OK, here's the deal. We bought the car back in November. It's an '86 SC with an 87/88 2.8L engine. It's always rumbled like mad, I mean the whole car shakes. When we first got it we replaced engine/tranny mounts, the harmonic balancer, and the flywheel&bolts. It helped a lot, but it still shakes pretty bad. The only suggestion we've gotten from anyone around here is that the crankshaft could have snapped, but at an angle so that it still turns, just quite roughly. It makes sense, but I'm not anxious to tear it down and put in a new short block... has anyone had that happen to their engine? Or does anyone know what else we might be able to do to fix the vibration? I can live with it, because I've gotten used to it, but if it's a crankshaft problem like that, it would seem that one of these days it will wear itself down to the point where the two halves will stop being in contact and I'll be SOL...

 

I think 86's were externally balanced....and the 87-present were internally/neutrally balanced......did you use an '86 flywheel with an '87 or newer motor????

 

All 2.8/3.1 share same balancer/flywheels.
The 3.4 is the opposite of the 2.8/3.1- It's internally balanced. ALWAYS USE THE BALANCER/FLYWHEEL FROM THE 3.4 in the swap from the previous version 60* engine.
If ya need a 2.8-3.1 flywheel, just pay for my shipping costs, ya can have one for free.
I got three now.

 

I think I read somewhere that the 2.8 flywheels became internally balanced half way through 1988...I could be wrong though...

 

Cali is correct on the internally balanced switch in 1987:
1987

• Generation II engine introduced in front-wheel-drive vehicles:
• Cylinder heads redesigned and cast in aluminum
• Cylinder heads require dished pistons and thicker head
gaskets with unique cooling holes
• Cast-aluminum rocker arm covers
• Splayed intake and exhaust valves
• Guide-mounted seals on both intake and exhaust valve guides
• Valve stem seal, oil shedder, and shield discontinued
• Intake plenum reshaped for efficiency
• Aluminum front cover and water pump housing
• Direct Ignition System (DIS) repalces distributor (FWD only),
fires 2 spark plugs simultaneously
• Oil pump driven by oil pump drive
• Internally balanced crankshaft incorporates "reluctor" for DIS
operation; ignition timing non-adjustable
• Compression ratio increased to 8.9:1
• Lower friction piston compression rings
• Model 700 TBI system introduced
• Serpentine accessory drive belt
• Internally balanced crankshaft used in engines fitted to RWD vehicles only:
• Cast with DIS reluctor, but DIS ignitiuon not used.
• One piece oil pan gasket

 

Actually, my father just informed me that they didn't replace the flywheel at all (some of this work was done on the car before I even knew they had bought it--it was a gift for me). It was slightly out of shape and I guess they banged it back to flat. We've since looked at it when we pulled off the tranny to replace a seal or something, and it seems to be perfectly fine. It's still the flywheel that was in it when we bought the car, which as I said started life as an 86 but got a later engine dropped in. So maybe it IS the 86 flywheel? How would I know the difference?


edit: they did replace the flywheel bolts, because for some reason the crazy previous owner had mismatched bolts in it. One was larger than the rest... or maybe it should have been? I have no idea, but it seems odd to think that one of the bolts would be larger than the others, especially since there's never one larger one when you buy a set...

 

Want one of my three 2.8/3.1 flywheels?
Just pay for shipping.
Luckily I'm not back east.
I'd probably would have used them for clay pigeons while shooting the 12 gauge shotgun.
I can probably scrounge up a set of the bolts, too.
Or just go to a wrecking yard, They're all over the ground. I reuse my bolts, just adding RTV RED (Loctite)

SOMEONE WANT TO EXPLAIN the economics of switching part designs of a motor? Especially the balancer, flywheel.
Insane if you think GM did that to the RWD vehicles engines.
NOW the FWD things, sure.....profitable car line.

Remember Pinto's had exploding gas tanks because Ford was not going to spend $.19 on a bolt, times how many millions of Pintos/Bobcats going down the assembly line.

 

Ked, they are the same flywheels and flexplates minus the counterbalance weights. He is probably still using a flexplate that has the counter weights still on it and switched to a motor that is internally balanced and requires just a standard evenly balanced flexplate.

 

So if I have an old flexplate with counterweights on it, and a new engine where the crankshaft is trying to do the balancing, they're fighting each other and throwing it off? Would the counterweights on the flexplate just be welded on? It sounds familiar...

Oh, and let me just make sure my Chilton's manual isn't feeding me a line of crap... 88 was when the battery got moved to the passenger side and the air intake changed to the split design, right? (I just noticed I said it was an 87/88 engine in the first post, it should have said 88/89) So, this is an 88 or 89 and should have the plain flexplate, not the one with counterweights. Right?

 

They are different Karl. I have 2 flywheels at work:

-An '85 flywheel (2.8 firebird)with a few weights on the back side.

-An '88 flywheel (2.8 camaro) with NO weights on the back side.

 

Don't just grind off the counter weights and assume it is then evenly balanced. You can have regular weights just to balance a flexplate, then there are the larger counterweights that counterbalance the crank.

aluminum or steel flywheels have more material and are generally balanced by just removing material in the apropriate spots to balance.

 

The 3.1/3.4 use the same crank and are internally balanced.

 

I have 3 flex plates.
I strongly know two are from my swap project `85 blocks (2.8's).
Third?
Not sure.
I DEFINETLY KNOW IT'S NOT FOR MY LT-1 engine!
Can mine be of use here?
Happy to get rid of them!
Just got rid of my 1969 Firebird Bench seat installed in a Firebird before Dec. 31, 1968 (Jan 1 1969 assembly line produced cars required to have headrest by US Govt law).
More space! Love it!