454, 455, or bigger for direct drive unit

[swampdonkey]

Hello everyone

Have been reading you forum for about 10 months, which is about when we purchased our 18x8 airgator. Not having any airboats in our area I have used your forum to educate myself. I THANK YOU ALL FOR THAT. Now I need some advice.

Our rig was powered by a 350 sbc direct drive with a 72x38 woody.
You noticed I used the term WAS. I want to install a Big Block. I was told that a 454 would bolt right in to our exsist mounts without having to modify our frame. Is this correct ? Would a 455 bolt in the same or are those blocks different. And if we would come across a 500 cadillac engine would that also bolt in or not.

If I can purchase a motor that will bolt in to the exsisting frame that would be the prefered method. So if you can let me know what motors can bolt in to a 350 setup it would be GREATLY appreciated.

Looking foward to your response. Also feel free to let me know which is your favorite Big Block. Because I want to put something in that will last, and have some relability[/list][/code][/quote]

 

[Waterthunder]

That is a large rig for a direct drive if you keep it direct drive. I would lean towards a 500 Caddy, 455 Buick or 455Old’s. You will make substantially more torque and power per pound with any of the above mentioned motors and you can purchase aluminum heads for all of them. Because Big Block Chevy’s are a bit heavy for a direct drive boat and B.B.C are hard to find cheap. A big block Chevy doesn’t offer much power or torque below 4,000 RPM now a caddy or the 455’s make all their power below 4,000 RPM.

 

[swampdonkey]

Thanks Waterthunder

So what your saying is that a 455 has more bottom end torque than a 454.
We have come across lots of 455s up here. Do you know of any one who has installed one on a chevy frame and if so how did the bolt pattern compare to the chevy one.
If we just have to change the engine plates on the frame I'm sure we could handle that but if we have to start widdening the frame well I'm not sure we're ready to tackle that.
Gear reduction might be a consideration in the future when we aquire a little more experience. But for now we what to stick with direct drive.
swampdonkey

 

[Waterthunder]

Out of all the motors we mentioned the 454 makes the least amount of torque plus they are much heavier. You will be able to fit all of them onto your motor stand if it previously utilized a small block Chevy. You may have to fabricate some new motor mounts but that’s it. Like I mentioned before you will always find Caddy’s, Old’s and Buick’s cheaper than a Big Block Chevy. I however do prefer to stay away from the 455 Buick due to some oil system issues that can only be resolved by modifying and prioritizing the oiling system. There are alot more aftermarket parts out there now for the Caddy's and Old's.

 

[Anonymous]

I would sure like to hear from someone that has a similar unit so you could let me know what your running for a engine and prop. Also what you would do to improve your unit.

Thanks Swampdonkey P.S. I am using my kids computer so I might not be logged in properly.

 

[swampdonkey]

THANKS WATERTHUNDER

Your input is GREATLY appreciated I will try to find a web site that might list engine specs such as; torque/HP and weights.
If any one has seen such a site please foward it to me please.
Also if anyone out there is running a BB with direct drive please let me know what kind of setup you have and what you think of it.
Swampdonkey

 

[Anonymous]

Hay mon, what do you want to know about a cadillac? Go to my special spot and order their catalog and all and I mean all your questions will be answered. WWW.CAD500PARTS.com The tele. number is 505-823-9340
They are located in Albuquerque N.M. They are the best and with the most info. So until next question, keep that gas running and the exhaust hot. slow henry

 

[RJ]

Great Website !!!!!!!!!!!!!