I'll check the float height. I'm not 100% sure of the spec. I think it's 35 mm with the cover held vertical.

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In stock condition both coils fire together. The only 'computer' is on the California emissions trucks with the ECC carburetor and it has nothing to do with the ignition although it uses the ignition signal to know how fast the engine is running (rpms)

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10 hours ago, matrophy said:

Brand new K662 kit from Carbs Unlimited with 60 primary idle jet. The 75 jet I installed lowered the amount of turns out of the idle mixture screw to 1-1/2 so well within the recommended 2 turns out max. It bothers me that I had to go so large on the jet though. The truck runs better than it did with the 60 jet but I am not sure that I didn't overcorrect.

 
I ordered a wideband AFR gauge, etc  - partly because it was either pay for a gauge or pay a shop to analyze my exhaust and partly because it seems like a cool gadget.

Correction - Kit is K646 for z24

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