drive plate weight

[WOTFTW]

so i noticed there is a weight on one side of the drive plate. im reassembling my motor now to throw back in and i just want to make sure i dont need to install the drive plate in any sort of specific orientation due to this. i was just gonna bolt her on there since my haynes manual says nothing about it but my dad was pestering me about it so id figure id stick with the safe side and ask.

[BillBoost37]

I'm usually good at figuring out what people mean etc. I've got no idea what a drive plate could be or what you are talking about. Can you toss us a pic or give us a description of what you've got happening.

[BillBoost37]

Drive plate as in ....flex plate? I'm a little more caffine into the day and my translator has come back to me.

Yes it is balanced/weighed a certain way for a reason. When you go to bolt it up, ensure all the bolts are started and nearly completely put in by hand. That means you have the correct orientation. One or two holes will be off if it's not right.

Trust me when I say..you don't wanna have the 180 degree flex mod.

[WOTFTW]

ya flex plate sorry. going by the lingo in the haynes manual. i know how to bolt it down lol. i guess i wasnt being specific enough. i know which way it is suppose to face and everything but does it really need to be bolted in the exact position it was in relation to the torque converter? the reason i ask is because the haynes manual says to mark the relationship from the flex plate to torque converter similar to how you mark the timing chain so you can place them in the same relative position. i forgot to mark the position. so can i get away with just bolting it up and throwing her back in?

[98regal]

ya shouldnt have a problom i just bolted mine up after my motor swap have never had and probloms if it was suposda be in a certen place it would just have a shake or vibbration most likely nope bolter up and go

[matt5112]

that weight is matched to your rotating assembly.

Best to keep it matched.

[99PontiacGTP]

Usualy if it is oriented to go a certain way it will only bolt up one way. I have done 4 or 5 motor swaps and have usualy needed to put the flex plate from the original motor onto the junkyard motor. No issues at all... Just pop er on and call er good.

[Rico]

There is no certain orientation between the flex plate and the torque convertor. What would you ever do when putting a new torque convertor in your tranny?..Take it back to GM and have them wave a magic wand or something? LOL

The torque convertor is balanced. The flex plate/rotating asembly is balanced. Put them together and they make wonderful music.

I hope I'm not wrong here. HAHA

[WOTFTW]

thats what i thought. just needed clarification for my dad since he still trys to be the overseer of everything i do haha

[WOTFTW]

i did however just read an article saying the flex plate weight is engine specific. so to me its starting to seem its balanced like a wheel is

[Rico]

You are 100% correct and it is specific to that rotating assembly. This is why the bolt pattern - as someone had already mentioned - is not concentrically symetric. So when you change your connecting rods the motor should be externally balanced but most people don't care. I was very happy when my last short block from Morad came with the flex plate. These people know what they are doing. I put all of the rods/pistons back in the same holes. Engine runs smooth as silk.

If I ever build a full-on racing motor the short block will going to the machine shop with the flex plate...for balancing.

[matt5112]

change your rods to what though?

They'll just be more stock ones.

And series III rods have a much tighter tolerance for rod mass as well.

[Rico]

I see what your saying Matt. It's best to have the rotating assembly balanced and use any stock flexplate. I've always wondered why the manufacturers don't balance the rods. I guess it's easier and faster to just throw it together with rods all different weights and balance it with the flexplate. Like you say, the L32 rods are close enough in weight that you don't really have to worry about the rotating assembly.

Let me ask you this: What about using a flexplate that was balanced with a rotating assembly with rods of different weights? Would you want to use that same flexplate on a brand new engine that has been internally balanced? You would think that the flexplate, in this instance, would cause the motor to be externally unbalanced. In other words the flexplate was designed to be used with a motor that was originally internally unbalanced.

Am I making any sense? I've had a few beers.

[matt5112]

Our engines are externally balanced.

Now what?

Heres more: the harmonic balancer has the same balance, the only difference is the flex plate.

Does it make sense? Nope.

But thats what I've found.

[Rico]

I light of your last comment, I wonder if we are doing more harm than good by internally balancing the L36 or L67 motor? This may be just one more reason why so many people have reliability issues with home rebuilds.

I play it safe...put the motor back together with the rods/pistons in the same holes and use the original flex plate. Maybe I've just been lucky but haven't had a problem yet. ---knocking on wood---

[matt5112]

I dont think the crank supports a fully internally balanced assembly.

[Rico]

Yea, I think the crank is specific to the 3.8 90 degree in that the weight is offset. But it can be "balanced" according to that specification. I mean rod weight when I say internally balanced...misuse of the termanology.

[matt5112]

Rod weight is all over the place because GM no cares.

Yet the 3800 is very picky...

[WOTFTW]

okay well i guess ill be giving marshall engines a call and ask if they internally balanced the motor. which im guessing not. then from there ill try taking it to a machine shop to get balanced

[WOTFTW]

new idea... the motor is already assembled so i think im just going to pick up a neutral flex plate that hasnt been balanced.