Hey guys. I've got a 331 cad. I am building for a model A coupe. I've researched just about everything about this engine. What I am looking for is some real world performance info. The engine has a dual quad intake from a El Dorado and I am looking to make 400hp or as close as I can get safely. I am aware of all the old hop up tricks and I have a engine guy who is going to do machine work for me. The problem I am having is he is wanting to have custom pistons made and a custom cam also do a ton of trick work to the block, heads and rotating assembly. I am more than up to date on engine performance so I don't need people to state the obvious. The info I am really looking for is someone who has built or been around one of these engines of which was modified and made good power. Also what parts or part combos where used. Is it really necessary to do all of this custom work on this engine to make 400hp or can I use the parts that are available on the open market? Thanks
A couple of random thoughts... 400 hp from a 'vintage-style' 331 cubic inch anything, without some 'special' parts, won't happen. You will need forged pistons, a very healthy cam, head work and more. It won't be inexpensive. .
Where do you think the extra power is coming from.......If your having a problem with a custom cam.... A bunch of head work .... And the rest of the necessary work you just stated.?
The engine guy knows what it takes to try to squeeze power out of your antique V8. Maybe the only problem is that you don't trust his wisdom and experience. You're going down a rough road to squeeze near 400 ponies out of an engine that originally wheezed out 160. Tiny valves and ports are your major stumbling blocks, it will take a true artist and whatever it takes to pay him to even come close to your goal. Having it be 'safe' or reliable at that power level is an iffy proposition. Off the shelf parts don't exist for what you're trying to accomplish.
I think you are going to have to look at later heads. The 331 heads are just to restrictive for much flow.As far as the rest of it. Readily available parts" for a 331 Cad? Just what parts are those?
Or you could bolt on a supercharger along with the forged pistons etc. What makes you think you need 400HP to move a Model A around? A 55 Eldorado with the 2 4s and 9:1 compression made 270Hp and that was the most powerful version of that engine. It hauled that giant whale of a car up to 110 MPH and 0 -60 in under 10 seconds, among the hottest cars on the road at that time. A model A weighs half what a Cadillac weighs. It will spin that car around like a big dog chasing its tail. Suggest you do a straight stock rebuild with duals and a mild cam. This should give you around 300 HP which is plenty for such a light car. If you insist on 400HP do what everyone else does: lie about it. Once you get it on the road you will have all the power you need.
I trust my engine guy 100%. The largest cam that is available Ive been able to find is a 270 Isky. Which is only 216 duration at .50 with 470 lift. The pistons that are out on the market suck to say the least. Iam pretty sure I will be running the 390 head. I guess I was hoping to find someone out there who had some experience with the performance applications on this engine who could share some trial and error type experience with me. I understand what it takes to make power. As to why Iam aiming for the 400HP mark. Hell why not. In my opinion the engine is the heart of any project and Iam a engine guy for sure. Also I want this car to be a bit on the radical side so the idea of a small A coupe with 400hp and a ton more in torque sounds right up my alley. So in conclusion if I could find someone who has built one of these engines using all the standard tricks and performance parts that are available who could share the results. I am just trying to find the line in the sand where a extra 1500-2000 dollars only gets me 20-40 more HP and then decide which side of the line to be on. When you start talking custom made forged pistons and custom ground cams it opens up a rabbit hole that eats money especially when your building a vintage engine. This is not my first trip around the block just the first vintage Cadillac engine Ive built.
If you won't be satisfied with less than 400 real HP, get another engine. Like a newer Cadillac or possibly a big block Chev. 400hp would be a piece of cake for a 429, 472 or 500 Cad and even a 390 would be better than a 331. If you insist on getting 400 real, streetable HP out of a 331 Caddy plan on a supercharger, and also plan on spending a shit ton of money.
Well let me state the obvious anyway. I got a 355 that makes a little over 400 and it is trick from the rotating assembly to the carb. I had a 331 in my '46 Coupe years ago that may have made 331. Mild port work, 3 deuces, Chet Herbert roller, and about 10.5-11:1 compression, short skirt pistons. Balanced rotating assembly, zero decked, set up on the edge of loose. I hope that helps a little bit. 1 HP per inch is pretty good on these old engines, you are looking at the 1.2 range.
