Caddy 331 or 500

I have a 1955 Caddy sedan, and was just pondering on if I should stick with the 331 and rebuild it. Or pick a 1970 Caddy 500 which would have to be rebuilt as well. I like the idea of all that torque and extra HP with the 500. But on the other hand want to stay true to the year of my Caddy.

Just want to hear some ideas and suggestions.

 

If you were choosing from two identical 55 caddys at a used car lot, one with a fresh 331 and one with a fresh 500...which would you buy? It's going to be like that when you sell it too.

 

Do what guys on here have told me "Do what makes you happy"

 

Very true.....very true....I was just smittin with the HP and torque numbers of the 500. But I really like that the original motor is all together still holding strong, except for a head gasket.

 

Go with the 500 man.

1shot

 

500 for the win.

 

Personally, with a big lumbering fleetwood of my own, i'd say 331.
That lil' engine surprized the shit out of me the one time it didnt stumble or slip when i dropped the hammer, and i could only emagine how much more plenteful the fun would be with a fresh rebuild. Sure did change my mind.
I'm even going a step further, .30 or .60 over bore, and clean up the ports a tiny bit when its torn apart for its rebuild.

 

Big 500 fan here.. go for it...

 

I think your asking the wrong question...

You should be asking:
Is it worth the time, trouble, expense, headaches, PITA, etc to install a 500, or should I go with a nice simple 331?

Do a little homework..............

 

yes I do realise that there is alot more work into just shoving the 500 in their. plumbing, headers, mounts, tranny, etc....plus the extra$$$$$$$ I figured if I stick with the 331 I might save a little more $ on the rebuild and transplant. from a purely economic view.

 

Go with the 331-My 54 ran as sweet as with its original powerplant-just imagine what it would be like freshened up!!!
I also did a 57 coupe with a 454/t400-with the benifit of hindsight-I wish I had rebuilt the 365!!!
Stay true-Cadillac got it right first time-you should to!!!!
Just my humble opinion!!!!!

 

Thanks Elricho, that's all I'm looking for is opinions.

 

I guess it depends on whether you are happy with a restoration car like all the others or a custom car unique to you ..

 

very true.....

 

A couple things to consider...I love Caddys, have one in my roadster, but you can get some good money in a caddy engine when doing a rebuild regardless if it's a 331,390,365 or a 500. Don't expect it to be cheap when springing for the internals.

Speedway carries most of the internal parts..cams, pistons, rings, etc..but have your credit car ready and don't tell your wife..hahah. If you said you were putting it in a hoodless roadster the choice would be easy. The 331's have a big amount of hop up aftermarket manifolds...3x2, 4x2, 6x2. So on a hoodless car that would be the direction that I would go in ( and I did on my roadster).

For a bigger sedan like you described the 500 would definitely pull that things along nicely down the road. Speed upgrades that are available for that big hog are pistons, and cam and lifters. Speedway also carries this stuff for the 500's.

A 331 will be easier to put in than the 500. Lots of things to consider

-Jerry

 

I'm putting a tri power 331 in my model a sedan. It will be hoodless and I think looks killer. But, I would do whatever you think is cool. Either one you pick will be a good choice.

 

I'd try to find a 59-60 390 it's almost a bolt in very similar to your 55 caddy.

 

It's not just that.
The 500 has an external oil pump that's gonna land smack in the middle of your crossmenber. The crassmember will require extensive modification before the 500 will even drop into the hole... And then you have the trouble and expense of motor mounts, headers, etc.

 

500's are popular here in Florida..............................in air boats

 

Now that I did not know about the crossmember . Thanks Pir8Darryl

 

Here's my view.

I completely rebuilt the 331 in my 1953 Cadillac Coupe. I had issues with lifters (cheap taiwan crap), and finally yanked it to put in a 2008 5.3l vortec out of 2008 Silverado.

Now, I am getting ready to build the 1951 Cadillac Convertible. I have gone both routes (and considered the 500 route as well, whose "numbers" are not as great as they appear...remember gross hp/tq vs Net hp/tq), but this time, I am staying 331, with a twist.

I have learned alot over the past few years, and I am building it "my way" this time. Cadillac 331, bored and stroked to 390. Adjustable rockers, solid lifters, mild cam, 390 heads with port/polish, and 3x2 edelbrock intake. She's going to be numbers matching, but pull pretty decent numbers, and I will back her up with a 700r4 (which you won't be able to see anyways).

Having "been there, done that", play with the 331. You will appreciate it more.

Charles

 

This is all true. I've been told that you can use the Eldorado rear sump pan that will make the crossmember issue easier to deal with....BUT they're REALLY expensive (read= ridiculous) and getting harder and harder to find. I think you'd probably need to relocate the radiator to the front of the factory radiator support OR fabricate a whole new setup to allow for a bit more room. Not sure on your year, but I know on some of the later Cad's (early 60's at least), the steering will GREATLY interfere with the headers/ exhaust manifolds. I only know of ONE person who makes a kit to change the steering to a rack style which is necessary without making a lot of other modifications (Ron Parks of RPM Engineering 760-329-1886). Sanderson makes block-hugger headers for the BB cad motors.

No doubt...that 500 is a BAD ASS motor. If it were me in a 49-62, I'd stick with stock or at most upgrade to a 390.....that'll go in easy easy easy. I've been faced with the same decision and at the end of the day the 331, 365 & 390 Cad motors are truly great and capable motors when built right and produce more than enough power to move those Cadillacs for what they are intended for. The factory intake manifold with a good 4-barrel carb and the factory style air-cleaner is the way to go for style, class, reliability and performance on a Cadillac with a hood (the stock air-cleaner is awesome!). Leave those crazy intakes and carb tuning woes to those crazy hotrodders with their exposed engines and greasy hair. IMO If you're building a more modern style custom or something other than a restoration or traditional custom, that's when the 500 might be worth considering.

If you don't want to run the stock transmission behind your OG caddy motor, or want to upgrade to a more modern OD transmission (like a 700r4) you can get adapters AND transmissions directly from Bob at Bendtsens Transmission Adapters (www.transmissionadapters.com). Some consider that to be the only weak or annoying part of the stock Cadillac drivetrain. Or at least not worth spending the money on having one rebuilt?

Captain Obvious says: "Remember kids, when having your stock Caddy motor rebuilt, make sure that it's done by someone who has experience and a good track record with these vintage beauties. Don't forget to use quality parts too.....and don't take candy from strangers in the park!"

 

Charles,
your Caddy is BEAUTIFUL!!! I had a 53 that I sold a few years back. I regret it all the time. 53's are it. I'll be in FL most of December helping my Grandfather with some things (Naples/ Ft. Meyers area). I plan to take some short trips to see other parts of the state I've never seen before. I'd love to see your cad in person and buy you a beer.
Glad to hear your running the 331/390 in the 'vert. 331's look the best to me.
-John

 

Charles and JohnJoyo great insight. Thanks for posting. Really good opinions that I am taking into consideration. I like the idea of replacing the transmission and maybe need to look for someone in the Huntington Beach area to rebuild and bore out the 331 to a 390?

 

I'd have a hard time not springing for the 500.

 

I hear ya Strange. It is Very tempting.