[Chevrolet4x4s]

I have been thinking about buying a 425 Cadillac for the roadster pickup(should weigh around 2000lbs) and cant find a lot of information on them.
Would this me a good option for the rpu? It will be left mostly stock for the time being,intake and headers, possibly a cam down the road.
I have heard of Pontiac bellhousings being used to adapt a manual transmission to the big block caddys,but the only flywheel I can find is an expensive aftermarket piece,is there a factory one that will work or should I just run the automatic for the time being?

Thanks
Shane

 

[techinspector1]

http://www.cad500parts.com/catalog/index.htm
...http://www.cad500parts.com/catalog/page031.htm
http://www.500cid.com/Home.htm
http://www.cadillacperformanceparts.com/

 

[fast68]

i had one in a 79 caddy 6 door limo it ran smooth great it had alot of power at low rpm and tall gear 2.21 ratio which seems to be what they were made to do from factory in the big cars and crappy ratios
i ended up pulling and selling mine even though i wish i had kept it now.
i pulled it with the exhausts and the y pipe and cat and all so i hooked up a fuel can and a battery and fired it up on the ground a couple times and ran it, just for fun



manual trans bellhousing for anything besides chevy will fit and work

should be able to find an old oldsmobile/pontiac or something flywheel on ebay or in a junkyard or somewhere

425 is oldsmobile
403
455
350

etc

same deal

i dont know which are balanced internally or externally though

 

[ericnova72]

Fast, the Caddy 425 and the Olds 425 are two completely different engines. Cad 425 is part of the 472/500 family.Bellhousing will fit, but flywheel/flexplate has to be Caddy.

 

[Chevrolet4x4s]

Thanks. Does anyone know what the gas mileage of these engines was,I have heard 16-18 with the 472s and 500s.

Shane

 

[cobalt327]

16-18 with the 472s and 500s.

Maybe if 7/8 of the way was downhill.

 

[carmanspd]

They do much better than you think. Had a '70 3/4 ton Chev with a 472, RV cam and Holley carb. Got 12-16 MPG and could break the 16.5X33's loose at 35 MPH. Also towed anything you could hitch to it with 600 ftlbs. of torque. 425 is from the same family and they are cropping up way more in rods. Do it to it. I'm currently thinking of using one in our '36 Olds project. They only weigh about 70 lbs. more than a 350 Chev.

 

[DoubleVision]

Shane, Since caddy`s aren`t that common something to keep in mind is usually there the same price at the yards for no matter the cubic inches, and that be the case forget a 425 and get a 500. The sites TI lined up will tell you what you need to know about caddy`s. They have cast iron rods, they are not very strong but caddy engines were really only meant to be low RPM torque chuggers that operated to 3500 RPM. It`s said a Olds forged steel rod makes a good replacement and is only slightly shorter. Early 70`s caddy`s had small chamber heads, the later smogger years had large chamber heads. Another weak link is the valve train, again, it was only intended for about 3500 RPM usuage. Finding early 70`s heads are recommended but you`ll have to find a piston that will keep the compression ratio low enough to operate on pump gas. In most cases the factory intake can be ported very successfully on these engines with a handsome power increase. Another advantage is these monsters don`t weight in much more than a small block chevy. Which ever engine you get, take a look at the intake, if you see 2 small holes in the carb pad on the primary side, these are quick warm up exhaust crossover holes so a special gasket must be used to block them, if a regular Q-jet gasket is used the holes will be open and the engine will ingest exhaust gasses with the intake charge and run like crap.