Hello folks, I’m new to this site and I have a few questions. Need some of yalls knowledge. I have bought my first airboat. It is a DD 20 ft trail boss with a 455 Buick. I am in the process of changing it over to a reduction drive boat, I know I may need to modify the motor stand and buy a new cage but that's about all I know. I think I may go with a gear reducer instead of a belt reducer because I think there is less work to do to the motor stand to convert it over. Here is my question what gear ratio and prop combination should I go with to make the most torque. I don't know the hp of the 455 I'm guessing around 330 but that is a guess. The motor right now will spin a 74inch 36pitch paddle prop around 3000 rpms. I would like to try and make this boat run dry ground if its possible, I don't know if a 20 foot boat can run dry. Any help would be appreciated. :?
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MY FIRST AIRBOAT
- Thread starter cudacat
- Start date
Cadillac Performance Pts.
Well-known member
Hi & welcome! crowhater can tell you about the 20" boat. He runs one. What year model is your 455 and is it stock? That will dictate HP, but the torque will not change too much. It doesn't on our Cadillacs anyway from early model vs. later ones. From what folks say, the gear reduction is better about not wanting to torque pitch the boat as bad as a belt. Seems more and more folk are finding that 2.30s and 2.68s benefit even the lower rpm higher torque engines as long as they hold up to a crtain amount of rpms and as long as you have the right prop, you can dictate your max rpm with pitch.
Cadillac Performance Pts.
Well-known member
Wouldn't be a bad idea to pull the pan and at least one head to inspect unless you know the source and quality of the build. Hard to hail a taxi in the swamp. Hard to get out on foot too.
Hi and welcome to the forum.
I used to build DD Buick airboats on our own hull years back.
The Buick is one tough old engine, most of our 70-71 models were 360 HP. We propped them DD with a 70x44 stick prop.
If you plan to use a redrive belt or gear I think you may want to look up some of the mods for the oiling system. It falls a bit short in hard usage and the RPM youll be running with the redrives.
IF it is still available there used to be a book titled "Hot Rodding the Buick" that had most all of the mods in it you will want to include. While a boss she had her shortcomings and the oil system was one of them. For DD applications she did quite fine.
I may still have a few links here for identifying WHICH engine you have and such. Ill try to look for them in the next day or so.
Dave (Waterthunder) here I believe has some experience with these venerable old birds as well.
Were it I, I think I'd go with the 454 and just scrap the old Buick even though they are heavier and less HP. They are a much newer and better design. The caddy is ok if ya make all the mods to it as well just a different set of mods.
Overall the Waterthunder LS2 engines are the cats meow these days, but then not all of us can run a cats meow. Im happy with my O-360 on a 11.6 hull.
Good luck with the old girl
Scotty
I used to build DD Buick airboats on our own hull years back.
The Buick is one tough old engine, most of our 70-71 models were 360 HP. We propped them DD with a 70x44 stick prop.
If you plan to use a redrive belt or gear I think you may want to look up some of the mods for the oiling system. It falls a bit short in hard usage and the RPM youll be running with the redrives.
IF it is still available there used to be a book titled "Hot Rodding the Buick" that had most all of the mods in it you will want to include. While a boss she had her shortcomings and the oil system was one of them. For DD applications she did quite fine.
I may still have a few links here for identifying WHICH engine you have and such. Ill try to look for them in the next day or so.
Dave (Waterthunder) here I believe has some experience with these venerable old birds as well.
Were it I, I think I'd go with the 454 and just scrap the old Buick even though they are heavier and less HP. They are a much newer and better design. The caddy is ok if ya make all the mods to it as well just a different set of mods.
Overall the Waterthunder LS2 engines are the cats meow these days, but then not all of us can run a cats meow. Im happy with my O-360 on a 11.6 hull.
Good luck with the old girl
Scotty
I run a buick 455,the torque from 70 was the highest at 510lbs stock and severly drop as time goes on,but most of the drop was caused by the heads. I run a 2.37 right now and am changeing to a 2.68 this weekend.I run a 3 blade psr from whirl wind, my boat is 14x7.5 and will burn up dry ground.FIRST thing you need to do is find out what year your block and heads are,if you get me the numbers i will help you with that, next,if you don`t have the oil mods done you need to.buick stock rods and bolts and crank are good to 4500 rpm,any thing past that you need to balance the crank and chang the rod bolts to a good set of arp`s and thn they`ll do what an airboat needs.hope this helps,and get me those numbers.
