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Discussion Starter · #1 ·
Looking for some help here. I have a sbc in my 1940 Olds Coupe, just rebuilt and has been running great. Recently put in a brand new Pertronix flame thrower dizzy and coil, set the initial timing at 16 degrees, all in at 3,500 rpm is 36 degrees. Engine ran awesome all the way through the rpm range. Recently I notice it was idling a bit rougher than normal, checked a few things, then checked timing again just to make sure it didn't move slightly. It reads about 18 degrees after TDC at idle, just about off my timing tape with vac can disconnected. I changed timing lights, plug wires and checked everything I can think of. If I turn the dizzy to try and get it close to 16 BTDC, the engine sounds like it's going to come apart, can't get close to 16. How the heck is the engine running great but the light says I'm know where near where I should be?
 

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Stupid question, is there a chance somehow the timing tape moved after you originally set the timing?
I know it's a far fetched question, but I had timing issues once and I was asked if I was using a balancer that had the marks degreed into the balancer or if I was using a tape because tape can move.
I don't know, my balancer has marks in it, so I never had that problem.....
 

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Discussion Starter · #6 ·
Yeah, I'm thinking the only explanation is the balancer otherwise the engine would just not run right. The tape moving not possible since I'm certain it would just fly off if it came loose (and I sprayed the tape / balancer with 3 coats of clear so that wouldn't happen). The balancer had to shift, maybe the outer ring. Never heard of this happening, but I suppose the crank key may have broke leaving the balancer free to rotate? Looks like I'm pulling the balancer soon. Not the easiest job considering how tight things are in this car.
 

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Before getting crazy with the tools, use a piston stop to verify the TDC on the balancer. If it's on target, no need to go further other than try to turn the damper by hand and check for wiggling/looseness. If it's off TDC, take it down the rest of the way.
 

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Discussion Starter · #8 ·
Before getting crazy with the tools, use a piston stop to verify the TDC on the balancer. If it's on target, no need to go further other than try to turn the damper by hand and check for wiggling/looseness. If it's off TDC, take it down the rest of the way.
Thanks for the reply but I'm confused. If the balancer/timing tape "0" mark is still lining up with piston at TDC, then the balancer can't be slipping or loose. If it's no longer reading 0 at piston TDC, then it had to have slipped and that would explain why the engine still runs perfect, but the timing is way off according to the light. My apologies if I'm misinterpreting your response.
 

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[QUOTE="1940Olds442, post: 4778490, member: 433839"
If the balancer/timing tape "0" mark is still lining up with piston at TDC, then the balancer can't be slipping or loose.
[/QUOTE]

I think he's saying you should verify this first before teardown.

Also I just read the original post again, and was wondering if its running good why mess with it?
 

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Discussion Starter · #10 ·
Agree, thanks for the reply. Good point, it is running great and I could just leave it, but something is causing the reading to be off and it's driving me crazy that I can't figure it out. If it is a slipping balancer, better to find it now before a real failure. Thanks again, I hope to get into it more tonight and will post my findings.
 

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Buy or make a piston stop and check the accuracy of your balancer mark to zero on the timing tab.
Info in link.
If you think the balancer is slipping just paint a stripe on it from the hub out to the outer ring. I use white out.
Keyway can’t shear off. If yours did the balancer would have left by now hopefully not taking your steering or brakes hardware with it.
Hopefully you’re plugging the vac pot on the dizzy for timing checks?


 

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the outer ring of a stock damper is just bonded to the hub with rubber. the outer ring does the damping and is constantly moving to oppose the crank twisting forces. The rings that I have seen get loose could not be moved by hand but would sometimes move constantly when checking the timing, as in the market would come and go between light flashes.
 

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Thanks for the reply but I'm confused. If the balancer/timing tape "0" mark is still lining up with piston at TDC, then the balancer can't be slipping or loose. If it's no longer reading 0 at piston TDC, then it had to have slipped and that would explain why the engine still runs perfect, but the timing is way off according to the light. My apologies if I'm misinterpreting your response.
Because your eyeball is referencing TDC as the line on the damper and the tab on the cover and NOT actual piston TDC.
In other words piston TDC you can't see with the engine put together so we rely on the mark on the damper as a reference.
Short of knocking a hole in the block so you can see piston TDC and double checking the mark on the damper is the same you need to make sure that actual piston TDC is represented at the damper correctly in relation to the tab. Do that with a piston stop.
 

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Discussion Starter · #14 ·
UPDATE....pulled the damper and could tell immediately that the timing tape was no where near where it should be using key slot as reference. Put it in vice and with minimal effort using breaker bar was able to turn the outer ring as far as I wanted. Not a smart choice to save a few bucks on a J-g's brand Damper.
Thanks for all the input, problem solved!
 
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