472 vs 500 on airboat

stan

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A friend is lookin to upgrade a  472 on his airboat from a direct drive application which he runs at 3000 rpm maximum to a gear drive which he expects to max out at 4800 rpm.The build I imagine to consist of boreing .030 over, kb pistons,76 cc heads,edelbroke intake,ARP fasteners along with a 236 @.050 intake and exhaust with .570 lift
Are there any advantages to using the 472 in this application or should we make it a  500 also any other recomendations would be appreciated thanks stan.
 

Maddog

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Dear Stan: Welcome to the board. I have run direct and geared Cadillacs in airboats since 1974. What hull is this going on? Weight? Generally one can say that the 500 is superior to the 472 in a low torque move the load setting. I would say 99% of the time. The longer stroke of the 500 moves the load earlier and more consistently that the shorter stroke. My philosophy is that I dont care how fast it goes, only that it never ever stop in the swamp, assuming any rational operation. The engine you all are considering needs a few things. First, you need to unshroud and port the 76cc heads for sure. Secondly, you will want slightly bigger valves like those sold by Torque inc, a member of this board. Due to shrouding of the largest valves in the original heads (in my opinion) the smaller valves offer better flow--especially at the rpm range you are thinking about. In other words, a "mid size" set of valves. By the way, 4800 is a perfect rpm for your project. A 2.37 gearbox or a 2.68 gearbox with the fattest propeller you can swing is ideal. That said, I happily ran a 2.08 gearbox for many years. The others are better. You need approximately 31 inch primary tubes for your headers. 1.3/4 to 17/8 or 2/0 inches on the tubes at the outside. I would choose a tube diameter right in line with the size of the exhaust valve or a shade larger. You did not mention your valvetrain. You MUST change from the stock valvetrain to a stud or shaft mounted rocker system like Potter automotive or Torque inc sell. If you dont, you will break the stock rocker system in just a couple hours operation and probably ruin the engine when the lifter pops out of the lifter bore, oil pressure goes to zero and the engine is destroyed before you even notice what happened. So if you cant afford to upgrade the valvetrain, dont use a Cadillac with reduction. The direct drive app is fine at 3000 for the stock valvetrain indefinitely. Once you cross 3600, forget it, at least in my experience under the huge loads of an airboat. A q-jet or Holley is fine for your application, as is an hei distributer, no vacuum advance, the crane adjustable advance kit with one light spring and one medium spring in the distributor. Use a good quality cap mounted coil from Napa, or better yet a remote msd pro-power coil. Cadillacs make a lot of heat, just as big horses eat lots of hay, so the radiator should be manly, located down next to the propeller, within 10-12 inches of it, using no thermostat at all, or a washer with restricted flow as your application desires. There are many other tricks and tips, but this isnt an airboating forum so go over to southernairboat.com for more info or pm me so we dont bore these guys. But whatever you do, safety wire the air cleaner and the oil breathers or they will go through the propeller sooner or later. PM me with any questions or post engine questions here. Regards, Charles "Maddog" Morehead 
 

randydupree

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maddog,its not an airboat site,but,it is a cadillac engine site! some great info in your post!
randy
 

cadillac512

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  Well,we sure can if we want to.(and I'll bet everyone wants to) :yes:. We have engines in everything from A-irboats to Z-cars.......so there you go.Airboat use is very torturous to the powerplant and really shows where the weak links are (right Charles?)Very useful information and will help anyone running a Cad. I say bring 'em on. :thumbup: :thumbup:

  Terry (equal opportunity Cadder)
 

Maddog

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Okay--you got it. truth is, we need a little more engine action anyway. The number of builds has gone down lately and the number of "other' posts has gone way up. So I'll invite the airboat guys with Cadillacs over. It's quite an varied crew.....LOL. Maddog
 

bondsman

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i think this is the stan that is already a member of southern airboat. just my 2 cents my caddy was a dd 472  i built it for dd.then decided to go gearbox i upgraded every thing except valve springs needless to say valve float set in cupped a lifter and wiped my cam.but i would say unless the money is there stay 472 it took  more money than what i expected to convert mine to a 500(514).and with my 472 it could move my barge plus 5 on the ground or the hill ,slower on the hill.and that was with a cam that the manufacture messed up on drilling the cam flange and it was 10 degrees retarded straight up,and i left it that way cause i wanted to use the boat the next day.i had my 3 blade stumpuller set at 58degrees and i could still hit 4300 rpm engine. with the cam degreed properly i probably could have had lots more. when my catastrophy happend, the whole bottom end had to start from scratch that is why i changed cranks but with the crank,and it beeing turned down 10/10 and having it ballanced it has cost me a penny or two.
 

stan

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Thanks maddog for the good info and I have other questions as well and yes bondsman I hang my hat .over at southern airboat also. the boat will be an alumitech 8x14 hull, stainless rigging far as the propeller no discision as of yet ,it may be a three blade super wide  sensench with a 2.68 :1 or maybe an 8 blade warp drive with a 2.37 . I woulld think that the engine horsepower and rpm would be a deciding factor in the selection. Now for the engine with mad dog's recomendations along with the proposed componets what would be a resonable estimate of horsepower and torque at 4800 ?
 

