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Help with 32/36 DGV jetting


Randalla

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My 620 with healthy 1800 motor has a brand new 32/36 DGV carb from Pierce Manifolds. The combination is not behaving very well. Specifically, the truck bogs badly off idle. At full throttle it's OK, though I'm sure it's not optimal. The carb came standard with .055 primary and secondary idle jets. After talking with Pierce, I ordered three additional jets (.057, .060, .065), thinking I was a running too lean. I currently have .060 jet in the primary and .065 in the secondary. This actually makes the bog even worse. I'm wondering what some of you with L-4 cylinder motors are running and what you may have learned. Thanks!   

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With engine off look down the carburetor holding the choke flap open. Have someone pump the gas pedal or work the throttle by hand. You should see a strong squirt of fuel from the accelerator pump. Does it????

 

Carburetors struggle to transition from idle to running on the primary. The engine isn't turning very fast so it has a hard time generating enough venturi vacuum to draw in enough fuel. The accelerator pump mechanically squirts a stream of fuel to get through this. Maybe not working or needs more adjustment? It s a new untried carburetor.

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10 hours ago, Randalla said:

talking with Pierce, I ordered three additional jets (.057, .060, .065)

I think you waisted your time on that with the jets. But since you have all these Datsuns you might have tried everything allready

You sure the timing is correct?

valve lash ok

got good spark plug wires/sparkplugs

 

 

you have the spring on the secondary that keeps the it closed till the mechanical part open?

 

I have a camed L16 with a L20 head and I just bolt the carb on and runs fine. I only increased the idle jet to 60 but that its. rest is stock setting from where evere carb came from.

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The 32/36 is a progressive carburetor with the secondary opening at around 50-60% pedal travel. Try holding just below that tip in point till you get some speed up before flooring it fully. I drove an L16 with a Weber and while it did not 'fall on it's face' when floored suddenly, it seemed faster if you 'step into it' more gradually. With a little practice you can tell where it performs best. 

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Thanks guys. I will try this today and see if I get any improvement. This is my first and only 32/36 on a Datsun. I'm an SU guy at heart and know those carbs inside out. Would love to swap out the 32/36 for SU's if I can find a manifold.

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So, hooked up the vacuum advance but no change. I'm getting a healthy squirt of fuel from the accelerator pump when actuating the throttle. The secondary throttle plate however does not seem to open when the throttle is wide open. Should it??? Assuming it would open under full acceleration. I can manually move the lever to open it, but the throttle cable only actuates the primary throttle plate. Does the other barrel open mechanically or by vacuum as RPMs increase?

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weber is a mechanical 2ndary so it should open there is alike a tranfer bar with a slot that opens the 2nd barrel. Its right there on firewall side of carb.

 

with fill movement of the linkage. it runs the main barrele and then opens the 2nd barrel.

 

 

orginal write up was bogs off idle. Now it should be no full trottle / power .if the 2nd barrel wasnt working

Edited by banzai510(hainz)
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Secondary is now opening up but engine still bogs. Beginning to think the distributor may be a tooth out. Will check top dead center tomorrow to see if everything is aligned as it should be. Car idles well, just farts and misses under acceleration.  

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17 minutes ago, Randalla said:

 Car idles well, just farts and misses under acceleration.  

 

1/ That could be the ignition wires/cap/rotor. Possibly the plugs. The cap and rotor have no real expiry date for them it's more a visual. If they look worn, cracked, corroded or carbon tracked...  then replace them. Wires and plugs under normal driving are good for 30K miles. Plugs can be filed and gaped. Once a year I remove the plug wires and wipe clean with a WD-40 wet rag. This will show you any damage. If not sure... replace.

 

2/ Check the valve clearance. A tight intake can sometimes not close tight.

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you should be able to go thru 0 up to 25deg on the timing light if the dist is installed correctly.

if you have to cranke the dist all to one side to say get 10deg BTDC thern I say your off a tooth.

