1974 620 Rebuild to stockish condition

[ggzilla]

The carb runs fantastic once it is warm.

Then don't put a kit into it. It won't make it run better than fantastic and often (even when careful) will run worse.

 

Instead, adjust the choke. That's the most common reason for running poor when cold, but great when warm. Super easy to go, yet many mechanics can't seem to adjust it correctly.

Take 5-15 minutes

 

0. In the morning while engine cold

1. Press accelerator pedal once to set the choke

2. remove air cleaner lid

3. If the choke is not completely closed (not even a gap), rotate the choke housing until it just closes

Don't go by the marks on the choke housing.

[Curt]

Ok, thanks. I'll try that this morning. After the many responses advising to not rebuild it, I think I'm going to have someone else do it. I'm pretty sure it needs a rebuild, I think it has only been rebuilt once, if ever in its 316k lifetime.

[Curt]

SWEEET! Was the choke! Fires right up now and idles. Still runs a bit rough and chokes itself out when you give it gas before the temp has come up, but I can live with that.

Thanks!, GGzilla.

[Curt]

I got the steering done, new tires n wheels, roof rust fixed and painted. Everything was running decent until today.

 

Drove out to the dump and it started falling on it's face and misfiring. It has always missed a little here and there, but today it was downright horrible. Any ideas? I'm thinking maybe the air fuel is fouling plugs? It's not smoking or anything. Just misfiring.

[Curt]

It is random too, but under load for sure. it will run fine then misfire a few times and back to running fine.

[ggzilla]

Inspect and test your spark plug wires. http://datsun1200.com/modules/mediawiki/index.php?title=Spark_Plug_Wires#Inspection

[dr.feltersnatch]

I would also pull the plugs and clean/replace them. Sounds like maybe the choke is causing it to be too rich on start up fouling your plugs

[Curt]

Ignition system is all new,(like 70 miles on them) It was running decent before. It was warmer today and it did idle really fast when it first started, I think the idle is too high too.   I don't think it is the wires because it was running fine before. But I'll give her a try. Pulled the #1 plug and here is what it looks like.

 

I could probably take a video. When it starts up it does sound like it is fouling the plugs. Kida sputtery.

I wanted to take some decent photos of it today but it is running strange. Looks better out of the garage. :(

[Curt]

Oh, and I got 4x4 720 leafs. Can anyone verify how many are in the leaf pack? It has one less leaf than the packs that are in the truck now.

[banzai510(hainz)]

valve lash is good you say.No tight rockers?

Then ck the points and condensor. ck for dist shaft wiggle on the points. push side to side and see if its enough to open the points up

You have the stock coil and ballast resisitor in place? feel the coil if gettting HOT.

 

then I would be thinking a car but that is just my opinion as these are pushing 40years old now.

[ggzilla]

Hi idle won't cause back firing or misfiring.

[dr.feltersnatch]

Here is what I would check.

Air filter dirty?

Vacuum leaks?

Points look ok and set properly?

Not sure what dizzy you have but if it has it check mech adv weights operation.

[Curt]

Thanks, I'll look into those. I didn't check the point adjustment because the distributor was new, probably should have.

It's like something changed overnight. All last week it has been running fine, same drive and everything.

[ggzilla]

Since it japenned on you normal drive, chances are it is some unusual problem. One that sometimes occurred with stock Datsuns back in the day was a loose wire inside the distributor. Another one is a bit o crud getting into the main jet. Solution for that is to drain the float bowl.

[UnderControl]

The bushings I ordered finally showed up. I haven't had the chance to install them, but early thoughts are that they aren't going to fit properly.

[Curt]

Damn, bummer. Yea, I'm still looking. I think I'll pull them out and drop em off with the parts guys and see if they can think of something close that will fit with little modification. There is room on the threads to have wiggle room. I'd like to find some that are not all bent up too. I'm sure someone has found something else that works aswell, it is just finding it.

[UnderControl]

For now I will use the endlink bushings. They are very close to fitting, will just need to shave a little off.

[ggzilla]

Did they send the wrong parts? That is fairly common.

[Curt]

Got the rear leafs done and lowered the front. I used the energy suspension bushing kit for the 720 to replace all the bushings. Everything fit perfectly on the old 620 shakles. I was concerned because the shakles that were on the 4wd truck I pulled the leafs from were different than the 620 shakles ( I think they were home made).

Sits just how I like it now. Eventually I want a set of 15x7 or 15x8 Western turbines.

[Curt]

Got a Weber kit. help needed... So, the bottom adapter plate hits the mount for the throttle cable stop. What's up with that? and how do I remedy this situation?

Thanks in advance. I can't be the only one to run into this.

[Curt]

I think I got it. You remove the original stop and replace it with the weber supplied throttle stop....

[Curt]

Weber is on and running. However, it is choking itself out and has no power and I can't get it to idle evenly. I did the idle screw and mixture adjustments twice. It almost sounds like it is flooding itself out and I can smell unburned fuel. Is the Weber kit k660 jetted too high for an L-18?

 I can hear it sucking in plenty of air, but it chokes out under any kind of load. Any idea? I know it is extremely hard to diagnose a carb without hearing it but anything helps at this point.

[Curt]

Got a ton of jets and fiddle around with the carb tuning. Lowered the main and Idle jets. It idled better but still was misfiring. I finally got a timing light on it and it is now dead on timed, however it is jumping around a little... I found that I have slack in the chain and the distributor/oil pump gear. I have a timing chain set on the way, I would like to replace the water pump and oil pump while I'm down there. Anyone have a source for nice quality oil pumps? Or is it a rebuild it kind of thing?

 

Does anyone know where I can get a new or low mile distributor shaft and or the gear that goes on the shaft?

[Curt]

It skipped a tooth. Also, they sent me the wrong chain I'm guessing? Is this an L20b chain? It is matched up at the top.

[Curt]

Update and help needed... Got the timing chain and gears replaced and that system is running fine. Triple checked that it is aligned correctly when I assembled it so the crank/cam timing is dead on. Position 2. if that matters.

So, It will start and idle rough at 20deg advanced. As soon as it is warmed up or I try to give it some gas it dies.

The timing is correct, Firing order is correct. Checked for leaks with carb cleaner around carb and plate, none to be found.

Is there anything aside from the hot lead to the choke and the vacuum advance lead that I have to hook up or block off when swapping on a weber?

I've got all the vacuum lines that used to go the the stock carb plugged.

 

On the carb front, it dumps gas into the butterflies like it should when you pull throttle link. Float level seems fine.

Any ideas?