azriel_strife

Ugh i really dislike the stock ignition.. some weird things today. -set the points, they were well above 25 thou, set them to 19 thou -reset timing to 34 degrees total, no vac. I lost almost 10 degrees of advance from setting the points. -Checked coil voltage, there is no ballast resistor on my fender, but coil voltage is 8.8 volts roughly. -Checked Coil resistance, 1.6 ohms. All seems to be in order, but the car is running worse than before, i get misfire and very jerky throttle response in low rpm. Advancing the timing seems to resolve this. I might just give up on it until my electronic upgrade conversion arrives.

I ordered a hot spark electronic conversion kit for my distributor today. my car doesn't have the ballast resistor either, so it should be an easy swap over.

It does run better without the vac advance plugged in, but it seems like it's still lacking timing under light load with no vac advance. If i advance the timing up to 38-40 degrees total advance it seems happy. This is what makes me think my balancer may have spun on the crank. Should i use the old screwdriver in the #1 cylinder to find tdc trick and compare it to the marks on the balancer? My distributor is an old points unit, so i'm not sure if i can adjust the vac advance on it.

ok, so i have set my total timing to 34 degrees at 3000rpm, and the car seems to hesitate under light throttle (vacuum) at 3000+rpm. Seems like it's getting too much vac advance. Other than that it is running and idling happily. If I unhook vac advance, it doesn't seem to do it anymore, but I lose a noticeable amount of torque on initial pedal press. I may have to check and make sure my balancer hasn't spun on the rubber. is there a good method of doing this?

So i was looking and I didn't see it before, the flywheel and block have been painted so the markings for timing on the flywheel and block were almost invisible. To my surprise each tooth on the block for timing is 2 degrees, what i thought was 10 degrees initial timing at idle was actually 20. it seems that my timing is way too far advanced. it also seems that the spot i thought was zero on the toothed indicator on the block is not zero at all. i need to go have a look again.

Sorry to revive an old thread, but it occurs to me that this port is before the throttle butterfly valve. My vac advance isn't doing anything at idle, and there is no vacuum signal from the port on the carb body. I would think to get a proper vacuum signal you need to have the port after the butterfly. can someone shed some light on this?

Looking to upgrade my 240z to electronic ignition, in need of a 280zx e12 80 unit to do so, please let me know if you have one..

Idle: 10-11 degrees (mark jumps around) 1000: 15 degrees 2000: 25ish degrees 3000: 30ish degrees The vac hose being connected didn't make any difference to the readings, so all of this is with vac disconnected. Max advance is right around 2800rpm, I cant see any difference after that no matter how high i rev. My good timing light kicked the bucket, so my replacement doesn't do offset.. I can't see beyond 15 degrees on the indicator for the pulley. so anything beyond 15 degrees is a best guess based on distance. If I advance any farther i get knock at low RPM high load. it;s likely my increased compression ratio from the F54 with flat top pistons and the N42 head. The amount of advance i am getting is quite high, wich leads me to believe i have a crappy emissions distributor, maybe I should consider getting a 280zx distributor instead. If anyone has an e12 80 ZX distributor available for purchase I will buy it right away.

I don't know how to tell, i'm assuming it's a stock 240z dizzy, it's a points unit. I read that 32 degrees was a good place to be with locked timing. just trying things at this point because I don;t have any information pertinent to my particular setup.

I'll have a look when I get some extra time here soon. I would think that i can only have one or the other if the advance range doesnt meet my engine needs, correct? so if i have to choose, i should tune for operation RPM, not idle? I am sitting at 32 degrees total advance @ 3000rpm without advance plugged in.

So I should set timing based on full advance and not at idle? it's set for idle as the FSM states. But timing is more important at driving rpm. Who said i don't have a timing light? It's set properly. I know my engine isn't stock, I know the distributor isn't even for this size of engine. It's got plenty of torque, i don't need the vac advance at all. I guess I'll just set it up for total advance instead of factory spec.

Yes it runs much better without the vac advance hooked up, because I believe it was getting too much advance for my compression ratio. thus backfiring through the carbs on detonation. This is what makes me believe this distributor is not right for my engine. The timing is set to stock 240 specs because I am using the 240z distributor, i thought that to be the best option, since stock timing spec is based on the distributors advance amount.

That is what made me think of the distributor, but I have already checked that.

So I found something else contributing to my issues. The car was running good for a few days, but then it cooled off a bit and it started backfiring through the carbs again. It only backfires around town at 2000rpm or below when I slowly apply throttle. I put 91 octane in just to be sure it wasn't the 87 i have been running. The fuel made no difference. (still running the points system from the 240 engine, my engine is an f54 with flat tops stroked to 2.9L with an N42 head, pretty high compresion) I decided to check the vacuum advance line to the dizzy. The line itself is fine, I checked the vac advance by pulling off the Cap and watching the advance work as i sucked on the hose, i blocked the hose with my tonuge and there are no leaks in the distributor or line. I decided to disable the vacuum advance so I blocked off the carb side with a bolt in the line connected to the carb. This completely solved all of my backfiring issues around town, the car runs amazingly, idles nicely, and runs flawlessly under all conditions at speeds below 80km/h. My guess is that it was getting too much ignition advance for the compression ratio of my engine build. When I take it on the highway however, it will hesitate (no backfiring) if you lightly apply throttle. Hesitation appears at sustained engine speeds of 2500rpm or more in any gear, but it seems to be just fine under WOT. Carb oil levels are good, plugs and wires are good, cap and rotor look good, Timing is set. I'm at a loss, should I be running different timing than stock for this Block/head combo?

