indydoug

I just bought a Summit #SUM-161350 balancer, and it did not come with a new timing tab. The note on the installation instructions states Chevy used two different TDC locations. Does anyone know if the stock timing tab will line up with the Summit 161350 balancer for a correct TDC indication? Engine is 1980 L-48.

MelWff

the instructions furthermore state to use an aftermarket bolt on tab

indydoug

I noticed that too. To quote verbatim, their "dampers are designed to be used with the aftermarket 'bolt-on' style of timing tab." Does that mean the stock timing tab cannot be used?

The last time I bought a harmonic balancer (and it's been a few years) it came with a timing tab, and both the stock tab and the aftermarket tab had the same "TDC" 0° point. I could have used either to set the timing. So I am wondering of anyone who has used Summit's 161350 can confirm whether or not the stock tab can be used. I'll find out eventually when I install it, but I was hoping to get an answer in advance.

indydoug

Now that the new balancer is installed, I'm answering my own question for future reference. The Summit SUM-161350 balancer is a direct replacement for a stock 1980 L-48 balancer, so the stock timing tab works perfectly. Both require the tab to be in the "2 o'clock" position (as opposed to older designs that used a "12 o'clock" position.)

maxmachz

Very interesting. When I try to shoot the light on my 1981, the balancer marks show up in the 12 o'clock range, not the 2 o'clock range. I thought my balancer had slipped, maybe it's just the wrong / a different one.......

7T1vette

If your timing had been set properly before the balancer change...and the distributor has NOT been moved, then you need to verify your engine's TDC location [mechanically] before you go any further. The mark on that balancer may not be in the correct location to use with the timing tab that is now on the car.

{You did remove/plug the vacuum advance line to the dist. advance can, didn't you?}

spikebot 81

Just for referance, I bought the summit balancer only the larger 8" model. The timing tab for the old balancer (also 8") was dead on TDC. The new summit was off TDC by almost 1/2 inch. This was checked with the cylinder head off and a dial indicator to find tdc.

7T1vette

If you are not looking for exact precision, you can take the #1 spark plug out, bring the piston up just short of the TDC position, stick a large plastic drinking straw into the spark plug hole and slowly rotate the engine till the straw just stops further movement. That'll be within a degree or two.

If you have rebuilt the engine with a close-tolerance valve train, you need to check it [properly] with a timing stop tool.

maxmachz

No, these HEI's are not vac advance......you unplug the computer to set base timing, then when done plug it back in to allow the ecm to set the advance curve.

7T1vette

Okey, dokey... Then, did you pull the computer when you set 'base' timing? If not, 12*BTDC might be right on.

maxmachz

Yes, pulled the plug, mark still shows up in the 12' o clock range. Timed it by ear for now, runs good, 16.5 mpg and no rattling or sluggishness. Still want it right though.

Thanks for replying