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Dampener question, timing questions - newer 2.8? by MLSist
Started on: 01-10-2022 08:04 PM
Replies: 7 (142 views)
Last post by: MLSist on 01-12-2022 08:48 AM
MLSist
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Report this Post01-10-2022 08:04 PM Click Here to See the Profile for MLSistClick Here to Email MLSistSend a Private Message to MLSistEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hey all - first time posting here. I'm a technician at a shop in the DC area, 25+ years experience - though this would be the first Fiero I've dived into. Quite a lovely car, all told,

We're installing a rebuilt 2.8 into an 86 GT. Original motor threw a rod through the side of the block so I wasn't able to use it as a core; I sourced another rebuildable motor, from Facebook Marketplace, and had our local machine shop rework the block and heads. It came without a dampener, and the dampener off of the original motor was toast (the rubber was badly worn.) So I grabbed a dampener off of the Fiero Store and modified it per their instructions (scribed a new mark 4.6" counterclockwise from the thick mark on it.)

Here's where stuff gets weird - the mark on the dampener that corresponds to TDC #1 (which I've measured using a dial indicator) is the ORIGINAL mark on this new dampener. The scale on the timing cover, I should note, is on the LH side of the motor - the RH side if you're facing the front of the motor. Poking around on this forum leads me to believe that all of these Fiero V6's had the scale on the RH side (LH if you're facing the motor) - the side closest to the trunk, which would make sense in terms of convenience given the orientation of the motor in the car.

The block has 2.8 LG cast onto the side of it — poking around Wikipedia leads me to believe this is a newer 2.8, out of a 90-95 lumina, silhouette or trans sport (Wikipedia lists a "LG6" variant that was used in this model.) Machine shop used the correct pistons, cam, etc, for a Fiero, though. https://en.wikipedia.org/wi...%C2%B0_V6_engine#LG6

So, I guess my question is - is there anything objectionable to using this newer, non-Fiero block? Everything bolts up to it properly, and externally I see no difference, aside from the timing scale, which... whatever, I can't say I'm too bothered by.

I've attached a couple photos of the timing scale and dampener for reference. The colored mark is the scribed one. You can see though how the original mark on the dampener lines up perfectly at TDC.

Eager to gather your thoughts! Thanks for reading.

[This message has been edited by MLSist (edited 01-10-2022).]

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Pyrthian
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Report this Post01-10-2022 08:29 PM Click Here to See the Profile for PyrthianClick Here to Email PyrthianSend a Private Message to PyrthianEdit/Delete MessageReply w/QuoteDirect Link to This Post
is that a different timing chain cover?
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Luperman
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Report this Post01-11-2022 01:30 PM Click Here to See the Profile for LupermanClick Here to Email LupermanSend a Private Message to LupermanEdit/Delete MessageReply w/QuoteDirect Link to This Post
Is this a automatic transmission? if so you will need to purchase a new flex plate for an 88 2.8 fiero, those are neutrally balanced the engines prior to 88 used a externally balanced flex plate, dont do like I did and reuse the old one (my ignorance) the car will idle very rough, they have them on rockauto for about 40 dollars, im waiting for mine to arrive shortly, I replaced my 86 2.8 with a 3.1 crate motor for a 92 chevy lumina.
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pmbrunelle
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Report this Post01-11-2022 07:14 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by MLSist:So I grabbed a dampener off of the Fiero Store and modified it per their instructions (scribed a new mark 4.6" counterclockwise from the thick mark on it.)


Fiero Store instructions assume the use of a Fiero timing scale, that is on the RH side of the engine.

If you're using the LH side timing scale, then you use the "standard" harmonic balancer markings. In a traverse front-engined car, this makes the timing scale visible from a position towards the front of the car.

Fieros use the RH side timing scale, because it is easier to see when standing towards the rear of the car.

If you can manage to view the timing scale as it is, there is no need to change it.

********************************************************************************

Pay attention to crankshaft balancing, as mentioned.

You should establish whether your crankshaft requires an external counterweight on the flywheel/flexplate, and then use the appropriate flywheel/flexplate.

Does the engine block have a crankshaft position sensor? Crankshafts with toothed wheels for crankshaft position sensors require a neutrally-balanced flywheel/flexplate.

The crankshaft position sensor looks like this:


If present, the sensor will be found on the RH side of the engine, about 2 inches above the joint with the oil plan. Axially, the sensor is near the middle of the engine.
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pmbrunelle
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Report this Post01-11-2022 07:19 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post

pmbrunelle

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quote
Originally posted by Pyrthian:

is that a different timing chain cover?


Correct, that is not a Fiero timing chain cover.

In a Fiero, this boss is drilled and tapped to M6x1.0:


The Fiero timing scale is screwed onto that hole (and another hole over on the LH side of the timing chain cover) with a tamper-resistant Torx.

The boss could be drilled and tapped now, if OP wanted to convert to a Fiero-style timing scale.
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MLSist
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Report this Post01-11-2022 09:53 PM Click Here to See the Profile for MLSistClick Here to Email MLSistSend a Private Message to MLSistEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by pmbrunelle:


Pay attention to crankshaft balancing, as mentioned.

You should establish whether your crankshaft requires an external counterweight on the flywheel/flexplate, and then use the appropriate flywheel/flexplate.

Does the engine block have a crankshaft position sensor? Crankshafts with toothed wheels for crankshaft position sensors require a neutrally-balanced flywheel/flexplate.

The crankshaft position sensor looks like this:


If present, the sensor will be found on the RH side of the engine, about 2 inches above the joint with the oil plan. Axially, the sensor is near the middle of the engine.


***

I didn't spot a CPS when I dressed the motor but will check when I get to the shop tomorrow;

Now I'm even more confused - the "LG V6" markings on the side of the block... reading that Wikipedia entry I referenced in my original post, the "LG6" was acutally a 3.1, not a 2.8. Given the difference in the timing scale, is there a chance this block is a 3.1? Again, I'm certain it came out of a Fiero (it came with a FIero base manifold, for example) but now I'm starting to wonder..... Thoughts??
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MLSist
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Report this Post01-12-2022 08:43 AM Click Here to See the Profile for MLSistClick Here to Email MLSistSend a Private Message to MLSistEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just got here. Here are some photos of the markings on the block - so again, timing scale is on the wrong side, and you can pretty clearly see "LG V6" on the side of the block. In regards to the crank sensor, there is no opening for a crank sensor.

My main concern here - is this thing actually an older, all-cast-iron 3.1?!? My concern there is that our builder installed the Fiero (flat-top) pistons in it, which would probably bump the compression ratio of this thing up far enough to cause spark knock, etc.... Thoughts? From some initial research even if it is a 3.1, if it's the older, cast-iron block/heads unit it will bolt right in. I'm not seeing any differences, externally. This also raises the issue of which flexplate to use - from what I see, most every 3.1 uses the flexplate w/no weight.

Thanks
Pablo
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MLSist
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Report this Post01-12-2022 08:48 AM Click Here to See the Profile for MLSistClick Here to Email MLSistSend a Private Message to MLSistEdit/Delete MessageReply w/QuoteDirect Link to This Post

MLSist

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Update: the casting number on the block corresponds to an 85-86 Fiero motor. So this thing is just a 2.8 that someone probably at some point stuck a different timing cover on. Mystery solved. No phantom 3.1 here. Ha. This also means it uses a weighted flexplate, which is what I've installed on it (the one that came off the old motor, which is now scrapped.)

Looking forward to getting this thing back on the road! Thanks for your help and sorry to be the first-time poster blowing things up with photos and walls of texts. Cheers!
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