Fucking datsun

Veeky Forums i need your help. i recently picked up a 1980 datsun 510 from a friend because it kind of drove and was cheap as fuck. It has weird hesitation/jerking problems, so i got the carb rebuilt thinking that would solve it but it's no better. Basically if i'm either barely on the gas or at WOT it's fine and goes smoothly, but anywhere in between it jerks and is an asshole. When i do WOT it'll hesitate and do nothing for a second then "grab" and go like a motherfucker.
Any ideas? i thought it might be the clutch but it's hard to tell if it's slipping or anything because the tach is wildly inaccurate

thx in advance

I had that same problem in my 85 Corolla. PM'd

How's the jetting on the carb? Fuel system all good? Spark all good?

did you tune the carb after rebuild? check spark wires and change plugs?

Jetting should be flawless now, the carb shop i went to does good work. fuel pump runs, filter is good, shouldn't be an issue. spark should be good, but the plugs and wires are a little old so i'm going after those next. brand new ignition coils on it.

I didn't tune the carb myself but the shop has test engines they tune them on. i'm probably gonna bring it to their shop to have them tune it further. i haven't checked the wires but ignition seems okay, the car idles and revs out fine in neutral, only experiences the jerking/hesitation under load.

timing was done by the last owner fairly recently, he replaced all vacuum lines, changed tranny and diff oil, and a bunch of other tweaks.
i would think it were the clutch if it seemed like it was slipping but i don't think that's the case. When i floor it, the RPMs don't go up before it "catches", the car just kind of does nothing until it decides to blast off

Vacuum leak most likely. Look up how to trace a vacuum leak with carb cleaner or starting fluid

this. prob a fault in the old spaghetti emissions system. desmog it and get a weber if you aren't required to im the car in your state.

Ugly car. Scrap it.

I'm in commiefornia, gotta keep the CA compliant carb and egr on it. Also did some further testing and i was wrong, it does have the delay/jerkiness while revving in neutral, just not as bad i suspect because it's under no load. when it does jerk/delay, it feels the same way as when you have your foot on the gas in 1st/2nd gear and abruptly take it off (in a manual)

Possibly something in the distributor not properly advancing the spark or the vacuum portion having issues.

Any little vac leak somewhere will mess with the vac advance/retarder causing all sorts of weird micro stuttery jerks

id also check dizzy cap/rotor as that has been a source of strange misses and stuttery lag on some of my old nissan/datsuns in the past

Accelerator pump diaphragm

I've had the same problem with my carb. No vacuum leak as there isnt any besides 1 hose to the distributor.

Someone told me its a lean misfire but something's wrong. The carb is a Weber and the problem is intermittent.

Fuel mixture adjustment changes nothing. Idle is correct.

Starts to bog/die when the car is off choke/warm.

I'll check that next, maybe take some sandpaper to the contacts in there.

You'd think the carb shop would've caught something like that but maybe not

fuel filter clogged?

your diaphragm is probably good if the carb was just rebuilt. the hesitation after WOT means you need more fuel though. The carb should have an adjustment for the accelerator pump (on my pickup you can hook the rod into several different links for more/less extra fuel; takes 3 seconds to do). Just set it up for a bigger squirt and see if that fixes the hesitation.

Check your clutch by holding the brake, putting it in 4th or 5th and letting out the clutch. If the engine doesn't stall your clutch is fucked.

fuel filter seems good, it's clear and upon inspection appears to be getting new fuel in. it's also brand new.

I'm taking it back to the shop saturday to get the carb adjusted on the car

will do

fuel pump?
did you put new metering needles in when you 'rebuilt' the carburetors?
for the record, the carburetors are more than 35 years old, you might want to just replace them

>not knowing how to work on your own carburetor

I meant to rebuild it myself but the thing had been fucked with pretty badly by some previous owner. motherfucker epoxied one of the venturis in place or some shit, god damn

no idea about the needles, something to ask the technician who rebuilt it. and my first impulse was to replace it but i couldn't find a single one online with california emissions.