Well, the car seems much better after the synch, it does stumble here or there if i stab the throttle, i can get around that by being smooth with my throttle application. I believe there is still some mixture fine tuning, i'll try 1/4 turn richer, and if that doesn't improve it, i'll try a bit leaner than it is now. Glad I grabbed that uni-syn tool.

I have the "just SU" dvd. it was very informative, 4 hours of carbs is quite the long watch! I got my sych tool and synched the carbs, they were out a bit, about half an inch on the beads on idle, and about the same on high idle sych. it seems to be running much better now, doesn't fire through the carbs when I blip the throttle anymore, it's sitting pretty happy at 3 turns out for mixture, I have yet to drive it and see if my crappy drivability still persists.

thanks, i ended up bypassing the stock green wire from under the console and running my own from the black/white wire. on the plug.

carbs are working sweet on the mechanical aspect of things, not getting stuck, dropping at the same rate, nozzles are at correct height and not binding, no vacuum leaks, needle height in pistons is set. topped up the atf yesterday, i'll advance the timing a bit at a time and listen for knock, I'll also try unplugging the vac advance, it might be doing some funny things.

If it's burping out the carbs, that would indicate too far retarded?

ok. I spent the afternoon on her today and if anything it's running worse than before. I set the valves cold to .008 intake and .010 exhaust, set mixture screws to 2.5 turns out, set idle speed, topped up the carbs with atf to make sure i was getting proper accelerator pump action. The car is running worse now than before, backfiring every time I touch the throttle, it runs progressively better each time I turn up the enrichment screws. It is most definitely leaning out somewhere, I may just be masking the real problem by adding fuel though. I ordered a carb sync tool, and I will try that tomorrow, but I don't know if the carbs being a little out of synch would cause performance loss of this magnitude. Thank you all for the input, it's nice to have a community like this, so tight and helpful.

While the engine is cold i'm going to set my valves (.010 intake and .012 exhaust?), then i'll set up the carbs for idling at 2.5 turns out, then i'll try and set my timing, then reset my idle. i need to get my hands on a carb sync tool, but local auto parts stores want 100 bucks for one. but i imagine if i do all of the above, it should reduce my issue if not resolve it. lets hope!

It won't idle well at 2.5 turns out, I tried what the z therapy video said and it wouldn't run right at all after setting them up how it instructed me to. highest idle is at 4.5 turns. if i try to blip the throttle at lower mixture settings it stumbles or hesitates. Carb backfire is a lean condition, it does this at higher RPM when i try to give it moderate gas to accelerate. seems much better if i go WOT. certainly isn't acting rich. I'll give it a shot at 2.5 turns out and try to bring up my idle with the set screws. maybe it will surprise me, I hope you are right. Wish i could locate someone in my area to help me figure this thing out, i dont have much experience with these carbs.

It's backfiring through one the carbs. I believe afterfire is when the exhaust has popping (i love the sound as as far as i can tell it's perfectly normal) I'm not entirely sure of the plugs, I suppose i should take a look, they are new, gapped to .35 so I didn't check them. I believe I am running the stock 240z ignition, but given the problem is intermittent I was looking at things that could work and then not work. I have sprayed a bit of ether around the manifolds and carb isolators where i suspected leaks but no change in rpm that i could discern. Both knobs are 4.5 turns out, since this engine is a good bit larger than the l24. I achieve highest idle at 4.5 turns. it runs like a top at idle and low rpm around town, then acts like a pile of junk when i actually try and drive it. it's upsetting.

hi guys, i have a set of brand new SU's carbs on my car, they ran good for a while, but now they have started acting up. The problem i have is that the car will run great until operating temperature or a bit above. I notice it the most when I get on the highway, or sustain rpm above 2000 for any length of time. as long as my revs are up, this problem persists, if I stop and let the car idle rough for a couple minutes it smartens up and runs nice again. at first i thought it was the stock mechanical pump not being able to keep up with the 2.9 stroker. I saw a lot of air inside the lines, it was boiling the fuel in the lines so I decided to install a carter pusher pump at the tank. this resolved the fuel boiling issue but my car still isn't running right. I've thrown a good bit of money at it now and nothing has changed. I have checked and rechecked the carbs for dirt, engine bay fuel filter was just replaced, and last chance filters are spotless, fuel pressure is right, bowls are staying full, and float levels are correct (I checked them right after it started acting strangely the last time) 2 things that i have not had the ability to check are carb synch and timing. But I can't see those being intermittent problems. It runs so happily when it decides to run right. I did back off the timing a bit to see if that would help with the backfires (lean) but it didn't do much. I'm contemplating selling these things and just getting a holley manifold and 390 carb. I can't stand being so frustrated with this beautiful machine.

Well I just ran my own wire from the black/white wire on that plug to the positive on the fuel pump, it's working now. Only explanation i can think of is that the green wire going to the rear pump wiring was shorted somewhere.