Need Detonation Diagnosis Help

[So Cal Mark]

I'm wondering if perhaps your crank pulley has been loose and hogged out the keyway. Your 2L shouldn't have much low end power with the timing at 0. Is your pinging at all rpms under load? Is it pinging on light load or heavy load, or both?

[luket]

Interesting theory, I wonder if I can see it w/o pulling the timing belt. I get out a mirror and take a peek. ping happens under any moderate load at 10deg advance, only under heavy load with less timing advance, worse at lower rpm range after a gear change. Checked my total advance and prob a bly in the 20 to 25 deg range. Didn't swap the fuel pump but I did pull the carb, tore it down and gave it a good cleaning, soaked all jets, replaced some o rings and got rid of some gunk. No luck on reducing the ping.

Perhaps a coolant system treatment might be a good next step, maybe I have a hot spot on one of the cylinders. Kinda grasping at straws here. Need a win soon on this one its kinda getting ridiculous

[luket]

For what's its worth I also measured 18 inches intake manifold vacc

[So Cal Mark]

at idle?
if you have 25 degrees of advance, along with 10-12 initial, that's borderline too much timing. At what rpm do you have 25?

[luket]

at idle?
if you have 25 degrees of advance, along with 10-12 initial, that's borderline too much timing. At what rpm do you have 25?

25 total advance (direct measurement, including initial timing) when i rev it, probably between 4000-5000 rpm

going to check your flywheel theory tomorrow with a dowel in the #1 plug hole and measuring the height of the cylinder, see if the notch isn't at TDC.

The timing belt looks a bit old, i wonder if it would be too soft and stretching under load. kinda a wacky idea

[majicwrench]

That dowel method will not get you close enough to tell much. If its off, can't be off much. Has head been surfaced?? Has car always pinged?? I would just set timing so pinging goes away. And like I said, EGR helps control pinging. Saw mountains of cars pinging in the 70's that had the EGR disconnected, or the infamous little ball bearing shoved intot the vacuum line.
' Keith

[fiatfactory]

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[luket]

Actually the intake leak was at #4, replaced the in take manifold, but I think it may still have a very slight leak from spraying it again. Also, my compression is lower in those Two cylinder , see above. Have been considering just doing a full top end rebuild, will prob take as much time as this stupid diagnosis and I should fix it with everything clean and tight, whatever it is, seeing as I'm confident its not the ignition system.

Is a cylinder head leak in 3 and 4 a common issue? The compression test is def pointing at these two

[luket]

Just redid my compression test "the right way" with all plugs out and got

1 - 150 psi
2 - 150 psi
3 - 80 psi
4 - 80 psi

Commencing to pull the head.

Thinking im going to take this opportunity (see i AM and optimist) to install a better intake / carb. probably a header. port and polish. valve guides and seals. timing belt etc.

ill probably end up starting a new thread as im sure going to have a lot of issues in the next month or so

headed down the rabbit hole

[luket]

You've done the head gasket between 3 and 4, was the intake manifold leak to one of these cylinders??

SteveC

Dead on steve, big tear in my head gasket between cylinders 3 and 4, good stuff thanks man! Never been so happy to have a blown head gasket, on with the rebuild!

[fiatfactory]

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