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Username Post: Damper mark question        (Topic#349110)
Junkyardwarrior 
Contributor
Posts: 305

Loc: Yuma AZ
Reg: 02-25-15
01-10-18 01:16 PM - Post#2720698    

So, this is more of a deal for my own curiosity. I am wondering if the good ol 350 had multiple positions that a damper could be installed in. Not on a single engine, but if the crankshafts varied over the years or models. This is inspired by 2 engines of mine. One had a minor disagreement with a damper and launched it off the snout of my crank. That said, I was under the impression the engine was a 383 from the seller (fool me once) so I bought a 400 balancer with removable counter weight since I didn't know if it was internal or external balanced. I installed the balancer, and the timing seemed off as it spit through the pipes with much anger. I found TDC on one, noting that the 0 mark was about 16 degrees off. Fast forward, I got a new engine that was known to be a 350. After taking the old engine apart and measuring the stroke, I determined it to be a 350 as well. The shiny SFI damper from the old engine went on to the new one, and I timed the engine off of the 16 degree issue from before, and it launched fire through the carb. I went ahead and located TDC again, finding the mark to be dead on 0. This has caused my curiosity to say the least.

"8 cylinders of why the f&@% not" - me


 




raycow 
Honored Member
Posts: 27372
raycow
Loc: San Francisco, CA
Reg: 11-26-02
01-10-18 01:51 PM - Post#2720703    
    In response to Junkyardwarrior

AFAIK, the keyway is in the same position on all cranks. However the timing mark location on the damper (relative to the keyway) was changed at least once over the years and possibly twice. This is because the stationary pointer on the timing cover was relocated. I don't know the actual year(s) this change took place, but others here may be able to help you with that info.

If you are working with a used damper, there is also the possibility that the outer ring may slip or creep (relative to the keyway) because of failure of the rubber-to-metal bond.

Ray

Those who choose an automatic transmission want transportation. Those who choose a manual transmission want to drive.


 
Junkyardwarrior 
Contributor
Posts: 305

Loc: Yuma AZ
Reg: 02-25-15
01-10-18 02:58 PM - Post#2720705    
    In response to raycow

Yeah fun part is the thing was brand new, on the car for not even a year. Now it's been on the new engine for about 2 years and the timing never moves unless I tell it to. Both engines used the exact same bolt on pointer and even the same timing cover, yet they read different. I don't know, maybe it's an anomaly, but it got me thinking.

"8 cylinders of why the f&@% not" - me


 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17149
grumpyvette
Age: 70
Loc: FLORIDA USA
Reg: 03-16-01
01-10-18 04:16 PM - Post#2720706    
    In response to Junkyardwarrior

http://garage.grumpysperformance.com/index.php?thr...

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


 
Shepherd 
Frequent Contributor
Posts: 1255

Loc: Lake George, NY
Reg: 11-11-15
01-10-18 04:19 PM - Post#2720708    
    In response to Junkyardwarrior

I had a similar problem with a sbc, damper was new, same issue, used a piston stop in the spark plug hole to find absolute tdc, it was 16 degrees off. The damper was wrong for the timing cover fixed timing tab. Got the right damper and verified tdc again and the timing tab and damper were right on. Depending on what cover you have determines the damper, relative to the timing mark.






Edited by Shepherd on 01-10-18 04:20 PM. Reason for edit: No reason given.

 
Rick_L 
Honored Member
Posts: 27332
Rick_L
Loc: Katy, Tx, USA
Reg: 07-06-00
01-10-18 08:44 PM - Post#2720735    
    In response to Shepherd

Here's the lowdown on this.

The key on the crankshaft on all SBCs is lined up with top dead center.

All SBC engines 68 and older had a damper that had the TDC mark on it lined up with the keyway in the damper. And a timing mark tab on the engine to match. Most 68 and older engines had the timing mark tab welded to the timing cover but some late 60s engines had a bolt on tab.

Most SBC engines 69 and later had a damper that had the TDC mark on it 10° CCW from the keyway. Most if not all these engines had a bolt on timing tab to match.

A few 350 engines from the 70s maybe 80s had a damper that had the timing mark 30° CCW from the keyway. The timing tab was welded to the timing cover. To time the ignition required looking in the gap between the long water pump and the timing cover. This setup is not very common.

Getting all this right is a matter of using the correct timing tab with the damper you have. As you can see, you can be off by -10, +10, +20, or +30 degrees if the tab doesn't match the balancer.

If it's off by 16°, the timing tab is in the wrong place because someone messed that up with a home made timing tab.





 
65_Impala 
Very Senior Member
Posts: 4002

Reg: 12-29-02
01-11-18 07:21 PM - Post#2720824    
    In response to Rick_L

You've pretty much got it Rick, but didn't all engines post 1986 change to have the timing mark 30* CCW from the keyway on the balancer?



 
Junkyardwarrior 
Contributor
Posts: 305

Loc: Yuma AZ
Reg: 02-25-15
01-12-18 08:13 AM - Post#2720845    
    In response to 65_Impala

Not gonna lie, now I'm more confused than before. Not by you guys, the info is great. I just don't know how the 2 engines were off from each other by that much. All the same parts. Same pointer. Same balancer. Only difference was the crank. Huh.

"8 cylinders of why the f&@% not" - me


 
IgnitionMan 
Valued Contributor
Posts: 3303

Reg: 04-15-05
01-12-18 09:32 AM - Post#2720853    
    In response to Junkyardwarrior

I am working on an MSD Ready to Quit right now that is doing the same thing, times just fine, but when rotor phase is checked, firing end sits between cap terminals.

Of course, the magnet under the pickup is installed reversed, directly from MSD.

As far as the damper goes, I remember small blocks had at least 3 different diameters of dampers. And, there were 5 different bolt on timing scales. Very easy to get the right damper, but completely wrong timing scale.

To get the engine to backfire that bad, there has to be something past a slightly incorrect timing scale, like cam off time, valve(s) too tight, firing order off, or, what the RtQ here has, reversed magnetic pickup phase..



 
Junkyardwarrior 
Contributor
Posts: 305

Loc: Yuma AZ
Reg: 02-25-15
01-12-18 01:02 PM - Post#2720868    
    In response to IgnitionMan

I'm not gonna lie to you, the valve springs in that particular motor were not up to snuff with the cam that I had in it. Probably didn't help my case that's for sure. I was decelerating and the light went green. Got back on the throttle and she popped loud. That's when I did the TDC check. The dizzy wasn't the most... quality item either. but that still is odd to me. You could feel it in the motor when I started timing it based off the 16 degree setup vs when I assumed the mark correct. It's just weird that literally part for part, exact same ones, were wrong on that motor but correct on another. I don't mean I bought the same parts, I mean literally took them off of one motor and put them on the other.

"8 cylinders of why the f&@% not" - me


 




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