Timing, carboration

[jezze]

Can outrageous backfiring cause internal timing problems(timing chain, ect)? Before I started messing with (and probably messing up) my carboration and timing my stock L24 would backfire, so loud actually that it blew my muffler. Also, my fisrt, second and forth cylider spark plugs are all oily/gasy looking, the others seem fine. One other thing, it looks as though there is some oil seeping from my head gasket above the first and second spark plug area.

I took off the cam cover and found 1st at TD. I set my distributer (153624 counter clockwise) to this, then tried it roughly 180 degrees off. The car runs at the appropriate setting, but seems to need a timing ajustment. So I loosened my distributer, and retarted it (I usually have it advanced all the way), and retarding it just made it worse. It seems the motor wants more advance, but ajusting the plugs on the distributer to achieve this takes away the goal of having the harmonic balacer set at TD and as a result threw the timing further off.

So at idle with timing set as it should the car runs fine, but once I apply gas the back firing starts as if the timing is off. I ajusted my carbs too by the way.

Someone mentined the advance mechansim in the distributer could be checked if I take off the vacuum line to the SU and suck on it. I did this and if move rather reluctantly, but it does move the 1/2 inch or so it is supposed to (if this is accurate I don't know.)

The points are fine, and the plugs are champions, but at least they are ajusted right.

Soooooo, any thoughts???

[78 280zcar]

Have you checked to see if the cam sprocket lines up with the cam thrust plate, the notch on the back of the sprocket should line up with the notch in the thrust plate at TC. Just something to look at!

[zman525]

this happened to me on my 72' but it just turned out to be the wrong firing order. I too blew the muffler up... sounded like someone fired a shotgun next to my head.... hmm... uve covered pretty much everything i could think of, if i were u id keep messing around with the distributer... advancing and retarding the spark.