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240z carb sync ignition timing disaster NEED HELP :(

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I am in desperate need of helps and suggestions! I have a 1971 240Z that I cant get to run correctly. I will try to be as detailed as possible in explaining my dilemma. I would like to preempt your responses with sincere gratitude as I have about given up in my attempts to solve this problem. I go to college in WV and don't have the money to cover the mechanic bill to fix my poor z car.

 

Specs: 1971 240z, rebuilt straight six, one wire alternator

 

Tools at my disposal: Every hand tool imaginable, a timing light, a carb sync tool

 

First, I bought my z with four working cylinders so I, along with the mechanic that worked there, rebuilt the straight six. After we were finished, the engine ran very rough, so I drove it over to my favorite mechanic who tuned carbs with only a screwdriver in about two minuets flat. I drove the z pretty often for a couple years after that  before heading off to college. After totaling my other car, I decided to drive my z to college. I drove it an hour and a half there and back several times until it broke down on me. I then towed it back home.

 

It took me a couple months to figure out the problem. In these couple months, me and my father had turned and returned every screw on the carbs so much that by the time I figured out that the problem was that the stupid bolt underneath the distributor had turned a half an inch, it was way too late. Now, I could only get my z to run for a very few rough seconds before it died. I then abandoned the z again after failed attempts to retune the carbs and headed back to college.

 

Now, onto my senior year, I decided to tow the z back to college and try to fix it in-between studies. I missed it :( I bought a Datsun repair manual and did my research. Through fine Datsun form sights such as this one, I was starting to make progress. I first bought a carb sync tool. I synced my carbs and played with balance screws and adjusted nuts through the directions of my manual. I also experimented with the distributor. First, I took it apart in order to better understand the part and ended up cracking the coil inside it. After a brand new distributor from auto zone I was back in business. I looked up how to get the timing from the manual and the internet. I found top dead center and set up the timing as best as i could. 

 

I made great progress and actually got it sounding half decent for the first time in years. After attempts of fine tuning I actually ended up making it very much worse. Then, realizing adjusting the carbs wouldn't make any difference unless the car was timed correctly, I bought a timing light. This is where I am currently stuck. As I look at the timing light, I am about four or five inches away from the mark! How is this possible?! As I turn the distributor closer to the mark, the car dies. Clearly something I did was wrong. If I can't get the car close any timing marks, how can I even begin to tune this motor? I am at a complete loss and need help! 

 

I don't know very much about motors, as I am just a body man. I learned some when I helped to rebuild the motor and from the internet and manuals but that's it. I have always been a do it yourselfer and refuse to bring it into a shop. Thank you all very much for your help. It is very much appreciated!

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Try this.

 

1. Set the timing mark to Top Dead Centre.

2. Remove the ditributor.

3. Take a photo of the distributor drive and upload here (look in additional options to do this when posting)

 

If the position of that drive is not  11:25 (you'll get what i mean if you read the part on setting the dizzy drive) then you'll never get your timing right and the oil pump will have to be removed to reset it.

 

Merry Christmas  ;D

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Another quick check is to set the timing to #1 TDC and check the position of the rotor button in the cap..is it pointing to number 1 cylinder on the cap? Have you checked the firing order? 1 5 3 6 2 4 From memroy, when the distributor rotor is at #1, it should be close to pointing at the radiator support panel or the front of the car.

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i think i know this one....

i think the harmonic balancer either:-

-does not suit your timing cover, ie the mark that is TDC, is not aligned with 0 degrees

when it is actually @ TDC. Basically the balancer is off another car which has its timing mark furthar out of phase from the wodruff-key slot than required.

has the timing mark incorrectly marked or notched.

 

check actual TDC of cylinder #1, by removing sparkplu #1, get to roughly TDC, check where the timing mark sits on the degree scale on the timing cover.

to get this closer you will have to index the crank essentially, lookup indexing crank & cam procedure.

essentially screwing in a bolt into spark plug hole with an adjustable stop. rotate crank til it hits/stops, mark 0* on pulley the reverse roatation back nearly 360* untill it stops again & mark @ 0*, TDC is in between the 2 marks.

repeat with less protrusion of the stop untill the mars are about 5-8mm apart as its then easier to measure & mark.

try this first, and get back to us, before you go to other troubles of oilpump shaft etc etc, as if its running already then it might just be this.

let us know the results.

also pm me to let me know you have posted the findings here, as i may not check.

nat0

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Just make sure you have the right TDC as the crank does two revolutions per cam revolution. Take your rocker cover off when you're  doing what Nato suggested above. The two cam lobes (inlet and exhaust) on the number one cylinder should be pointing up in the air at approximatey ten and two o'clock (I think, I might be getting engines confused) This will be the start of your compression stroke, hence why youre setting the spark up for this position.

