High Performance Big Block Cadillacs
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Author Topic: Early 472-500 heads on a 425?  (Read 1948 times)
Cop Car Racer
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Posts: 3


« on: February 15, 2015, 09:55:35 AM »

I now have a 1976 500 for my project. It seems that these projects always take longer than I planned. I have read that some people have put 425 heads on a 472-500 to raise the compression. I understand some say thats not a good idea. But I was wondering if the reverse is possible. Wouldnt early 472-500 heads give a small bump in compression on a 425 and flow better? I know you guys dont like the 425 and always say build the bigger engine. Is it possible? The 425s are cheap. Im a Dodge guy with alot of engine building experience with an eye toward the big caddys. The hot dodge setup is the 408. Its a 360(4" bore .030 oversize) with a 4" stroker crank. It seems that the 425 is all that and more stock 4.08x4.06. It seems to me it just needs compression, cam, and better heads, intake and exhaust. I am still working on the 500 drag race motor(got the cam, collecting parts) but I was considering a 425 as a street cruiser with maybe 375 hp and 480 torque. That would be 440 Dodge power numbers from a smaller engine. The big 440 torque beast only has a crank stroke of 3.75 in. Any input will help. Please dont say build a 472 or 500 because I already am
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~JM~
Shop Keeper
C5
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Posts: 1853


« Reply #1 on: February 18, 2015, 06:56:01 AM »

I've never messed with the 425. I would think that you could use the small chamber 472/500 heads on a 425, but you may have problems with too narrow a bore & valve shrouding. The 425 is supposed to be about 100 lbs. lighter than the 472/500 due to a thinner block casting, more lightning holes in the block & a much lighter crankshaft.

Nothing wrong with building a 425. Supposedly they out-rev the bigger Cads. The 368c.i. Eldorado oil pan is a real nice rear-sump pan. You will need both the oil pan & oil pick-up.

What do you plan to drop the engine into?

I say try it out & please let us know of the results.

Good luck
~JM~
« Last Edit: February 25, 2015, 07:34:03 AM by ~JM~ » Logged

PS. You don't have enough cam. Grin

...Summit has a kit for $99.... Shocked
Cop Car Racer
C1
*
Posts: 3


« Reply #2 on: February 23, 2015, 12:44:17 PM »

The 1977-1979 cadillacs are usually cheaper than the 472-500 cars. I need a transmission for my 500 project so I was considering buying a complete 425 car to obtain a a working turbo 400 and driveshaft, radiator, etc. That would leave me with a 425. Not really sure what to put in into. Possibly a truck. I put a 440 Dodge in a 91 Dakota but it was a tight fit. Its on youtube under "440 Dakota" its the blue one. Thats a good tip on the rear sump oil pan. Most trucks I have built require a rear sump. My plan is to put the 500 into a Ford Crown Victoria expolice car. I really like those cars ever since I drove them as taxis. The caprices are also nice. I like the Vics because they have four wheel disc brakes, modern four link rear suspension, 03+ has rack and pinion steering. The 8.8 rear axle might be able to handle the torque. Vics have a huge engine compartment to accomodate the 4.6 sohc motor. However those motors lack torque. They make up for it in high rpm power, but I think a 500 would be a much better engine for the 4000lbs Ford. Having the distributor in front makes engine swaps easier. I'll keep you posted on results. Thanks for the reply.
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~JM~
Shop Keeper
C5
*****
Posts: 1853


« Reply #3 on: February 25, 2015, 07:38:40 AM »

Here is a posting on the various Cadillac Oil Pans & what they look like: http://caddy500.com/index.php?topic=611.msg10531#msg10531

I mis-communicated the info on the rear sump pan that I was describing. It comes from the 368c.i. powered Eldorado.


Good luck on your search
~JM~
Logged

PS. You don't have enough cam. Grin

...Summit has a kit for $99.... Shocked
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