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I just tried pulling the needles out of my old SUs, but both needles were stuck hard in the cylinders. I ended up just dropping the old cylinder + needle combo into rebuilt carbs on the car and ... drumroll ... it runs much better! The car won't start anymore with the mixture screws all the way in, but runs great around 2 turns down with a nice blue-ish spark from my colortune. I'm very pleased. I'd like to get a new set of needles if possible - does anyone know a good source these days? It looks like MSA is out of stock on their N-27s. By the way, here's what the needles I pulled out look like - the pitting is worse that I had thought, and I'm guessing that was effectively "thinning" the needle causing the rich condition:

I got the carbs and intake manifolds from Paltech and just bolted them on as-is. I really have no idea what their history is, as I just bought the full set from him rather than having him restore my originals. I’m assuming he aligned the nozzles. The pistons drop freely with a nice solid clunk at the bottom when I pull the oil damper out, so I’m assuming the alignment can’t be terrible right? I’m going to swap those needles in an hour or two and I’ll post an update.

I’m going to text him tomorrow and see if he’ll get back to me. I actually have the stock needles from my original carbs now that I think about it. I’ll try swapping them in tomorrow while I’m waiting for Jeff to get back to me.

The needles looked ok to me when I pulled them out today. No pitting or scratches as far as I could tell. I didn’t see any markings on them to indicate what kind of needles they were though. It was getting dark though, so I could check again in the morning. Should they be marked on the shoulder?

Ok, so I replaced my OEM ignition coil / ballast resistor today with a Pertronix Flamethrower coil and new resistor. The car seems to run a bit stronger, but the mixture is still way too rich. My colortune is showing bright orange even with the mixture screws all the way in. Backing them off at all just causes the motor to bog down and run like junk. I also tried re-seating the needles according to the Z-Therapy DVD instructions, but that made no difference. I'm not really sure where to go from here.

My set point is 23mm down from the roof of the lid, which comes out to 14mm up from the base of my Float Syncs. I'm actually maybe 1mm off from that, but if anything I'm a little low so I can't imagine that's my problem.

As always, I've got some good news and some bad news. The good news is that I installed a new K&N fuel pump, and the process couldn't have gone better. The float syncs are now showing near perfect fuel levels in the bowls, with the bonus feature of being able to tune the levels without Hoover's ladder. The bad news is that something is still very off with the mixture. Using the standard 2 1/2 turns down on the mixture knobs the car will barely start, runs very rough, and pours enough dark smoke out of the tailpipe that people on their afternoon strolls cross to the other side of the street. Good thing they're already wearing masks. As I turn the mixture knobs leaner and leaner, the car runs better and better. I bought myself a Gunson Colortune, and verified that even with the mixture knobs cranked all the way up I'm still running rich (see video below). I made sure that the chokes are pushed all the way up, so I don't think that's the problem. I suppose the next thing to check is that the needles are seated properly in the carb piston, or possibly the needles are just totally wrong themselves. Anyone have any other debugging advice I could try? Is it possible that my timing has something to do with this? I'm pretty sure I'm somewhere between 15-20deg advanced, but this is honestly my first experience with a timing gun so it's possible I'm screwing that up. I tried shifting the timing around a 5deg each way and didn't see an appreciable change in the spark color. EDIT: I just had another thought. I have no idea what the story is with the coil on this car, but it looks like it's the factory original one. Is it possible that my mixture isn't actually rich, but I'm just not fully combusting because of a weak spark from an aging coil?

Ah yeah you're totally right, I was just setting the fuel levels with my funnel while my gas tank was in the shop. I re-adjusted yesterday during the brief period that my fuel pump actually worked, and and had to make minor adjustments as you'd expect. Just out of curiosity I calculated how high that vertical hose would be to get to 4psi: p = ρ g h p = pressure in liquid (N/m2) ρ = density of liquid (kg/m3) g = acceleration of gravity (9.81 m/s2) h = height of fluid column - or depth in the fluid where pressure is measured (m, ft) Using ρ=750 kg/m3 for the density of gasoline and 4psi = 27579.04N/m2 for our pressure we get a column height of ~3.75m = 12.3'. That's a lot of hose!

Sorry, not sure I follow. I've been using Randalla's Float Sync's during all of my tuning, which were really helpful in immediately diagnosing that my float bowls were drying out.

Looks nice, I've never heard of these guys before. They recommend mounting vertically, do you have any pics of how you mounted it on your car?

Well, it's been almost a month since my last update. The fuel tank is back in, and besides a quick adventure with a blown heater hose I've still been struggling with this damn fuel system. It looks like I've just had my second mechanical fuel pump quit on me in a month. It seems like everyone has had some issues with these reproduction pumps, but two in a month sounds like very bad luck. My first though was that my return line was plugged and putting too much backpressure on the pump, but I was able to blow through the return without too much resistance. Can anyone think of what else could be causing these pumps to die, or is that just how it goes with these pumps? I'm strongly considering just biting the bullet and going with an electric pump (probably this K&N one) unless someone wants to talk me out of it.