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I wouldn't be surprised if a combination of offset drive and offset plug leads is the issue. As discussed - get the basics sorted and it will all come together. It would also pay to check that the bob weight assembly hasn't broken a spring or lost one of it's balls (ouch!).

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  ???  Had a similar problem to yours. The dist you bought was it an electric unit or points set up. Also have you checked the following items out.

  Compression test (Blown head gskt) , Spark plug leads (Faulty), Crct spark plugs (essential), Distrbtr cap (cracks/ corrosion), Coil (dfctve),  Carbie's (Float units).  Suitable main needles,  Fuel pump & filter.  Just for starters.

Also do not alter oil pump at this stage, to check if the Distribtr is out 180* simply change the distrbtr leads so that the #1 Pstn on the distrbtr cap is occupied with the #6 lead & reset your other leads accordingly. 6 2 4 1 5 3  then test it by starting.Simplest way I know of how to check this out.

 

                                                                      Good luck. Regards:Alan.  ;)

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Wow! What a great site! Thank you for all your suggestions :) I was previously in Vermont and haven't found the time to respond.

 

I cant believe I forgot to mention that I had put in an electronic distributor instead of the stock. Maybe this makes a difference? I think I'm going to start over from the beginning. I was kind of teaching myself how to set the ignition timing as I went... even though I did it and redid it several times, I might have gotten something wrong. It has been a while since I did it and now I have some more things to conciser..

 

I have another question. In my z car manual it writes about how to begin to tune the carbs by setting them back to their original settings. However these directions are not very clear. Does anyone know of any other publications that have directions more easily followed?

 

Thanks gentlemen!!

-Graham

 

P.S. Other bits of information that might be of value: I put a performance cam shaft in, and one of the biggest problems is that I had the car running pretty well, with almost zero backfiring, but I couldn't get the idle down below 1000 without it running really poorly.

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;) Thats better Graham , now we all know whats happening with your situation. Per chance when you installed your Elctrnc dizzy did you use your existing "Spacer/Block cnctr" unit to the motor. If so this is your problem. Had the same bloody experience, what happens is that it puts timing out about two leads if you use your existing distrbtr cnctn set up. Hence the 5" timing problem you mentioned previously. Me thinks!!.

I bolted a Elctrnc unit up to my existing 260 Points Dizzy set up & had similar dramas. Upon fitting the 280Z Spacer it all disappeared. "The Forum" does work.

 

                                                        Regards :Alan  ;D

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??? So gathering by your response the spacer would be your major problem. Try putting a listing in the WTB section & also try the wrecking yards for one. I believe any of the 280Z models will do. Remember it is The Spacer you are after. Regarding Manual, look up ( WWW.Velocebooks.com) or try your local book stores for book titled "SpeedPro Series" The SU carburettor high-performance manual .Around $40 - $45 price . Very informative, gives you all the needle sizes ,etc,etc.

 

                                            Regards: Alan.  ;D

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Everything on this posting is on the money, and if you follow it you'll be right.

 

BUT, as a qualified mechanic, I would suggest you try to find a mate of a mate who knows what he is doing to show you. L series engines are relatively easy to work with to sort out the problems you're having, but it can be a complete mystery to try to sort it out from written instructions and manuals without knowledge of what those instructions mean... You will be amazed how much quicker you will get to the bottom of it, and understand the problems if you can have someone show you how to do the things that are being suggested on the forum.

 

Cheers

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you dont mention anywhere how long that fuel has been sitting in the tank, I was caught when I got my car home from p/o it had been sitting for two years I drove it on to the trailer so I new the engine ran. I spent hours on it just like you fiddling with timing and carbys, but the fuel was stale, I think the octane level was so low the timing was trying to compensate and I couldn't get it right, stupid me I thought I should replace the fuel but didnt, after spending money on coils plugs etc. the last thing I did was change the fuel and " it should have been the first" and I should know better, but Ive been out of the game for 30+ years now and restoring my Z is giving me great pleasure, annnd lots of pain OH Ouch ache ache! LOL

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Hey Gents!

Its getting warmer and I'm back in the garage! I just wanted to say thanks again for the posts! I hit up a junk yard and found a 280z spacer and adjustment plate that I lost and now I'm trying to get it to sputter after a long cold winter! I replaced the distributor with an electronic one; replaced the spark plug wires, and the dist. cap. I'm sure I'll have some more questions soon! Wish me luck and thanks again!

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I found i could run maximum advance with an elec. dizzy on my L28 (turn the distributor full counter-clockwise) and have not had any pinging noises when using premium fuel.

