440 vibration issue damper question

[G Force]

I have a 1971 440 engine that was rebuilt. It is not an original 6 pak engine but now has a 6 pak on it.
It has all the 6 pak internals (rods etc) and an internal balanced steel crank.

At 3200 RPM there is a minor steady vibration when in park (727)

When the engine was rebuilt,,, the oriiginal damper was sent to Damper dudes for a re-build.

Question--- Because I now realize it is probrably not a 6 pack damper ,, could this cause the vibration?

Note the flex plate and converter were replaced.

Thank for any help or insight

[charger50071]

Not sure, the six pack rods are heavier than stock so it could make a difference. I always use an after market dampener.  I had a machine shop balance one of my engines and I was chasing a vibration for over a year, turns out the idiot incorrectly balanced the crank. It does happen.

[G Force]

Yea,,  my engine builder ordered and  re-furbished and balanced Steel crank from an outsource company.
Problem is you don't find out till much later where the problems are.
I am chasing this vibration problem for 4 years.

[firefighter3931]

G force, it sounds like you have a mismatched combination. There is a specific balancer for forged crank 6 pack engines. It has a scalloped plate welded to the face which is apparent upon visual inspection.

If your converter/flexplate are designed for an internal balance then this will also cause vibration issues as well. B&M makes a flexplate for the forged crank/external balance (6-pack) engine when using a neutral balance torque converter. The Converter will be neutral balance if there are no weights welded onto it...you will have to check yours to be sure. The correct B&M plate for a neutral balance converter and forged crank 6-pack engine (external balance) is pn 10238

http://www.bmracing.com/index.php?id=products&sid=3&cat=7&subcat=20


Ron


* below is a pic of the correct 6-pack dampner ; notice the scalloped weight welded on 

[G Force]

Thanks for the reply Firefighter!

Just found out from my engine builder that
The engine was balanced with the harmonic balancer attached when we balanced the crankshaft.
So at this point does it matter if the Damper is a 6 pak style or not?
The converter has no weights on it and the only thing I know about the flesx plate is its SFI approved.
Where should I look next?
Appreciate the feedback.

[John_Kunkel]

A '70-'71 440HP originally had external weight on both the damper and the converter, if the engine was internally balanced with the existing damper it needs no further external weights.

[firefighter3931]

A '70-'71 440HP originally had external weight on both the damper and the converter, if the engine was internally balanced with the existing damper it needs no further external weights.

  you need a nutral balance converter and flexplate.

The converter has no weights on it and the only thing I know about the flesx plate is its SFI approved.
Where should I look next?

Ok so we know the converter is a neutral balance piece but the SFI flexplate is an unknown at this point. What brand of flexplate ? Part number ?

The B&M sfi plates come in several versions. The correct one for yours will look like a solid disc. The plate i linked to above has a cutout in it for the forged crank/external balance motor. Here's a pic to look at to compare....the middle one is what you should have for the internal balance. If you have the bottom plate then it is incorrect.


Ron

[RD]

JK and Ron are very correct, but also.. just to remember, no matter how balanced an engine is, at some rpm range there will be some type of vibration because you can never correctly balance an engine for all the rpm ranges, as well as have it maintain balance considering all the variables (engine parts, conditions, etc.) other than the actual rotating components that were balanced.

a stock 400 that i had would have a vibration in park at 2400 rpm, yet there was no such vibration at any other rpm.  dont know what it was, the damper, crank, and converter were all original to that engine. just my 2 pennies