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Projects Olds 303 vs Cadillac 331

Discussion in 'Traditional Hot Rods' started by eightballgrifter, Sep 4, 2018.

  1. [​IMG]


    What are the opinions on these two motors? It's come to a bit of a crunch time in my long term T build. The car is being aimed at an early 50s build period, and so far I have managed to collect most of the parts I need. The thing that's bugging me though is that I'm not certain my stock flathead is going to deliver the power I want in relation to the depth of my pockets for go faster parts. I know fast always = $ no matter what motor but I figure both the Olds and the caddy are going to have a good head start as they sit plain stock. my idea is to get hold of a motor when the time comes, refresh and fit as stock with a view to building more power as and when. So what are the views on power potential and parts availability? From what I've researched so far it would seem the caddy may be more expensive to build?...

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  2. oldolds
    Joined: Oct 18, 2010
    Posts: 2,681


    It seems to me that there are more hop-up parts out there for the Olds motor. To rebuild any of the 3 motors you mentioned you can expect to spend about $5000, if you are not doing any of the work yourself. The last time I looked the major engine rebuild kit for a 303 was right around $2000. That is for stock type parts. If you want to get serious hot rod stuff inside the price goes up quickly. Custom machine work adds up quickly as well.
  3. Rocket-Boy
    Joined: Jun 21, 2008
    Posts: 88


    ill be the first... early Olds and early Cad are not a cheap mill to build.
    This of course is dependant on how much power you are after of course. Caddy speed equip is harder to come by and hence more expensive, but if you want the nice early Olds parts they will hurt your pockets just as much.
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  4. daddy_o's_diner
    Joined: Sep 8, 2007
    Posts: 2,769


    The Olds will be way cheaper to hop up then the Caddy.
    Caddy speed parts are crazy expensive. I've done two of them.
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  5. 48fordnut
    Joined: Nov 4, 2005
    Posts: 3,528


    There are factory parts for the olds 303, 324 ,or 371 that do well. The 57 371 fits in the same place as a 303. Probably a 394 as well.
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  6. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,086


    Your car your decision, but i think i would go with the olds. In a t you wont need much power anyway. I know one of the guys at the local cruise in has a t powered by a little ford 260 and it is pretty damn quick.
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  7. Dreddybear
    Joined: Mar 31, 2007
    Posts: 5,912


    I have both. I agree with daddy-o, Caddy speed stuff is hard to find and pricey. That being said I scrounged and I only have about 2k in my fully rebuilt Caddy. It's a 59 390 with 4x2 hollys. My Olds I have maybe 7-800 bucks in it and I expect to be done under 1200. The speed parts are way easier to find for the Olds but some of them are still kinda pricey or hard to find.


    It's smelly and dirty but I've driven the everloving pissballs out of it.
    Last edited: Sep 4, 2018
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  8. F&J
    Joined: Apr 5, 2007
    Posts: 13,147


    You are new to old school street-driven hotrods, Eh?...see the last quote below from "oldsman41"

    100% true because the Olds was
    "The" OVH8 to lust for when Cad & Olds came out with the new V8s in 49..brute torque at any RPM

    True for sure, as the Cad was not the number one choice of rodders back in the early 50s, so far fewer parts were sold for the 331

    Pure Fact..especially in an old style rod on skinny never will be able to street race a modern car on sticky tires......So a question....where does one use "big horsepower" on a street driven old style hotrod?

    mine is a true daily driver for 8 months, as it is the only usable car I have right now. 1955 Olds 324. I bought the entire drive train from a standard shift crashed car, then added some stuff including a NOS Crower hyd cam.. I have yet to make a full throttle launch, as it smokes both bias even if I hit it too hard "after" getting into 2nd gear.
    Here's real horsepower... :)

    DSCN1330.JPG DSCN1135.JPG
    ^^^^ No matter how much horsepower and torque you have in an early rod, you will not outrun these two cars...pure fact! That Officer stopped me to BS twice that

    last Thursday, late night, I see low set headlights behind me out on a hilly State road, and this old Model A with a Merc flathead kept up with me just fine. Saw who it was when we lined up at a traffic light many miles later. The rod belongs to "Vintage Glass" and has been on the road for years..

    Find whatever motor you can in your Country, and just get it out on the road.

