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Old 09-01-2018, 02:44 PM
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Triple Dellorto's and Vacuum advance

Hi All,

I read somewhere that vacuum advance should not be used when using Triple Webber carb set up. Is the same when using Triple Dellorto's?

Regards
Phil
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Old 09-01-2018, 05:07 PM
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It's the same deal yes. It's not the case that you shouldn't, more that it's not easy and perhaps not worth the faff. I've had mine working with vacuum advance and it makes a few better mpg but was a lot of effort and I always had a background worry that maybe I have too much advance under load.
I don't think you can do it with all Dellortos - I heard some don't have the vacuum port.

Anyway, I'm going distributor-less now so I'll have something else to worry about this year.
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Old 09-01-2018, 06:50 PM
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Thanks John, You're right, I couldn't find a vacuum point.

Phil
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Old 09-01-2018, 07:24 PM
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Hereís a picture of mine with the vacuum lines attached. I think you can just about make out where the vacuum ports are. As you say, you might well not have them. I wouldnít bother again. Iíd recommend taking a couple of mm out of the mechanical advance in the distributor and set the max advance to 34 deg (at 3500 rpm or so)
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Old 11-01-2018, 11:58 AM
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Triple Dellorto's and Vacuum Advance

Thanks Jon,

As you can see from the attached photo, I don't appear to have those ports like yours.

How would I go about taking a couple of mm out of the mechanical advance in the distributor and set the max advance to 34 deg (at 3500 rpm or so)?

Phil
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Old 11-01-2018, 01:11 PM
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See attached link from Datsunzgarage. He also advocates not using vac advance and then limiting the max advance using a spot of weld....

http://datsunzgarage.com/weber/
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Old 11-01-2018, 02:59 PM
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Hi Phil- I think you do have the ports - I’ve circled one in red.

To use them, you have to remove the plug and screw in something to attach a vacuum line to. I think they’re m6 threads.
But I’m not recommending it!

For the dizzy work -
You take your distributor apart - just some screws for 240z, 260z to lift the breaker plate out, A bit more involved on 280zx but still not hard.
You’ll find under the plate a thing that looks like this:

You can see a spindle with arms and slots in the arms. The breaker plate attaches to the top of the spindle. The pins in the slots are attached to the weights under need. As the dizzy spins faster the weights move out, so the pins move out too and in doing so they rotate the spindle that the breaker plate is attached to, advancing the timing.
So you add about 2 or 3 mm of weld on the outside of the slot, reducing the amount of advance it can add.
Then you reassemble and run the engine. Point a timing gun at the crank timing markers with the engine running and you’ll see advance increases as you accelerate the engine. It’ll reach a max at around 3500 rpm. Twist the dizzy so that it shows 34 degrees advance at that max.
Now let it return to idle. If it shows 15 - 20 deg of advance now you’re probably done.
If its at the high end you might have trouble starting. So let it go cold again and try to restart it. If it starts then your done. If it doesn’t you need to open it up again and file a bit of that weld away so it can advance a bit more. Repeat.
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Old 11-01-2018, 03:04 PM
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but.... if you're newly on triples, this might not be the most urgent job. Fuelling is much more critical - if you've not set it up on a rolling road, I'd really recommend getting a wideband AFR gauge - it's the only way to be sure what the mixture is doing.
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Old 11-01-2018, 04:29 PM
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Thanks Jon,

Gives me something to think about but not yet ready for set up as I haven't even yet put the engine in the car. Would I need a wideband AFR gauge just for setting up the once or should it be a permanent fixture?
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Old 11-01-2018, 07:17 PM
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You can certainly use it just while youíre setting up and figuring it out and remove it after. Thats sort of what Iím doing - Iíve had it 2 years but I just havenít finished setting up yet
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Old 12-01-2018, 07:59 AM
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Thanks Jon
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