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77 with 350 auto
my timing mark with the timing light shows at 4:30 position after TDC.
pulled #1 plug and brought up to comp stroke and timing mark is on the money..
pulled distributor cap and verified rotor pointing at #1 cylinder and #1 on the cap
In oder to get the engine to run right the distributor vacume advance mod is turned to
The 10:30 position and the timing mark is still about 2 1/2 inch past (after) TDC.
Need suggestions
if the TDC mark lines up correctly. can't be a bad harmonic balancer. although double checking that couldn't hurt.
pictures of your distributor could help. not clear about your clock numbers, and where you have number one cylinder plugged in.
Did you remove the cap and rotor and check if the advance weights are frozen?
Are you disconnecting the vacuum advance when checking initial timing?
Is the idle speed correctly set?
Sounds like you verified the TDC mark on the balancer. Good.
So check everything in post #3&4 first.
If all that is OK your distributor may have been installed "off" relative to the camshaft. Off a tooth, or even two.
It'll run fine, it just puts the vac can at an odd position.
Corvettes have very little room back there and seem to work/fit best with the vac can "nipple" pointing to around 8:00 to 9:00 when properly timed.
You should have an HEI right?
It is possible to reclock the distributor and set the timing pretty close to perfect on a non-running engine.
It sounds like you are almost there.
Find TDC (compression stroke) then move the mark to the preferred initial timing degree mark. Don't move the engine again.
Note where #1 spark plug wire terminal points. Mark on engine with a piece of tape.
Remove cap and ensure rotor points at same spot.
Note where the vac can nipple points , mark it, and decide if you want to rotate it to 9:00
Now there are 2 ways to "move the can", you can try moving all the wires one terminal on the cap, that will just wind up moving the van can, once you point the new #1 back to your marked spot. (or)
If the vac can is way off pull distributor, bump oil pump pushrod a little in the right direction with a long screwdriver, and re-insert the distrib. (It rotates a few degrees (like 20) as you insert it.) Line up the vac can exactly where you want it, and start with the rotor a little ahead of where you want it to stop, then insert distrib.
Rinse and repeat until both vac can and rotor point to where you want them to.
Then slightly tighten distrib, and then remove the rotor.
Pointed ends on HEI magnet / pole piece point directly at each other when the engine fires. Assuming you never touched the timing since step one, very slightly (only 1/4"-1/2") rotate the distrib until the pole pieces line up exactly. (with points you do this until the points open or close, with a test light ,I forget which one fires the plug.)
Reinstall rotor and make sure it still points to your #1 mark. Retighten distrib.
Engine is almost perfectly timed +/- a few degrees.
This is one way to time it for an initial start on a brand new engine when you need to ensure it runs immediately so you can break in the camshaft. Or to fix where the vac can "points"
Red arrow points to the one triangular point of the magnet that you can see from here. If you look inside you will see it lined up with an opposite one that moves with the advance weight plate.
Last edited by leigh1322; Feb 18, 2021 at 09:14 PM.
Timing