Maddog

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Assuming 10:1 compression, with the right camshaft, and the other components outlined, I think you will have 425 horsepower but about 700lbs of torque. Thats the key. IF you put a full effort on the heads and the intake, and changed the pistons to get to 11-1, you would push 500hp. These are real numbers, not the boat ramp bs we hear and read. In my view, as a man who has run a 5, 6 and 8  blade warp drive propeller, and the powershift and the sensenich, there is no decision there---run the wide blade sensenich. It pushes 20-22+ % more on my boat with strain gauge testing compared to the Warp drive. And the noise difference is like straight stacks out of the engine versus mufflers.    :twocents:  Maddog
 

a1mudpuppy

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Maddog needs to do a run with us next time we are around the BIG O, right Stan. Get all of us from S.A and Cadillac Form to hook up on a ride.
With that said and we are talking Caddys in airboats hear. I should  be able to run .060 flat tops with my 120cc heads or am I looking to do some head work? It should be about 9:2 to 1 comp. I've got the oversized valves with the bigger springs. Also got the Cad Company Stage II, Elderbrock intake with a 750cfm carb., elc fuel pump and stock HEI dist. with a MSD Digital GM High Energy Modules with Rev Limiters. I don't have the card from Cam Techniques so I don't know what it is off the top of my head. But with that said what do you think the HP and Torque will be on my build... which should be done this week .. I hope. I'll be running a 2:38 gearbox with my 4 blade Whirl Wind looking to go to the Master Blaster 2.3 if I ever sell the 4 blade.
 

stan

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aint a bit of tellin mudpuppy I would think the cam would be a big deciding factor maybe you can post the data from the card .I have dealt with cam techniques and they have down me well. The engine that I'm currently runnin on southern style is built with a 236@.050 intake and exhaust,.570 lift with cmd 1.74:1 roller rockers on 108 lobe seperation and it does welll. 9.2:1 compression with kieth black pistons. 120 cc heads with larger valves and good springs set 118# closed 345# open ,edelbroke intake with 850 demon and headers. I try to opperate at 4800 maximum and I would guess I'm at about 385 real hp Mybe 475 boat ramp as maddog desciribed lol .I put the tubo tech eight blade set at 8 and 12 degress on behind the 2:1 belt drive and it is real strong on the hill still gettin stuck in mudtussocks though had to get pulled out twice at orange lake last week by  zz4 and aircraft powered boats but I'll get over it. This 472 were building is my first venture in the 10:1 relm with 76 cc heads and 472 so I'll need all the advise i can get .Madog is 11:1 do able if so than what precautions must be undertakin.A while back My motor man that I use mentioned to me that he has built iron head engines to 11:1 to run on pump gas but then again he don't know cadis.
 

stan

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Bondsman,I also feel your pain as I have been down the road of expense and breakage myself .The last time it was my own fault though for assuming that the fancy aluminium pulleys for my caddilac were marked right for the timing ran the engine for about a 100 hrs before a spirlock let go in the piston. No problem threw together me a junkyard motor it lasted about 1 hr before disentegrating darn it ran good ,had more push than any engine before runin 50 dgrees total timing at 4500 rpm can you say detonate.Seems the mark had about 20 degrees advance in it .I don,t assume nothin no ,more I check everything.
 

Maddog

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Agree we need the cam specs. Stan, if you go to a wide blade propeller, no zz4 chevy will be pulling you anywhere.  :twocents: Maddog
 

bondsman

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stan you could always do 12-1 or better and run propane,since its cheaper right now and it would be a great enviromental standpoint on running clean alternative fuel in an airboat.
 
A

Anonymous

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Yall boys with thier  toys !that cool !  Boat ramp  dyno! More people that come up ,the pounds and hp go up ! :backinmyday:  just remember  pounds get you there !
 

stan

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minor set back . machine shop man called to tell me that block was ready cept that he checked it and his helper read the dial on the indicator wrong looks like the ole boy took  .075 off the deck gota take him another block.
anyone know what a good block bored .040 ,baked,and decked .075 can be used for other than an anchor.looks like we'll  go for the 500 .
 

STDog

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stan said:
minor set back . machine shop man called to tell me that block was ready cept that he checked it and his helper read the dial on the indicator wrong looks like the ole boy took  .075 off the deck gota take him another block.

:yikes: :yikes:

And he's not finding you another block?

anyone know what a good block bored .040 ,baked,and decked .075 can be used for other than an anchor. looks like we'll  go for the 500 .

Very thick gasket? Probably o-rings and copper to bring the height back up?
 

Chris S

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Well, an old school build with 403 Olds pistons and 7" rods took a deck cut of .050, Iirc.  Anyone feelin' a little ole-skool?

Someone worked hard for that screwup, those blocks don't cut easily........  :shakehead:


Chris
 
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