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silverz

Ignition Timing 240Z

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Hi,

This question has probably been asked before but I can't find it. Can anyone confirm the ignition timing settings for a 240z ? (L24). My owners manual says 17 deg at idle. I take it this is 17 deg advanced but when I set it on that it runs well at idle but pings and rattles like crazy when I drive it. I have backed it off to about 10 deg advanced, however it is still not running as good as it should.

I have a friend up for a visit who reckons the Hitachi Carbs are just like the SU's on his Daimler and is going to help me tune the car so it is not running so rich but we need to make sure everything else is right first (including the ignition timing)

Any advice will help.

Thanks

regards

Peter

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Beacause my motor is set for the circuit I might be a couple of degrees higher than what a road should be. My set up is L28 with standard injectiona and Haltech F9 Fuel computer running a 280ZX electronic dizzy regraphed to suit the setup and cam, 76 degree Nissan grind.

 

I initially set my timing at idle to be 15 deg BTDC. This gaves me a start point to get the timing where it needs to be at 4000rpm, which is 32-34 degrees BTDC.

 

If you have access to a manual check what the timing should be at 4000rpm and set to that, and don't really worry about what the timing will sit at at idle.

 

Once the timing came into the zone the motor came to life sounding really crisp and revving freely upto 6500, I don't like free revving motors to much, and pulled really strong once I was able to get onto a track for a test.

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Peter

 

Make sure you remove the vacuum advance hose when setting the timing at idle.

If your L24 is stock standard, ensure you run only 98 RON fuel (plus an additive for valve seat protection). The carbs are more likely to causing pinging if lean rather than rich.........check your plug colours they should be a nice clean medium grey colour not sooty (rich) or white (lean) .

 

cheers

 

Alan

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Thanks all for the advice. We are going to have a go at tuning again this weekend. Will go right over the carbs after rechecking plug and points gap, timing etc.

 

I don't know about 98 ron, there are only a few places here you can get it apparently. I also have been told it has evaporation problems in the heat. I wonder how lead substitute with octane booster would go,  I have seen this for sale.

 

regards

Peter

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Hi Guys,

 

While we are on the topic of timing, I find that i can't rotate the dizzy to get any higher than 12 deg idle timing as it's limited by the flat with the "track" through it. What can I do if I want to try out more advance setting?

 

SUlio

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you can file a slot on the track eg file the "stop" from the track. Did that on mine. 

 

Or copy the track to another bit of metal and make a new clamp with mega amount of movement.

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you can file a slot on the track eg file the "stop" from the track.

 

Ah Lurch advised to do the same, thanks Modular.

 

Sulio

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Hi,

My friend showed me how to tune the Hitachi's today, we went right over them checked and reset the float levels changed the oil in the dashpots etc (put 2 stroke mower oil in them! it was the lightest oil I had). We ballaced the Carbs by listening to them with a rubber tube which wa aneat trick, we leaned the Carbs out until it sounded just right.  Checked the points gap all good at 22 thou, set the timing 17 deg advanced for trial run. Throttle response etc was brilliant,friend was impressed how hard she went. He has a Daimler SP250 hence knowledge of SU type Carbs. 

However pinged when opening her up. We thought no problems we will just retard the timing slightly. Then I thought what if I close the gap up to 18 thou first and try that?  Did that and I don't know what we have done wrong but now on full advance it is only just over TDC - advanced by a few degrees only. We have tried resetting the gap opening it up again to 22 thou even 24 thou still can't get anywhere near enough advance.

Does anyone have any ideas what could be causing this? we did notice the plate under the points can be moved to an advance position like the vacuum advance would do  and back to the normal position. When it is moved to the advance position it doesn't spring back like we thought it should, perhaps there is a broken spring?

 

It has us beat, does anyone have any experience with this sort of thing? advice would be appreciated.

 

Thanks,

Peter

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All sorted now, the problems were that the points weren't fully home at the top, the screw was tightened without the points plate fully home and the small lead (low tension lead) to the points had a short in it.  These little things make a big difference. Points gap now 22 thou and timing 12 deg advance at idle. Nice and crisp performance and even though I think she still runs a bit rich our work on the Carbs has increased responsiveness and it doesn't smell anywhere near as fumey. The Carbs seemed very simple to tune, provided you use the cool listen to the tube trick. My friend is impressed with how Zeds go.

