wtf?

[FairladyZS30]

so im driving my z and as i start out in first gear it struggles alot and then my rpms drop but doesnt turn off and my carburator making aair poping sound......but i also blew an oil seal on the piston can that be effecting this?

[Ramses]

When you say popping are you saying that it is backfiring through the carbs? do you have carbs? What year? On my '73, I had a backfiring through the carbs, and when I adjusted the timing on the dist, it went away. We need more info please. It could also be the vacuum being disconnected, but again not enough information.

[FairladyZS30]

yes it is a 73 and i did to the timing...before it never did that but now its doing it

[beandip]

Well is seems you answered your own question. Hello ! What did you set the timing at? Is the vacuum advance operational ? What ignition is in use, and are there points? Have you adjusted the mixture on the SUs ? Since you said the Z is a '73, is it running SUs or flat tops? Gary

[FairladyZS30]

i set the timing to 0 .....and yes they are point single points adjusted the mixture no i was trieng to figure that out and is running su's

[beandip]

Set the timing at 10 degrees before top dead center.

[naviathan]

You set the timing at 0 and you're wondering why you have a problem? Never worked on a car before have you?

[SteveJ]

i set the timing to 0 .....and yes they are point single points adjusted the mixture no i was trieng to figure that out and is running su's

If you truly set the timing to zero, as others suggested, that could be a big part of your problem. You want to initiate the ignition of the mixture before top dead center to allow it to propogate in time to cause enough expansion of combustion gases to drive the piston down. By setting timing to zero, you give the piston a very weak push.

Also, what did you set your dwell at for your points?

[FairladyZS30]

Set the timing at 10 degrees before top dead center.

will do, i red in the break down manual to set it at zero at top dead center but ill try what you said thx

[EScanlon]

Fabian:

The Break Down Manual would be correct in stating that the "0" indicator should be at the top dead center of the piston's travel, as that IS what it is supposed to indicate.

The spark plug however, is part of the Ignition System, and it's sole function is to ignite the gasoline vapors being compressed in the cylinder. Since the combustion isn't instantaneous AND complete, it needs a bit of time for it to progress to the "fully ignited" state which is when it can exert the downward push on the piston.

This is why you set the timing of the spark to occur just before TDC (Top Dead Center), so that by the time TDC is reached, the combustion is now reaching the point at which it's expansion rate is the greatest. If you set it too far in advance of TDC, you're actually going to be trying to compress the expansion. Set it too close to TDC and the expansion will occur much later in the cycle and you'll lose potential thrust.

Hope that helped explain it.

E