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240z carb sync ignition timing disaster NEED HELP :(


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#1 greylandimports

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Posted 25 December 2010 - 03:12 AM

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!

#2 peter mc

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Posted 25 December 2010 - 08:48 AM

hi check that you have the timing light pickup facing the right way on no1 plug  as they will read incorrect if they are on back to front

#3 Scoota G

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Posted 25 December 2010 - 09:16 AM

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

#4 Zedman240®

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Posted 25 December 2010 - 09:27 AM

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.

#5 nat0_240_chevZ

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Posted 29 December 2010 - 09:41 PM

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

#6 peter mc

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Posted 30 December 2010 - 07:52 AM

yer good call nato :)

#7 RB30X

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Posted 31 December 2010 - 07:42 AM

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.

#8 Ben

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Posted 31 December 2010 - 05:57 PM

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!).

#9 xa1973

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Posted 31 December 2010 - 09:47 PM

Make sure the harmonic balancer hasn't spun off a worn woodruff key..........

#10 zeds4ever

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Posted 04 January 2011 - 09:31 PM

  ???  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.  ;)

#11 greylandimports

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Posted 06 January 2011 - 02:14 PM

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.

#12 zeds4ever

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Posted 06 January 2011 - 03:58 PM

;) 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

#13 greylandimports

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Posted 06 January 2011 - 07:16 PM

Well then I must search for such for such a thing!

I'm on the hunt for good carb tuning instructions! Can anyone suggest something for a first-timer??

#14 zeds4ever

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Posted 06 January 2011 - 10:02 PM

??? 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

#15 jamo240

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Posted 25 February 2011 - 10:45 PM

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

#16 Linton

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Posted 26 February 2011 - 07:47 AM

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

#17 greylandimports

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Posted 03 March 2011 - 03:08 PM

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!

#18 Veloce

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Posted 20 March 2011 - 08:27 AM

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.



#19 d3c0y

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Posted 21 March 2011 - 05:31 PM

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.

#20 zeds4ever

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Posted 25 March 2011 - 08:51 PM

;) 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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