Looking for advice about this 620 carb...

[mike_dmt]

 First of all, I was hoping someone could identify it for me. I'm helping my nephew with his first "real" project, which is his "new to him" '79 620, and if you've seen my other posts, I'm more of a muscle car guy, and the older Datsun stuff is new to me. I like it, for sure, I've always wanted a 510.

 

Second, you'll note that what looks like an air rail on the exhaust has been disconnected, and there are open ports on the manifold under the carb. Can we just delete it, or what? There looks like a bracket by the crank pulley where a pump might have lived, but she ran away from home from the looks of it...

 

 

 So, we we're hoping to adjust the air/fuel mixture to not only make it run better, but it wont idle for very long. He's had to learn the heel/toe technique. Good for racing, but gets old for everyday driving.

 

 Big question is: Is it worth rebuilding for the price of the kit, or should we just get a Weber?

 

 Thanks for any ideas and advice in advance

[q-tip]

Just get a weber, solves a lot of problems, and adds a little power

[mike_dmt]

Thanks. Anyone else want to weigh in?

[ggzilla]

Looks like the original L20B carb

 

Don't rebuild it. Find the leaks and fix it. Look for cracked vacuum hoses or unplugged hoses.

[bananahamuck]

If you grab the top of carb ( without filter) and move/twist does carb feel like it is loose at all ?? If it does unbolt and tighten screws that hold the bottom on... I try NOT to flip carb over as that has caused trouble for me in the past.

 

You can also flush some of the crap / water out by taking out the two screw in plugs that are right under the float bowl ( 12mm and real hard to access but it is possible with carb on car)  flush out  using vent tube.  BE CAREFUL as there are washers on the plugs that need to be on there or it will leak onto exhaust.

 

 

Many of us have cut those pipes off at the fittings on the manifold and mig welded them up.. You could try pulling them out and using a plug but those things are usually  rusted in there like death at a nursing home.

 

I always at least try the free/cheap things first with my sons cars  cuz even something that doesn't work gets them more familiar with their cars.  And imma reeeeeealy cheap person.

 

 

And welcome where in Washington do you live?

[mike_dmt]

 Spokane. Yeah, someone before us got in there and messed around. There's quite a few hoses and lines that are plugged off or removed. I need to lay my hands on a vacuum line schematic.

[ggzilla]

Plugged lines are OK. Unplugged ones are a problem.

 

You can plug every hose on a the carb and it will run good when warm. Just don't plug the breather hoses that go to the fuel tank.

[bananahamuck]

There is a line at the base of carb that goes to Distributor and the gas lines most of the rest can be removed/plugged .  Do not remove the electrical lines as they are what make the carb work,, and it won't without them.

[mike_dmt]

 So, the question remains, should we rebuild it? I tried to adjust it, but was able to turn the air/fuel screw all the wai on to the seat, and it still ran... lol

[ggzilla]

No don't rebuild it.

 

Your symptoms are of an air leak. Find the leaks and fix them. It is not usually the base gasket, nor the manifold gasket. Its usually the small hoses and the vacuum devices like the choke pull-off.