 

you never mention if the motor was apart or oil pump out so we would never guess that the oil pump spindal would be off a tooth. YOU JUST SAID YOU INSTALLED A NEWER CARB

Edited by banzai510(hainz)
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I think you mentioned changing jets to larger and still bogs or made worse, I was going to say it might be really rich, you can change accelerator pump jets as well.  If you can drive smoothly through the throttle pedal eg gradual and into full open does it stutter?  Does it do it under load on the street and when sitting in neutral and trying?  Under load on the street could indicate timing/spark issues but if both then probably carb.

 

If it drives smoothly through the throttle progression then the emulsions and main jets are okay but its that quick transition that needs help from 10 20 perc to Wide open.

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Still struggling with this. A couple more pieces of info. I verified I installed the oil pump spindle in the correct position, so that's no longer in play. Also pulled the distributor and removed the points plate to verify springs were intact and weights were swinging freely. All good there. The engine does not stumble as badly when not in gear with a load on it. If I very slowly increase the throttle speed it does not stumble too bad. Just feels like it does not have much power. Compression test revealed even compression across all four cylinders (150-160). Beginning to wonder if I got some bad Chinese ignition components. Thinking about swapping out coil and condenser with others I have.   

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is this stock coil and ballast?

 

a long time agi I had off idle issues on my 510. Its was the condensor. another time I think I had a crack in the carb adapter plate.  another was a worm dist shaft causing point bounce.

my ither car befoe I bought the car the guy put aAccell Supercoil in there and it would run like crap . Find out he didnt install the extra ballast resistor with the stock resisitor and the points were arching out.

 

hope this helps

 

 

I dont know what ingnition you got . if rinning point IGNITION you get full voltage at the entry of the ballast and about 6volts at the coil while running. then I say your ok with the point coil set up.

also feel if coil is HOT

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75% of carburetor problems are ignition.

75% of ignition problems are carburetor.

 

'Cutting out' could be...

1/ badly adjusted valve lash or bad valve sealing to seats. When the cylinder fires the valves have to be able to contain this explosion. Set cold to 0.008" and 0.010" intake and exhaust. That'll get you going then later when engine hot check that they are 0.010" and 0.012". 

 

2/ high voltage jumping to ground and not firing cylinder. Can be anywhere from coil to any spark plug. Go out in the dark (dark garage even better) and rev it up a few times watch for blue corona or blue/pink sparks jumping between wires or to valve cover, between nipples on the cap and coil to negative post on the coil. May also jump from wire down the side of the spark plug to ground. This won't show all just the bad ones on the outside. Inside the cap and the rotor you'll have to visually check for carbon tracking. Carbon tracking is a very fine burnt trail from previous arcing on the caps inside or outside surface. Can look like a fine crack. Once burned it's easier to spark along this track the next time If wires look bad..... they are. If any doubt replace with quality wires, cap and rotor. The high voltage spark is lazy and will always find the easiest path to ground. With solid good ignition parts that easiest path to ground must be the spark plug gap.

 

3/ are the plugs clean or covered with black dry soot or worse, wet and oily? Fouled plugs can decide to not fire, sometimes randomly. Cleaning or replacing should fix this but not the cause. Dry sooty is too much running with choke on and plugs don't have time to heat up and self clean themselves. Wet and oily is a worn engine. Sometimes a hotter heat range will help remove the oil. This is not fixing the cause.

 

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Thought I'd circle back on this post, after finally discovering my problem. Turns out most of the issue was due to a significant vacuum leak between the new Weber 32/36 DGV, and intake manifold. The mounting screws supplied with the carb were a shade too long, preventing the carb from fully seating. After some modifications, a bit more advance and slightly richening the idle mixture, she now runs like a top.

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48 minutes ago, Randalla said:

Thought I'd circle back on this post, after finally discovering my problem. Turns out most of the issue was due to a significant vacuum leak between the new Weber 32/36 DGV, and intake manifold. The mounting screws supplied with the carb were a shade too long, preventing the carb from fully seating. After some modifications, a bit more advance and slightly richening the idle mixture, she now runs like a top.

A few people have had that problem of the screws being too long. Glad you found it.

 

I hope you used loctite on the threads this time.

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