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Cadillac 500, torque-prop


Well-known member
Can/will a Cadillac 500 with a 1.77 belt drive be loaded down to peak torque 3,000 rpm and swing/perform with a super wide blade prop designed to run at 1,700rpm
My superwides liked 1800 rpm or above. I had a 2.12 rotator with a 2 blade on my 472 set on 2 turning 1900 on the prop. Set on 1.5 I ran a 3 blade at 1850 and it pushed ok.
dcm5899 said:
Can/will a Cadillac 500 with a 1.77 belt drive be loaded down to peak torque 3,000 rpm and swing/perform with a super wide blade prop designed to run at 1,700rpm
You are really asking two different questions here, one does and the other does not have enough info to provide an answer.

The short answer to the first part is YES, a superwide blade set COULD choke the RPMs down to 3000.
Whether that would be a productive endeavor or not (I suspect it would not be), would depend on what specific blades you're talking about and the strength of your motor.
The second answer would be subjective at best due to unknown variables. Most importantly, how do you define 'perform', how big (heavy) is the subject boat, and how strong is the engine?

An original 500 w/forty years wear and a factory valve train on a heavy and/or narrow hull will not 'Perform' anything
like the alternative, which would/could be a freshly rebuilt 500 w/shaft rockers on a light and/or wide hull.
We really need more information to give an answer that is not making a lot of assumptions based on nothing.

Generally, the reason to run a gear reduction is to facilitate more engine RPMs and getting past the 3k limit, thus putting more HP
into the thrust equation. No matter how it's boiled down or implemented, more HP in the front side = more thrust out the backside.
Generically, if you are turning the same RPMs you will be generating the same power. That would kind of defeat the primary purpose of having the reduction to start with.

Why are you wanting to only turn 3k on the motor? Is it a tired engine with factory rockers like one of mine?
Are all these pieces of the puzzle that you have on hand and want to use, or are you missing a piece or two and shopping for the last one to make the best combo? There are better options if that later case is applicable to what you're doing.
What specific prop/blades you are referring to would help as well, as I'm not familiar with any optimized for 1700 RPMs.
Not being a smart ass there, I would be interested in trying such a blade set myself. Evidently I'm not keeping up with the program.

There is plenty of Caddy experience here to be had, but I can't help but point out that the more details you share the more accurate your answers will be. Making assumptions in order to answer generic questions, is not the best way to arrive at the correct answers, imo.
The past 5 years or so I have spent many a day in the shop with Mr Branch. Have met quite a few airboaters from all over the United States who run the Cadillac platform. The one thing that is gospel with this engine platform is you can't take an old tired salvage yard take out and think it will live long on a gear drive. It is not a 5.3LS these old bruisers can hurt themselves up top.

Looking into the crystal ball, if you had a very well cared for 500 with say 70k miles on it and changed out the timing set with one of Mr. Branch's modified roller Cloyes kits. Your chances on a stock engine surviving at 4,000 rpm got better.

If you replaced the stock 40 plus year old springs with new O.E. Equivalent and changed out the seals your chances of that totally stock engine surviving got better yet.

As per Mr. Branch, many of the stock engines utilized on a gear drive fail because they are pushed to exceed 4,000 rpm, have valve springs that are 40 - 50 years old and totally limp or at some point in the engines life someone altered the springs. The stock valves themselves are a weak point, but for the purpose of a low rpm stock budget application we will exclude that discussion.

If running a factory cam and spring set and the engine is not misused or abused many folks have gotten a few years of service with minimal upgrades.

Where the wheels fall off the bus are when the cam is changed, high pressure valve springs are installed or the engine is pushed to an rpm over 4,000 as any one of these will provoke a failure.

Now do not think for one moment that I am suggesting a stock 472/500 is a good gear drive choice. I'm just stating that in his many years of building these engines and racing these engines the ones that break the top end usually have the aforementioned in common.

Shaft rockers are available from Mr Branch as are the timing components that I mentioned. He has used or worked on many of the different type of shaft systems from his own tool steel pedestals with stock rocker arms to T&D Systems full roller design which it the best in the world and used by many top race teams. If you choose you can also purchase parts from other suppliers see how that goes for you.

Generally speaking for those who don't know, your looking at about $1,000 in parts to upgrade the timing set and convert to a mid-grade shaft rocker set up.

