Auto-Marine engine balance question.
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=13768
Printed Date: May-21-2024 at 7:43am
Topic: Auto-Marine engine balance question.
Posted By: Ryan351w
Subject: Auto-Marine engine balance question.
Date Posted: May-24-2009 at 12:43pm
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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! |
Replies:
Posted By: eric lavine
Date Posted: May-24-2009 at 1:25pm
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no, you need mass from the Flwheel, on an automotive engine they rely on the torque converters weight for mass, and a thicker flywheel on a standard car with a clutch ------------- "the things you own will start to own you" |
Posted By: Ryan351w
Date Posted: May-24-2009 at 2:10pm
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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 |
Posted By: eric lavine
Date Posted: May-24-2009 at 2:55pm
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yes because the flywheel is balanced on its own, not as an assembly ------------- "the things you own will start to own you" |
Posted By: Gary S
Date Posted: May-24-2009 at 5:17pm
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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 ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: davidg
Date Posted: May-24-2009 at 6:36pm
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I am with Gary. Do a budget rebuild on the motor you have. Trying to convert that Mustang motor will be a nightmare, and as Gary says, the rotation will not be right anyway.
I just did a budget rebuild on mine for around $750, but that did not include boring the cylinders and new pistons. It was grinding crank .010 under, new rings, bearings, gaskets, timing set, and lifters and cam. On the heads, I just lapped the valves. Your cylinders and pistons may still be okay, but have your machinist check them out to be sure, and if they are okay, just hone the cylinder walls. However, it may take you some time to do that. If you can get by this summer, do it in the fall/winter. |
Posted By: eric lavine
Date Posted: May-24-2009 at 6:42pm
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BTW, im with these guy's on rebuilding your engine. its easier than what your going to get yourself into ------------- "the things you own will start to own you" |
Posted By: Ryan351w
Date Posted: May-24-2009 at 8:11pm
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I guess I should clarify... The motor that is in the boat is a 351w standard rotation.
The motor that I'm planning on replacing it with is a 351w standard rotation. (Contrary to popular belief, not all mustangs are 302's) Automotive flex plates are NOT balanced individually; they are offset by 28 ounces. My question is, are boat flywheels also offset by 28 ounces. By the way, I know you guys are boat people, but the only cars that have torque converters are automatics. Manual transmission cars also have "flywheels" just like boats. Is there anyone on the board that actually knows what they are talking about? Do you honestly think that someone asking a question about internal/external balancing wouldn't know what a "reverse rotation" motor is? BTW, this is a supra, not a correct craft... |
Posted By: davidg
Date Posted: May-24-2009 at 9:01pm
| Ryan...Try a little humility on your standard rotation Supra engine. That should do the trick. |
Posted By: BuffaloBFN
Date Posted: May-24-2009 at 9:13pm
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I've talked to a bunch of folks seeking info on this or that...many get that large mouth bass look when RR is mentioned. ------------- http://correctcraftfan.com/diaries/details.asp?ID=2331&sort=&pagenum=12&yrstart=1986&yrend=1990" rel="nofollow - 1988 BFN-sold "It's a Livin' Thing...What a Terrible Thing to Lose" ELO |
Posted By: SNobsessed
Date Posted: May-24-2009 at 11:17pm
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. ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Ryan351w wrote:Posted By: Gary S
Date Posted: May-25-2009 at 12:49am
Try to help a guy out based on info he does not give and what do you get?. I do happen to know Mustangs have more than 1 engine, am I supposed to guess you found a 429 for your Bayliner,I mean your supra. If your going to be a Di*k about it why don't you go over to the supra site and ask there. Or better yet "tuberworld" ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: lewy2001
Date Posted: May-25-2009 at 2:28am
Where is 79 when we need him.  ------------- If you're going through hell, keep going http://www.correctcraftfan.com/diaries/details.asp?ID=2999" rel="nofollow - 89 Ski <a href="http://www.correctcraftfan.com/diaries/details.asp?ID=5685" ta |
Posted By: Ryan351w
Date Posted: May-25-2009 at 2:40am
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Ok
I'll admit that I might have been short fused, but the answers I was getting had nothing to do with the question. I've been machining and building motors for over 14 years. Cylinder head porting, line honing, boring, milling, balancing etc etc. I've built 3 302s, 3 351s my current 408 stroker and a couple mopars with my buddy. And I understand no one had anyway of knowing that. I can tell which way a motor spins and if its std or reverse. I have personally never dropped a car motor into a boat but my dad and his buddies have numerous times but they were chevy motors and an Olds 455 in a flat bottom river rat. So I was just trying to confirm the counterweight question with the flywheel specific to the ford, and pleasure craft in particular. Cylinder wall clearance I understand as being tighter in a marine app. because the internals don't get to the temps that they do in a car. So yeah that makes sense. I thought I did give the correct information based upon the answer I was looking for, which is/was do auto and marine engines share the same balancing technique and the same 28oz counterweights. And no I didn't specify which size motor I found, but since I was specifically referring to a 351 and not will a 429 or 302 fit where a 351 once was I guess I thought it was clear, I apologize. Well there we are.... |
Posted By: SNobsessed
Date Posted: May-25-2009 at 11:50am
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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'! ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: eric lavine
Date Posted: May-25-2009 at 12:48pm
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I would think with 14 years of doing this, you wouldnt be asking the question, i read your question 18 times, and you know what i get a better answer from my kids when i ask them how school went.....I think the problem here is your question....not the answer...
