# Engine change/compatibility

**URL:** <https://community.cartalk.com/t/engine-change-compatibility/27067>\
**Category:** Maintenance/Repairs\
**Created:** [February 27, 2009, 9:15pm UTC](https://community.cartalk.com/t/engine-change-compatibility/27067 "2009-02-27T21:15:27Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![dollek](https://avatars.discourse-cdn.com/v4/letter/d/76d3ee/32.png) [@dollek](https://community.cartalk.com/u/dollek)\
**Post date:** [February 27, 2009, 9:15pm UTC](https://community.cartalk.com/t/engine-change-compatibility/27067/1 "2009-02-27T21:15:27Z")

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I have a 1984 Caddy coup de ville. The 4100 engine is on its way. I want to know what is compatible as a drop in.  
  
 4500?, Northstar? 350ci of some sort???  
  
 Thanks in advance

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**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\
**Post date:** [February 27, 2009, 10:00pm UTC](https://community.cartalk.com/t/engine-change-compatibility/27067/2 "2009-02-27T22:00:48Z")

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I’m guessing the 4500 and 4900 will swap, it’s the same block. You might call a parts recycler (AKA junkyard), they have interchange catalogs that might help. I doubt the Northstar would be a drop-in.

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**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\
**Post date:** [February 28, 2009, 3:37am UTC](https://community.cartalk.com/t/engine-change-compatibility/27067/3 "2009-02-28T03:37:50Z")

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I believe that the 350 was an optional engine that year, or years close to it with the same body style. The 4100 wasn’t a good seller so Caddy began to offer the Chevy engine as a more powerful option.