Just a quick update: the bypass surgery was a success. I just got a 3/4" to 1/2" barbed adapter off of Amazon and replaced the Y adapter with it - everything fits great with no leaks. I was able to run the car for a few minutes and it seemed to be cooling normally, at least in my driveway.

Fortunately I just rebuilt the whole motor, so it came out super easily. My new plug is stainless, so hopefully I can get it back out again when I decide to finally out the heater back in the loop.

Got it, thanks guys. I actually have an extra block plug, and it fits perfectly. I’ll order a 3/4” to 1/2” barbed reducer and that should get me set. Very happy to avoid any under-the-dash work as that’s a whole mess I’d rather avoid.

I was thinking about that too, but that’s dumping hot water from the head right back into the water pump inlet, right? Wouldn’t that make the engine run a bit hotter all the time? I’m keeping the intake warming piping, so I guess I’m doing that anyway. Something like this?

Has anyone had any experience deleting the heater core from the cooling loop? While debugging some unrelated issues on my '70 240Z, my heater outlet hose decided to crack and start leaking coolant all over the place. I had bought replacement input/output hoses a while ago and just never installed them because it seemed like too much of a pain. That assumption was verified today - after a ripped cardboard glovebox, some busted knuckles and a half-removed blower fan I've decided this is a rabbit hole I just don't want to go down any further right now. I live in Southern California so having a functional heater just isn't a big issue for me right now. Here's my plan: plug the outlet elbow in the cylinder head with some kind of BSPT(?) plug, and then replace the "T" with just a straight piece of pipe or a coupler if I can find one. Any reason this won't work? I figure this will basically be the same as having the heater valve closed as far as coolant flow is concerned. What size is the thread on that elbow? I've seen a few posts on here and hybridz, but none with a conclusive answer. Z Car Depot has this 13/16" BSPT plug which they imply is the right part.

My 11/70 with VIN HLS30-15257 has a P30 block (#020294) and a E31 head.

Well I still haven’t gotten my tank back, but I ordered a set of Float Syncs from @Randalla and spent an hour or so getting a “static” float level. The float syncs are really nice and made it a snap to get the levels set. I used a small squirt bottle to pour fuel into the input line with a funnel, and then just rotated the float sync to drain it back out into my bottle to reset. Really interested to see how well the “static” float level corresponds to the levels when the engine is actually running.

Hi Bill, sorry to dredge up an old thread, glad to hear things worked out for you. Do you have a link to that service manual you go the float level diagram from? I haven't seen that figure before in the FSM I've been referencing (http://xenonzcar.com/s30/files/FSM L20aL24engine.pdf) so I'm curious to know where it's from.

I pulled off my fuel tank today and dropped it off at a shop to get cleaned out and then have some Red Kote applied to the inside, and black paint applied to the outside. It should be done in a week or two. I'm also going to order some new stainless lines etc so I can actually do this thing right. Hopefully I'll be back to messing with the floats in a month. I also ordered some of that Hormel Dried Beef on Amazon for when I get back to calibrating the float levels. Any recipe recommendations @siteunseen or should I just feed it to the dog?

Well if it’s not one thing it’s another. I got the floats looking ok-ish and reinstalled them in the car. Turned the key and nothing. I pulled the line from the bowl inlet and turned the key to make sure the pump was at least working, and got nothing out of the fuel line. So, it looks like my brand new mechanical pump is dead now. The bad news is that I disconnected the input line to the pump and sucked some fuel through my Mighty Vac and what came out looked like a nice aged scotch. I had drained and refilled the tank about two weeks ago, so this must mean that the inside is absolutely disgusting and some of that nastiness must have peeled off and caused an aneurysm in my pump. I was avoiding dropping the tank, but it looks like that was a bad move. Looks like I’ll be dropping the tank next weekend and getting it cleaned out. What a day.

Hmm I’ve got a Nov ‘70

Yup it’s gas. I tried my old floats/valves/lid combos from my original carbs and got the same basic results. I’m beginning to think maybe my adjustment factor is off? These are 4-screw carbs if that makes any difference.

Speaking of math escaping us, I may have inhaled too much of these gasoline fumes. Does the diameter of my measuring vessel matter? My cup is around 80mm wide, but it shouldn’t matter as long as I’m filling slow and steady right? Archimedes is rolling in his grave right now. I’ve got my tab bent really damned low and I’ve finally gotten to my 18.5 mark, but the float is pretty much topped out against the lid. Doesn’t seem right at all, and worries me that any minor variation and I’ll start spewing gasoline out of my bowls.