its free information, so maybe you should start again... But again with 14 years of doing this, you would figure out it is cheaper to rebuild what you have....Im a fckin smart-ass and it took 2 years to be accepted ------------- "the things you own will start to own you" |
Posted By: Ryan351w
Date Posted: May-25-2009 at 12:51pm
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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 |
Posted By: eric lavine
Date Posted: May-25-2009 at 12:52pm
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are you telling us this from reading this or from your 14 years of vast Knowledge? ------------- "the things you own will start to own you" |
Posted By: Ryan351w
Date Posted: May-25-2009 at 1:01pm
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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 |
Posted By: Ryan351w
Date Posted: May-25-2009 at 1:02pm
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My 14 years of vast knowledge.
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Posted By: eric lavine
Date Posted: May-25-2009 at 1:04pm
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and we still dont know what your question is, post it, short and simple ------------- "the things you own will start to own you" |
Posted By: eric lavine
Date Posted: May-25-2009 at 1:06pm
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i figure with your vocabulary, your about 28 years old, so that means you started rebuilding engines at 14? ------------- "the things you own will start to own you" |
Posted By: Ryan351w
Date Posted: May-25-2009 at 1:08pm
| Are marine engines balanced with external weights the same as their automotive counterparts. |
Posted By: boat dr
Date Posted: May-25-2009 at 1:14pm
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The Boat Doctor says...............................................................................................................................................Hope that clears up the confusion.... ------------- boat dr /diaries/details.asp?ID=4631 - 1949 Dart /diaries/details.asp?ID=1533 - 1964 American Skier |
Posted By: BuffaloBFN
Date Posted: May-25-2009 at 1:14pm
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. ------------- http://correctcraftfan.com/diaries/details.asp?ID=2331&sort=&pagenum=12&yrstart=1986&yrend=1990" rel="nofollow - 1988 BFN-sold "It's a Livin' Thing...What a Terrible Thing to Lose" ELO |
Posted By: Ryan351w
Date Posted: May-25-2009 at 1:16pm
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Pretty good guess actually, 30 and I was 16. My best friends dad was and is a nostalgia super stock racer with a 63 dodge. 500 inch big block 725 hp that he raced. So when my buddy turned 15 he bought a 73 duster and we learned motors transmissions, rear ends all from his dad. When I turned about 17 I think, I stated working for a friend of his dads working on cylinder heads. Seats and guides, valve jobs, some minor port work. Then I moved to block machining for 3-4 years. Everything from inline 4 bangers to 426 hemis to straight 8 Packards.
I don't and never will claim to be the end all be all to engine knowledge but I'm no slouch either. |
Posted By: eric lavine
Date Posted: May-25-2009 at 1:19pm
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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 ------------- "the things you own will start to own you" |
Posted By: eric lavine
Date Posted: May-25-2009 at 1:24pm
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stick around, we can teach eachother ------------- "the things you own will start to own you" |
Posted By: Ryan351w
Date Posted: May-25-2009 at 2:00pm
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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 |
Posted By: davidg
Date Posted: May-25-2009 at 2:01pm
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I have rebuilt a couple engines, and read many articles on engine building. I am NOT an expert, but do have some observations on what I think Ryan is getting at....
