Chevy flexplate balance weights

[1977 chevy trucks]

I have a chevy v8 flexplate that I dont recall what it came off of...It has no balance weights,which I think is unusual.The engine I want to use it on has balance holes drilled in the harmonic balancer,anyone know if this will work? Enlight me,please.

 

[ChevyHiPro]

Hello and welcome to the forum!
Apologizes for such a long delay in responses, but sometimes, life just gets busy!

The flexplate (often called flywheel) usually doesn't have weights.
The 400 CID rotating assembly requires them due the the stroke length.
The harmonic balancer can't compensate by itself for the crank throw of the longer stroke 400 rotating assembly.
So, the flywheel has weights on it.
If your engine has a standard 302 (stroke = 3.00"), 305 (3.48"), 307 (3.25") or 350 (3.48", LS1-3.62", LT5-3.66") crankshaft in it, no weights are needed.

Hope this helps with your flywheel issue!

 

[1977 chevy trucks]

Thanks,it helps a bunch.I know what you mean about being busy,I`m like a farmer{which I`m not},busy as hell in spring and fall...

 

[ChevyHiPro]

BTW, those Chevy SBC (Small Block Chevy) flexplates (flywheels) come in two sizes, they are described by the number of teeth on the outer edge.
I'm doing this from memory, so I probably don't have the exact numbers right, but it's something like the small one is 153 teeth and the large one is like 168 teeth.
So, before you do anything with it, I'd suggest to count the number of teeth and mark it on the flywheel with a felt pen.
That way, when the need comes up, you'll be able to tell straight way what you got.

BTW, again, I love those '70's pickups!
The '76 Cheyenne I have, my wife bought it new in '76!
It's been through a lot, got +300,000 miles on it and it's a daily driver now!
I've swapped the engine several times, rebuilt the trans several times, replaced a whole lot of other stuff, but it just keeps on going!
I'm considering registering it as a Classic, but here, Classic's have to be 30 years old or older (no problem there) and are limited to 3,000 miles a year.
So, that probably won't happen!
I've got an '85 Silverado, but I still don't think it's as classic looking as the '76!
Anyway, enjoy your vintage truck and don't be a stranger around the forum!
Stop in from time to time and keep us posted on how it's going with your '77!

 

[Philip]

Bringing this old post back to clarify some of the info. All Chevy V-8's and the 194, 230 and 250 6 cylinder engine used a nuetral balance flexplate/flywheel. The exceptions to this are the 400 sb and 454 BB. The tooth count is 153 for the small plate and 168 for the larger one. The bolt pattern on all of the flexplates/flywheels are the same and the wrong type will bolt on and cause vibrations in the engine. The starters were also different. The 153 tooth wheel used a starter with a straight across bolt pattern and the 168 tooth used a starter with a staggered pattern. There is a third type starter used with the 168 tooth flywheel and a 621 bell housing, it has a staggered pattern but a cast iron nose to fit in the bell housing. Although the 400 sb and 454 BB had an unbalance flexplate/flywheel the unbalance is not the same and they will not interchange. All 400 sb and 454 BB engines had the 168 tooth flywheels and a dowel in the crankshaft flange to properly align the weighted portion of the flexplate/flywheel.
Harmonic dampeners also changed through the years. Early small blocks used a 6 3/4" diameter dampener and later engines used an 8". The small block 400 had an offset portion in the outer ring and the 454 had a weight cast into the inner hub to add weight to externally aid in the balance of the crankshafts as there was not enough room in the block to enlarge the counter weights on the crankshafts. All dampeners have drilled areas in the outer ring to balance to specs during the manufacturing process. There will also be drilled areas in flywheels for the same reason. Some shops that balance engines will drill the dampener and flywheel during the balancing process to save time, this is a bad practice and if having a rotating assembly balanced specify that you do not want any changes made to the dampener or flywheel. If the dampener or flywheel are changed during the balancing procedure when those parts go bad either the new ones have to be matched to the balance of the old one or the entire rotating assembly will need to be rebalanced. This is especially critical on the dampener, if the outer ring slips or comes off there is no way to match balance the replacement part. The rotating assembly on the 400 sb and 454 BB can be internally balanced using heavy metal inserted into the crankshaft counter weights. If this is done the dampener and flexplate/flywheel then used are the more common nuetral balanced parts.

With the introduction of the one piece rear main oil seal the crankshaft flange size and shape changed and a completely different flexplate/flywheel were used. The LS family of engines saw another change in design.

 

[72 K20]

With the introduction of the one piece rear main oil seal the crankshaft flange size and shape changed and a completely different flexplate/flywheel were used.

I have noticed that the TBI , one piece rear seal blocks have a rather substantial weight on the flexplate !

 

[hurst01]

This is true. An exception was the Mid-90s LT1 that were Internal Balanced that had no weight on the flywheel and a neutral harmonic balancer. I have used many of the flywheels that had this counterweight on the LT1 engines. The weights are spot welded on. I merely drilled through the weld without drilling through the flywheel and knocked the weights off making it a neutral balance flywheel.