Hey guys, 1985 Fiero 2m4 SE w/ recall 2.5 Duke engine and 5-Speed Isuzu manual.

My daughter removed the subframe, and we pulled the motor off the cradle. Attached to the cradle, to the front LEFT of the front of the engine (meaning, basically passenger side, forward-most part of the frame) ... basically more or less under the battery... there is this little doughnut looking thing attached to the frame. I have no idea what this is, and for the life of me I cannot comprehend what the purpose of it would be for... perhaps maybe harmonics or something on the cradle??? Would love to know your thoughts. It looks factory...





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Also, another question. When we removed the engine and got it up on the stand, it occurred to me that this 85 engine does not have a harmonic balancer? I guess I just assumed that all Iron Duke / Tech-4 engines were externally balanced, but this one just has a simple 2-pulley gear on the front, and no harmonic balancer. The flywheel is also not weighted either. I guess the 1984 model year was the only one that had the harmonic balancer (and some 85s)? I guess that explains why the balancer is so hard to find new?

Went and checked my 84 Fiero cradle and mine does not have the little donut thingy. Weird. No idea what it could be for.

84 Dukes are externally balanced. My 86 duke is internally balanced. So I would guess your theory to be correct.

That is the drive line dampener for the passenger side CV.

[This message has been edited by skywurz (edited 11-13-2023).]

The above is mass mounted on/in rubber to stop/reduce some type of vibration & likely not just engine "noise." Is "bolted" on the bottom & often very hard to remove w/o destroying it. Can be a sound problem because cradle sections are "hollow" & the damper changes the "note" where whatever tries to make a noise. IOW the mass "De-tune" the cradle so won't make the noise @ specific Hz range.

Even if is for "Engine Noise" is stops/reduces the cradle acting as a "sounding board" like Pianos & others have to amp the sound level.

Fiero OE Dukes Are Not External balanced vs 87 & older "Fiero" V6Aare & Require Correct Flywheel/Flex-plate. Many 84 models have 85-86 long blocks as Recall/Warranty replacements & even the Flywheel/flex-plate bolts to them & why you Must make sure you have Flat or Roller Lifters before buying cam/valve parts.

Dukes Did Not have Harmonic Balancers on Pulley end of the crank to save GM $ to make them.
Later 87+ had these as part of replacing the Cam Gear because GM even installed them for 90's Dukes. Older Dukes could use a HB but GM didn't care to design one to fit them & thus No in the aftermarket bothered w/ them too. If you have/added this then know the HB rubber can Fail because also the outside is a pulley, more so when oil/grease gets on the rubber.

HB stopped/reduce rotational "noise" that causes problems most can't see the problem until whatever part dies like the Cam Gear.
If you see the gears before failure, the Cam Gear wears unevenly before the teeth break.
If you draw a circle & divide three sections, you often have way Worn teeth around ~ 0° 120° 240° while other areas can look new. This is partly or fully cause by build the engine w/o a HB.

Later Dukes even had a Chain Timing set but Chain sets often hate engines w/o HB too & fail.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 11-13-2023).]

Thanks guys! I appreciate the response!!!

This drive line dampener looks pretty shot. I don't see anything like this on Rock Auto... do you think this one looks salvageable? I assume there's a rubber block mounted between it. I can just clean it up I suppose... unless you guys know where I can get a new one?

Ogre... I'm having this engine rebuilt and I will need to replace the flywheel since I see tons and tons of cracks on the clutch surface. Is this anything I need to worry about? I assume GM figured the design was good enough. Is there anything I can easily adapt from a later Iron Duke to improve the balance? I plan to have the entire rotating mass balanced by the machine shop.


Thanks!!!

It's non wearing. It's just a weight to reduce vibration and sound. Paint it and move on.

Todd;
the 3.4 uses a neutral balance flywheel and harmonic balancer unlike the 2.8 . Don't mix and match. FS has Brand new Neutral balance flywheels for pretty reasonable price. sleek

quote Originally posted by sleek fiero: Todd; the 3.4 uses a neutral balance flywheel and harmonic balancer unlike the 2.8 . Don't mix and match. FS has Brand new Neutral balance flywheels for pretty reasonable price. sleek

Thanks Sleek, different Fiero! This one is for my daughter's Fiero, which has the 2.5 and a 5-Speed Isuzu.

She got the motor out a couple of weekends ago and we pressure-washed the cradle and motor.

My Fiero, the 87 V6 is still sitting in storage. But I'm building the 3.4 V6 separately in my garage also... well, I'm going to make her do it... hah...

It is a chunk of metal designed by an engineer, to fix a problem caused by an engineer.

quote Originally posted by buddycraigg: It is a chunk of metal designed by an engineer, to fix a problem caused by an engineer.

Haha... good point. I suppose it took an engineer to fix the hairline crack failures that an engineer caused in the first iteration of the Fiero. I have two degrees with the word "engineer" on the end of them, and not once have I done something I felt was perfect... there's always room for improvement or even corrective action.

I was always confused by the weird hockey puck shaped thing on the frame and never really knew why it was there.

When I bought my 1984 2m4, as i was dissasembling the harness in preparation of pulling the engine out, the harmonic balancer was resting on it (whatever idiot removed the right most engine mount and just left the engine resting on the subframe) I actully originally thought it was an engine mount, i kind of just ignored it from then on leaving my questions unanswered.