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  9. Moriarity
    Joined: Apr 11, 2001
    Posts: 14,402

    Staff Member

    I love the 331 caddy in my 40 Ford. Speed parts are expensive.... I bought a 50000 actual miles engine from a 49 caddy that was being “street rodded “. ( that poor car) and added a Horne intake and Mallory distributor. The rest is stock and far more powerful than the 85 hp flatty it replaced.[​IMG][​IMG]

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  10. Thanks everyone for the replies so far. The pics of the motors have only helped to confirm that it's the way to go. Just to add a bit more context. The previous rod I built was a model A truck with a hot 265 Chevy backed by a closed drive 3 speed and banjo rear. It ran great, but for the T I was looking at something set slightly earlier in date as it needs to run a pre 54 motor to fall into the VHRA vintage engine class. I totally agree with the comment about "how much power do you need"....or can use....the 265 in my truck span the tires with ease, so I'm not shooting for the moon here in terms of power. I guess what I'm hoping for is a nostalgic motor that I can have some fun developing over the coming years and hunting down parts for. I do have a lead on a 331 over here which may be for sale so ultimately that might make my choice for me! Thanks again for the input, as you might imagine there's little experience of these motors over here in the UK as far as I have been able make out, that said some good info on the cad motors on a couple of web pages relating to Allards!

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  11. tubman
    Joined: May 16, 2007
    Posts: 4,055


    You could do what I'm doing for my "T". I am building it to initially use a 258" 8BA I just finished, with Edmunds heads, a Navarro universal dual manifold, an Isky MAX-1, and a Mallory flattop, I am running the truck pumps and the stock 8BA type overdrive transmission. The engine and transmission mounts are set up for this drivetrain. When I set up the mount system, I took a bunch of measurements to make sure my future plans would work out. I also have a rebuilt '51 Olds with some speed equipment under the stairs in my shop. I have a set of Hurst mounts for this engine, as well as an adapter plate to run the Olds against the Ford Transmission. This should allow the Olds engine to be simply dropped in place of the flathead, should I decide to go that way. The adapter I have uses an 8BA type throwout arm, so the clutch linkage should not be a problem. The idea is to run lake headers on both engines designed so the under car exhaust outlets fall in the same place. A little planning with the throttle linkage and the electrical and fuel connections should make an engine change a one evening deal. I think a flathead radiator should cool the Olds pretty well, and I can just cap off the two extra connections. The project is temporarily stalled out while I am putting new valve guide seals in my Corvette. When that's done, I should be able to get back on this project. Hopefully, it will work out for me. The only weak link in the chain will be the '50 Ford transmission, so I am looking for a T86 or maybe an early Ford four speed to take it's place.

    Oh yeah, I have a '56 Chrysler hemi with the proper Hurst mounts and adapter plate under the stairs as well. I also have the adapter plate for a SBC and am looking for a good deal on a set of SBC Hurst mounts. I don't have an engine yet, but that should be the easiest thing to find of all this stuff.
    Hnstray and eightballgrifter like this.
  12. I was just talking to an engine builder friend on Monday about this exact subject. He, having built and watched raced a few of these said the Cadillac 331 is the best out of the Nailhead 322, Olds 303/324 and Cad 331. The first choice he said was of course a 352/392 Hemi....The reason I stared the conversation was he's building a Cad 331 for a customer now.
    kidcampbell71 likes this.
  13. borderboy1971
    Joined: Oct 20, 2008
    Posts: 544

    from Canada

    Here's my experience. I'll be building a 394 olds for my 32 sedan. I will be keeping everything on the car pre 64. I've been collecting speed parts for the 394 for awhile now. ORIGINAL speed parts. I can pick up a catalog and order new parts that are likely better and in some cases cheaper but they aren't true pre 64 parts. It has been a real challenge finding parts I want at at times expensive. But the challenge has honestly been alot of fun. It's been like a treasure hunt. Enjoy your build.
    kidcampbell71 likes this.
  14. Thanks, yeah I agree, searching out parts is a big part of the fun of it, especially with the research that goes alongside. Thanks to everyone that's taken the trouble to reply, it's giving me plenty to think about!

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  15. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 8,947

    Rusty O'Toole

    In the years BC ( before Chev small block) the Olds was for guys who couldn't find or couldn't afford a Cadillac engine. Nothing wrong with the Olds except smaller displacement and HP. The Olds does excel in strength and being overbuilt. Some models can be bored a full .250 oversize that's a quarter of an inch. A popular combination for drag racing was to bore and stroke a 371 Olds to 480 cu in.

