Had 350 olds rebuilt, broke in fine. HEI distributor (summit racing new). Set engine to TDC and then adjusted timing mark to 12 degrees before. Dropped in distributor. Started fine and appears to run fine in driveway but when check timing with light it shows around 4 degrees After. Rechecked distributor and looks right (brought to tdc and advanced to 12 degrees and rotor points to #1 on cap). Used 2 timing lights same. Advance hooked up to timed vacuum port on car (check w and without vacuum hose plugged). Stock replacement balancer but original timing tab.
Any ideas what I’m doing wrong.
im going to recheck tonight and probably pull distributor and reinstall
thanks

 

I'd roll the #1 piston to TDC on compression stroke and check harmonic balancer first.

 

What’s the easiest way to do that on an installed engine.

 

Use a ratchet to turn the engine with the #1 spark plug removed and your finger in the hole. When the compression starts pushing on your finger its the compression stroke. Remove your finger and start watching for the piston to come up. When the piston is TDC the balancer should be lined up with 0 on the timing mark, or 0 to 0 if the balancer is marked with timing marks.

 

I stuffed a wine cork in the plug hole and it popped out with a loud noise at TDC.

ej69, the rotor will turn when the distributor is stabbed due to the helical gear engagement. I would just set the timing using the light and not worry about re-stabbing the distributor.

 

You did nothing wrong. You are fine. It's not set by dropping into the block by eye. If both lights told you the same exact thing, guess what they are correct. Set your timing with the light.

 

But if I went to 0 on compression TDC and then moved to 12 degrees so timing set for fire up why is it not reading 12 degrees but 4 degrees After TDC
other engines I’ve dealt with i go tdc and then move balancer to degree I need and it’s all set on fire up

 

Perhaps the hei module is retarding the timing, or the magnet isn't phased perfectly with the rotor. Best bet is to just set the timing while the engine is running.

 

Also, wouldn’t it be running like crap at 4 degrees ATDC

 

Sure seems like it would. When I had a HEI in my 350 I had to run about 20 degrees advanced! That was on a smogger HEI.