mr mikey

You're so right, can't believe it wasn't carb related after all . I don't idle at 400rpm, but I also didn't want it stalling right below idle speed. I've got it set to idle when fully warm at 700rpm, but if I'd set the gap to 700rpm(.006"), then it would stall the second it started to go below that. I guess I could've set it to .005"(mathematically stable down to 550rpm), but my gauges go from .006-.004", no .005" feeler gauge. I guess what I did, was give myself a 300rpm buffer zone below idle speed, as a precautionary measure.

Ok, I kept going down in size of feelers until it would idle at 400rpm, so I'm guessing the size it requires is .004". I had to mill the bottom lip off each fin so it wouldn't scrub the pickup, but everything seems to work fine now. Thanks a bunch, this thread can be closed now.

Ok, set to .010", and it idles down to about 1300 then loses spark. Set to .008", and it's down to about 1000rpm, any lower and it loses spark. I tried adjusting to .006", but the very bottom of the "fins" on the dizzy shaft are touching the pickup. The fins look like they're straight until the very bottom, and they stick out a little. I figured I'd been ripped and gotten sent a worn out dizzy, so I ordered a new one and the fins are the exact same way. Anyone notice their electronic dizzy's "6-point star piece" on the shaft being shaped like this? The gap throughout top to bottom is the same, except the very bottom, each "fin" of the star piece has a lip that sticks out a little farther?

Ok, I reversed the polarity on the ignition control module, where it reads the spark trigger, and it fires right up and idles fine(with a slight hiccup every so often). So used that time to make sure carbs were set, advance was correct, etc etc etc. Only prob with running reverse polarity is you cannot rev it any, it'll only idle(set idle to 700rpm). Reversed the polarity back to correct, and it still does the same thing. Base timing is at 9 degrees advanced, advance tube plugged. Everything is doing right, but now have an issue. My old service manual is well used, especially in the ignition areas. I need to know what to set the hall effect trigger to, as far as gap is concerned. I cannot see the numbers, too much smudge. Local guy told me that I can't just set it to almost touching, without touching, because it would cause the ignition module to see too many breaks in the magnetic field, and the spark control would be all over the place. So I guess I can't set it like I do the gap on an old magneto engine.

Well, I found something interesting. When I began to idle it down, the moment it starts acting up is when the spark becomes erratic, then I lose spark and it stalls, then regains spark the second it begins to reverse rotate. Talk about weird.

The first ones are the same as what I had on my 70 240z, can't find them now and have no idea what brand they are, can anyone help? The second ones are Keystone Turbines(no clue if they're legit or knockoffs though), with some cheapy tires on it currently until I can get her finished, then the circuit tires go back on. and yes, those first tires/wheels are a mix-match, we got American Bronze tires put on them, but one was defective a couple weeks later, took it back for exchange and all they had was Remington, so I have (3) American Bronze tires and (1) Remington. For 30yr old tires, they're still doing great, no cracks forming or anything. They're 185/80-13's, used for cruising only. The circuit tires(not pictured) are 205/60-13's.

Well I stopped trying to figure it out for now, got alot of body work to do. But if someone could confirm their advance at these 3 rpms, it would give me an idea of which way to adjust. With the vac advance hooked up, in neutral, no engine load. 18 degrees @2200rpm, 15 degrees @2000rpm, 12 degrees @1800rpm. If I adjust idle to 1700, you can hear it go from a perfectly smooth idle to an every so often hiccup, like it's either loading up or ignition is being cut for a split second.....then adjusting down to about 1650rpm will make it die and do it's reverse rotate thing. Floats are set per Blue's post, and that's with the jets set to 2 turns down.

Yes, I can take more pics. All vacuum hoses that lead directly to a vacuum source have been blocked off, so any/all accessories you see with vacuum hoses are just dead hoses. I'll eventually mill down the blockoff plates I made for all the components and install them, just been super busy with work. Also, the heater crossover channel(preheats manifold)has been blocked off internally. I need to figure out how to get the screw-in hose barbs out to replace with brass plugs.....they look like they're in there pretty good, didn't want to break one. I'll get more detailed pics when I get back, gotta go outta town, cousin is getting married in Indiana. I don't like that drive.

I borrowed a pair from my buddy off his 240z, and they did similar, but what they would do is let you idle it down to 700 and stay running fine for a while. Then after about 5min or so, it would just act like you turned the key off(with the exception that it would still reverse rotate and spew smoke from the relief vents of carbs).

No, not on the base timing setting, it said in the instructions that it wasn't necessary, because the adjustments were fully mechanical. I did use a timing light to check max advance at 3500rpm, and it is sitting on the 36 degree mark on balancer.

I set it per the instructions for the dizzy. Set the dizzy so the rotor is centered on the #1 plug wire contact, align the dizzy to the 0 mark on baseplate, stab dizzy so baseplate mounts to engine when balancer mark is aligned with 0 mark on timing tab. Then loosen dizzy hold-down and rotate the dizzy so it's pointing at 9 degrees advanced on baseplate, then lock-down dizzy.