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Hi,

After driving around for a week I am still not satisfied the car is going right. It hesitates initially under acceleration, sometimes backfires then takes off, though feels flat and not as responsive as it should.

 

I still think the timing is not right. I fiddled with the points gap again today and this has made no difference. I now have it on 18 thou.

 

There is a painted mark on the timing pointer plate attached to the engine that looks like it is at 17 deg (as per the timing settings in the owners manual) I have advanced the distributor as far as it will go but the marks on the pulley still will not line up.

 

Any less advance it runs like crap.

 

Clearly I have done something wrong, does anyone have any ideas?

 

Regards

Peter

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hello silverz.

 

Got 2 things to check that were wrong when i had a very similar problem .

1. The obvious vaccum leak. I know, I know. But i have forgotten to attach it a few times. I had a doozy where my vaccum hose melted to the exhaust manifold allowing a leak in despite everything looking ok.

 

2. the other thing was that ( laymans description here ) vaccum advance lever inside the dizzy had dropped off the advance mechanism. Whipped out the dizzy and found the screw and it hadnt gone too far phew - odd shaped bugger with about 3 rings of thread - and retightened it back down. Now i got advance. Problem is that the screw and thread was very finicky and is not really secure enough for my liking.

 

These 2 things i checked for my current setup which is twin SU's and not the dellortos. I also cant seem to speeelll vacuum correctly.

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2 marks on the pulley??

when using a timing lite  are you looking @ small indent in the pulley or a painted line???

The dissy could also be 1 tooth out on the oilpump drive, have to remove oil pump and redo if this is the case, but another way is if your dissy has 2 sets of bolts, one set going up and one set going down, the upper & lower body can be twisted on some dissy's allowing upto another 1/4 turn on the timing.

 

answer above q's,

hate to sound patronising but was all the bolts on the dissy tight?

nat0

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Thanks for the useful advice,

I went and had another crack at it, and this is what I did.

 

Pulled the points off and put them back on making sure they were positioned correctly set points gap at 20 thou and secured points. Sprayed WD spray under the points backing plate and made sure it was moving freely for the mechanical advance/retard. Applied grease where I could so the plate would slide over it when mechanical/vacuum advance/retard operates.

 

Checked vacuum tube to vacuum advance, found ball bearing in tube blocking it off (I didn't put it there so it's been there since I owned the car) Removed ball bearing and sucked on the tube, couldn't make the plate with the points on it move but could see the spring from the vacuum unit contracting. Left hose off to set timing.

 

Put Dizzy Cap etc back on and started the motor, had to move the distributor position immediately to keep motor running as it was now way too far advanced. Set timing using the definate groove in the pulley as the mark (can't find any painted line) set timing at 17 deg (suspected this would be too much advance but decided to use it as a start point as that is what the owners manual says) Reattached vacuum hose.

 

Went for  test drive. Pulled cleanly from low revs though still very slight hesitation from idle. No pinging even when up hill accelerating in third gear at 1000 RPM. Hit the Highway and gave her a burst through the gears, pulled cleanly up to 6500 RPM, next thing I know I am seeing triple digits on the MPH speedo. Quickly slowed down before something silly happened.

 

I think it is going alright now. The slight hesitation may be a slightly bent jet needle in the front carb which we think may have damaged the jet as well. I am sourcing these items at the moment.

 

I will know for sure once I have driven it for a week, the early mornings were causing drama last week, required prolonged warming before it would go.

 

Thanks for all the advice, After this I am definately considering changing to electronic ignition.

 

Thanks all,

Regards

Peter

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How did it work out in the long run with the timing set at 17 degrees BTDC?

 

Any pinging?

 

I'm getting ready to try the same setting ...

 

Thanks!

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Our fuels are considerably different in quality to fuels from the USA.

 

Consult the factory service manual for a USDM 240Z and go from there.

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