Ok i bought a new Harmonic balancer, and I am having a few problems:

1. They are different sizes, the diameters are both 6 3/4in. but the thickness of the outer ring is different, fig 1.
New:1 5/8in. Old: 1 3/16

2. BTDC marking in relation to the key way on the crankshaft is different, fig 1. according to the timing marks on the new one, the marks are 30 degrees apart, fig 1.

ok heres my questions,
1. Is it possible for the outer ring to have moved on the old one?
(the elastomer ring is sticking out bout 1/8 inch)

2.before i took the motor out, it ran good, and i had replaced the distributor 2months ago,and the timing and everything was ok, i set it using the marks on the old balancer


misc. info :
they are the same length on the hub that slips over the crank snout, fig 2. The thickness of the outside ring doesnt really bother me as much, because the old one is a solid outer ring, and the new one is a hollowback one, fig 3. also both dampers weigh the same.
Before i took the motor out, it ran good, and i had replaced the distributor 2months ago,and the timing and everything was ok, i set it using the marks on the old balancer
I am rebuilding the motor, it has 140k miles on it,

 

Yes the balancer does slip.

 

It is possible that the outer ring slipped on the old balancer. It is also possible that your new balancer is for different application. Over the years GM has had different timing tab locations and corresponding balancers.

Its best to locate tdc on #1 piston to verify the accuracy of the timing tab to balancer.

 

what you have is a balancer for a 350. the 305 timing mark is at 12:00 and the 350's are at 1:00. same size just different timing mark positions.

 

i thought the same thing however a 350 balancer is 8 inches while both of these are 6 3/4 inches

i work at a parts store, and i checked the computer and the book both said the same part number (ch305-2n) for my application, and the new one is different so i ordered another one cause i think this one may either have been assembled wrong or boxed wrong.

 

the older 350's ('67-'69) had the 8" balancer. check the books again. go to www.fluidampr.com and you'll see their are three different balancers for the 350's. i used to run a super shops before they closed down.

 

on fluiddampers site they list a 6 3/4 for internal and externally balanced small blocks, they dont list anything about the timing tab locations,
Thanks for your responses they have proven very helpful, but i think i will have a better idea when the second one comes in.

if you think of anything else let me know

 

like i said in the first post. the aftermarket doesn't list them for 305's. just for small block chevy. i sent you there because you said the computers at work listed 8" balancers for 350's. for some reason, GM made the balancers for the 305's at 12:00. when the second one comes in, it will be the same.

 

The first balancer I repalced for my 78 350, I order a balancer for a 305 and that did not solve my vibration so I orderd another one from a different auto parts store and was able to get one for a 350 and the timing mark was in a different postion

 

It has everything to do with application. The diameters are consistent, but that's about it. The thickness, mark location, etc. can all change, depending.

I put a '94 Caprice crate engine in my car. It had a much thicker damper and the mark was in a different place. On my car, the damper has to be thin in order to clear the oil cooler lines. Also, you can't see the timing marks if they're up around 12:00 on a TPI car. On a TB car, the timing marks can be on top. I had to use my old damper (and timing chain cover) on the new engine.