Based on all his posts, I think he has been involved in or around building too many full on race engines, and is getting too hung up on trying to precisely balance these boat engines that spin at 3500-4400 rpm max. A couple of my thoughts: - Some engines are internally balanced, and some are externally balanced. Depends on specific engine. Check to see what yours is. - On engines that are externally balanced, I am not sure, but, isn't the balancing done at the harmonic balancer on the FRONT of the engine?? - The other kind of balancing that he is referring to is the fine-tune balancing the rotating assembly that racers do so the engines won't fly apart at 8,000 rpm. Not needed on our boat motors...in my opinion, as they operate at much lower rpms. Commentary.....Does it make a difference anyway on the engine he is considering? The engine exists with some form of balancing on it now (internal or external). No need to fine tune the rotating assembly as it will be a lower rpm application. Shouldn't he just need to bolt the flywheel and damper on and put it in the boat?? Not sure what else I am missing here. |
Posted By: Ryan351w
Date Posted: May-25-2009 at 2:10pm
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Dave,
exactly some are internal and some external. Fords are external and yes the harmonic balancer is on the front and is counter weighted on an externally balanced motors. But there are weights added to the rear of the crank welded to the flexplate or flywheel as well. And that is really my question if marine and auto share the same offset weights. |
Posted By: eric lavine
Date Posted: May-25-2009 at 2:20pm
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Dave I too think thats the case, under 5k you do not need to balance any of the internals because they are close...when you spin them up past that mark you need precise weights of the pistons, rods etc.
i think Ryan refers to internally balanced as this process. such as a 400 sbc, its a special harmonic balancer, flywheel and its all bolted together and spun on a balancing machine WITHOUT the pistons and rods, thus this what is meant by an internally balanced engine. you cant use a 350 FW on a 400....but you could use that FW on any other SBC"s, those parts such as the 350 crank is balanced by itself along with the FW and HB. ------------- "the things you own will start to own you" |
Posted By: eric lavine
Date Posted: May-25-2009 at 2:24pm
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when you refer to internally balanced i think your meaning is the rods weigh the same the pistons weigh the same and so on...that is a balanced and blue printed engine. when you refer to internally and externally that refers to the crankshaft. ------------- "the things you own will start to own you" |
Posted By: eric lavine
Date Posted: May-25-2009 at 2:39pm
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to help you better understand, when i build a stroker 383, you use a 350 cube block and a 400 crank, i have to buy a 400 FW and A 400 HB, and send them out to have the three parts balanced together, to make them as one....that is what is considered an internally balanced engine. you cant use the 400 FW or HB on a 350 crank. but you could take the FW from a 350cube and slap it on a 265,283,327,305,307 because they are externally balanced engines
I will then weigh each piston, rod, and grind them for perfect weight within a gram or so of eachother so those parts are balanced this is a weight balance not a reciprocating balance ------------- "the things you own will start to own you" |
Posted By: davidg
Date Posted: May-25-2009 at 2:45pm
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Ryan;
Interesting discussion. I guess I am confused on the offset weights you keep referring to. Perhaps they are used in automotive applications, especially with flexplates/automatic transmission applications....not sure. But, I just put my flywheel on my 351 Ford this weekend. There were no weights that I could see, or had to add. I also know that there were no weights on the crankshaft as I just assembled the engine a couple of weeks ago. So, my thinking is that you should be good to go if you bolt the flywheel and damper plate on. If you need the proper flywheel, you should be able to use the one off of your tired Ford 351. That would be the correct one for your boat obvioustly. Eric....On the issue of flywheel weights, I did not know there differences. What do our Ford typically use in these inboards?? |
Posted By: Ryan351w
Date Posted: May-25-2009 at 3:27pm
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Since nobody wants to believe me,
