SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: beerjet on September 07, 2009, 04:56:58 PM

Title: Aluminum or steel
Post by: beerjet on September 07, 2009, 04:56:58 PM

Flywheel or flex plate.
BBC
500"
6k rpm range

What are the pros and cons.
what would be the way to go.

-beerjet-

Title: Re: Aluminum or steel
Post by: GT Jets on September 07, 2009, 05:17:42 PM

Quote from: beerjet on September 07, 2009, 04:56:58 PM

Flywheel or flex plate.
BBC
500"
6k rpm range

What are the pros and cons.
what would be the way to go.

-beerjet-

Dumb question #1.................Jet?

I am the aluminum flywheel's biggest fan. Plenty strong, can spin them 10,000 RPM, rigid enough for high compression starting, yet still light weight.

Oh yeah, replaceable ring gear too... :thumbup:

Was just involved in this very topic on the "other" site....But that was a hydro... :screwy:

GT

Title: Re: Aluminum or steel
Post by: beerjet on September 07, 2009, 09:16:19 PM

Quote from: GT Jets on September 07, 2009, 05:17:42 PM

Dumb question #1.................Jet?

Yep !
Thats kind of where I was leaning.
Just wasnt sure if there were any major reasons NOT to run one .

-beerjet-

Title: Re: Aluminum or steel
Post by: GT Jets on September 07, 2009, 09:47:42 PM

Quote from: beerjet on September 07, 2009, 09:16:19 PM

Yep !
Thats kind of where I was leaning.
Just wasnt sure if there were any major reasons NOT to run one .

-beerjet-

Other than the lighter weight, I really don't have any negatives.

I have one on my old retired marathon motor, I have one on the SBC in the Southwind, and I have a modified flexplate in my current jet boat motor...Hated the flexplate, so I made a round aluminum disc the diameter of the torque converter bolt pattern and bolted it up tight....the dics was balanced with the crank so I'm not worried about that, but it would never pass tech for racing...(Needs to be SFI rated).

That's all I got. :-\

GT

Title: Re: Aluminum or steel
Post by: electrowoman on September 08, 2009, 08:09:51 AM

Aluminum flywheels really let the engine rev fast.... don't fly out of the water
without a rev limiter   :o

Title: Re: Aluminum or steel
Post by: crewchief22 on September 08, 2009, 08:14:38 AM

Not going to rev any faster than an engine with a flexplate.  If anything I think the added weight of an aluminum flywheel would help for the times it does unload.

Title: Re: Aluminum or steel
Post by: HDriderTH on September 08, 2009, 09:10:37 AM

Aluminum here "O"   ;)

Title: Re: Aluminum or steel
Post by: electrowoman on September 08, 2009, 02:51:29 PM

If it had a flex plate why would you put on an aluminum flywheel  :screwy:

Must be bowtie thinking  ???

Title: Re: Aluminum or steel
Post by: beerjet on September 08, 2009, 06:08:19 PM

Quote from: electrowoman on September 08, 2009, 02:51:29 PM

If it had a flex plate why would you put on an aluminum flywheel  :screwy:

I like the added inertia of a flywheel in a (relativly speaking) higher HP application.
In a crusier with stocker power I guess it wouldnt matter.
It's really just there to start the motor anyways and as a result has to be balanced.

-beerjet-

Title: Re: Aluminum or steel
Post by: GT Jets on September 08, 2009, 06:55:32 PM

Quote from: electrowoman on September 08, 2009, 08:09:51 AM

Aluminum flywheels really let the engine rev fast.... don't fly out of the water
without a rev limiter   :o

Not really a Bowtie thing, more of a compression ratio thing, the aluminum flywheel is more rigid (way more)  and is a lot easier on the starter.....

Honestly the main reason we use aluminum in the Rock Dodger was two fold, I feel like I am giving away secrets here, but here goes....

The first reason we like a light flywheel has nothing at all to do with acceleration, but decelleration....If a whitewater boat can't slow down quickly, you wont be able to pick up the throttle and power through a rapid, you have to risk lack of control because of low nozzle velocity compared to hull speed (read; no steering)... :screwy:

The second is, well, you can run two ring gears on the aluminum (and steel) and the reason I like to do that is we can run two starter motors, one up top and one block mounted....Having a working starter in some cases can save you from losing your boat to a swell or rock if the engine dies.... :thumbdown:

These reasons are not common, but I have become a large fan of them for other reasons..

1- you lose 20 +/-pounds of weight over an iron FW. :thumbup:
2- they look bitchen polished if they are visible  :thumbup:
3- they allow for killer throttle response  :thumbup:
4- less rotating mass  :thumbup:
5- I have never seen one fail  :thumbup:

GT

Title: Re: Aluminum or steel
Post by: 75 fantasy on October 13, 2009, 10:08:45 AM

Quote from: beerjet on September 08, 2009, 06:08:19 PM

I like the added inertia of a flywheel in a (relativly speaking) higher HP application.
In a crusier with stocker power I guess it wouldnt matter.
It's really just there to start the motor anyways and as a result has to be balanced.

-beerjet-

i have a few of questions.
1. so if i had a bbf 460 stocker(right now), would a flex plate be beneficial?
2. if i built a mild bbf 460 would it still benefit me(the plan - cam,maybe heads,6-71 blower[not alot of boost])?
3. would the motor require internal/external balancing using a flex plate?


i know vague specs but any help would be apreciated.
thanks in advance, 75 fantasy

Title: Re: Aluminum or steel
Post by: 75 fantasy on October 16, 2009, 12:10:53 PM

no opinion's :( i was watching a flex plate on ebay that ended.

Title: Re: Aluminum or steel
Post by: beerjet on October 17, 2009, 09:13:40 AM

It's really preference.
All they are really used for is start up.
The aluminum seems to have the most "pros"
Durability, rebuildability, and weight.

-beerjet-

Title: Re: Aluminum or steel
Post by: HDriderTH on October 17, 2009, 10:00:35 AM

YUp mines aluminum, Nordie had ir in his hand yesterday. Turned out there was flexplate bolts in there, only about three or four threads engaged. So, we swapped out the bolts and instaled the new motor plate. We moved the motor plate from the end of the tranny to between the trans and motor, like it was originaly. Got OC's rear motor plate, Sanger, and had it cloned. Your flexplate should come balenced if it's for a 454.

Title: Re: Aluminum or steel
Post by: jet boat performance on October 21, 2009, 08:28:08 AM

Got Billet steel in my boats (both blower motors) but like the Aluminums alot   ;) , 5k motors are likley fine with a quality Flexplate Tom