350/400 SBC Timing Tabs

[dannobee]

The middle of the two piston stop marks is true TDC. If that's what you're showing in the pic, the timing mark is off 10 degrees. The 0 on the balancer should line up with the 0 on the timing tag.

[dfarr67]

I also have a GMPP chrome timing cover and bolt on 8in timing tab- which I also installed just to see where the '0' landed on it- same spot as the welded on tab. What am I missing for factory timing tabs- I am having timing issues with the EFI and the guy helping tune guessed I was 9-10deg advanced.

[dannobee]

Did you perform the piston stop method like this?

https://www.motortrend.com/how-to/accur ... iston-tdc/

[dfarr67]

I just found that today- and it's the best one I've found to date.

My photo doesn't show correctly- it has just run up against the counter clockwise piston stop- I hadn't marked out the midpoint yet between stop marks- that midpoint lies on the left crest of the TDC groove cut in the balancer. What I get out of this is that TDC and the '0' on the tab are very very close (or good enough for me). If I am incorrect- I'm missing something fundamental.

Depending on how the piston stop worked- it could have been 20/10/5 degrees on either side of TDC.

[dfarr67]

Went and talked to a mechanic today- he at first said the same as above, but when talking face to face, some more information is exchanged.
The photo shows the balancer run up against the piston stop when turned CCW and shows +10deg, if I were to reverse and run the piston up against the piston stop CW it would show -10deg, so my thinking is the '0' on the tab is correct........as it is the reference point I was using.

What happened before when using a wire pointer- I set it at where TDC is on the balancer- where you see it now---->we ended up running +10 more degrees than we realized.