Balancers and timing tabs...

[bigwheel15]

Ok so ive been playing around with getting my timing just right and have been trying to figure out why I couldnt get it timed down right as to get it running decent it would be way off the timing tab. I have a 6 3/4 inch balancer on currently with a timing cover that has the tab off to the drivers side. So what im thinking is I have the wrong balancer for the cover im running, is this correct? I have an 8 inch balancer to swap over if this is the one im supposed to be running with my timing chain cover.

Any help is appreciated guys!

[68gmsee]

If the engine is running okay and not vibrating, keep the one you have. Just check for exact TDC on the compression stroke for number 1 piston and see if it matches the tab. If it doesn't, scribe or mark it with paint or a marker. Of you can get a balancer timing tape.

http://www.amazon.com/Mr-Gasket-1591-Timing-Tape/d...

[GASoline71]

If it is the original balancer, there is a chance that the inertia ring (outer ring) has slipped on the hub. The rubber between the two can rot and let oil in there and it will slip over time. So the mark will just keep moving and moving.

Gary

[chengny]

Diameter of the balancer is not the issue.

And, although it's possible, failure of the flexible damper (the rubber coupling) is unlikely. It is bonded with strong adhesive at the factory to both the outer mass and inner hub.

If the bond between the three components of the balancer does fail, an index shift between the crankshaft and timing mark can occur. But (even though it's become conventional wisdom and is commonly blamed) it rarely happens.

More likely it's a parts specification problem. Often, a post-1976 balancer will be mounted on an engine with a pre-76 timing chain cover. The timing mark on a 76+ balancer is not compatible with the location of the timing tab on a pre-76 chain cover. In 1976 GM moved the slot on the balancer - CCW about 12 degrees.

Before the shift, when #1 cylinder fired and the distributor was properly timed, the balancer mark was at around 2 o'clock.

When post 76 SBC's are timed correctly, the balancer mark will be at about 12 o'clock when #1 fires.


Here are some images to help explain.

This shows a late model balancer on an engine with an early timing cover (what I'm guessing is your situation). The drawn-in arrow points to the hub keyway on one end and to where the timing mark would be on an early SBC. The actual mark is what you would find on a post 76 balancer:



A 1986 350 with stock balancer and timing cover/tab:



An aftermarket balancer with dual timing marks:



So anyway: if you want to time the engine using a timing light, you can either change the balancer or TC cover so that they are compatible. I'd just use the timing light and shoot the timing up around 12 o'clock (that's about 10 BTDC). It should be at least driveable if not quite factory spec at that point. Then, if you want, you can dial it in. Use the "hit ping under heavy load & retard a ****hair" method.


Note: the dates and degrees cited above may not be accurate.

[GASoline71]

Originally Posted by chengny

And, although it's possible, failure of the flexible damper (the rubber coupling) is unlikely. It is bonded with strong adhesive at the factory to both the outer mass and inner hub.

If the bond between the three components of the balancer does fail, an index shift between the crankshaft and timing mark can occur. But (even though it's become conventional wisdom and is commonly blamed) it rarely happens.

Seen it on at least a half dozen balancers over the last 35 years... I rarely if ever... reuse a stock balancer anymore.

Gary

[SkeksisNV]

Originally Posted by GASoline71

Seen it on at least a half dozen balancers over the last 35 years... I rarely if ever... reuse a stock balancer anymore.

Gary

I have seen it slip on mine before also. The outer ring had actually shifted aft and started to wear into my timing cover.

[chengny]

I guess frequency of that type of failure is subjective. I only meant that it wouldn't be the first thing I'd suspect.

Re-up of the deleted image:

[bigwheel15]

Originally Posted by chengny

I guess frequency of that type of failure is subjective. I only meant that it wouldn't be the first thing I'd suspect.

Re-up of the deleted image:

Thanks again for all the responses guys, and yes this picture shows exactly what my situation is. Would anyone know the distance or how I could find out the distance from the original mark to where the new mark was made? I could then measure and mark my current balancer and go from there.

[68gmsee]

Originally Posted by bigwheel15

Thanks again for all the responses guys, and yes this picture shows exactly what my situation is. Would anyone know the distance or how I could find out the distance from the original mark to where the new mark was made? I could then measure and mark my current balancer and go from there.

I wouldn't try to overanalyze the problem. I recommend doing what I mentioned in my post above.

Just find exact TDC in the compression stroke and it's as simple as getting a timing tape or scribing lightly with a metal tool. I did that on my 69 and I used a piece of hack saw blade and then painted the mark.

