Do I have the right harmonic balancer?

[340MPR]

Hi guys I'm after some help on the harmonic balancer that my father in law had on his parts shelf, I know that he picked it up with the intent of putting it in his 69' 340 but looking up the part number I'm not sure if it's right. It's a Powerbond PB1004N, PowerBond PB1004N PowerBond Premium OEM Replacement Harmonic Balancers | Summit Racing and looking it up it's for a 72-73 340. I know that the timing mark will be out 90* which I can re-mark easy enough, I checked and the holes line up with the pulley so no problems there but is the balance of the piece itself correct? I'm using this on a fresh 69' 340 with forged crank, I appreciate the help thanks guys.

Mike N.

 

[moparmat2000]

I think 72-73 340s were cast crank engines. Not sure if those are internally or externally balanced

 

[Locomotion]

The Summit link/ad is confusing. It says it's for "internal" balanced cranks. But under the main headline it shows 318/340/360. The later 340s and all 360s are all OEM externally balanced. So while it would "fit", it would be be incorrectly balanced for later OEM 340 & 360s, which have cast cranks.

For your application, if that balancer doesn't have any extra metal cast or bolted into one side of it, than it would be correct for an OEM 318 or forged crank 340. You are correct that you'd need to move the TDC mark if you have the corresponding older timing cover, or use a newer cover and leave the mark alone. They probably left out all 1971 & earlier applications because of the timing mark change. Although I think the timing mark was relocated in '70 or '71.

If there is still any uncertainty, call Summit or buy a different brand that provides clearer, more accurate info.

There was a small block pulley bolt hole change which involved one hole that was offset, but I don't recall when that occurred.

 

[moparmat2000]

Summit racing brand makes I believe the same balancer for 318, 340, 360. The only difference in their neutral balance one, and their external balance one is a bolt on weight that the 360 one comes with. That being said, everything I put together I have my machinest internally balance so i dont have to deal with external weights on everything and drivetrain vibration issues as a result of incorrect weighting. See pix. Get with summit on which balancer and weight to use. I have a summit 318 neutral balance damper I will use on my 408 with a neutral balance crankshaft.

 

[pishta]

If it says for internally balanced crankshafts, its correct...CID be damned as we all know you can internally balance any crankshaft with the proper added weights. It would be up to end used to find and mark correct TDC for what tab he is using.

 

[SGBARRACUDA]

That is the one i used on my 416.

 

[340MPR]

Yes my crank is internally balanced and there are no weights on the PB balancer so it sounds like it will work. I don’t have enough knowledge on the changes that happened over the years and worried that maybe the weight or factory balance of the harmonic balancer’s changed over the years as well. Sounds like any balancer for an internally balanced crank will work?
Mike N.

 

[pishta]

yes if the balancer says "for internally balanced" that means the damper is neutral (ie. in balance to itself) so it would not add any balance to the crank. same as a flexplate or a flywheel, they are all neutral balanced ( in balance) so if you add a bunch of 0 balance parts, flexplate, flywheel, damper...you still got a 0 added balance to the crank. This made assembling motors easier as everything past the crank was the same 0 balance. the cast 340 and 360 were spun up on a balancer when assembled (Detroit balanced) and the balance was obtained in the damper that would also be considered a balancer on these cast crank motors.

 

[cudamark]

Yes, it should fit your application as far as balance goes. As you know, the timing mark is in a different spot. That changed in the '70 model year. '69 and earlier have the timing indicator on the passenger side. '70 and newer changed over to the driver's side. I'd use a piston stop to verify where TDC is and remark the new balancer accordingly. I'd also double check the pulley bolt pattern. The transition from 1971 to 1972 saw a change in that pattern. It's minor, but, you want to make any changes with the parts on the bench and not having to pull parts off again. '71 and earlier had one offset bolt in the balancer and pulley, so, it would only go on one way. In '72 both balancer and pulley had equally spaced bolts, so, the pulley could mount any of 6 ways. To convert either balancer or pulley to it's opposite requires you to oblong one of the pulley holes. A rat tail file will usually do the trick to make a round hole into a slot.

 

[340MPR]

Thanks for the help guys, I double checked the pulley and yes the holes line up with the balancer and re-marking the timing mark is an easy fix. I also looked a bit further and found the part on Dayco’s website and confirmed it’s a neutral balance.
Thanks! Mike N.