Auto-Marine engine balance question.

Hello all!
New to the boards, and was suggested to drop by with my question from "wakeworld"
I've cruised around here reading the info and alot of good usefull stuff on here! Thanks!
I have a 351w pleasure craft motor thats REAL tired. A whopping 100psi in cylinder 1,4,6 the worst one is 70psi. hahaha thing probably doesn't make 100hp! So instead of rebuilding the thing I found a used motor out of a mustang, complete carb to pan. So my question is in regards to the balancer and flywheel/flexplate assembley. I know 351w are 28oz in cars but are they the same in boats? Can i just unbolt the flywheel/velvet drive coupler from the existing motor and bolt it on to the new one and let er rip?
Thanks everyone!

I'm reffering to the imbalance weights on the flywheel/flexplate and balancer. This year vintage 351w utilize 28oz imbalance on the flywheel/flexplate and balancer. At least they do in the automotive world. My question is do marine applications utlize the same counter weights? I gotta believe that pleasure craft doesn't pull apart a complete motor to rebalance it.
And some manufactures rely on the convertor for the balancing, chryslers do, but ford convertors are neutral balanced and the counter weights are welded to the flexplate.
And some motors are neutral or internally balanced. My 408inch small block is internally balanced, if i could start it without the flexplate it would run without anything just fine.
So can i just remove the complete flywheel and velvet drive coupling assembley from the crank on my marine motor and bolt it to the automotive motor and have the counterweights match? IE do both automotive and marine motors utilize the same balancing weights?
Ryan

The main thing you need to know is what rotation motor do you have now? Most older Correct Crafts are right hand all car motors are left. The next problem is more than likely the Mustang motor is a 302.I realize the current state of your engine,but your going backwards. If you need a right hand motor,by the time you mess with the Mustang motor,you could just rebuild the 351

BTW, im with these guy's on rebuilding your engine. its easier than what your going to get yourself into

Ryan...Try a little humility on your standard rotation Supra engine. That should do the trick.

Ryan351w wrote: Is there anyone on the board that actually knows what they are talking about?

Ryan - I think you already got the right answer - car engines don't work well in boats, Piston to wall clearance being a major reason.

I think the info you are seeking isn't forthcoming because we use boat engines.

But you are welcome to give it a try & let us know how it works out!

Just take your flywheel/flex plate to a clutch shop (they usually have FW balancers) & they will mix or match to suit.

& yes, you could use some manners.

Where is 79 when we need him.

Ryan - I think you just passed the initiation ritual, so let's start over - Welcome to the site!

We will probably kid you about having a different brand, but we will help none the less.

FYI, a boat engine has MORE piston to wall clearance, not less, because the pistons get very hot from the constant load (& expand) but the block stays cool & doesn't expand as much.   Usually, the engine ends up with scuffed pistons. This is why we are trying to discourage you from using a car engine.


I am not a mechanic so can't answer about a counterweighted flywheel, but have never heard of this before. Certainly a Mustang web site would know, or again you could have it measured on a balancer & then you would know what to do.

The traffic is light on here because of the Holiday, so you may get more info tomorrow when everyone gets back to 'work'!

AHH ok that makes sense on the piston wall.

Ok heres how and why an engine is balanced.
I'm not being rude just dropping some info.
First of all the pistons are weighted and then the heavy ones are lightened to match each other with in about 2%
Then one ring pack is weighed.
Then one set of rod bearings.
Then the rods are weighted, big end and then small end and they are ground to match each other also.
Then the flywheel and balancer are bolted to the crank and the crank is chucked up onto a balancer, big fast lathe that can pick up the harmonics. Then you take the weight of the piston,rod,rings,bearings and add weight to the rod journal with this special clamp. Spin the crank up to about 2000 rpms or so see where its off.
The reason there are weights on the balancer and flywheel is because there isn't enough counterweight on the crank to compensate for the the piston,rod, etc.
The other alternative is to drill a hole in the counter weight of the crank and add mallory metal which is twice as dense as steel. Therefore adding to the rotating weight and essentially offsetting the piston, rod pack.
They reason they don't do that is because mallory is rediculously expensive and its not an easy job. Not something they would do on an assembly line. When they can just grab a balancer and flywheel that has a weight welded to a stragegic location to offset the piston,rod pack.
So thats why you can't just attach a 302 flywheel from say 95 on a 351 from 74 it will vibrate itself apart. Same thig if you were to put a flywheel from a 95 351 on an older 351 because in 94-95 or so they changed the offset of the weights to 50oz and in a different location.
That just scratched the surface but hope it makes clear why I'm asking this specific question.
Ryan

14 years of automotive racing engines, not marine.
As everyone pointed out there are "major" differneces in the the two.
Maybe there is something wrong with the question, but it seems straight forward to me.

I hope after you read my response above you see that the flywheel is not balanced to itself on most applications. And why I'm asking this. When the motor is neutral or internally balanced, IE mallory is used on the counter weights of the crank as stated above then and only then is the flywheel (stick) or flexplate (automatic) balanced to itself and no weight is added or needed to make the WHOLE assembly balance.

So your kids practice the socratic method on you?

Ryan

and we still dont know what your question is, post it, short and simple

Are marine engines balanced with external weights the same as their automotive counterparts.

Ryan351w wrote: Are marine engines balanced with external weights the same as their automotive counterparts.

I think that depends on the year of the motor.

The guy giving you the polite grief will help if let him. Don't try to teach when you are asking questions!

And try bolting your damper and flywheel to the crank and spin them in a balancing machine.

27?
lol,
on a 351 windsor, you can take a flywheel whether its 20 ounces or 50 ounces and, or even a flexplate and swap them, they do not recognize rotation. these parts are balanced for an externally balanced engine
and are balanced on thier own. on an internally balanced engine you must have the harmonic balancer and flywheel attached to the crankshaft and have these three balanced as an assembly. a small block Chevy 400cube is internally balanced. a 351 ford is not.....im not a big ford guy so i dont know lets say if a 390 or 460 is this way

Eric,
you have two things right in your statement, and that is that they don't care which way they rotate, and second you can interchange a flexplate with flywheel but they have to have the same offset weight.
But put a 28oz on a 50oz motor, or vise versa?let me know how that works out for ya. If that was the case then why do they produce both? Why not just make one, seems more cost effective. It might not seem like a lot but when the weight is 5.5" from crankshaft centerline at 5000 rpms, it will wreak havoc.
Your backwards on your internal and external balancing. Internal you don't have to balance the whole system with balancer and flywheel. But if your right I better go pull my 408 motor apart cause its been tearing itself apart for the last 2 years. Which is internally balanced, I didn't even have a balancer or flexplate when I balanced it.
But when you have weights on the balancer and flywheel then you balance them as an assembly, thats why they call it external, because there are weights outside of the motor.
And I don't have a clue on the 390 or 460 either....I'm a small block guy.

http://www.carcraft.com/howto/ccrp_0803_engine_balancing/index.html