I thought the same thing about the timing, especially the way it reverse rotates, but it not hard to crank(actually very easy to crank).....my camaro is base timed at 18degrees advanced, so I know how an advanced engine sounds when turning over . The linkage has been checked for slack and worn joints and such, it all seems to be fine. I can spray wd40 around the throttle shafts to check for revving from vac leaks and the idle speed never changes(unless I accidentally overspray into the barrels haha). When I bought it, I was able to drive it the 2hrs to my house, but it chugged and rolled coal when I tried to pull any real hills. Tore the carbs down per the video and found a bunch of crud in the bowls, so I went nuts with a toothbrush and scrubbed all the internal components, and readjusted per the video.....it hasn't been right since. Car is '74 260z, Engine is '74 260z, carbs are '72 240z. Distributor is a "NOS/OEM" electronic ignition distributor listed for a 260z with the GM electronic control module.....it had the Crane(Allison) Fireball 2000 or whatever it's called, but it kept going thru control modules(found later that the setups are finicky when it comes to quality). I have all the answers, except the one to my question lololol.

The smog stuff is actually unhooked at the source, only using blocked tubes to seal off any leaks, I haven't gotten around to making the blockoff plates for everything yet, as this current issue is draining every bit of mental capacity I can put towards the car . I'll get some nipples to cover all the spots, or if you think maybe the parts are internally broken and hemorraghing through to the exterior, like a vac leak thru the housings.

The needles are in the same place, but when fully warmed up, it does get a teensy bit of sooty exhaust when you get on it good with no load on engine, so I might play with the height of the needles a little.

Here's how she does when easing off gas, started shaking a little at 1800rpm and fell on it's face at 1700rpm.

Well we're still using a kit we got a couple years ago that included new valves, we've run the engine with the drain screws removed and the "hollow screw to clear vertical tube" method to make sure the level doesn't go too high and it always stays within a millimeter or 2 of where we adjusted it. So I don't think it's bleeding past, unless it just randomly sticks when we aren't testing the level. The way it dies confuses the heck outta me too, when it dies it stops rotating, then it rotates backwards spewing smoke out the blowback holes in the carbs. I'll take a video in a bit showing what it does when it dies.

Yeah I was mainly just wondering for labor cost.....my guys' time is worth alot more than my spare time, so if something is to be done and will sell alot for a good enough price, I'll put one of them on it.....if not alot will sell and price will be low, I'll tool around on it in my spare time.

Yeah I'm running an AD244 alt with a v-belt pulley swap to an external regulator with high amp internals, ampere gauge swapped to high-amp ampere gauge and volt meter combo gauge, and everything seems to be doing right, it peaks at 15.2v with no accessories on, which is still in the green range.

Exactly, nothing is making sense here.....I've been having this exact same problem since I joined the site, surprised my patience lasted this long to be honest. All gaskets on the engine(minus head gasket) have been replaced. I used the method of setting the lids on top of a small pint jar and slowly filling via syphon pump to set float levels. It's a tedious process, but it gets the levels dead-on. The only reason I haven't sent both sets of these carbs off to be redone, is at first I couldn't justify the cost of him doing them(rest of car wasn't in very good shape).....but it grew into the "You cannot defeat me!!!" routine.....now I'm getting close to sending them off .

Yes, we have completely disassembled and cleaned every part every time we take them down to check and readjust float levels. These are the round-top SU carbs also, forgot to mention in the original post, off my 72 240z.

We always check the fuel level with a clear hose attached to a hollow screw that is screwed into the bowl drain spot. Then stand the hose up beside the bowl and turn the fuel pump on. As far as the floats go, they're, in lamen's terms, just like a foam rubber surround of a speaker. They're a block of airy foam that has a layer of rubber glaze coating them. What's the interest in these? I can have the tooling made here and start making them, just needa know what normal replacement cost is for them.

When setting to idle speed, I can't get the rpms to go below 1550, else the engine will just die and chug smoke out the carbs when it dies(seems to reverse rotate a little when it does that). We've rebuilt the carbs and adjusted the floats going on 8 times now per the directions of the SU carb builder dude with the video, and it STILL does this. I'm at a loss. The car has a new distributor in it with the GM module conversion, and I've both based timed it and checked the 3k rpm mark too, everything there is in order, so not sure what it is. Set valve clearances when I changed the valve cover gasket. It's not putting out the exhaust and the vac readings are stable, so not a burnt valve. Brand new fuel pump installed, new lift pump, filter, etc etc etc. Been dealing with this for a LONG time(over a year) on a constant basis, so anything that could be checked/changed for maintenance has been done. WIT'S END BOYS AND GIRLS!!! -Mike. Ps. Thanks ahead of time for any/all suggestions. Before I removed the carbs to clean(lotsa sludge in the bowls), I actually was able to drive this thing the 2hrs home from where I bought it......you just don't know how many times I've watched and rewatched that SU tuning video.

agreed....get a euro balance tube with block plates installed so the air doesn't share, then run cable lifted carbs, instead of the SU carbs. Got ahold to (2) 42mm mikuni's i'm working on fitting to my 2nd 260 atm

If everyone fails you....pick yourself up and buy yourself a damn welder. Only problem with me having a welder, is the fabrication possibilities are endless

Well, haven't been able to do much except buy parts. My back has been giving me fits and it almost looks like this car will never get finished unfortunately. The people that were supposed to do the metal work(new floors, front half of trunk floor, front wheel tub under battery rotted out) have just up and disappeared with my down payment, so I spent more money going and getting the car back from their shop. I also have wayyy too many projects, if anyone wants to point me towards someone who can do good work without charging me an arm and a leg, I'd appreciate it....or if you'd rather take this project off my hands, I'll list it on classifieds here. -Mikey. I'm so tired....