Projects flexplate, with or without counterweights?

hello..
im in need of a new flexplate for a sbc,,,
I called Napa and they said they had 3 kinds for the year i need..
#1 with no counter weights
#2 with counterweight
#3 heavy duty..
I have a stock chevy engine with an OD...

thank you for the info in advance

 

When I get off work (about 3 hours) I can get you the number that is on the FP from a 700R4 I just pulled from an '89.

Did you go to the link I posted from Jegs on your earlier thread?

Engine is a 350, right?

 

Trans don't care what flywheel unless it's neighbor is epileptic.

 

Yes I did look up the keys link. Thanks..thing is I need to button it up today...Napa has all 3 in stock.

 

What year is the engine? What size is it? Let's start with those questions.

The 2 piece rear seal engines use a different bolt pattern on the flexplate than the later model single seal design. Also a 400 uses a flexplate with different balancing than any other sbc.

 

I wanted to make sure he didn't have a 400.

 

One year 3 options? Doesn’t sound right.
The buzz word for the design change is “2 piece rear main” or “1 piece rear main”.

All of them SBC up to 1985 are 2 piece rear main. These are no weight flex plates. There’s 2 options 153 tooth and 168 tooth. It’s the starter bolt pattern difference (Except the sbc 400 which is its own thing)

1986 was the first year for 1 piece rear main, since the end of the crank is different there’s a different bolt pattern and counter weights on the flex plate to make up for the removal of weight off the crank.

So 85 down is no weights
86 up is with weights
You can’t physically mix them up. They will not bolt up.

 

Got a picture of the back of the block?

 

It's a 1996-2000 block.ty

 

I’m more than reasonably certain it’s got Counter weights and smaller bolt circle at crank for 1 piece rear main.

 

if it's indeed that year engine, yes, it should look like this

 

That narrows it down, now what starter do you have? If it has straight across mounting bolts then get the flex plate with 153 teeth. Starter with mounting bolts on a diagonal uses the 168 T plate. There is also a heavy duty, 168 T flex plate for the one piece rear seal engines

 

Yes I checked the block number.
10243880
So I had the correct flexplate all along.
I had a problem when the bolts holding the flexplate got loose and I heard the noise.
I had to elongate the bolts on the flexplate to bolt the torque converter...
I have a 700r4.

Turns out I have a 4L60E tonverter and the holes don't match...
Aren't the converters used on the 700r4?

Btw I didn't want to post year of engine because the thread gets shitcanned..

 

Not to hijack, but I have a question for squirrel and 31vicky. Gm built crate 383 strokers using a one piece seal. The info I have seen, shows the stroke length slightly different than a 400 crank, and obviously with it being a 1 piece seal it's not a 400 crank. I'm just curious if you guys know if that uses a special flexplate or flywheel all of its own, or if they managed to internally balance it and use a normal flexplate/flywheel. Just curious.

 

Here's how I elongated the hole...
What's the dealio?
Do I have to elongate the hole on the new flexplate?

 

I'd measure your bolt pattern on your torque converter and head to Napa. Should be pretty easy then to figure out the one you'll need. Being as new as your engine is, I believe there were only 2 flexplate available for that. 1 for a 4l60e, and the other for a 4l80e.

 

Like @borderboy1971 said, measure your bolt pattern. There are three bolts so measure from the center of the converter hub to center of bolt hole x 2. It will check either 11 1/4” or 10 3/4”.
Edit- there are also dual pattern flex plates, I used one behind a 400 SBC with the 700R4 in my old ‘82 Blazer.

 

Concur...... BUT- Internally/externally balance will play havoc with the plate....... Engine is known, as well as the trans........... BUT- Do we have the correct plate? The mill $ ?......

 

When I rebuilt my externally balanced '90 (1pc RMS) SBC for my 46 Olds I upgraded to an internally balanced 383 assembly with neutral 153T SFI flexplate. Don't forget to use a matching quality crankshaft dampener.

 

They make a couple 350 crate motors that requires a externally balanced flywheel or flexplate. Here for example. https://www.jegs.com/i/Chevrolet-Performance/809/19210007/10002/-1

{Flywheel / Flexplate: Like all small block V-8 engines produced since 1986, the 350 HO engine has a 3.00” diameter flywheel flange bolt pattern. Small block V-8 engines produced from 1958 through 1985 had a 3.58” diameter flywheel flange bolt pattern. This change in bolt circle diameter was made to accommodate a leak-resistant one-piece rear main seal. Due to revisions in the crankshaft design, a 350 HO engine must have a counterweighted flywheel (or flexplate) for proper balance.}

 

So on my original question,Napa gave me 2 choices: with counter weight/without..
When I looked at both they were excactly the same.
2 diff part number 2 diff prices...same flexplate ..
I'm running the stock dampener.

 

Did your original flexplate have a counter weight? It sounded like the original one you used was correct with the exception of you obliging the holes for the torque converter. Get the same flexplate except with the correct holes.

 

when i got my runnig gear....i got an engine,trans and torque converter..
this guy traded me for an f1 truck shell....
he dint tell me years or what they came from..
im not smart enough to look up numbers....i had to buy the rest and piece together...

 

Look at Figure 3 in Post #19 from @mgtstumpy , if the crank flange you have is completely round like that one and you have the seal holder shown than you definitely need a flex plate that has a balance weight on it.
You stated having a 1996-2000 block , in that case it has to have the one piece seal.

 

I can’t answer for Napa.
But as far as I know Your 96-2000 Chevy 350 came with a flex plate with a counter weight.
I don’t know everything but that flywheel is what I’d put on that engine.

 

Vicky and Mr Squirrel are right ,
The one piece seal crank is a different bolt pattern,,,,and takes the flexplate with the crazy butterfly looking counterweight.

Tommy

 

we looked up engines from 96 to 2000 and they came up with that flexplate you posted except the torque converter is 10.75 pattern,,, i redrilled the holes using a jig,,,should work fine

 

i have a torque wrench and locktite,,,,should be able to button it all up tonight..
60 lbs should to the bolts

 

the converter holes aren’t very critical placement. The crank holes is another story. The need lock-tight and torque to 60.

How did yours get loose (video from other post) and then over there in that other thread you spoke of an engine vibration. Now this flex plate counter weight is pretty important,,, So did the flex plate you removed have the weight or not? Were the crank holes modified?

 

So,when I out this engine/transmission together about 9 years ago,, I was younger/dumber and it was my first time doing it...
Too far away to rent/buy a torque wrench and locktite,too excited to do it the right way.
I THINK I just tightened the bolts as much as I could but I didn't use locktite or a torque wrench...

Were the crank holes modified?
NO.
Does the old flexplate look like the one posted in SQUIRRELS/VICKYS post?
YES ....
I probably didn't tightened the bolts that well, I probably pushed the flex plate too much when the engine was flooded and I kept turning the starter...
When I took the old flex this morning,I was able to remove the bolts with my fingers...
A broken tooth on the flexplate gear and elongated crank dowel hole we're all the damage to it...