: 67 Cadillac Eldorado 429 to a 425

03-09-11, 10:42 AM
I have a 67 Eldorado, the Motor is ok, but will cost a lot to buy a new/rebuilt motor. I found a 425 rebuilt motor, would this fit into my car? would this be a mistake to swap it to the 425? The 425 is still a 7.0, but the 429 does not have any upgrade parts for it, I put Fuel injection on it and it runs better, but I want to make it more of a pleasure to drive with easier parts to find. Anyone have any thoughts? I know some of you will think I am crazy to want to do this, but the 429 is so hard to find parts for and mostly year specific , Please help with ideas if it will drop in and can I use my Original Transmission.

03-10-11, 09:14 AM
From other posts here, the 429 and the 425 did not share the same transmission mounting pattern, so you will need a TH400 or an adaptor to put that 425 in your car. You will find that there are few options for your 425 engine either, except carburetor / fuel injection.

03-12-11, 12:10 AM
My experience is, redrilling 2 trans hole for the engine bolts will let the 425 BOP engine bolt to the 67 trans, no adapter plate. You'll need the right oil pan, exhaust manifolds, misc. Bruce Roe CLC # 14630