How is the flex plate balanced?

nielsmobers · 03-10-2003, 04:16 AM

I've bought a new flex plate on recommendation of an USA garage because the installed flex plate has a balance problem. The new flex plate looks like a hobby project, the gear wheel and the balance weight are welded on and there is no sign of any balance tuning. Is the flex plate made by a computer welding machine and is that the reason it isn't 'balance tuned'?? It does not look like a precision component. An other question: is it necessary to center the flex plate or is it only possible to fix it one way.

Niels

matt1190 · 03-10-2003, 12:34 PM

the plate is accentric in that it'll only bolt on one way, in a certain bolt pattern. Typically your entire engine should be balanced at the same time,..rods and pistons,...harmonic balancer, to flywheel. Whoever balances it will probably drill precise holes in the plate.

nielsmobers · 03-11-2003, 10:13 AM

Is it also possible that if new components (balancer and flex plate) are bought, that it is allready balanced, or is it allways nessesary to balance the engine. USA garages in my neighborhood tell different stories, one tells me that it has to be balanced, the other tells me that if the components are made for that car you don't have to balance?!? Now I'm confused... Is it a possibility to install the flex plate and then check if the car is balanced. Is it also possible to balance the engine by adding weights on the outside of the balancer like balancing a wheel.

trevor'72 · 03-11-2003, 01:24 PM

You're correct to some degree. But here how it goes:

First things first things are alswyas balanced! Or they must be if you expect you engine to last!

Ok, even from the factory all engine parts qre balanced, baybe not as exact as if you have a machine shop balance every thing, but it is all balanced. If you have decided to rebuilt your engine and have bought new pistons, rods, crankshaft, balancer, flywheel(manual tranny) or FLEXPLATE(auto tranny) or any one of these parts even if you keep the rest stock it becomes necessay to have your engine balanced! All these parts make up the rotating assembly and must work together and in harmony!!!! Now I don't want to confuse you but it is entirely possible to replace items and keep the balance "within factory specs". Let's say for instance that you have a running (or did run) engine that is fine. If the balancer cracks or the flexplate cracks or gets way to hot (or other damage occurs to either part) you will most likely have to replace these parts. If you engine is stock then a stock flexplate should just bolt on. Yes the welding on the flexplates lookds kinda rought but if the part is new and is the correct spec (ie balance for you engine, size, number of teeth) it should be fine. If however your engine has been rebuilt before and balanced that may be a different story. When my motor was balanced my machine shop balanced my flywheel (manual tranny equivalent to a flesplate) to be in harmony with the rest of the engine. So if your flexpate that you took off your motor was balanced (ie drilling or other methods of removein/adding wieght) by a shop then you must either get the blueprinting from the shop (tolerances of the rebuild, tells how each part was machined) to be able to duplicate the balance of the previous rebuild to have the rotating assembly re-balanced.

Hope this has heled and maybe clarified a few things. Good luck with the motor!

Jeff65 · 03-17-2003, 05:00 PM

What niels is saying is there is "factory balancing" which is good enough for the rpm range of the factory vehicle. Then again there is "performance balancing" which is an extra effort made in a precision machine shop to carefully match components to eke out the best possible performance. Factory balance is good to about 6000 rpm redline. If you intend to push the engine to the limits, say 8000+ rpm then you need the extra effort of precision balancing. There is often very little difference between the two, but if winning is your goal, every little bit counts!

trevor'72 · 03-18-2003, 11:24 AM

to be reved in the 8000+ range as you mentioned it'd be a good idea to get an after market, internal balance crank and a good set of rods, h-beam or other. Stock parts, balanced or not will not standup to that kind of rpm. The internal balanced crank will not suffer form flex as the expernal balanced cranks do.

sleeperstang · 03-25-2003, 10:33 AM

You guys couldn't have posted this topic at a better time.
I'm having the same problem with my car. My 289 engine has just about died on me due to vibration problems which I think have caused rod knock. I'm planning on buying a rebuilt 302.

This is where things get confusing. Say I get my 302, and it's a 60s block, so it uses a 28 oz imbalance. My mustang currently has a C-4 tranny, but in the garage I have a T-5 that will go on some time in the next year. I will have to go with a flywheel from a newer mustang, which I already I have. I know that it will have to be machined down to 28 oz imbalance. The question here is could it be swapped and not have problems without having to take the engine out and have it rebalanced.

I guess my question breaks down to, is the imbalance swappable between automatic and manual balance factors?