Their has been a lot written about the 331 Cad. on the HAMB. You should find all you need with a search. Iskenderian still makes roller cams for the 331 I think but beware of the older ones. He told me that the new old stock one I put in my '50 Cad. engine that "they were kinda soft". I used the stock valve springs in my '55 heads and run Rotella oil so I'm hoping it lasts a while. I don't put too much milage on my roadster now. Chevrolet roller lifters work in the Cad. 331 but be sure to get the right length connectors. I'm running a Horne 4 pot with Stromberg carbs. It's amazing how street able it is. I'm told that roller tappet cams are very forgiving. This one sure is. You know I don't know why you are shooting for a certain H.P. number on a street engine. Just put on the later '59-'62 heads a good cam and some carberation and you will have all the H.P. you need in that car. The blue engine I put in my '48 Ford. '57 Eldorado heads and manifold. Engle solid lifter cam and adjustable rocker arms. Eleven and a half to one compression Johns pistons. Don't know how much H.P. it makes but it pushes the heavy four door along real good. Gary
...less than a grand for both.... Really, use a later 390 and just tell folks it is a 331. Only the die-hard Cad guy will know the difference. .
At the risk of sounding like a dick.....if 1500 bucks is the decision maker ..... Any make or model of vintage power plant is not for you..... It's just a cold hard fact........none of them are cheap ......Your dealing with engines that are 50-60 years old....(stating the obvious) .....A stock PROPER rebuild is not cheap.... And once you want to make a little power..... You need to be prepared to get your wallet out.
I recall someone in your neck of the woods that modifies later caddy engines, they may have some tips or contact info, don't recall the name though, may be these guys in Albuquerque New Mexico Cadcompany.com
Thanks guys. With your help and a little bit more research it looks like I am on the right path. I am sticking with the 331 .30 over, forged custom pistons, 390 heads with port work fine tuned on a flow bench and 202/160 chevy valves put into them, custom cam, two four intake, blue print and balance, adjustable rockers. With a lot of attention to the details I feel that I will get close to my goal and will be happy with the performance.
Red--- A good dyno tuner will be able to wring out some extra HP with careful carb and ignition tweaking, save your money and reserve some extra dyno time, it is money well spent.
Unless of course you have a friend that is an engine builder then you can knock at least 20% of the price of parts. the 331 cad is a respectable engine, it pulled the original body around very well and in a light body it could be quite snappy. One HP per inch was basically unheard of when the engine was new. Today most of the fellas are not getting 1 HP per inch out of their engines and those that do are getting it the hard way. If the cad were mine unless I was trying to break some sort of a record I would accept it for what it is a good engine choice for an old hot rod, build it to what I considered to be within my grasp and be happy with it.
Just getting ready to fire my motor. Pretty much stock rebuild. Bored 30 over with Eldo tri-power. Just building it that way wasn't a cheap build.But what I wanted for the coupe. I'll let you know it runs. Caddy's were heavy and needed a lot of torque to move that weight. Hot rods weigh less than half sometimes less. My coupe should run great as is.......
@redsteely Did you try Schneider cams. I think they have some more aggressive cams available but, they have limited cores for the 331.
Ok so plans changed a little. We have a short block together. Although after putting the heads with intake on flow bench the intake is a major choke point. It kills the speed and flow the heads move after being massaged. So I am going to run a blower. Looking for some inspiration. Wanting to run a 671. If any of you guys have experience or pictures of set ups I would appreciate the info. I am trying to put all the parts together for a setup. Thanks
just read your last post so some of this may be later, but 1) you can also stroke it using the guts from a 390. 2) there's a guy in utah who custom grinds cams for these things. salt flat racer as I recall. PM if you want his info. it's at the office, not here today. 3) the 2x4 is not considered the best intake option for these things. all the old allard racers swear by the original 4bbl. the extra carbs just look cool. as for the blower--sounds like fun!
Just curious... was this a stock Cad dual quad? and did you do any work to the manifold in an attempt to improve it's flow?
Now that the pistons and heads are configured (10:1 maybe), what are your plans after deciding to supercharge?
I'm putting a '32 coupe together with a '55 331 Caddy using 390 heads and a 4-71 on a Cragar intake. Where did you ever find the belt drive set up?
I am running a '55 331 in my '55 Stude and it was bored 0.030 over, Isky 262 cam, stock '58 365 heads and valve train, low compression pistons, Sanderson headers, '56 intake and carb. On the basis of it's performance I would be lucky if it makes 250 hp.
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