which way is it balanced? LT1

[Jclgodale3]

Accidently started a pissing match over at that other place about whether my 94 LT1 I'm putting into the 68 Vette is internally or externally balanced. Which is it? If externally balanced, do I need a weighted flexplate for the Turbo 400?

 

[Twin_Turbo]

internal. No need for a counterweighted flexplate or balancer.

 

[CNC BLOCKS]

Accidently started a pissing match over at that other place about whether my 94 LT1 I'm putting into the 68 Vette is internally or externally balanced. Which is it? If externally balanced, do I need a weighted flexplate for the Turbo 400?

If the engine is a 94 it should have a one peice rear main seal and the flex plate should be weighted. The balancer should be neutral.

The late flywheels will not fit the old cranks as the bolt pattern is different and so it the ID of the hole in the center of the flywheel.

 

[Jclgodale3]

Accidently started a pissing match over at that other place about whether my 94 LT1 I'm putting into the 68 Vette is internally or externally balanced. Which is it? If externally balanced, do I need a weighted flexplate for the Turbo 400?

If the engine is a 94 it should have a one peice rear main seal and the flex plate should be weighted. The balancer should be neutral.

The late flywheels will not fit the old cranks as the bolt pattern is different and so it the ID of the hole in the center of the flywheel.

So...which flywheel will work for a Turbo 400 transmission? Anyone got an interchange number or suggestion? Someone has already mentioned a later model Yukon?

 

[MYBAD79]

Are you using the stock rotating assembly ?
I'm wondering why you don't just look at the old flexplate or flywheel that came off that engine to see if it's internally or externally balanced - or did you get just the engine (no flexplate/flywheel) ??

If your rotating assembly is externally balanced and you don't have the flexplate or flywheel that was used to balance the assembly how can you possibly know where to add weights or drill holes to reduce weight/mass without removing the rotating assembly and have it balanced ??

Remove the oil pan. If the crank counterweight at the rear of the engine has holes drilled into it then it's a good indication it's internally balanced and the flexplate (flywheel) is neutral. It is still possible that the rotating assembly was so out of whack that it needed holes in the crank and in the flywheel or flexplate but I don't think it's very likely.... then again, anything is possible....:ill:

 

[Jclgodale3]

Are you using the stock rotating assembly ?
I'm wondering why you don't just look at the old flexplate or flywheel that came off that engine to see if it's internally or externally balanced - or did you get just the engine (no flexplate/flywheel) ??

If your rotating assembly is externally balanced and you don't have the flexplate or flywheel that was used to balance the assembly how can you possibly know where to add weights or drill holes to reduce weight/mass without removing the rotating assembly and have it balanced ??

Remove the oil pan. If the crank counterweight at the rear of the engine has holes drilled into it then it's a good indication it's internally balanced and the flexplate (flywheel) is neutral. It is still possible that the rotating assembly was so out of whack that it needed holes in the crank and in the flywheel or flexplate but I don't think it's very likely.... then again, anything is possible....:ill:

A couple good points. I already have the oil pan off and the original flexplate on the shelf that came off this engine. I will look at both tomorrow and report back...thanks folks

 

[Jclgodale3]

Well, does this clear it up? See pics of flywheel and crank journals below. Original flywheel from the engine appears to have a "weight" welded to it. But...both front and rear journals on the crank appear to be drilled for balance? So... do I need a weighted flywheel? Or an unweighted flywheel?:bonkers:

 

[TimAT]

You'll need to use that flexplate or one similar to it.

The 2 piece seal cranks have a weight built into the rear hub and the 1 piece seal cranks don't- that's why the weight on the flexplate.

 

[Jclgodale3]

I was going to use my original Turbo 400. So I need a 168 tooth flywheel for a 1 piece rear seal. (and with a weight) Do they make these?

 

[MYBAD79]

You can have a (competent) shop measure the imbalance of your flywheel and have them duplicate that imbalance to another (new) flywheel... basically duplicating what you have...

You have holes drilled into the crank and weights on the flywheel, maybe the holes were drilled during a previous balance job and the weights on the flywheel added later... do you know the engine ran fine before you got it ??

Edit: the holes are at the front of the crank which indicates you need a neutral balancer. Are there holes drilled at the rear of the crank as well ?

Internal or external balance doesn't really matter, the only important thing is that the entire assembly is balanced as an assembly. If you know the engine was fine with this flywheel you can duplicate it and swap a new flywheel with the same imbalance and it'll be fine....

The Turbo 400 is a auto trans so you'll need a flexplate and not a flywheel....the pics you posted are showing a flexplate, not as flywheel, flywheels are for manual transmissions with a clutch...

 

[Jclgodale3]

The Turbo 400 is a auto trans so you'll need a flexplate and not a flywheel....the pics you posted are showing a flexplate, not as flywheel, flywheels are for manual transmissions with a clutch...