Oh yeah alot of people may say get rid of it :roll: ,but in my opinion buicks are mean if done right :twisted:
Oh yeah alot of people may say get rid of it :roll: ,but in my opinion buicks are mean if done right :twisted:
JOE, the last three numbers on the block are 681 and i found a couple numbers on the heads one of the numbers i found witch is stamped in four or five places is 7544 or 7455 i can t remember and the other number. i will look this evening. i am pretty sure the motor is a 71 or 72. i couldn't find any info on the heads.
Heres a page for some general familiarizations, scroll down to the 455 section, I got more sommers still looking for ya.
http://www.taperformance.com/newpage1.htm
Off the top of my head it seems like there were some different pistons used in these old birds too. We liked the .250 dished pistons the best. I had one customer pout the factory 9.5:1 pistons in his and blew a hole in it after about 20 hours. The dished pistons are about 8-9:1 compression ratio.
Edelbrock and Offenhauser used to make case aluminum performer intake manifolds for them, I always swapped the cast intake for one of these.
You can port and polish your heads yourself since there is so much meat there its hard to screw them up, and I had great success with adding larger exhaust valves on my personal boat. I am a fan of the Rochester Q-Jet series on those engines as well. Tiny primaries and huge secondaries. I always changed out the metering rods for a big blunt set that dumped the gas in when ya hammered it.
There are some tricks to setting the secondaries and when the vacum gets them open. Requires a small allen wrench to set up but it lets you set the secondaries where YOU want them not where someone else thinks is best. You want them WFO when the throttle is WFO. I never saw a single one that was right just out of the car.
Ill find more on these blocks just got a lot to chase through.
Scotty
http://www.taperformance.com/newpage1.htm
Off the top of my head it seems like there were some different pistons used in these old birds too. We liked the .250 dished pistons the best. I had one customer pout the factory 9.5:1 pistons in his and blew a hole in it after about 20 hours. The dished pistons are about 8-9:1 compression ratio.
Edelbrock and Offenhauser used to make case aluminum performer intake manifolds for them, I always swapped the cast intake for one of these.
You can port and polish your heads yourself since there is so much meat there its hard to screw them up, and I had great success with adding larger exhaust valves on my personal boat. I am a fan of the Rochester Q-Jet series on those engines as well. Tiny primaries and huge secondaries. I always changed out the metering rods for a big blunt set that dumped the gas in when ya hammered it.
There are some tricks to setting the secondaries and when the vacum gets them open. Requires a small allen wrench to set up but it lets you set the secondaries where YOU want them not where someone else thinks is best. You want them WFO when the throttle is WFO. I never saw a single one that was right just out of the car.
Ill find more on these blocks just got a lot to chase through.
Scotty
Cadillac Performance Pts.
Well-known member
Another ACE in the Buick world is another friend of mine. He is Mike Phillips from Automotive Machine and Performance. He is a little closer to most of us in Philpot KY. He has done the Engine Masters Challenge with me several times and knows his Buicks. His number is 270-729-5556 if interested. Great guy! Has a parts program as well as crate engines.
Cadillac Performance Pts.
Well-known member
Olf Art":1fafzi3d said:Richard, I KNOW Mike Phillips ..... hadn't heard his name in years. Really good guy. I'll have to call him and just say hello. Thanks.
Philpot ain't a real big place.
Yeah, but Mike ain't small!
crowhater
Well-known member
cudacat":3fa7cc19 said:
I talked to you in depth the other day on the phone. If you have the money to spend I think a 2.68 with a 3 blade super wide will work on your boat. The reason I am selling my 3 Blade Falcon and 1.7 reduction is because I am moving to the above mentioned combo. From the area you said you run and as little as you will ever run dry I think the 2.68 setup is over kill. If you get a smaller reduction and want a prop to try out just give me a call and I will let you try out my Falcon. Heck I will let you try out the reduction and prop if you like.