Jughead

Thanks for that clarification. Actually, I've experienced both backfire & front-fire, depending on mixture setting. Just couldn't get the right mixture, which is why I yanked the valve cover. In order to get it to run right i've had to enrich the mixture to the point where it fouls the plugs. Then, when I lean it out, it starts to front-fire.

Thanks Zed Head. The pointer is pointing to the first notch in this picture - the furthest to the left, when they're on top & you're viewing from the front of car. There are 5 notches. At idle, under the timing light, it points to the 3rd notch from to the left (10 degrees). And I've double / tripled checked the wires. However, I haven't started the car since adjusting the valve clearances. Do you think that might make a difference?

OK, hopefully the 7 pictures above are worth 7,000 words!. I think I found the mark @siteunseen indicated above. It looks to be right above the notch. All these pictures were taken without turning the engine. Does this indicate the need to reposition the cam sprocket? The damper pic is blurry, but the 2 white marks are (from right TDC & 10 degrees). Let me know if a clearer pic would be helpful

I'll provide a picture. Dan you clarify where/what the "damper" is?

Thanks siteunseen. Mine is a fairly original 1972 240Z. Does anyone have one that looks like mine?

Zedheads, Background: I’ve been having trouble getting my carbs adjusted and eliminating backfire. I’ve rebuilt both carbs with Z-Therapy kits, adjusted both floats, used a Colortune & Float Syncs to set up carbs, and a Uni-Syn to balance them. Ignition is new Pertronix electronic setup from MotorSport with a 3.0 Ohm coil. Still the car backfires under load when driving. So, I checked my valve clearances. Most of them were too tight, and I’ve adjusted them all to Haynes’ specs. When I checked the cam sprocket position, it appears that I have a “textbook” example of a stretched timing chain (see picture below), with the notch on the sprocket to the left of the engraved line on the locating plate. I’ve read the Haynes manual and watched the Z-Therapy video on how to adjust the position of the sprocket, and I’m planning to do so next weekend. In Preparation, I have a few questions for the experts: 1) Would this sprocket position (and the tight valve clearances) explain why I was unable to set my carbs? Between the clearances and the sprocket position, which would be more likely to cause issues? 2) Would it make sense to try to adjust carbs now with only the valves clearances adjusted? Or is it a no-brainer to reposition the sprocket? 3) How will repositioning the sprocket affect the timing light reading? 4) Based on the picture below, does it appear that the sprocket has been already repositioned by a previous owner? 5) Anyone been through this procedure, and have any advice (e.g. potential “gotchas”) etc.? Thanks much in advance – I’ll report back with results!!! Jughead

Mine don't have the caps. (See pics.) Don't know if they ever did. (Anybody know?) Anyway, It's the inner bushing that seem to react to starter fluid more than the outside ones... Thoughts?

Nice car, BTW!

Yes please! I am actually on the Z-Therapy waiting list, but am trying to eliminate all possibilities first. I'd hate to put 2 beautiful new carbs on just to have the same issue!

So, I removed the dash pots and pistons. Turns out the the rear jet nozzle is stuck (again). I used the nozzles from the Z-Therapy rebuild kit. What's the best way to loosen it up and keep it loose? Can/should you oil them? I seem to remember Steve using oil in the video.

Both Carbs go down to 4 - 4.5 turns to get a decent mix per the Colortune. I know I probably need to adjust the floats (again), but would that cause my car to run poorly? In other words, if the mixture's right (per ColorTune, "push pin" test, and muffler smoke/sound), does it matter how many turns I have to screw the adjuster "nut"? BTW: I forgot to mention that I used Float-Syncs to check the float levels & they both show the level at approx. 9/16" above the metal base of the Float-Sync.

I own the Z Therapy Tune up and "Just SU" videos and am on my 3rd viewing. I've rebuilt both carbs using Ztherapy kits. Balanced with a unisyn. Set mixture using push pin and Colortune. The engine idle smoothly. Vacuum is @ 20 PSI. No smoke from exhaust. But... It backfires out of carbs under load when I drive. When I enrich mixture, the plugs fouls and and backfires out of exhaust. Timing is set at 12 degrees (verified with liming light. I have installed a Pertronix ignition with a 3.0 ohm coil which I got from MotorSport. New plugs, wires, rotor, cap. As stated above, I sprayed starter fluid on throttle shaft bushings and it affected idle negatively. I did both carbs individually and got similar results. I have NOT adjusted carbs or check timing chain stretch yet (was hoping to avoid this). Thought about what to (re) check? Thanks!! (Will report back!)

