LA small block timing is suddenly way off

stillsteamn said
. At this point the distributor rotor points about 30° past the cyl 1 post on the distributor cap, with the distributor set where i previously had it. This means my previous ear tuning (fast smooth idle) must have been 30° advance timing,.

No Wrong. A distributor rotates at HALF crank speed. This means the relationship of the rotor is not the same as crank degrees. That would be more like SIXTY at the crank.

AGAIN you are GUESSING. STOP guessing. JUST STOP

GET A PISTON STOP Do this RIGHT

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stillsteamn said
This means my previous ear tuning (fast smooth idle) must have been 30° advance timing, but the engine did seemingly run well and i never detected any knock or ping. Aha, but i then found that the harmonic damper has at least 3 other strike marks around the perimeter. .

Amazing. DO IT RIGHT

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stillsteamn said
So other than the fact that i have been using about 30° advanced timing at idle which is probably not good, i no longer think i have a timing problem causing the bad missing. I can turn the distributor in the retard direction to properly set timing, and i did try this a couple days ago but it was making the miss even worse (daughter in car feathering the throttle and keeping the rpm's up to keep the engine limping along). But i still have not found the real problem, so maybe i had a backfire that did something to one of my edelbrock 1404 carbs. The name of this thread is now wrong, but before i started thinking i had a timing problem i did remove all 4 fuel/air idle screws and shoot a blast of compressed air in each hole to remove any debris from the idle circuit, this tip came from an edelbrock youtube video i saw earlier from an edelbrock guy. I also pulled out all 4 metering rods and wiped them off but they were clean.

See you are just going in 40 different directions.

GET the timing marks CORRECT

THEN figure out what the cam timing SHOULD be and estimate whether it IS correct. This is easy to do, as the intake event occurs somewhat near TDC, so even if you do not have a degree wheel, you can measure around the dampener and compute inches / per degrees to work this out.

AFTER you have proved to yourself that TDC is right, that cam timing is as correct as you can "see" it, then attack your distributor

YOU NEED A timing light which works with MSD

YOU NEED to figure out what the mechanical advance is, how much it advances, and whether it's stuck, rusted, or has other problems.

If you cannot do any other thing after you get the timing marks checked (did I mention with a piston stop)

Time the thing at high RPM at about 35* with no vacuum, then see "where you are."

PISTON STOP

Remove the no 1 plug. Wrench the engine or bump it so the piston is "down a ways." Unhook the battery ground

Install the piston stop. You may need to play with the length. Wrench the engine around carefully until the piston stops against the device.

CAREFULLY and accurately make a temporary mark onto the balancer next to the TDC on the timing tab. You are NOT trying to stop the piston at TDC, but rather down in the bore somewhat.

Now wrench the engine around CCW until it again stops on the device. Make a SECOND mark next to the TDC timing tab onto the balancer.

NOW you have 2 temp marks "some distance" apart. True TDC will be 1/2 way in between, and if the original is correct, that is where it will be.

THEN measure around your damper, circumference, carefully and accurately, figure degrees per inch around, and mark off the correct distance for something say, 60 degrees, 50 degrees, or 40 degrees. having done so, CHECK your work carefully. You MUST MUST use a tape for this first measurement.

Then take a pair of dividers and divide this distance into halves, quarters, etc. to get down to 10's of degrees, etc.

NOW you can see what advance is "doing."

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