I pull some outside sources and site them here. http://www.rpmmachine.com/engine-balancing.shtml It won't let me copy the paragraph i want, but scroll down to "internal/external" Just about half way. But heres an excerpt... "If you're rebuilding an engine that is internally balanced, the flywheel and damper have no effect on engine balance and can be balanced separately. But with externally balanced engines, the flywheel and damper must be mounted on the crank prior to balancing." http://www.carcraft.com/howto/ccrp_0803_engine_balancing/index.html page 2. "Internal vs. External Balance Packaging is also an important issue. During the design of the 400ci small-block, a major engineering hurdle was insufficient real estate inside the small-block crankcase for the larger counterweights demanded by the 400's supersized 4.125-inch piston. This was especially difficult in the rear of the engine because the rear crankcase area on a small-block Chevy is restricted by the placement of the oil filter. The solution called for external balance weights placed on the harmonic balancer and flywheel/flexplate. One advantage to external weights is that they are generally lighter because they are positioned at the extreme ends of the crankshaft. The disadvantage is that these offset weights impart their own twisting forces back into the crankshaft, which is not good. This same situation occurs with the 454ci big-block Chevy, which is also the only production big-block that uses external weights to balance the engine." "Small-block Fords have always been externally balanced, but because Ford is a name synonymous with change, the Blue Oval engineers altered the amount of the external balance when the engines morphed to a one-piece rear main seal. Early small-block Fords used 28 ounce-inches as the external weight amount, changing in 1981 to 50 ounce-inches. Like small-block Chevys, parts can interchange between early and late engines, but to guarantee smooth engine operation, the crankshaft, balancer, and flexplate/flywheel must all be kept within the same balance family." |
Posted By: eric lavine
Date Posted: May-25-2009 at 9:43pm
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dude, your making me reach for another beer.
its been about a year(for a stroker), i may have the 2 mixed, but the meaning is the same...thats something i dont forget. I took a 351 flywheel off and put it directly onto a 302 for my test stand and i spin that beoch at all it has, at times for 1/2 hour solid, I know that thing is spinning at 6k,without any vibrations....but then again i have had a bad trans coupling and the harmonics will snap a 2" input shaft off of a transmission. ------------- "the things you own will start to own you" |
Posted By: Ryan351w
Date Posted: May-25-2009 at 11:43pm
FYI - These are the weights on the crank that I was talking about that need to be drilled for either lightening or adding mallory metal.. 
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Posted By: Ryan351w
Date Posted: May-25-2009 at 11:49pm
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Eric,
As far as swapping a 302 for 351 flywheel, if the 351 was a later model ie one piece rear main=50oz imblance, same as 84 i wanna say 302 and newer were 50oz. OR if the 302 was older I THINK those were 28oz but not 100% on that. The meanings are not the same between internal and external. Otherwise they would just be refereed to as balanced. NOT a specific location or type of balancing. This is not a "same difference" |
Posted By: davidg
Date Posted: May-26-2009 at 12:10am
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Ryan.....attached is a picture of the crank in my boat. I assume it just has the normal counterweights found on standard production engines.
What is stopping you from just using the Mustang engine? It is balanced already. It is standard rotation. You have a flywheel that was being used for marine purposes from another 351. Just bolt that on, and your damper, and go. I would want to be safe as well, but, I don't see what is stopping you at this point?? 
|
Posted By: Ryan351w
Date Posted: May-26-2009 at 12:43am
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Dave,
SWEET Motor color!! 74 block too, same as whats in my car, from what I've gathered the 74 was last year of the "stonger" stock blocks. I guess they started using a lower nickel content in 75. Agreed the auto motor is a balanced motor, what my entire question is about, do the marine engines share the same offset weights on the flywheel as the auto. This is what I'm talking about. Here is an external balance flexplate 
here is a neutral or internal balance. No weight. 
|
Posted By: davidg
Date Posted: May-26-2009 at 1:32am
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I do not recall any kind of weight on the flywheel at all. Take your trans and bellhousing off your Supra and see what it looks like. Either way, it should work, right?? It works with your current set up.
I think the biggest difference you may find is, as folks have pointed out, is the larger clearance between the piston and the cylinder wall. But, it may be just fine. |
Posted By: KENO
Date Posted: May-26-2009 at 2:00am
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Hey this is getting interesting.
I stayed at a Holiday Inn Express last night so let me tell ya' what I remember The short simple answer is that all stock 351W engines are balanced the same whether it is a car or boat engine. They all have 28 oz. external imbalance. 302 engines could be 28 or 50 So there's the straightforward answer you were looking for, now you can put the parts on the car engine and see how it does in the boat. This is only from my memory banks, and I can't remember what I had for supper last night. Keno |
Posted By: davidg
Date Posted: May-26-2009 at 2:32am
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Ken....I like the line about staying at the HIE. I was about ready to use that today in one of my posts on this subject but didn't. I am not an engine expert, BUT.........
