ATI Dampener Degrees (was Dumb Question number 455)

[DuckRyder]

Im coming up with more like 17.5 degrees off vs the generally accepted about 7 degrees...

Can that be right? I don't see how i could mess this up but i seem to have an above average capacity for that recently...



Thanks Brent for pushing me to actually check it.

[blykins]

Adjustable pointer?  I've never seen one 17° off. 

Can you outline your procedure for checking where TDC is?

[DuckRyder]

Adjustable pointer?  I've never seen one 17° off. 

Can you outline your procedure for checking where TDC is?

Factory pointer from 1972 Truck. ( think you sent me an adjustable one, have to look.. but it definatly is not on the truck. )

I set it at 30 before on the compression stroke of number one... put piston stop in and turned it clockwise until it stopped and maked the first mark (i just used the edge of the pointer) so we can give them credit for a sharpie width)

Turned it counter clockwise until it stopped again - marked second mark again using the edge of the pointer.

Measured distance between two marks and placed mark halfway between at 0.



Added photo of pointer.

Also note there is a picture in prior post, they are taking a minute to load for me.

[blykins]

Are the hub/shell indexed correctly?

[DuckRyder]

I want to say it came assembled, but i'll have to pull the pulleys off and check i guess.

[cjshaker]

I've used 2 ATI balancers, and both were exactly 7* off, as seems to be the case with everyone who uses them (because they're actually made for BBC engines, IIRC). Your TDC method seems sound, and even giving a little leeway for chain slack, that number definitely seems to be off. Do you have a stock balancer to throw on to compare to?

[CaptCobrajet]

95% chance that TDC is at 353 on an ATI if you just bolt a stock pointer  on a stock timing cover.  Best to check for sure as others have said.   That being said, the answer to your question is your 36 you want will most likely be at 29 if you don't adjust it.

[DuckRyder]

I've used 2 ATI balancers, and both were exactly 7* off, as seems to be the case with everyone who uses them (because they're actually made for BBC engines, IIRC). Your TDC method seems sound, and even giving a little leeway for chain slack, that number definitely seems to be off. Do you have a stock balancer to throw on to compare to?

That seems more inline with what I remember that I saw when I checked before putting the heads on with a degree wheel. TDC landed somewhere in the aTi Logo.

I don't have a stock balancer on hand, but i do have a Powerbond. It appears the keyway is straight down at TDC or about 225 degrees. so if i put my keyway straight down i come up with TDC in the aTi Logo and the keyway seems to be at slightly less than 220 (218?) on the balancer.

Which if my math is right coincides with the 7 degrees we think it "should be".

I guess the question is how did I mess the numbers up with the piston stop?

95% chance that TDC is at 353 on an ATI if you just bolt a stock pointer  on a stock timing cover.  Best to check for sure as others have said.   That being said, the answer to your question is your 36 you want will most likely be at 29 if you don't adjust it.

Thank You

I think i'm going mark it as 353 = 0 and see how it runs.

I don't want to just throw the powerbond on because i think the spacer was shortened for the ATi and it is probably a better balancer anyway, degree marking not withstanding.

[My427stang]

Your procedure sounds good, the only thing I don't like is one side being dictated by screwing the stop in.

Now that it's together, bring the piston down, tighten the stop in a little bit more, and recreate your test by turning the engine one way until it stops, then the other.

I assume you may have already did that, but the way it was written concerns be that one side of it may be off.

The next thing would be to pull the balancer and see if the numbers come together with the new balancer., if you are still off it's likely you. 

One last comment, I see no benefit for that ATI for your application, if the second balancer lined up, I'd be done

[DuckRyder]

Thanks everyone:

I did it again and came up with 7 degrees.

I'm fairly confident in conjunction with the checking i did on the keyway that this is right, but cant explain why it came up different (i did it essentially the same way aside from starting earlier.)

<shrug>

Another picture: