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4SPEED427 · A Poncho Legend!

Crank damper timing mark issue. Help?

cdnpont · Canadian Poncho Superstar!

Setting up my initial valve lash tonight, and it appears that the outer ring on my crank damper may have slipped. If I rotate the engine to get #1 to TDC, visually the piston is well on its way down by the time my pointer ends up on TDC on timing tape. I applied the tape using the original TDC line on the damper. I do realize that my pointer is non stock, and will not likely register in the same spot as a stock pointer, but this seems wildly out. Should the damper TDC mark be at near 12 o'clock when #1 is at TDC? It is a used damper of unknown history and the rubber actually looks pretty poor.

The pointer in the picture is at about where #1 TDC is falling (without using a piston stop) Am I missing somthing here? Is a failed damper common?

4SPEED427 · A Poncho Legend!

I am thinking you must have a damper for a different style of cover/pointer.

4SPEED427 · A Poncho Legend!

I seldom/never do any stuff with the later small blocks but didn't some of them have the timing mark in a different spot, about that far off what we would call normal?

JC2+2 · Poncho Master!

Is this a SBC engine and could the dampner maybe from a '80's 305 or 350? Those engines had the timing marks at 12:00. In that case you need an older style dampner.

cdnpont · Canadian Poncho Superstar!

So they did have dampers set to read at 12 o'clock, interesting Jc, thanks, I only ever knew of two different types and they were only ever different by about 10 degrees or so. The heads are on Carl. So I'll need a piston stop to find true TDC. Ever use one?

I'll probably just order a new Damper, a piston stop and a new timing tape and we'll go from there. Should I also grab a damper installation tool?

Cheers, Mark

4SPEED427 · A Poncho Legend!

I have never used a piston stop, no, so I'm not much good to you there!

When I needed to put my damper on the 327 I looked in the factory manual just for kicks. It says to use a hammer and a block of wood or something like that!

I did that with a twist. I shimmed the back of the crankshaft real hard against the engine stand so that when I was hammering on the balancer (with a wood block of course) I hopefully was not doing any main bearing damage. I have always heard that is why not to just hammer on the balancer.

4SPEED427 · A Poncho Legend!

I happened to see this on the Nova site just now. Wouldn't this be about the difference you have there?

Stephenzone · Canadian Poncho Superstar!

Nailhead wrote:
....just looking at the pic I'd say the pointer is about right for #1 TDC and the number ring has slipped about 30 degrees. Is that outer number ring tight ? If you got a old damper just compare from where the key way is to the line marked for TDC.

on my 427, 454 and older 350. the keyway on the crank points straight up for number one to be at TDC

67Poncho · Uber Guru

Yes, the keyway will point just past the 12 o'clock position!

65sssd · Poncho Master!

I have the same problem with the 350 in my blue SD rag. It's out ruffly 30 degrees also. It isn't a fluke and doesn't hurt the motor. I just dialed my timing light to make that my base line TDC. The motor runs great. I might fix it when I have more time but I'm having too much fun driving it to work on it. Paul.

seventy2plus2 · Canadian Poncho Superstar!

I know 67rag396's original damper on his 396 had slipped, and at the POCI shows there is usually a guy selling 1 piece dampers as the Pontiac ones were known to slip.

cdnpont · Canadian Poncho Superstar!

I tried all I could to get the damper ring to move, It won't move even one iota. Even side to side...nothing, no play, nada. So I decided to try to pull the timing tape off and perhaps reset it back on to what I've found to be my best guess at TDC. So when I pull it off and ruin it, I see some faint marks on the damper...right where my pointer was positioned. Looks like somone else faced the same situation with this damper and struck new marks. So, I think I may just stick with this one, buy a piston stop, find TDC and apply a new tape. I think this damper is setup for timing marks at around 12 o'clock, likely from an engine with the timing cover like on the left in Carls post...or the maks indicate the slippage over time.

And could a damper have actually moved this far?

Cheers, Mark

seventy2plus2 · Canadian Poncho Superstar!

why don't you just put on a new damper?

cdnpont · Canadian Poncho Superstar!

I probably will do just that Clint. No worries about being out of balance. Just trying to figure it out the mystery.

JerryA · Addicted!

First thing you should do is find tdc #1. Use a piston stop, if you don't have one make one from a spark plug. Once you have tdc established you can go from there

cdnpont · Canadian Poncho Superstar!

All is well now. The damper that was on the engine was one that timed TDC around 12 o'clock. Replaced it with a Summit damper. Used a piston stop to determine TDC. It was actually slightly off the mark on the new damper. The crank keyway sits at around 1 o'clock for TDC.

New damper and tape, correct TDC position...

Old and new comparing keyways at 12 o'clock to TDC marks (green tape)..

Thanks for the help.

Cheers, Mark

seventy2plus2 · Canadian Poncho Superstar!

keep in mind when using a piston stop, you need to check it both ways (crank going clockwise and counter-clockwise). That's because as the crank rolls over the top with the piston at max height, there is a few degrees where the piston doesn't go up and down. Mark it going clockwise, then couter-clockwise, and TDC is between the two marks.

cdnpont · Canadian Poncho Superstar!

Yes, I did it both ways, thanks. Mind you, the only way to EXACTLY find TDC would be with the head off and a dial gauge. Cheers.

seventy2plus2 · Canadian Poncho Superstar!

cdnpont wrote:
Yes, I did it both ways, thanks. Mind you, the only way to EXACTLY find TDC would be with the head off and a dial gauge. Cheers.

Great, you know your stuff. I would have never thought about when the crank rolls over the top, but I saw it on a show one day.

koolconvertible · Poncho Master!

a cam degree wheel is very helpful when finding TDC. handy at build to degree in the cam too.....

davelacourse · Poncho Master!

cdnpont wrote:
Mind you, the only way to EXACTLY find TDC would be with the head off and a dial gauge.

Yep, that is how I did it - back and forth .010" deflection and determine dead center - thankfully the pointer on my Moroso unit (looks similar to the one you have on your motor, Mark) was adjustable to get it juuuuuuuuuuust right.

Dave

pontiax · Poncho Master!

[edit]The three most common locations for the timing mark on the damper

The exact years of the type of damper timing marks overlap one another, depending on the exact application.

The pre-1969 damper has the TDC line on the outer ring at the 2:30 oclock position- or 2º before the keyway centerline- i.e. the line is to the LEFT of the keyway, looking at the front of the damper or engine. The keyway is seen in the ID of the damper nose.
The damper used from 1969 to about 1984 has the TDC line at the 2 oclock position- or 10º before the keyway. You'll find that aftermarket dampers are the 10º type, as are the bolt-on tabs sold by the aftermarket, unless they're adjustable.
Note: This includes the SBC 400, although the 400 damper is counterweighted because the engine is externally balanced, and the 1985-present 4.3L V6 with its respective 6.75" damper (raised outer lip) that has both a 2 o'clock and a 4 o'clock position (for some vans eg. G-series, Express, and Astro/Safari). Do not mix and match internal and external balanced dampers!
A third timing mark was used from (some) 1978 to about 1995, and nearly all 1984-1995 (exc for 1985-present 4.3L V6 and van applications). It is at the 12 oclock position- or 40º before the keyway. This damper uses a timing cover that has the tab welded on at about the 12 o'clock position - the timing covers with this setup had either the 6.75" (305 and pre-1985 90 degree V6) or 8" (350/5.7 only). Professional Products lists the years for this type damper line as being 1984-1995 and is a 6-3/4 diameter damper.