Thread pitch on the drain plug is 8mm x 1.00mm.

parallel thread?

yes. ORB style. Has a washer seal.

Awesome. I've never bothered to take my drain plugs out due to a healthy sense of "If It Ain't Broke" instilled in me by accidentally breaking things.

Note: the nissan FSm states 23mm down from the roof of the fuel bowl, not the margin so the new height will be 19.6mm down from the margin for a '72 (We measured ~3.4mm from the roof to the margin on a 72 fuel bowl lid.

OK, today/tonight was a really rough experience, but I might have found an easier method of setting float heights. I was using the sight glass method today for the first time on my new engine to set the floats. The front carb went OK, but the rear carb was giving me fits. I decided to take a different approach and I cut a plastic water bottle in half so that the bottom of the bottle was roughly the same height as the carb bowl. I set the lid on the open container with the float hanging inside and measured down 20mm from the bottom of the gasket (3mm from bottom of gasket to inside of lid) and I put a sharpie mark on the plastic container. I then turned on the pump. With the container setting on top of the SU bowl to get the correct angle, I could now watch the fuel fill the "bowl" and watch the float itself. This is by far easier than messing with the real bowls each time. Within seconds, I could tell what the height was without the need for a sight hose or the hassle of wiggling the lid into place and risking gasket damage. I could make changes to the float in 1/4 the time it took me to put the lid on the carb bowls and it was super easy to see the fuel height directly rather than indirectly through a sight glass.

In the end, I decided that I need new float valves ASAP. I have emails out to all Z owners near me. I have to get it ready for a race next weekend. Hopefully I'll have the parts I need tomorrow. If not, I'll be making an emergency plea for help. I'll take pics of the setup tomorrow if I have time.

Another stoke of brilliance. An example of "thinking out of the float bowl"? Sorry...

I dream of a floatless SU fuel supply. Maybe someday...

Ive had a couple of experiences with sticky float valves too. Also the back one. Others near me as well... More heat back there?

Jeff, would like to see what you have done, any pics?

Nice idea. It's time-consuming to take off and reinstall the lids every time you adjust the tang on the floats. You need an electric FP though.

Why are the valves sticking? Seems like the only part that can go bad is the rubber tip on the needle, or there's dirt in it. I got new valves but the rod that sticks down and contacts the tang on the float is smaller diameter and more wobbly than the older type. If it hits the tang at an angle it can stick - the older type doesn't. Maybe you can swap the new needle part into an older valve body, or just swap the rod into a new valve.

Does Nissan sell the valves? MSA has a kit that includes them (new type) and some gaskets (but the little hose is a throwaway). They have good hoses, too, have to buy them separately.

Maybe mount the SU Fuel Bowl cover/float assembly to a screw on lid for a plastic container like a small peanut butter or relish container. Mark a stripe 20mm down from the inner roof of the float bowl cover and test away. You could possibly start in the kitchen sink with a 4psi pressure regulator attached to the faucet then check with gas on the motor.

Edited June 26, 201410 yr by Blue

Jeff, would like to see what you have done, any pics?

Here is what I did. Keep in mind that I am thrashing to finish my race car, so I didn't take the time to perfect the plastic bowl, but it does work.

I like Blue's idea of doing the bowl work first using water.

I wasted WAY too much time this weekend trying to get my float heights set. I'm not sure I ever did get then right. I have to get to bed, but I'll explain more later.

I have used my sight glass on 4 screw and 3 screw carbs. The 4 screw carbs I had no problem since you can lift the float lid right off. On the 3 screw, I put a longer fuel hose from the rail to the carb so I can twist it around without fighting the shorter hose. The only problem with either is the gasket. Mine had the cork gasket and they would curl up. The other had paper gasket and didn't give any problems. To save time I only used 2 screws on the float lid. Maybe took 10, 15 mins tops on each carb.

I do agree, being able to get a good eye on the level without having to bend over and estimate the level will work well. I was able to get it within 1mm of the mark.