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Tring to start with basic timing on my 74' L48 automatic.
I'm trying to follow Lars documentation.
The problem: At TDC, the HB timing mark can't be seen...
Here's what I did:
1) removed cyl#1 plug
2) cranked till my finger blew off the hole
3) looked for timin gmark on the h balancer: couldn't se it. Figured, ok maybe it's on the wrong stroke...
4) Cranked until finger blew off the hole
5) The timing mark is located at around 12:00 as you look at the HB.... I actually have to go to the pssngr side of the car to feel the mark
WTH?
Do I just suck at finding TDC?
BTW, there was no timing cover timing marker mounted at all... So, I just installed one.
From: At my Bar drinking and wrenching in Lafayette Colorado
Use the instructions in my TDC paper and determine the facts. E-mail me for a copy. If balancer outer ring has slipped (very common), do not run the engine until you replace the balancer - very dangerous.
Lars V8FastCars@msn.com
yeah , Iread that one as well.
I just didn;t think it was possible for the mark to be so far off..like, where you can't even see it.
but, I'm also reading where the HB can slip I guess..
I dunno..
I have it running, and could definitely hear/feel a sweet spot rotating the distro..
Harmonic balancer is likely slipping….. was in the same boat on my 77L48. Didn’t think much of it since I don’t use that mark to set timing but when I was under there replacing motor mounts I looked up and saw the outer layer of the harmonic balancer had slipped/moved toward the timing cover by more than 1/2 inch.
could be what you’re experiencing. Not an overly difficult job to replace. Did mine with both the shroud and radiator in place.
I didn't even think about the balancer "self destructing" and slipping on the rubber cushion....I was thinking of the whole HB slipping on the crank without a key...
Either way, I would replace the HB or insert a key if missing...
I imagine your rotating assembly is going to vibrate without correction...
From: At my Bar drinking and wrenching in Lafayette Colorado
Use the instructions in my TDC paper and determine the facts. E-mail me for a copy. If balancer outer ring has slipped (very common), do not run the engine until you replace the balancer - very dangerous.
Lars V8FastCars@msn.com
Tring to start with basic timing on my 74' L48 automatic.
...
5) The timing mark is located at around 12:00 as you look at the HB.... I actually have to go to the pssngr side of the car to feel the mark
...
BTW, there was no timing cover timing marker mounted at all... So, I just installed one.
That your cover had no timing tab is an oddity to me and C3 Corvettes. Do you have the original engine? There were truck 350 engines of the late-'70s, '80s, that had the timing tab at 12:00. Also, your water pump has some blue paint on it, which wasn't a GM engine color until several years after '74. Feel around on your current timing cover to feel for the 12:00 tab or a rough spot where the weld may have been ground away.
Last edited by barkingrats; Sep 3, 2023 at 09:54 PM.
Once again: You need to do an accurate TDC check and verification.
yeah, I really wanna get this TDC sorted..
I actually bought alarge bolt at my local HW store, & ground it down smooth per your paper...
Sadly, the threads didn;t match, so I abandoned that & tried the old school thumb blowhole...
I'll have to look for that 12:00 potential timing tab/mark ..
I don;t know if the engine is original or not: nothing suggests it is, but I have nothing to base that on proof-wise.
Thanks Lars, for chiming in.. your papers are invaluable!
~R
From: At my Bar drinking and wrenching in Lafayette Colorado
The "thumb in the blowhole" method with only get you on the compression stroke - it's nowhere close to accurate enough to determine TDC. Buy a TDC check tool and do the job right - there's no substitute for proper tools. Even with an Internet order (Summit or Jeg's) you'll have the tool in 2-3 days. Just buy the tool and git-r-done right so you know what you're dealing with.
Lars
From: At my Bar drinking and wrenching in Lafayette Colorado
Good plan. That will give you accurate, factual data on your timing lines and balancer alignment, and you can then make the right decisions and corrections without any guesswork.
Lars
Lordco has several types of piston stops cheap. Got mine there. Nice that your new tab has the red slider so you can add a mark that you can see. Mine was hard as mines at 12 o'clock as well but I have the short water pump so impossible to see without sticking you head down next to the alternator fan. Real dangerous and a pain. Wish I had that red marker to use.
Help! Harmonic balancer mark is ....off