Yeah...I started with calling it a flexplate, then mistated in more recent post with flywheel. The flexplate in the picture is the one taken off this engine. This is the first time the engine has been opened up. It had 74,000 miles on it so the drills in the crank and the weight on the flexplate were done when the engine was manufactured for the car in 1994. So I can buy a non weighted 168 tooth flexplate for a 1 piece rear main seal and have the balance duplicated from the original? Where? Machine shop? Driveshaft specialist?

 

[MYBAD79]

what's the old flexplate 153 or 168 teeth?? And what's wrong with it? why do you want a new one?

The transmission should work with either 153 or 168 teeth flexplates.. not ??

If it's cracked or warped then yes, a good machine shop should be able to balance a new flexplate to match the old one.

 

[Jclgodale3]

what's the old flexplate 153 or 168 teeth?? And what's wrong with it? why do you want a new one?

The transmission should work with either 153 or 168 teeth flexplates.. not ??

If it's cracked or warped then yes, a good machine shop should be able to balance a new flexplate to match the old one.

It is the smaller flexplate and the Turbo 400 convertor will not bolt up to it. (to small of bolt pattern on the plate that was on it)

 

[MYBAD79]

now it makes sense .... :noworry:

 

[vetteoz]

So I can buy a non weighted 168 tooth flexplate for a 1 piece rear main seal and have the balance duplicated from the original?

You won't find a off the shelf 168 tooth flexplate to fit 1 pce seal that doesn't have the weight. As previously noted; all the 1 pce seal cranks have a different crank bolt PCD from the early 2 pce seal cranks and are all ext balance at rear.

So I need a 168 tooth flywheel for a 1 piece rear seal. Do they make these?

Yes
http://www.summitracing.com/search/...r-Tooth-Quantity/168-tooth/?keyword=FLEXPLATE
If you go to a 168 tooth you need a new starter and a lot of the later blocks are not drilled for the offset starter.

It is the smaller flexplate and the Turbo 400 convertor will not bolt up to it.

Which convertor bolt pattern is it
10 3/4 or 11 1/2"

These flexplates are all 153 tooth for late 1 pce seal engines same fitment as your stock one;
just need to pick one with correct convertor pattern
http://www.summitracing.com/search/...r-Tooth-Quantity/153-tooth/?keyword=FLEXPLATE

 

[Jclgodale3]

The block is drilled for either starter. (cross bolt or straight bolt) The flywheel pattern for the converter is 11.5". I'm assuming since the original flywheel on this engine is weighted I need a 168 tooth with an 11.5" torque converter bolt pattern that has a weight welded in the same location. I noticed all the weighted flywheels have the weight welded perpendicular to the alignment pin hole on the crank. Hope this works:cussing:

 

[vetteoz]

I noticed all the weighted flywheels have the weight welded perpendicular to the alignment pin hole on the crank. Hope this works

Correct;
any off the shelf replacement flexplate for a 1 pce seal will be setup to match the factory balance regardless whether it is 153 or 168
This GM 168 flexplate has both convertor patterns
http://www.summitracing.com/parts/NAL-14088761/

 

[larrywalk]

I noticed all the weighted flywheels have the weight welded perpendicular to the alignment pin hole on the crank. Hope this works

Correct;
any off the shelf replacement flexplate for a 1 pce seal will be setup to match the factory balance regardless whether it is 153 or 168
This GM 168 flexplate has both convertor patterns
http://www.summitracing.com/parts/NAL-14088761/

I agree...
1. Any stock one-piece rear main seal crankshaft requires an unbalanced flexplate or flywheel.
2. All cranks will have some balancing holes drilled in the counterweights to balance the crank. This does NOT indicate whether it requires a neutral balance or counter-weighted flexplate.
3. The TH400 and TH350 torque converters are interchangeable; the mounting holes in the flexplate can have a 10 3/4 or 11 1/2 bolt circle; some flexplates have 2 sets of holes with both. If your flexplate doesn't match your new converter, new holes can be drilled.
4. The tooth count on your flexplate or flywheel determines which starter you need - the larger requires the offset bolt pattern starter nose; the smaller requires the in-line starter bolt hole nose. Starter noses can be swapped with the older design starters.

From the appearance of your flexplate, why don't you reuse it?

 

[mrvette]

Far as I can remember I have never dicked with a 153 tooth fly/flex, and for the life of me, I can't see what in hell it would bring to the table for the change....what did it accomplish??

since apparently the bellhousings and back of the engine are the same shit, why change?? just because they CAN??

:amazed::nuts:

 

[vetteoz]

since apparently the bellhousings and back of the engine are the same shit, why change?? just because they CAN?? :amazed::nuts:

On a 4+3 at least ; a 14" 168 tooth flywheel will not fit in the bellhousing hense the smaller one