Harmonic damper/crank pulley-Interchangeable parts issue or manufacture defect?

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polarman

polarman

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Alright folks, here we go with silly questions from polarman again. So I installed the harmonic damper on my new BPC4083CT engine the other day. I pulled the crank pulley from the old 318 and took it to work to paint it up. I got home to install it, and no matter how I clock it, all 6 bolt holes will not line up. In some positions, 4 holes will line up, and in other positions 5 holes will line up. The harmonic damper is a Powerforce with the appropriate weight for the externally balanced 360 that the engine builder recommends (this particular damper was recommended by Summit over the phone). So my questions are- is this a parts compatibility issue that I overlooked, or is it a manufacturer defect and they missed the mark on one of the holes in the harmonic damper? An easy fix would be to elongate one hole in the pulley, but I wonder if that would negatively affect the balance of the rotating assembly. Please quell my curiosity and let me know what you think. Pics to follow momentarily...
 
polarman said:
Alright folks, here we go with silly questions from polarman again. So I installed the harmonic damper on my new BPC4083CT engine the other day. I pulled the crank pulley from the old 318 and took it to work to paint it up. I got home to install it, and no matter how I clock it, all 6 bolt holes will not line up. In some positions, 4 holes will line up, and in other positions 5 holes will line up. The harmonic damper is a Powerforce with the appropriate weight for the externally balanced 360 that the engine builder recommends (this particular damper was recommended by Summit over the phone). So my questions are- is this a parts compatibility issue that I overlooked, or is it a manufacturer defect and they missed the mark on one of the holes in the harmonic damper? An easy fix would be to elongate one hole in the pulley, but I wonder if that would negatively affect the balance of the rotating assembly. Please quell my curiosity and let me know what you think. Pics to follow momentarily...
Click to expand...

KIMG0354.JPG
 
Same issue with my 318 in my d200, my pulley was a pre '70 which had an offset hole. I ended up finding a post '70 pulley at a local swap meet and the holes all lined up. Problem solved.
 
You are overthinking this. At some point the bolt pattern changed. Line up the ones that line up, and oblong the other one. The End
 
Yep, 2 choices, slightly modify or get correct one. You could trade yours for correct one if you want also.
polarman said:
The car was originally built by a friend of mine with various parts and pieces. The pulley is likely from a '68 318 or 273.
Click to expand...
 
Elongate that hole that will not align. Done it several times, there is no change to the balance. The pulley isn't balanced, or un-balanced. I sure would like to know why they did that though!
 
4spdragtop said:
You could oblong one hole slightly. I dont think it would affect anything.
Click to expand...

This is the way March bottom pulleys come, on the big blocks anyway, so they fit 'em all early or late. Pretty sure all pulleys are neutral balance, although it does make you wonder why they ever needed the offset hole in the first place.
 
The way bigger pain is the one offset hole on the torque converter/flex plate interface. What was the reason? All the engines were internal balanced with neutral balanced converters until 1970 or so, but everything had that one hole out of wack.
 
Oblong the hole, I did and Have had no issues. Actually when using a March pulley just make sure to use a flat washer on the oblong hole. Gives the shoulder of the bolt more support
.
 
I used a BBC blower drive kit on my 354 Hemi...had to oblong one hole.
 
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