[jimib]

I need to buy timing tape (and a modern timing light) to accurately time my rebuild. The research I’ve done on harmonic balancer size is inconsistent. I have a stock (original) balancer on my engine (400). The MSD part #8985 appears to be a favorable choice on Summit. Anyone know the size? Any benefit to upgrading the balancer? This is just a street car.

[b-man]

The 1967 and earlier balancers are 5.75" in diameter.

Do yourself a favor and replace it with a new one, any 40+ year-old balancer even if it looks great is going to fail before long.

[jimib]

Thank you b-man. It doesn’t seem like a part that can go bad but I guess it does. The part in the picture is what I checked out on the Butler Performance web page; I bought many parts from them.

[b-man]

The rubber loses its bond after a number years is the problem. I spoke directly with the manufacturer and he said the bond is really only reliable for about 6 or 7 years.

Not exactly sure if that's true, but it's definitely food for thought.

[jimib]

Originally Posted by b-man

The rubber loses its bond after a number years is the problem. I spoke directly with the manufacturer and he said the bond is really only reliable for about 6 or 7 years.

Not exactly sure if that's true, but it's definitely food for thought.

WOW, maybe this is why my rebuild (on the run stand) randomly vibrates?

[b-man]

No matter what, any new rebuild deserves a new balancer. They really almost never look worn out, but most of them are.

The one pictured above is going on my new 1964 421 HO build, everything will be new including this one part that many of us tend to overlook at rebuild time.

[jimib]

Originally Posted by b-man

No matter what, any new rebuild deserves a new balancer. They really almost never look worn out, but most of them are.

The one pictured above is going on my new 1964 421 HO build, everything will be new including this one part that many of us tend to overlook at rebuild time.

This is my 2nd rebuild on this motor and the 2nd time I overlooked this part. Thanks for the excellent info.

[67GTONUT]

Ugh..... Pretty sure mine is original also..... Looks like I am calling Butler this week also....

[b-man]

Bonus: The seal will also have a new surface to ride on with the new hub supplied along with the balancer.

[Zooguy]

Originally Posted by b-man

The 1967 and earlier balancers are 5.75" in diameter.

Do yourself a favor and replace it with a new one, any 40+ year-old balancer even if it looks great is going to fail before long.

Just making sure i am understanding right .... My 1966 389 SHOULD have a 5.75” balancer so i would get a 5.75" timing tape for the balancer and line up the tape with the mark on it

[ftwmlp]

Originally Posted by b-man

The 1967 and earlier balancers are 5.75" in diameter.

Do yourself a favor and replace it with a new one, any 40+ year-old balancer even if it looks great is going to fail before long.

I gratefully followed b-man's excellent advice when installing my rebuilt 66 389 a couple of years ago. However, the balancer I took off, I firmly believe is 5.25" diameter. For Zooguy, at the time I could not find a timing tape offered for that diameter. The one I replaced it with (same part number from Butler) was supposed to be the same diameter (in my head).

[b-man]

Wrap a piece of masking tape around the hub.

Measure the circumference (length of your masking tape) and divide that by 3.1416.

The hub with the timing marks on it is what you want to measure. The balancer is bolted to the hub and its larger in diameter than the hub it’s bolted to.

[242177P]

Tape? Tape?!? Dial-back timing lights don't need no steenkin' tape...

[lust4speed]

Old post, but what the hey...

The bad news: Over the years I drag raced my '67 I had three stock balancers loose the rubber.

The good news: The cast ring is still held on because of the flared cup shape of the inner hub.

Always knew when they failed because I'd shut off the engine and the ring would continue spinning for a couple of seconds. Back then no one carried new assemblies so we'd just grab another one off a pick-a-part car -- but old is old, and they were all on their way out. Nice that new balancer assemblies are available.