Anyway guys, help me out here. What does 28 or 50 ounce balance (or imbalance) mean? I also saw the term inch/ounce, or ounce/inch. Not sure what those mean. Can someone explain what those numbers and terms are. |
Posted By: JoeinNY
Date Posted: May-26-2009 at 2:43am
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So KENO is right the answer is yes the marine engines share the same weight offsets as the automotive. As long as you sticking with a 351w to a 351w you can just bolt up the flywheel and damper plate and it will work. If it was different, its not but someone may need to know this someday you can take your auto engines flex plate and your boat engines flywheel to a balancer and tell them to make the flywheel match the flexplate. I had to do that when I went from an older 302 to a newer 302. Believe me if you have 50 oz imbalance parts on a 28oz imbalance engine you will notice.. and quick.
If its a seasoned automotive engine you probably wont have any immediate problems running it in a boat.. probably. IMO worth a shot to save a summer. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: JoeinNY
Date Posted: May-26-2009 at 2:56am
It means exactly what it sounds like, the combination of the flywheel(or flex plate) and the harmonic balancer are 28 or 50 in oz out of balance because the crank rods, pistons, etc need the extra weight for the entire rotating assembly to be balanced. Either to keep the rotating weight down, or some other design concern the stock cranks didnt have big enough counterweights to allow the engine to be internally balanced so it could use balanced flywheels and balancers. So what really happens here is the engine minus the flywheel and dampener is not balanced, in fact it is off balance by 28 in-oz. The flywheel and balancer are also off by 28 in-oz total but 180 degrees different than the engine, and when put together all are in harmony. In a race situation internally balanced is better.. but in a skiboat boat, any balance is good balance. Inch-ounce is what is sounds like an ounce of weight located one inch off center. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: KENO
Date Posted: May-26-2009 at 9:43am
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Hi again
Another night at the HIE and I wake up thinking that Ryan will have to look at things like the housing for the timing chain and gears. The one from the car engine is probably aluminum and the boat version is cast iron but....there is a boss cast into the marine one with 2 threaded holes that you mount the raw water pump bracket to that is not there on the car housing. I'm assuming this is a PCM in the Supra with a belt driven pump. The boat engine is a rear sump, your car engine.... I wouldn't know, but I'd swap oil pans and the suction line for the oil pump too. Then the dipstick tube needs to be swapped too. That's what I remember for now. Keno |
Posted By: eric lavine
Date Posted: May-26-2009 at 10:19am
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Brass cast plugs also, I could see the crank 3 pics up needing balanced with the FW and HB, because of the swing and the extra weight added for swinging that crank, I dont think that is a stock crank, the flex plate does not look to be dowel pinned or have an ecentric to time it to the crank ------------- "the things you own will start to own you" |
Posted By: dizuster
Date Posted: May-26-2009 at 2:30pm
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Seems you have a lot of questions about balancin'. Please let me try to explain a little for you. Obviously the current motor is balance, so all of the pistons and stuff weigh the same. Then, as you know with external balancing (also called outside balancing), the flywheel and the balancer must also weigh the same.
I think the safest thing to do is when you get the new motor, put the balancer and flywheel from the current boat motor, on the new motor. The new motor should have all of the pistons and stuff weighing the same anyway, so as long as you swap the balancer and flywheel, they should match too. What do y'all think? Sounds like the safe way to go to me. That way you won't have no problems. Rev that bitc* up!!!! |
Posted By: Ryan351w
Date Posted: May-26-2009 at 3:44pm
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Keno, Joe, Thank God you guys chimed in I was going crazy! Thats exactly what I was trying to find out. Interesting point about the timing cover and cold water lift pump. I didn't even think about that. And yes it is a belt driven fresh water pump. And I was defiantly going to swap oil pans and pickups. Gaskets are already in stock actually!