Blu ran a modified 514 Branch engine on a 1.53 drive with a 3 blade WhirlWind Whisper Tip 2.0 and it worked fairly well. I would think with the added gear of the 1.77 that prop or a similar type by another manufacturer would be a reasonable choice. In fact his boat is used on their web page to advertise the 2.0 it is the blue metal flake Predator.

Hope this helps ...SWAMP
Cad Company (Home of the world's fastest Cadillac engines) suggested prop loading the engine at peak torque 3,000 rpm not horsepower 4,500 rpm, which would put me near the 1700-2200 optimal rpm listed for the superwide blades. Currently have a 3 blade 78" Whirlwind model?? similar to a Power shift, pitching that prop to load at peak torque would put it way out of the rpm range it's designed to run. Has anyone actually run a superwide 2 or 3 blade at 3000+- engine rpm?
Good Stuff DCM tell Courtney and Chris I said hello next time you call up for advice to CAD CO

Dan in Nebraska gave you good data

Good Luck
dcm5899 said:
Cad Company (Home of the world's fastest Cadillac engines) suggested prop loading the engine at peak torque 3,000 rpm not horsepower 4,500 rpm
Why? Are you trying to break in a new motor?
You may benefit by calling WaterWalker and talking to Andrew about a 2 blade Maximus. My bet 78 or 80 inch length. They tend to act a little like a stall converter in a car, allowing the engine to spool a bit before loading, then they bring a bit of snap helping the boat to break.

With the 1.77 you may benefit with stronger push, but limiting your rpm to 3,000 is like ordering a Whopper with no meat. :lol:

4,000 engine / 1.77 ratio = 2,259 blade RPM

Andrew (863) 676-7767 is extremely helpful and could really provide you with a good recommendation and idea on what the blades would offer you compared to what your running now.

Just curious what brought about this need to choke the engine to 3,000 ?
When will you guys let the caddie die in peace?

New caddies a third of the weight and twice the torque with a proper tune!
The 472/500 Cadillac platform owns it's place in airboat history. I don't ever see these powerhouses leaving the sport until the last crankshaft has been turned or bearings dry up.

In fact that is one of the reasons Mr Branch has been teaching a few of us how to use other bearings in the platform.

The 555 inch build in his shop now should be done by late January. That engine is a FANTASY to most Cadillac fans. The next one I am gonna put together with Mr Branch will be so unique it will ensure a wide cross section of high performance parts will be available years down the road for the rotating assembly's.

Ford Piston blanks
Dodge Hemi / 440-6 Rods
Chrysler rings & bearings
Custom shaft rockers (Ford)
Recycled core components 500/472

We have plenty of time yet to choose the camshaft and I have two in my parts supply already. One a solid lifter mechanical with lifters so no cost to use it, the other a big custom grind hydraulic roller that I will need to buy a set of roller lifters if we use it. Guess we will see where the budget leads us but we have options.

Will ask Kwan to post pics once things start to get going with the build.

I need to save a bit before we start that one but it will be built by mid 2020. Think we will call this ProtoType engine FRANKENSTEIN.

The 472/500 Cadillac die in peace...lmao
you need to tell us what you have modified on your caddy. If it is stock don't turn past 4K for sure. If you have a good shaft rocker setup and upgraded valve springs 4500 is no problem. with the 1.77 you may be better off with a 3 blade R on it. with the 2.12 on mine I started with a 2 blade 80" S (Super wide) and ran the engine between 4000 and 4200 depending on how I wanted the boat to perform. I upgraded to a 3 blade and took some pitch out and ran it the same rpm and was happy with that as well. Mine was a 472 with a stock bottom end, MTS#10 cam and lifter kit, small block chevy valve springs, non adjustable shaft rocker system from MTS, aluminum edelbrock intake, and a holley 870 carb. I had over $2k in upgrades to my "free" caddy. They do work and hold up just fine but you have to do some purpose built upgrades for sure. By the way the 3 blade S setup was much more efficient for me. Less pitch same max rpm and lower cruise rpm. Boat went anywhere I wanted it to go.
Dan are you aware MTS and 500CID are gone?
They changed MTS to 500CID after Marty's death. Recently 500CID was taken over by a fellow in Illinois who is a racer. He is the owner of CadillacHighPerformance.com and is doing LS and ground effects now also. Marty's brother is affiliated and they still have most of the products MTS offered. He has also done some type of business arrangement with CADCO as he is the distributor now of their BoogieMan line of components.

The new guy (Issac) is looking into new product lines and has a TopFuel nitro car in the works I'm told. Nice web page he put together. Check it out