    Either will do a job for you but it sounds like the Olds is the best and cheapest choice today.
  16. CadMad
    Joined: Oct 20, 2012
    Posts: 451


    I know which way I would go.
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  17. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,086


    Ok Vhra i get it now.
  18. dan griffin
    Joined: Dec 25, 2009
    Posts: 414

    dan griffin

    If you get the Cad. motor have the heads magnafluxed before you spend any more money on it. The heads are prone to cracking if the motor has been over heated. A 303 Olds can be bored to 324+.060=3/15=334 ci.
    Joined: Dec 8, 2015
    Posts: 212


    28B1AEA8-34DD-44F8-B2BC-9358004E4597.jpeg 23D3111B-D75A-4221-82D1-6654157D1B56.jpeg 08AE3917-B9D6-433D-97A5-23C471C192EF.jpeg The olds is a great choice and ross racing engines is a great source for speed part. He’s done two engines for us and they perform wonderfully. There may even be a caddy in our future on the next project
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  20. Paul
    Joined: Aug 29, 2002
    Posts: 14,247


    One word: Olds.
    'nuf said
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  21. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 7,263


    Dimpled Caddy or Olds valve covers just add icing to the cake :D

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  22. southcross2631
    Joined: Jan 20, 2013
    Posts: 2,662


    The Olds gets my vote, having grown up with a Olds powered 33 Chevy coupe.
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  23. Tough looking motors all of them! Thanks for the heads up on manga fluxing heads on a caddy!

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  24. Well it's been a while, but updating this thread as I finally tracked down a motor...Ultimately the choice was made on what I could get my hands on....and it turned out to be a Caddy331.
    It came with a few nice parts, and I have managed to track down one of the holy grail Caddy speed parts in a Hilborn mechanical injection. I've only mocked it is for the photo as there is a lot to do including complete strip down and rebuild of, well everything really including the injection as it hasn't run for ever so needs a thorough going over. Other mods are in the planning stages with a few parts in hand, but hopefully this will be one great race motor!
    Thanks to everyone who chipped in to this thread, your advice was appreciated, Jim

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  25. Bert Kollar
    Joined: Jan 10, 2007
    Posts: 895

    Bert Kollar

    In the 50's we had both in our hot rods but the Olds was preferred because it was a more rugged engine internally. That's why more parts are available.
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  26. saltracer219
    Joined: Sep 23, 2006
    Posts: 617


    Having done a number of these engines, as a machinest I think the Olds is superior to the Cad in lower end strength and has a better oiling system than the Cad. Also as been said already the Olds has far more used and new speed equipment available.
  27. It certainly does seem as though there is still more speed equipment available for the olds which suggests they were by far the more popular choice, which I'm guessing in part is due to the reasons mentioned above as well as availability I would imagine.
    For me the Cad engine will do just I said it was what I could find and I'm pretty happy with it... lucky enough I have all the speed parts I need to complete the motor within reason, and even at a little over the stock power of a 390 in a light car like my T will be more than enough

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  28. belair
    Joined: Jul 10, 2006
    Posts: 7,932


    You couldn't have lost with either choice. But you killed it with that Caddy. I like the look of the Olds better, either will run hole in the wind and eat one in your pocket. Best of luck.
    eightballgrifter likes this.
  29. My 37 had a 303 Olds. Before I switched to a Caddy . The Olds. was easier to keep cool even with a cut down fan . But the Caddy was much lighter and car wasn't nose heavy , it cornered a lot better , had more torque but was harder to keep cool . There are used Caddy speed parts out there but you pay the price. Olds. parts are easier to find but still pricey . You can't go wrong with either choice , and that's my two cents !
    eightballgrifter likes this.
  30. pkhammer
    Joined: Jan 28, 2012
    Posts: 325


    I was looking at early Olds, Cadillac and Buick engines for my latest build but a friend made the decision easy when he gave me a '55 Cadillac 331. The Olds mills were no doubt more popular in the 50's with hot rodders and the availability of parts these days is much better than the Cad. The Cad does have benefits that I like however; lighter weight, easier mounting, starter on the right, and no cast-in bell housing on '55 and later blocks. I love the early Olds, Buicks, Hemis, etc but with 270 hp in stock form ('55) the 331 will make a great hot rod engine.
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