Eric, Brass plugs absolutely. But I'd put money that is a stock crank in Daves motor. They have to drill holes in the crank from the factory. Its normal to have machining tolerances and those tolerances need to be corrected by proper balancing. The flexplate/flywheels don't have dowels or eccentrics. The bolt pattern on the back of the crank is drilled in such a way that the flex/fly can only be bolted on one way. The only thing that I can think of off hand that has an eccentric is the fuel pump, driven off the front of the cam. Timing is done on the balancer, which utilizes a woodruff key to align the balancer to the proper orientation on the crank. Dizuster...I don't even know where to begin with you. |
Posted By: KENO
Date Posted: May-26-2009 at 8:37pm
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Hi Again
Here are a couple of pictures of a flywheel from an 86 or maybe an 87 PCM 351. You can see without any trouble where the imbalance is in this flywheel. It's not stuck on or welded on but it's cast with the imbalance in it. The second one shows it's a Ford and has the part number. And like Ryan said, it only bolts on one way so you can't screw up the balance. The bolt holes may look evenly spaced but they're not. Gotta go now, I used up all my brainpower trying to get these pictures into the computer then attached and I won't even say how long it took. Keno 
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Posted By: eric lavine
Date Posted: May-26-2009 at 10:44pm
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i pulled that 460 apart and on the front once i pulled the harmonic balance off there was a big counterweight also keyed behind it. next then the front seal, i would say it weighed roughly 2 pounds...not the seal, the weight lol ------------- "the things you own will start to own you" |
Posted By: eric lavine
Date Posted: May-26-2009 at 10:45pm
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BTW, 460 exhaust manifolds $1607.00 cost for the pair, without risers
can anyone do better? ------------- "the things you own will start to own you" |
Posted By: Ryan351w
Date Posted: May-26-2009 at 11:19pm
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Keno, thanks for the pics. That makes sense that its acutally caste into the piece.
Ryan |
Posted By: SNobsessed
Date Posted: May-26-2009 at 11:31pm
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Learn something new everyday.
Thanks for bringing this up Ryan, now I know what to expect when need to remove my flywheel. I'll make sure & mark 'this side up'! ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: Ryan351w
Date Posted: May-27-2009 at 12:09am
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SN, don't mention it man.
But don't worry about marking the flywheel it will only bolt on one way, as far as clocking goes. It will look close but only fit in one orientation. One thing that might make it easier is mark which side faces out. The flywheels do have a slight off set front to back. When put on wrong on a car the trans wont seat but I couldn't tell you about a boat. So I will definatly be marking that. Or just look as to what side the counter weight faces. Ryan |
Posted By: KENO
Date Posted: May-27-2009 at 12:44am
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I noticed that I went back to the future or something. My camera thought it was 5/25/2012.
Also figured I'd point out a couple of balancing type holes at around the 3 o'clock position in the first photo. I'm guessing that since it's a big cast piece, each one is a little different so they have to drill to get the right imbalance. Sounds kinda goofy. The picture shows the side that goes toward the crank. |
Posted By: Ryan351w
Date Posted: May-27-2009 at 12:51am
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Keno, didn't even notice you had your flux capacitor set and 1.21 gigawatts flowing!! haha!!!
I also have those same holes in my flexplate for me car....its kinda interesting. I would tend to agree with your assumption on that. |
Posted By: tmcboat
Date Posted: April-22-2018 at 7:49pm
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Hi All, In 2016 I bought a 1984 ford marine 5.8 liter engine and installed my pmc 1973 28oz flywheel and a new 6.53 inch 28oz. 3 bolt harmonic balancer so I could use my pmc 3 bolt pulley. When we started the engine up we notice a slight wobble in the harmonic balancer- about 1/32 inch. I didn't think much of it and the boat runs good and has about 110 hours on the engine but still has the slight wobble in the harmonic balancer. . My PMC engine has a drive shaft tied directly to a volvo penta stern drive. I have read 2 blogs. One says that PMC used the 28oz flywheels and 28 oz balancers up till the late 1980's. Ford auto/not marine engine switched to a 50 oz flywheel and 50 oz. balancer after 1981-I hate to think that I have to pull the engine and lower unit to install a 50 oz flywheel and 50 oz harmonic balancer when the engine runs good now. I am going to pull the harmonic balancer and use a dial indicator to see if the crankshaft end- snout the balancers fits on is out of round. Your thoughts and suggestions please thanks, tmcboat |
Posted By: KENO
Date Posted: April-22-2018 at 7:56pm
See the answer somebody gave in your other post 
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