71 LA 340 timings moved!! how?? looking for help

nm9stheham said

That is not what is being said. There are 2 advance mechanisms: mechanical and vacuum. What it being suggested is that the vacuum advance mechanism has broken on some odd fashion and is jammed and that is starting the total ignition advance at a very high number. That could happen, and the mechanical advance would still work... which is what you are seeing when you rev it some.

And yeah you had better back the way back down I would start in the 10-15 range with your high static CR; looking at your engine parts, SCR computes out to around 10.6 and could be more. And the DCR is in the mid 8's and that is pretty darned high for iron heads. No wonder it was carrying on... it was very, very likely to have been detonating, IMHO.

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Hey.. sorry about delay kinda lost interest sadly, bit like a sulking child lol!! anyway back at it as the issue is still there although alarmingly made 80% better by replacing Carter high volume elec fuel pump for a Holley Blue... fuel pressure now holding solid at around 7.5psi

Today I'm just in the middle of swapping back dizzy cap and rotor arm as noticed some play in the rotor arm on the shaft, but original one is solid..

I'm not running vacuum advance only mechanical. Oh and compression is 10.75:1

Checked timing with gun last week and checked for slack in timing chain, also checked it all lines up at TDC which it does, although waiting for piston stop tool to confirm 100%

to show the timing we are seeing its......
32 at idle
38 at 2.5k rpm
40 at 3k rpm
42 at 3.5k rpm

That was holding throttle and slowly increasing.

Was not going to hold revs any higher with that sort of timing, but blipped the throttle and saw 50!!!!!! so yeah something is well out..

Will update if I get anywhere after reading the above comments