Thanks!

trevor'72 · 03-25-2003, 01:50 PM

The balance factor as you mentioned is specific to the motor. Not the trans. With a manual the flywheel could be matched to the balance of the flexplate if you aready have one (I would imagine any competant machine shop could do this

) I'm not sure about the bellhousing meeting up...C4...T5...are all 302 block the same bolt patern? HOPE SOMEONE ELSE CAN HELP ... but that's another story. If you order a flywheel for that year of motor 80s or 60s or what ever it will be balanaced correct. (either 50 or 28 oz imbalance, new or old respectively) With a manual trans there are other parts that will be rotating, for instance the pressure plate. When my motor was balanced last year the shop "balanced" my brand new pressure plate. All you'll need to do after that is make sure that the pressure plate is at 0 balance. Most often the balance of the pressure place isn't checked even when they are replaced by ford, so I wouldn't worry too much about that one, unless of course your intentions for the motor are to sing it like an elementary school choir after a helium gulping contest.

Good luck in your search!

nielsmobers · 03-26-2003, 03:16 AM

After I removed the transmission I discovered that the transmission mount was gone completely, I've replaced it and it seems that the vibration is under control. The vibration wasn't the problem, but muffling this vibration was. I assume that most mustangs have a little vibration, or not?? Looking back I feel stupid that I've replaced everything except the mounts. Two times I brought my car to a shop to let them discover where the vibration came from, they also didn't detect the broken mount!?! There's one advantage, I no longer need the repair manuel to remove the transmission...

I want to thank you guys for the very helpfull replies, you helped me discover a lot about my car.

Niels

hobgoblin351 · 03-28-2003, 01:21 PM

Balance Daniel-son Balance! Hey Trevor hats off to ya great explanation of engine balance. Sleeper you can probably find an aftermarket flywheel with the correct balance weight for the T5 swap. There are enough people doing it these days that someone is probably making them. Oh and Niels, yes most engines do have some form of harmonic vibration in them. It is usually slightand it would repeat in multiples. ex; if the vibration happens at 2000rpms, it would happen at 4000rpms

03-10-2003, 04:16 AM	#1
nielsmobers Registered Member Join Date: Jul 2002 Location: Holland Posts: 28	How is the flex plate balanced? I've bought a new flex plate on recommendation of an USA garage because the installed flex plate has a balance problem. The new flex plate looks like a hobby project, the gear wheel and the balance weight are welded on and there is no sign of any balance tuning. Is the flex plate made by a computer welding machine and is that the reason it isn't 'balance tuned'?? It does not look like a precision component. An other question: is it necessary to center the flex plate or is it only possible to fix it one way. Niels

03-10-2003, 12:34 PM	#2
matt1190 Registered Member Join Date: Jan 2003 Posts: 66	the plate is accentric in that it'll only bolt on one way, in a certain bolt pattern. Typically your entire engine should be balanced at the same time,..rods and pistons,...harmonic balancer, to flywheel. Whoever balances it will probably drill precise holes in the plate. __________________ 66 coupe: 351W 30 over. Fiberglass shelby parts + flares

03-11-2003, 10:13 AM	#3
nielsmobers Registered Member Join Date: Jul 2002 Location: Holland Posts: 28	Mixed messages Is it also possible that if new components (balancer and flex plate) are bought, that it is allready balanced, or is it allways nessesary to balance the engine. USA garages in my neighborhood tell different stories, one tells me that it has to be balanced, the other tells me that if the components are made for that car you don't have to balance?!? Now I'm confused... Is it a possibility to install the flex plate and then check if the car is balanced. Is it also possible to balance the engine by adding weights on the outside of the balancer like balancing a wheel.

03-11-2003, 01:24 PM	#4
trevor'72 Registered Member Join Date: Feb 2003 Posts: 35	Yes You're correct to some degree. But here how it goes: First things first things are alswyas balanced! Or they must be if you expect you engine to last! Ok, even from the factory all engine parts qre balanced, baybe not as exact as if you have a machine shop balance every thing, but it is all balanced. If you have decided to rebuilt your engine and have bought new pistons, rods, crankshaft, balancer, flywheel(manual tranny) or FLEXPLATE(auto tranny) or any one of these parts even if you keep the rest stock it becomes necessay to have your engine balanced! All these parts make up the rotating assembly and must work together and in harmony!!!! Now I don't want to confuse you but it is entirely possible to replace items and keep the balance "within factory specs". Let's say for instance that you have a running (or did run) engine that is fine. If the balancer cracks or the flexplate cracks or gets way to hot (or other damage occurs to either part) you will most likely have to replace these parts. If you engine is stock then a stock flexplate should just bolt on. Yes the welding on the flexplates lookds kinda rought but if the part is new and is the correct spec (ie balance for you engine, size, number of teeth) it should be fine. If however your engine has been rebuilt before and balanced that may be a different story. When my motor was balanced my machine shop balanced my flywheel (manual tranny equivalent to a flesplate) to be in harmony with the rest of the engine. So if your flexpate that you took off your motor was balanced (ie drilling or other methods of removein/adding wieght) by a shop then you must either get the blueprinting from the shop (tolerances of the rebuild, tells how each part was machined) to be able to duplicate the balance of the previous rebuild to have the rotating assembly re-balanced. Hope this has heled and maybe clarified a few things. Good luck with the motor!