The way I find TDC is to remove the #1 spark plug, remove the coil or ignition wire, have someone click the starter (I use a remote starter switch) and when you start to feel compression, stop. Now you can disconnect the battery terminal, install a socket on the crankshaft pulley and slowly continue turning the engine by hand (easier if all the plugs removed). With a long wooden dowl or similar tool inserted in the spark plug hole, feel the piston as it reaches the top. You are now at TDC and the tab "0" mark or TDC is where the harmonic balancer scribe or mark should be.

[HarleyHogRider]

I found I have been having the same problem fluidampr's timimg marks for years. Thankyou to 05-04-2012 10:30 PM chengny's post. I actually got a hold of a Nick Orefice Ph. (716) 592-1000 | www.vibratechtvd.com| www.fluidampr.com Performance & Heavy Duty Dampers Made in the U.S.A.

Who says "Pre 69 the timing marks are off 10 degrees".

But I am hanging on to this info you posted a few years ago:

In 1976 GM moved the location of the timing tab on the 350 about 12 degrees CCW.

Prior to 76 the tab was at about the 2 o'clock position. Starting in 76 model year the tab was moved to the 12 o'clock position (behind the water pump).

Pre 1976 the keyway and the outer mark lined up. After 76 the timing mark is 12 degrees CCW out of alignment with the center line of the keyway…..
Before when #1 cylinder fired and the distributor was properly timed, the balancer mark was at around 2 o'clock.

When post 76 SBC's are timed correctly, the balancer mark will be at about 12 o'clock when #1 fires.

Now back to wrenching on it!

[LS short box]

The best way to find true TDC is buying or building a piston stop for #1 cylinder. Take all the spark plugs out and rotate the engine over by hand until the #1 piston is stopped by the piston stop. Then mark the the balancer at the 0 degree on the timing tab. Then rotate the engine the opposite direction until it stops. Again mark the balancer. Between the those two marks on the balancer will be true TDC.

[HarleyHogRider]

The use of a piston stop for finding true TDC works great unless you are using angled plug heads. At least it doesn't work on mine as I already tried that and they are ProMaxx Performance 2168 Patriot Performance SB-Chevy Aluminum Freedom Series Heads. the stop just won't seem to stop the piston in either direction. So I am going to use an MSD Timing Tape and apply it to the Fluidampr using the info a previously posted. Hoping the 10 degree difference info I got from Nick Orefice at Fluidampr will help. He is going to run all this information up the management chain to see if he can get this corrected for those earlier engine timing marks to be corrected.

[AcampoDave]

Originally Posted by SkeksisNV

I have seen it slip on mine before also. The outer ring had actually shifted aft and started to wear into my timing cover.

I once saw one fly out from under an old Econoline van and go bouncing across several lanes of traffic. Ir could of been the whole thing hub and all, not sure but wow, fortunately it missed everybody.

[HarleyHogRider]

I have used a Fluidampr since about 96 with zero problems except for the timing mark issues previously mentioned.

When I advised the Fluidampr folks of the timing mark issue they were very appreciative of the feedback. "We are 100% sourced and made in the USA. We are a small family owned business, with a staff of about 100 total. We do appreciate your information and taking the time to let us know of this error. Thank you and again sorry for the lack of information on the early SBC."

[LS short box]

Didn't know about the angled plug thing. I wonder if you put an extension on the end of the piston stop would help?

[HarleyHogRider]

I didn't try a longer bolt in the spark style piston stop but due to the angle I don't think it would matter.

My Dampnr didn't come with instructions but I hunted some down online and in it they offer this information:
"Check the ignition timing marks. Some engines have been equipped with different timing tabs over the years. The engine's tab may not be positioned the same as the one for which Fluidampr is designed.
 Use the positive stop method to locate true Top Dead Center (TDC). Remark or relocate the timing tab as required.
 Finding TDC -Top Dead Center may be found by installing a positive stop on top of the block (if the heads haven't been installed) or by threading a positive stop into the number one spark plug hole. Adjust the stop so that it contacts the piston at 15 to 30 before TDC. Mount a degree wheel to the damper and install a pointer on the block. Carefully rotate the crankshaft by hand clockwise until the piston contacts the stop. Be careful as the position approaches TDC-what you want is positive stop, not a hole in the piston. Note the reading on the degree wheel. Then rotate the crankshaft counterclockwise until the piston once again contacts the stop and note the reading again. TDC is located exactly halfway between the two readings (within the area the engine did not rotate). Adjust the pointer as required. If you don't have a degree wheel, mark the damper next to the timing pointer "0" mark at each positive stop. Then divide the distance in half. That is TDC."

My feedback to them was that if they advertise it to fit the earlier years it should fit right out of the box and the customer should not have to redo the timing marks that should have been in the correct place to start with and then have to go through trying to find TDC especially after the heads are on and you only find out about the problem after you have fired the motor and tried to time it. I just hope that with all the info I gave them that they will make some changes because I personally like their product.