Rear Counterweight Question
 

Hey Guys,
Recently, while fixing an oil leak on my rear main seal, I discovered that the rear counterweight was damaged and needs to be replaced. The S5 TII long block that I purchased came with an ACT lightweight counterweight, flywheel, clutch combo. When purchasing the rear coutnerweight, I realized that the part number was for an S4 instead of an S5. I found that I do have S5 rotors and an S5 front counterweight, so, I will be replacing the rear counterweight with one for the correct series.

Now, to my question. How is the rear assembly balanced? Is that counterweight balanced to the flywheel / clutch? If I get an S5 counterweight do I need to change out the flywheel and clutch as well to match?

Finally, I will be daily driving this in stop and go traffic for a few months until I start tracking the car. I would imagine that the ACT 6 puck clutch will be a pain in the ass to use in traffic. So, I have a stock clutch and pressure plate that I may want to use for a bit. My question is, will the ACT lightweight counterweight and flywheel work with a stock TII clutch and pressure plate?

Any help on these questions is greatly appreciated. :icon_tup:

Jason

the counterweight matches the rotors and front counterweight. there is no such thing as a "lightweight counterweight". the turbo flywheel will work with an s4 or s5 engine, you just need to use the correct counterweight. you can use a stock clutch/pp with the lightweight flywheel.

If it came with a s4 cw get another s4 cw. Someone could have it rebuilt with S4 rotors and front cw. If you change the rear for a s5 and rotors and front cw are s4 say bye bye bearings in under 1k miles.
How? Rear counterweight is what balances the rear of the motor

The rear counterweight is balanced to to match the rotors and front counterweight. You can run your current setup act flywheel with the s4 counterweight and stock clutch but your engine wouldn't run as smooth because of the different series rear counterweight. I would get that s5 rear counterweight as soon as possible

I pulled the exhaust manifold and found that the rotor tubs were machined, apparently meaning they are S5. What I dont get is this motor has been running like this for 20k-30k miles. Any thoughts on why damage hasnt been done yet?

If the rotors are machined my next question is do you have a port on the motor? If it does ask the previous owner of the motor or builder what rotors are in there for sure. I say this because people do sometimes machine the rotors.

I am surprised that the rear stationary bearing is fine. If it is s5 rotors and you know for sure get a s5 cw then.

Yeah, it was street ported by a company called Neptune Speed. Unfortunately the guy I bought it off of got it like that so he doesnt know much more. I guess the only way to tell it to pull the motor apart and thats not something I really want to do since the motor works just fine according to the guy I bought it from.

Well, since this has been on since rebuild, about 20k - 30k miles ago, then something must be right with the assembly correct? If so, I guess Ill purchase the S4 rear cw and rebuild if or when things go wrong. Whats the worst damage an unbalanced assembly can do? Is it just replacing the bearings during rebuild?

Jason

Damage that will happen is chewed up bearings hopefully you notice before the rotors smacks the housing. Which would also take out seals...

You are correct if it has been like that 25k miles then the builder used s4 rotors since they are lower compression, and can handle detonation a bit better than s5 rotors. which is why he might of used them, is my guess. So get a replacement s4 cw, if it is a s4 cw.

Are you sure it was 'damaged' and not balanced?

Bullshit. In theory it DOES sound like a bad idea, but i mistakingly ran a s4 turbo motor for 8k miles with a s5 rear counter on it. never had any idea otherwise, and the bearing still looked useable*althought the rotord were not(overheated)*.
I could see a motor going 30k miles without to bearing wear off enough to rotor/iron contact.

and What are the percent of people that machine rotor bath tubs? 5 percent... maybe? less than... this sounds like a s5 assembly, but if ur still not sure, find a way to measure the bath tub depths.. with out dissasmbly :D

Was the motor ever tracked or raced on? At the higher rpm is where it becomes more unbalanced.

Op could you try and take a picture to be sure. I'm sure the person who assembled the motor would be competent enough to use matching cw and rotors. You should know as well that the balance is the important thing.
But I can't say much as I did not rebuild that motor.

sounds like a s5 assembly to me ,,potentially they rebalanced the s4 rear weight,, but methinks they maybe just got it wrong

i had an s4 motor build with s5 interntals, and then bought the flywheel counter weight for it, and then swapped flyswheels to another s4 forgetting that i had s5 stuff inside the other s4..... it's much easier to remember whats what now that i build my own.

Hey Guys,
Here are some photos I took and had posted in a previous thread about my leaking rear main seal. Hopefully these should help.

As far as I know, this motor has not been tracked yet, just used as a DD. However, I will be tracking it in the future which is why I would prefer to do this right from the beginning. Hopefully avoiding pulling apart the motor though.

Damaged Counterweight:
<a href="http://www.flickr.com/photos/jmartin/5530537055/" title="IMG_8109 by Nosaj_08, on Flickr"><img src="http://farm6.static.flickr.com/5093/5530537055_2b942e8617.jpg" width="500" height="375" alt="IMG_8109" /></a>

Photo of Exhaust Ports:
<a href="http://www.flickr.com/photos/jmartin/5543263933/" title="IMG_8131 by Nosaj_08, on Flickr"><img src="http://farm6.static.flickr.com/5292/5543263933_a062d65710.jpg" width="500" height="375" alt="IMG_8131" /></a>

Photo of Rotor Tub:
<a href="http://www.flickr.com/photos/jmartin/5543843108/" title="IMG_8130 by Nosaj_08, on Flickr"><img src="http://farm6.static.flickr.com/5056/5543843108_f86f382e2d_z.jpg" width="480" height="640" alt="IMG_8130" /></a>

I can see the rotors has machining grooves, but would think he would have the cw right.
There is another way to know for sure. Taking front cover off and weighing the front cw. I know its not ideal, I still can't tell what rotors he used.
Does anyone know the different in weight for front cw? I'm on a phone replying to this thread.

i have posted a thread that shows you how to tell front masses apart

its all in the width of the weight ,, as rotors got lighter,, they made the mass thinner

off top of my head-
s5 is 23.4 mm
s4 is 26 mm thick

ok so good news and bad. But first, I called the guys over at Neptune Speed and have to say they are extremely helpful. I told them about the situation and they had no problem helping me out. So, the good news is I am now more confident that the rotors are S5. Neptune Speed, who was the shop that rebuilt the motor, told me that whenever they do a rebuild, even if its street ported, they stay within the same series of rotors and counter weights that was in the engine to begin with. If they are rebuilding an S5, they wont put S4 rotors in as a replacement. So, that goes on to the bad news. If thats the case, then this rear counterweight was added later and could have already done some damage. Would the best thing to do at this point is add in an S5 counterweight and run it as long as I can until rebuild?

yeps,, turn to a known counterweight and suck see,, i think you will be fine