 

In regards to tuning the SU's it's pretty strasight forward, i suggest watching some youtube vids, i found this one helpful

He's using HIF carbs which are very similar the Hitachi/SU so the principles are the same.

 

 

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If you look at the bottom of the dizzy you will find that you can undo a bolt which adjusts the limiting plate to give you more advance. So in regard to being able to run it at full advance it depends on where the plate has been adjusted to.

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;) By the way you will need a elctrnc or similar type coil to match your dizzy. 260Z coil not suitable.

 

                                                                        Regards: Alan.  :D

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Hello Gents!

My first day back in the garage from a long winter and i had a lot of success! I went to a junk yard and found the spacer and adjustment plate underneath the distributor from a 280z. I put those on and reread my manual on carb tuning. I figured out one of the things i was doing wrong was adjusting the throttle speed screws while they were almost all the way screwed in. I saw in the manual that it says to unscrew them for a lower idle (among many other things). Now i have my idle at a little under 1000 rpms! Now to the problem...

 

I have been messing with all the adjustment screws and nobs and here is where I'm at. The idle sounds semi-smooth but when I rev up the engine the car 'tops out' at 3000 rpms. It starts to break up real bad and does not rev much higher. I'm trying to adjust the distributor to find the sweet spot but I'm having no luck. My assumption is that the timing is off because it idles at low speeds o.k. but at higher rpms where the timing becomes more critical- it cant do it. Am I correct? Or might I have the air/fuel mixtures off in the carbs and that's causing the problem?

 

-Thanks guys!

 

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Hello Gents!

My first day back in the garage from a long winter and i had a lot of success! I went to a junk yard and found the spacer and adjustment plate underneath the distributor from a 280z. I put those on and reread my manual on carb tuning. I figured out one of the things i was doing wrong was adjusting the throttle speed screws while they were almost all the way screwed in. I saw in the manual that it says to unscrew them for a lower idle (among many other things). Now i have my idle at a little under 1000 rpms! Now to the problem...

 

I have been messing with all the adjustment screws and nobs and here is where I'm at. The idle sounds semi-smooth but when I rev up the engine the car 'tops out' at 3000 rpms. It starts to break up real bad and does not rev much higher. I'm trying to adjust the distributor to find the sweet spot but I'm having no luck. My assumption is that the timing is off because it idles at low speeds o.k. but at higher rpms where the timing becomes more critical- it cant do it. Am I correct? Or might I have the air/fuel mixtures off in the carbs and that's causing the problem?

 

-Thanks guys!

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OK you arent making life very easy on yourself here.

Set everything to what the factory settings are and see if it runs ok like that first. 10 - 15 degrees of advance, mixture knobs 2 turns out, idle air 1.5 turns out. I cant double check those settings because im still at work but they are pretty close. Car should run fine like that and should rev out. I did this when i bought my car and it ran  really rich but it drove fine. If you can still only rev it to 3000rpm i would maybe look at pulling the rocker cover off and checking the cam timing - it might be a tooth or two retarded.

 

After it runs properly like that - then set up the idle etc. You need to make sure the two carbs are flowing the same amount of air though when you adjust the idle air screws.

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??? You don't mention bout changing the COIL to a 280z unit ,260Z not suitable. Would suggest you check the vacuum unit in your DIZZY if this is not functioning properly it will cause similar problem. Suggest you check these out before doing anything. Check your carb pistons are in sync, to do this remove air filters units. Raise pistons to max with fingers, release pistons & note if they  fall in unison. If they don't this can also be part of your problem. By the way I note that a lot of guy's use trnsmsn oil etc for carbie tops. The recommended oil is 20 grade engine oil or if you wish the oil they use on chain saw blades fill about 1/2" above piston reservoirs. Finally are you using an electric fuel pump or a mechanical unit. 

 

                                                      Regards: Alan.  :D

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This Z really knows how to kick me when I'm down!!!!!!! I opened up the two knobs under the carbs and it ran rich but it was running real smooth! When I reved it up it still wouldnt go above 3000 RPMs so I bought a timing light and a week later when it came in the mail I went down to set the timing. When I started the car it was only running on three cylinders!!! I checked all the connections, pulled all the plugs, cleaned everything up.. but no luck. The spark plugs are sparking and they are wet with fuel when I pulled them out. What could have happened???? The cylinders that are NOT working are 2,3,5. I bought a compression tester online and I'm waiting for it to come in. I really hope the problem isnt loss of compression. The motor was rebuilt not even 1500 miles ago (about). The reason we rebuilt it in the first place was that it was only running on three cylinders.. so I'm not hopeful. How could this have happened? Could running the car out of timing and carbs out of tune do this??? I don't have the experience to rebuild the motor. I did it five years ago with a mechanic and I don't think I can do it by myself. Any ideas??  :'(

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