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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Need a beyond simple explanation on what is the next step in this situation- I'm used to grouped oem parts of known history. EFI- problem was the use of a different timing chain cover that allowed no timing tab provisions (LS 24X ecu on SBC)- so I used a bent wire along with a piston stop and set the wire at where the balancer TDC is indicated in this picture. When tuning we were running into ping which the tuner suggested strongly that he thought the spark advance was 9-10 degrees advanced over what his Spark tables were commanding and thought the balancer might have slipped- EFI base timing in this case will be set to zero. Fast forward with a new 400 SBC balancer on this 383 oem roller block/one piece rear main seal- looks like the original Pro Products balancer was OK, the new balancer needed to be rebalanced as this is not a true oe 400 crank, the replacement cover is claimed mid 90's truck TBI- but what bothers me is the non factory spot welds- looks like hand tack welds. So I ran this back and forth twice and then again with the stop adjusted out a little more to try and tighten things up- so to me the TDC on the balancer is confirmed good to 1 mm but I don't know how to approach the timing tab- markings on balancer were based on '0' notch. I have a GMPP cover and matching bolt on tab- and later installed it with the bolt on tab bang on to where '0' is shown here. I suspect I am good to go and with timing set to this indicated zero/TDC would retard 10 degrees over the initial problem set up which was advanced 10 degrees and giving me trouble. I've been told the 400 and 350 share the same timing marking orientation. Am I being clear enough?
Yes your marks are telling you that you're 10° advanced from wherever you thought you were. I.e. if your builder told you to time it to 0°, and you lined up the marks, you were setting it to 10° retarded. If he told you to set it to 10° advanced and you lined up the marks, you were at 0°. All your ACTUAL timing was 10° behind wherever your marks told you it was.
If it was mine, I'd probably cut a new mark on the damper at 0; maybe get a tape for it. Alternatively, remove the tab, and replace with a short piece of a hi-tech infinitely adjustable muffler bracket.
Align it correctly with the 0 slot on your damper.
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.
Seems pretty simple at this point.
You've got he TDC figured out in terms of how it lines to something. Whether it's 10, 15 or 20 degrees of spread doesn't matter.
Where I would go from here is something similar to Kingdom's universal solution. I'd get a timing tape that matches your balancer circumference and glue it on. Then I'd get one of these adjustable pointers and dial it in.
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.
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.
If that's the case, then you've got it.
Maybe do the forward and reverse a couple of times to eliminate any errors in measuring.
08-02-2021, 04:47 PM