03-18-2003, 11:24 AM	#6
trevor'72 Registered Member Join Date: Feb 2003 Posts: 35	balance to be reved in the 8000+ range as you mentioned it'd be a good idea to get an after market, internal balance crank and a good set of rods, h-beam or other. Stock parts, balanced or not will not standup to that kind of rpm. The internal balanced crank will not suffer form flex as the expernal balanced cranks do.

03-17-2003, 05:00 PM	#5
Jeff65 Registered Member Join Date: Jul 2002 Location: Oklahoma City Posts: 208	What niels is saying is there is "factory balancing" which is good enough for the rpm range of the factory vehicle. Then again there is "performance balancing" which is an extra effort made in a precision machine shop to carefully match components to eke out the best possible performance. Factory balance is good to about 6000 rpm redline. If you intend to push the engine to the limits, say 8000+ rpm then you need the extra effort of precision balancing. There is often very little difference between the two, but if winning is your goal, every little bit counts!

03-25-2003, 10:33 AM	#7
sleeperstang Registered Member Join Date: Jun 2001 Location: Lynwood, CA, U.S.A. Posts: 82	??? You guys couldn't have posted this topic at a better time. I'm having the same problem with my car. My 289 engine has just about died on me due to vibration problems which I think have caused rod knock. I'm planning on buying a rebuilt 302. This is where things get confusing. Say I get my 302, and it's a 60s block, so it uses a 28 oz imbalance. My mustang currently has a C-4 tranny, but in the garage I have a T-5 that will go on some time in the next year. I will have to go with a flywheel from a newer mustang, which I already I have. I know that it will have to be machined down to 28 oz imbalance. The question here is could it be swapped and not have problems without having to take the engine out and have it rebalanced. I guess my question breaks down to, is the imbalance swappable between automatic and manual balance factors? Thanks! __________________ 65 Mustang Coupe...Comp Cams 262 Xtreme Energy, T-5 conversion, Romac Balancer, 620 Front Springs-4.5 Mid-eye rear springs.......work in progress

03-25-2003, 01:50 PM	#8
trevor'72 Registered Member Join Date: Feb 2003 Posts: 35	The balance factor as you mentioned is specific to the motor. Not the trans. With a manual the flywheel could be matched to the balance of the flexplate if you aready have one (I would imagine any competant machine shop could do this ) I'm not sure about the bellhousing meeting up...C4...T5...are all 302 block the same bolt patern? HOPE SOMEONE ELSE CAN HELP ... but that's another story. If you order a flywheel for that year of motor 80s or 60s or what ever it will be balanaced correct. (either 50 or 28 oz imbalance, new or old respectively) With a manual trans there are other parts that will be rotating, for instance the pressure plate. When my motor was balanced last year the shop "balanced" my brand new pressure plate. All you'll need to do after that is make sure that the pressure plate is at 0 balance. Most often the balance of the pressure place isn't checked even when they are replaced by ford, so I wouldn't worry too much about that one, unless of course your intentions for the motor are to sing it like an elementary school choir after a helium gulping contest. Good luck in your search!

03-26-2003, 03:16 AM	#9
nielsmobers Registered Member Join Date: Jul 2002 Location: Holland Posts: 28	problem solved... I think!! After I removed the transmission I discovered that the transmission mount was gone completely, I've replaced it and it seems that the vibration is under control. The vibration wasn't the problem, but muffling this vibration was. I assume that most mustangs have a little vibration, or not?? Looking back I feel stupid that I've replaced everything except the mounts. Two times I brought my car to a shop to let them discover where the vibration came from, they also didn't detect the broken mount!?! There's one advantage, I no longer need the repair manuel to remove the transmission... I want to thank you guys for the very helpfull replies, you helped me discover a lot about my car. Niels

03-28-2003, 01:21 PM	#10
hobgoblin351 Registered Member Join Date: Sep 2002 Location: NYC Posts: 245	Balance Daniel-son Balance! Hey Trevor hats off to ya great explanation of engine balance. Sleeper you can probably find an aftermarket flywheel with the correct balance weight for the T5 swap. There are enough people doing it these days that someone is probably making them. Oh and Niels, yes most engines do have some form of harmonic vibration in them. It is usually slightand it would repeat in multiples. ex; if the vibration happens at 2000rpms, it would happen at 4000rpms __________________ 1970 Stang Conv: en:Boss351 (balanced/blueprinted) mech cam(240*@.050/.540 lift) Scrw in studs/comp cams rllr rkr Mldn valves 2.19in 1.71ex ported polished cc'd hrdnd ex Keith Black FT pistons(10.25/1) Weiand Excellorator manifold Holley700 DP mech 2nds MSD 6 box and Dis Headers/2 1/2 inch duels tr: modified FMX re:9-inch/3.89 limited slip

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