Crankshaft Pulley

[Kolbenfresser]

I'm rebuilding my 66 383 engine with a stroker Kit and new 440Source forged crank.
I have a new neutral balanced Balancer from 440 source as well.
I thought I could use my old OEM cast iron 3 groove pulley (only need two grooves), but I guess I'm wrong.

The original balancer had the one bolt hole indexed, so my old pulley does not line up one bolt with the new balancer.
I could enlarge that one hole in the pulley to make it fit, but now I think that pulley is maybe balanced with the old cast crank & balancer and it will throw off the balance of my neutral balanced stroker kit.
Do I have to buy a new pulley (steel pressed or billet) or is this one (picture) neutral balanced ?
It looks like a swiss chees with that many drill holes

Thank you for your help

 

[4spdragtop]

That's a lot of "holes" lol. The offset hole reminds me of the 70+ vs 69- sb holes.

 

[Lefty71]

A machinist would have to check the balance to know the answer for certain, but yes, you would think theres no way that pulley is neutral balance with that much material removed from only one side.

 

[Vaanth]

I'm rebuilding my 66 383 engine with a stroker Kit and new 440Source forged crank.
I have a new neutral balanced Balancer from 440 source as well.
I thought I could use my old OEM cast iron 3 groove pulley (only need two grooves), but I guess I'm wrong.

The original balancer had the one bolt hole indexed, so my old pulley does not line up one bolt with the new balancer.
I could enlarge that one hole in the pulley to make it fit, but now I think that pulley is maybe balanced with the old cast crank & balancer and it will throw off the balance of my neutral balanced stroker kit.
Do I have to buy a new pulley (steel pressed or billet) or is this one (picture) neutral balanced ?
It looks like a swiss chees with that many drill holes

Thank you for your help

View attachment 1716558744

View attachment 1716558745

View attachment 1716558746

The pictured pulley was made by Mapco for Chrysler. It is a cast iron pulley compared to the stamped/formed steel type. Mapco supplied both types of pulleys to Chrysler and other companies, including the aftermarket. The three groove cast iron pulley, Chrysler part number 2516370, was used on mid 1960s trucks with 383 for power steering, alternator and fan drive. The pulley might have been swapped onto your 1966 Chrysler 300 engine at some point in the past.

The Mapco part number of the pulley is C251. The name "Mapco" is usually cast with the part number on the pulley face, but the balancing drill points have removed it.

The pulley was independently balanced similar to harmonic balancers, or vibration dampers. Thus it is considered a neutral balance. Because it is cast iron, and not a high precision casting in the bell area, more material removal for balancing is not necessarily uncommon nor a problem.

The following images show another Mapco C251 pulley with balancing drill points on both sides:

The drill points on your pulley are likely original, but if in question, it should be checked to be sure.

All 1966 383 engines were internally balanced with a forged steel crankshaft. Unless changed, the crankshaft is not cast iron. The cast iron crankshaft was introduced in the 383 in 1970 and 1971 in some two barrel applications (ref. TSB 71-9-5).

Regarding the offset pulley mounting hole, 1964 - 1971 harmonic balancers and the lower pulley have an asymmetric pulley bolt pattern with one bolt offset (except the 361 and 413 heavy truck engines). This was changed in 1972 to be symmetric. Most aftermarket balancers, regardless of intended application have a symmetric pattern.

Elongating the hole in the pulley to match the balance is acceptable and any balance effect will be negligible.

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[CRUZE 418]

#4

 

[Kolbenfresser]

The pulley might have been swapped onto your 1966 Chrysler 300 engine at some point in the past.

Hello Vaanth,
Yes, this is possible.
My Chrysler is an original California Car (San Diego) with pollution air package, but it came with no factory aircondition.
Instead an aftermarket under the dash aircondition was installed. Maybe that was the cheaper option those days ?
With additional AC belt, a 3 groove pulley was required or came with the installation kit.

Thank you for that detailed information,
This is very helpful to me.

 

[oldkimmer]

440 source will have the pulley u need. Show some pics of your top pulley. Kim

 

[cudamark]

If you're not going to use the aftermarket A/C, I'd replace that pulley with a factory non-A/C one, or a light weight aftermarket one.

 

[Kolbenfresser]

I've enlarged the offset hole and will use the 3 groove die cast pully.
I know it has the grooves in the right position and the right diameter for my belts...