Whats the chance a '66 429 would fit into a '64 with Turbo Hydromatic?

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Not a clean drop in engine swap due to a frame change in 65 —-67  that makes that swap a big job and complicated to be doing to keep the explanation simple ( much additional labor and parts )  

Best Always to rebuild —-the one year —64 429 engine you now have for best results and having the car stay with the stock engine it came with for value purposes 

The 64 429 engine is not like any other 429 in other years for a list of differences reason that would make that job a difficult swap to be doing into a 64 Cadillac 


Yea I figured as much, however mine has more freeze cracks than a Minnesota lake. Been looking for one in the Pacific Northwest (98382).

Thank You for the response.

You could use the engine block from the 66 engine and all the other parts from your  64 engine to put together a new engine that will work in your 64 

Motor mounts and some other odds and ends  will be in a different location due to the frame change in 66 but should be workable 

You will have a second set of heads power steering and possibly other parts left over and usable  to keep or sell to offset you expense 

Everything from the heads up and the front engine cover of your 64 engine can be put on the 66 short block —if it’s your short block that is damaged 

You will have the correct crankshaft  in the 66 short block for that trans ( very important ) as it came out of a car with the turbo trans in it 

You of coarse will be rebuilding all parts going into the new engine 

This may be the way of the future when the 64 stock engine is getting impossible to be rebuilding or replacing 

I do think about this stuff — way to much —- LOL !!


The engine will not be the stock engine from the factory due to its new engine block number but just viewing the engine in the engine bay it will look like the stock engine except for the motor mounts which are not visible unless you inspect under the engine 

This may be a very good option the more I think about the future of keeping our Antique Classic Cadillacs rolling down the road 

She’s so fine who knows where the money went — applies here !!! 


Pls disregard the above post 




the 66 has a different transmission completely, a 66 block will not mate up with a 64 transmission, with or without the adaptor plate.  So to try to install a 66 block to a 64, it would have to go in with a 65-up transmission, and the motor mounts and trans mounts won't line up.  Really it's easier to put a chevy engine in there once you go through that, because interchange parts are more readily available.

Hey Mark 

Very good point about the trans that I did overlook and that is why I am glad you are always on here to give great advice when and  if  I go astray ( which is not to often )

Looks like rebuilding the stock 64 engine in front of the turbo trans ( a unique engine trans combo for 64 only in some models )  is the only easy way to get a fresh engine in that year with the turbo  trans and trans spacer ( also unique to only the 64 trans ) 

Thanks again for your words of wisdom 


If you have everything including ALL externals and oil pickup (1965/66 had a front sump oil pan) off your old 1964 429 you would basically just need to modify the engine mounts. 

The 1966 429 has the same bolt pattern on the back as the 1964 429 and other than the motor mount ears, the core block is basically the same. if you swap out all the externals including oil pan, front cover exhaust manifold, flexplate, starter and adaptor ring from a 64 to a 66 and the oil pickup (66 has the front sump) and make mods needed for the motor mounts you can put a 66 429 In a 64.  We've had members here with 65/66 429's in 1964's, and even had someone way back with a 66 429 hooded up to a 1963 and his Hydramatic (with issued due to gap between  3 3/16" driveplate opening and 3" THM crank raised end).

If you have the Turbo Hydramatic transmission with the 66 429 you could bolt it in with the 429 but might need to make mods to the front driveshaft section. You might have issues with the Neutral Safety Switch and of course the Shift Quadrant indicator would need to be switched out due the 65 and later THM trans having a dual drive range and as seen in the 1965 indicated below. The bottom line is you can bolt a 66 429 into a 64 if you have all the parts from the old 64 429 and make the mods to the motor mounts. Perhaps others that have made the  modes can chime in.

It is of course easier to go with a 1964 429 with the Turbo Hydramatic crank, but if you have all the goods to transfer over and an excellent donor 1966 429, it can be done and has been done.


ask anyone who's actually used a later model 429 how many cracked adaptor plates and flex plates they went through before giving in and finding the right block.  My friend did this in a fleetwood and cleaned me out of adapter rings that wouldn't stop cracking.  Type in 'flex plate' or 'vibration'  in the search bar and you'll find a host of people who found the wrong engine in a car they bought.  Just because it's 'been done' doesn't mean it actually fits.  

Given the fact the 1964 and 1966 429 has the exact same bolt pattern for the transmission and flexplate, and diameter of the raised mounted area of the crank for flexplate is the same, there is nothing preventing the 1966 429 from being used in the 1964 with the original THM transmission if ALL parts are used from 1964 and of course the motor mounts are addressed. I have been "cleaned out" of over 3 dozen adaptor rings by original 1964 owners needing adaptor rings for original 1964 429's because something was not right or something was left off (e.g. that starter support bracket) ... so the bolting up the "Buick Borrowed" Turbine 400 to the 1964 429 was not a perfect solution in itself. My Cadillac has had a THM with the adaptor ring with no cracks or issues for about 163,000 miles, but  know of some owners that for some unknown reason was cracking adaptor rings. That last convertible parts car I brought in around 2010, a bone stock 1964 deVille convertible, had went through 2 of my adpator rings and the owner basically gave up.  I have known 65 & 66 429's going into 64's with no issues. It is not a perfect solution, but saying it will not fit the original 1964 Turbo Hydramatic is incorrect.



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