# 67 400 Harmonic Balancer Questions



## Sick467 (Oct 29, 2019)

My original harmonic balancer is beyond due for replacement and it measures 5-3/4" outer diameter. I have read that the 67 and earlier models were this 5-3/4", but Ames sells one (#N585 @ $229.oo) that is 5-1/2". * Is this a concern?*

Butler sells one too (#AAC-630155 @ $180.oo). They don't give a diameter. Here's their description....

59-67 Pontiac 6-Bolt Performance Damper 2-Piece Assembly (Has Stock Timing Marks Only), Hone to Fit

"Hone to Fit" - *What's that all about?*

Anyhow, I guess this is one of those parts that is not an quick and easy buy due to my lack of knowledge on the subject and the sellers information being odd.

I'm open to suggestions on what balancer to buy. My engine build goal is to land around 400 to 450 HP.


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## PontiacJim (Dec 29, 2012)

Sick467 said:


> My original harmonic balancer is beyond due for replacement and it measures 5-3/4" outer diameter. I have read that the 67 and earlier models were this 5-3/4", but Ames sells one (#N585 @ $229.oo) that is 5-1/2". * Is this a concern?*
> 
> Butler sells one too (#AAC-630155 @ $180.oo). They don't give a diameter. Here's their description....
> 
> ...


1964-67 6-bolt is 5 1/4" diameter. 1968 and up 4-bolt is 6 3/4". 

Don't see any aftermarket 5 1/4" dia. replacements - all are 5 1/2". I don't see a problem and no one has complained about them not fitting. Will it change the "true" timing marks? Not sure, but if concerned or want to simply verify any differences, 

Here is what I found showing the differences. No timing tapes for a 5.5" Dia. balancer, just 5.25". You can use an online timing tape that you can print out using the 5.5" diameter. You will have to find TDC of your engine so you can place the timing tape/mark on the place where your timing scale on the timing cover shows "0". 

Balancer Diameter - Circumfrence Length of Timing Tape

5.2500 - - 16.493
5.5000 - - 17.279

Balancer Dia. - Spacing apart of each degree starting at the "0" TDC mark on the tape.

5.2500 - - 0.045815
5.5000 - - 0.047997 

Personally, .002" difference in timing mark scale is probably not much to be concerned about - the engine and its rotating parts are not that exact nor have tolerances that close. 10 degrees @ .045815 = .45815. 10 degrees @ .047997 = .47997. The difference between 5.25" and 5.5" and 10 degrees on the balancer is .02182", .02" is 1/50 of an inch, more than 1/64" and less than 1/32". I can't even see 1/50th of an inch on my ruler at my age.


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## Sick467 (Oct 29, 2019)

Thanks Jim, very helpful as usual. Just to be clear, I was measuring the part of the balancer on the right of the photo below, but the part to the left measures the 5-1/4" that you mention.










There just over an 1/8" between the part on the left and the timing tab. The 5-1/2" balancers will fit, but it will be close.


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## RMTZ67 (Mar 12, 2011)

I bought mine from butler. 1/8 gap. Timing mark didn't line up, hence the timing tape.


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