What exactly is the Starter fluid test? What's the procedure and how do you do it, and how do you interpret results? I'm having a helluva time tuning my carbs. I sprayed starter fluid on throttle shaft bushings today and it affected idle negatively. I did both carbs individually and got similar results. What does this indicated? THANKS!!

Thanks Steve. I have the FSM. I couldn't find the Condenser in the diagram(!). I think I had the condenser going to the negative side! Would that cause the spark to be lighter than expected? (The coil's new).

Help!! I replaced the coil and ballast resister in my 1972 240Z, and suspect I may have the wiring wrong. (ugh) 1) Can anyone verify my understanding of the wiring in my coil/condenser/ballast resister area? Please see my schematic below and let me know if it looks correct. If not, what do I have wrong? 2) Where does the wire from the coil condenser connect to? 3) There are 2 Black & White wires (1 to the coil; 1 to the resister). How do I verify which is which? Thank You! Jughead

Do you mean the timing chain at the cam sprocket?

Which notch on the pulley should I align the pointer to? I have a 72 stock 240Z. It came with Emission Control, but I removed the air pump long ago and it's run fine since - until I changed the points, plugs, cap, rotor & condensor! ? According the Haynes, static ignition timing should be 10 degrees @ 550 RPM. Does that mean I use the 3rd notch from the left, since they're 5 degrees apart? I'm pretty sure it's the original distributor. I'm using a timing light (and yes - it's connected to the #1 wire.) I really appreciate help, guys!! Jughead

Hi all, I need clarification on setting the timing on my '72 240 Z correctly. I've studied the available manuals, but am still unclear. I have changed plugs, wires, caps & rotor, points and condensor. I am using a strobe light to align the triangular pointer to the notch on the pulley. I've chosen the 2nd notch from the left - with the notches on top, looking from the front of the car. I chose this notch because the Haynes manual says that the left-most notch is TDC, and that each notch to the right of it is a 5 degrees advancement. I've marked the pointer and notch with whiteout for visibility. I have verified that I'm on the #1 compression stroke by by making sure the rotor is coming up on the correct position in the distributor. However, I cannot get the pointer to align with the notch! When I turn the distributor body to align the pointer & notch, I can get them about an inch part, and that's by turning the distributor all the way to where the marking on the disti body shows all the way retarded. Obviously, I'm missing something! Any suggestions? I'll report back with results...Thanks!!!

Update: Found a broken female spade connector om wire to resistor. Renewed it and now I have voltage to resistor....and the car runs nicely...THANKS!!!

@SteveJ: Thanks for the advice. I measured the resistor at both sides No current. So I swapped the module in the back of the switch with a "new" module from an old ignition switch that came in a box with the car. Same result as originally described - no voltage at either resistor terminal and same (non) starting symptoms. What would you try next? A new module? Thanks!

@K Koehn: Did you resolve this issue? I'm having the same issue with a '72 Z running carburators. Mine starts for a second then stops. I"m getting no spark when I turn with a remote starter, BUT when I start with key, and hold the key on the START position it runs. Ignition switch issue? How would I diagnose this?

(1972 240z) Hi all, I removed my distributor for inspection and cleaning. I did not disassemble beyond removing cap rotor and points. My question. What is the procedure for reinstalling? How do I make sure that the firing cylinder is synchronized with the cap/rotor? How do I ensure that I'm not installing the distributor 180 degrees off? Do I need to make sure that the cylinder is on the Compression stroke? If so, what's the best practice for doing so? Detailed procedures much appreciated. I'll report back with results and credit to contributors....Thanks!!!! Jughead

Update: Ended up just disconnecting the buzzer. It was easy. It's located under radio - driver's side. Follow the buzzing sound under dash, then feel for it. It vibrates. I then accessed via the fuse door. I removed 2 screws from fuse box to move it out of way. Once done, you can pretty easily "pull the plug" on the buzzer (look for green and black wire) . The red warning light still lights, but it's fine. Some day I'll figure out the root cause of the original problem and plug 'er back in. Until then, no annoying buzzer!

Hi All, ('72 240Z) My seat belt buzzer won't sop buzzing with ignition on and only the driver on board. It does not buzz when in neutral. Where is the problem likely occurring? What should I check, and in what order? Could the issue be under the passenger seat? Thanks!