Hi Z-heads!!

Got a pinging problem I hope you can help me with. My Brother-in-law rebuilt my '73 engine a year ago. GREAT....except for the pre-detonation!! It's worse when it's cold....then it's just bad on hard excelleration. It seems to disappear around 3500 RPMs. (Can't quite remember,as it's winter here and the car is in hibernation!!)

We've played with the timing and even advancing it doesn't clear it up completely. Could we have gone a tooth or two out when putting on the timing chain? Would that cause this problem?

My B-I-L doesn't think he messed that up, but I remember that the new sprockets didn't have the same line-up 'groove' as the original.

Any ideas?

Thanks,

Zedguy

My brother-in-law doesn't 'ping' at all...but I have a Nephew who SERIOUSLY 'pings'!!!

steve

Have you checked the timing with a timing light? It should be 5BTDC static timing. Have you checked to see if the vacuum advance is working?

Do you have the correct spark plugs and gap?

Have you verified the point gap if you still have points?

Could you have a pair of plug wires that are swapped around and that is whay you think is pinging?

Lots of questions with no real answers, but it will give you some ideas anyways......

What octane gas are you using? Perhaps you've got some bad gas?

I wouldn't suggest setting the advance to 5 BTDC arbitrarily. Many Z's have had a distributor swap in their past and just suggesting a setting may kill performance or kill an engine. Different markets came with different dizzys as well.

Much better to set your timing using total advance of 32 Degrees BTDC with the vacuum advance off and plugged @ 2,500 RPM. So, no matter what the initial mechanical advance is setup for, you'll know you've got it right.

Yeah!! Done the timing light...plug gaps....vaccum advance. I use the highest octane I can get at the pumps!

Thing is, I never had the problem before the rebuild....so something changed?! What would happen if the chain was off by a tooth or two?

Zedguy

The new sprockets did not have the same line up?Until you verify why you may be overthinking the problem.If you are 1 tooth off then the dist. advance adjustment could be ending where it should be begining.

That's why I suggested the 5 BTDC as a baseline setting. If the distributor has no more adjustment left just to get to 5 degrees then it will show that the timing gear is indeed advanced and the problem will become more obvious.

. If the distributor has no more adjustment left just to get to 5 degrees then it will show that the timing gear is indeed advanced and the problem will become more obvious.

Ahh! true!

No need for the sad face 2mz's. I was agreeing with your observations.I was just trying to paint a more visual picture.I actually thought of a course adjustment and fine adjustment as on a microscope as reference but ,I thought I would leave that to EScanlon.(And I mean that as a praise for detailed and correct info) Daniel

I guess I should have explained my reasoning in my first post a little better...... guess I'm getting too much radiation from my monitor...:cross-eye

Thanks Everyone!! Will try that!! One thing about living in 'The Great White North'.....you get 6 months to tinker with your Z and 'overthink' lots of problems!!

Much appreciated!

Zedguy