Just brought home a 1973 620 - I need some help

[SHIFT]

Just so you know...datzenmike knows just about everything about pretty much every Datsun model in North America.

 

A manual for the 620 would be a good thing, but I know how money can be tight sometimes.

 

Here's a quick tutorial on float adjustment. Use this at your own risk, if you screw the float up, you'll probably have a dead carb. Be careful, go slowly and LOOK at what you're working with before you start removing and bending stuff.

 

This is a trial and error process, so be very careful of the bowl gasket, don't overtighten the 3 screws on the front or you'll bend the plate and it will leak like crazy. I want to say you'll need to bend the float down a smidge in this case. My experience has been that with the fuel at the line in the glass, the carb will run too rich. I like about 1/16" to 1/4" below the line. I'm at a fairly low elevation, maybe you'll do better with it right at the line. Make sure the truck is off, preferably with the keys in your pocket. When you loosen the 3 captive screws, fuel will drip/pour out of the bottom of the carb where the glass meets the carb. It's supposed to do that, when you put it back together, crank the engine a few times to refill the fuel bowl before you actually try to start it.

 

Here you go, have fun:

 

 

Reassembly is just the reverse of these steps. Make sure the truck is cool when you do this as the fuel in the bowl will pour right out onto the exhaust manifold.

 

I adjusted the float... I tried bending it down and it did not work... bent it up and it seems to have done the trick. The fuel is about 1/8 inch below the line and the float actually looks level now.

 

BTW, the fuel did not fill back up at all when cranking it over a few times... I actually had to pour gasoline into the carburetor to get the chamber filled up again. Fuel pump problem? The chamber seems to fill up just fine while the truck is running... I'm going to definitely get a new fuel filter just in case that is contributing to the problem.

 

The truck does way better on the hills now but I'm still having issues with bogging out when I hit the peddle too fast.

[SHIFT]

I might check your timing and your vacuum advance. If your timing is a little retarded and/or your vacuum advance isn't working, the truck might run Ok but when under load you might see more of a difference.

 

My timing was off recently on my Roadster and I had similar symptoms - it was fine around town but when I got on the freeway and put some load on the engine it would really bog down and I'd get some misfires. It also ran hotter than normal.

 

I checked the vac advance and it seems to be working. I still need to get a timing light to check timing.

[datzenmike]

With engine and air filter off, look down the carb and pump the throttle by hand. You should see a strong squirt of gas spraying into the barrel closest the valve cover. If it is weak or no spray, then the accelerator pump has worn out. When thew throttle is depressed the motor must transition from the idle circuit to the primary barrel. Because air flow is light there isn't enough vacuum to draw in fuel needed and the engine will bog or fall on it's face on sudden accelerations. It's particularly bad going around a corner in third and stepping on it. The motor bogs and then stutters and then surges ahead. A rebuild kit will have a new accelerator pump in it.

[SHIFT]

 

BRAKES.

You have a vacuum booster to help reduce peddle effort. To test it, shut motor off and pump brakes several times to release any residual vacuum and hold down gently. Start motor and the peddle should drop down slightly as the vacuum builds.

 

I checked the booster as instructed and the peddle does drop slightly when I start the motor. The brakes still don't feel right to me... maybe I'm just not used to the way drum brakes feel? I'm pushing the peddle fairly hard to stop.

[SHIFT]

Here is a shot of the intake coolant outlet fitting. Yours was likely removed and a bolt threaded in to seal it.

 

ah-ha... so I need an "intake coolant outlet fitting".

[SHIFT]

With engine and air filter off, look down the carb and pump the throttle by hand. You should see a strong squirt of gas spraying into the barrel closest the valve cover. If it is weak or no spray, then the accelerator pump has worn out. When thew throttle is depressed the motor must transition from the idle circuit to the primary barrel. Because air flow is light there isn't enough vacuum to draw in fuel needed and the engine will bog or fall on it's face on sudden accelerations. It's particularly bad going around a corner in third and stepping on it. The motor bogs and then stutters and then surges ahead. A rebuild kit will have a new accelerator pump in it.

 

Thanks datzenmike. I'll check this in the daylight tomorrow. Honestly, if the accelerator pump is shot, do you think it would be advisable to ditch this carb now- before it causes me more stress? I don't think I have the patience or will to start rebuilding a carburetor on my kitchen table. If I wind up getting a weber conversion kit- is it difficult to set up? How will it affect some of these hoses and fittings that I was going to hook back up?

 

Any idea why none of the rebuild kits or Weber Conversion Kits have a "1973" 620 on their list? They have 1972 and 1974 but no 1973 wtf? Which conversion kit or rebuild kit is right for my truck since I can't find my truck year on their list? How do I identify for sure what engine I have in the truck?

[SHIFT]

With engine and air filter off, look down the carb and pump the throttle by hand. You should see a strong squirt of gas spraying into the barrel closest the valve cover. If it is weak or no spray, then the accelerator pump has worn out. When thew throttle is depressed the motor must transition from the idle circuit to the primary barrel. Because air flow is light there isn't enough vacuum to draw in fuel needed and the engine will bog or fall on it's face on sudden accelerations. It's particularly bad going around a corner in third and stepping on it. The motor bogs and then stutters and then surges ahead. A rebuild kit will have a new accelerator pump in it.

 

ok... I went out there with a flashlight... I'm obsessed with this thing already... it seems as though the stream is strong but when I was pumping the throttle- gasoline sputtered and sprayed up at my face- it happened twice as I pumped the throttle 5 or 6 times.

:confused:

[datzenmike]

ah-ha... so I need an "intake coolant outlet fitting".

 

It will run without it but may be best to 'put it right' for the winter. As stated the intake will have a hose going to a T so that the blocked hose from the thermostat housing can connect and then down to the other side of the motor to the lower rad inlet like this:

 

 

 

 

Your engine size is stamped on the block just below the head and behind the dipstick handle. On your engine it's the rear dip stick pictured above. It's good to check this with a truck this old you never know if someone has swapped the motor or not.

[SHIFT]

Your engine size is stamped on the block just below the head and behind the dipstick handle. On your engine it's the rear dip stick pictured above. It's good to check this with a truck this old you never know if someone has swapped the motor or not.

 

Got it... it's an L16.