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Old 07-21-2006, 03:31 PM
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500inch Cad + Manual trans

So my '67 Deville daily driver now stops well thanks to disks up front and a lot of advice from you guys.

Now the emphasis moves to making it go faster! To achieve that I have purchased 2 cad motors a 425 and 472, both of which i believe I can build to 500 cu in, the better one will get rebuilt. The questions is this though, which manual (4 or 5 speed) will mount to a 500 inch Cad motor and live with the torque generated? I'm looking to build the motor out to about 500BHP.

Any ideas guys???
Yep, i guess you pre-empted me, I just found a previous thread.


Last edited by 67caddychris; 07-21-2006 at 03:55 PM.
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Old 07-21-2006, 04:30 PM
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no manual trans will bolt to the caddie's, you will need an adapter and a piliot bushing I belive. call trans dapt to see if they can get you the adapter.
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Old 07-22-2006, 09:15 AM
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You can use the correct depth aftermarket (Lakewood) bellhousing for Buick, Oldsmobile, & Pontiac engines as long as there is a provision for the starter on the correct side of the engine, some stock bellhousings had the starter bulge on BOTH sides but run as much or more than a Lakewood from what I've seen on Ebay.

The clutch mechanism would be best accomplished by using pieces of different cars for a hydraulic clutch, as NO GM cars of this body type ever came with a manual transmission. Even if you could find the parts from a donor "B" body (like Impala/Caprice, Electra/LeSabre,and the like) you would still have to fabricate certain parts because of the body and frame differences.

Next problem is the flywheel, these are completely custom for ANY Cadillac engine in the past 40+ years, as NONE came from the factory with a manual transmission, they ARE available from a couple sources and are usually at least twice the price of a more common engine type like the Buick, Olds, Pontiac, and Chevy.

Your next problem would be the transmission, you have a HEAVY car, and an engine with a LOT of torque, and the only thing readily available to work with these two factors are TRUCK transmissions, and there are few available in a two-wheel-drive configuration, but they ARE out there with a LOT of searching. I would look for something in a NVG-4500 or similar.

The main problem with these transmissions and the available bellhousings are the main opening in the bellhousings are for a smaller car-type (and sized) input shaft, the trucks use a larger opening. Any competant machine shop can make this adjustment.

To achieve that I have purchased 2 cad motors a 425 and 472, both of which i believe I can build to 500 cu in, the better one will get rebuilt.
To put it shortly and sweetly- AIN'T GONNA HAPPEN ON A BIG BUDGET.
You are not going to want ANY part of the 425 for this car, sure some parts will interchange but just because they "fit" doesn't mean they will work for what you need, the ONLY part you may want to use is the somewhat better oil-pump on the 425, but for the sake of parts life buy an aftermarket pump from one of the Cadillac performance places (I believe there are only 3 or 4 of them so you are again limited here also)

The 472 shares bore size with the 500, and that's IT. You would need to swap in a new crankshaft, rods and pistons, plus the heads would be a good candidate for a swap for the flow necessary for the 28 added inches. The Edelbrock intake manifold is a "MUST" for these engines if you want to go above stock, and then you need to look into the $$$ for building a valvetrain to hold up to more than stock for any amount of real power.

Been through most of this, and done that, with the Caddy big boys.
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