I know the flywheel is neutral on the '88's and the flywheel is what balances the '85-'87's, but what are the differences inside the engine itself? If an externally-balanced engine was accidentally installed in an '88, would swapping to a balanced crankshaft be the extent needed to correct the situation? I'd prefer correcting the engine rather than retrofitting a pre-'88 flywheel.

If the flywheel from the externally balanced (85-87) engine was used then you have no issues.
The balancer, crankshaft and flywheel work together to cancel harmonic and static balance conditions.
If the neutral-balanced flywheel (88) was used with the externally balanced (85-87), you need to change to the proper externally balanced flywheel.
It is way more easy to change flywheels than crankshafts, don't even think about it!

Joe

I am aware that changing the flywheel would be simpler, but that's not the point. That's not what I asked.

A shop is replacing my '88 V6 with a new/remanufactured stock V6. They were aware of the differences and ordered by the numbers off the OEM engine block an internally-balanced V6. What they were shipped may or may not have actually been internally-balanced, despite the block and head numbers matching the OEM numbers - it's been installed and runs great except for what feels like an imbalance issue. I want my car to be correct for being an '88, which is what I am paying them for and what I will accept, which means using my original flywheel and correcting the engine to be internally-balanced.

So we are back to my original question - it is just the crankshaft they have to change to correct the engine to be internally-balanced, or are the engines themselves different where the existing new engine needs to be pulled and the correct engine installed?

Could it be that the engine that was in your car was externally ballanced and that you installed an externally balanced flywheel on the new internally balanced engine? I believe there are block clearance issues with the new crank in an old block. The block numbers should tell if it is set to be internally balanced or not. They also changed journal sizes at some point, so that could also be an issue. (I thrink this is all correct, but I am old and some times wrong) Larry

The engine they ordered was matched to the numbers with the engine in the car. The original flywheel was used. I have owned the car for 160,000 miles and I have no reason to believe that the engine was not original. Since the vibration issues did not exist before the engine was swapped and the same flywheel was used, the vibration must be coming from the engine. It might not actually be a problem between internally and externally balanced engines but I'm trying to narrow down the possibilities. I am hoping they don't have to pull this engine out and put another one in but I paid for an '88 spec motor to replace my '88 spec motor and that's what I expect the job to be done with.

You're actually asking two questions:

1. Is your engine block an '88?

2. If it is, can you simply change the crankshaft to make it correct?

I'm not sure you're going to get a definitive answer because most known part sources contain errors and omissions... even the one directly from GM. Regardless, this info might help you make up your own mind:

The P22 (illustrated parts manual) lists three different part numbers for "partial engine" blocks:

'85-'86 = 10159544
'87 = 10159543
'88 = 12508003

From the list of 98 engine parts on that page, it appears that the only components included in the "partial engine" block (other than the block itself) are the main bearing caps, so you can assume that the '88 block is indeed different from all other years. How different is anybody's guess since the manual doesn't get in to details. They may be interchangable or not.

The problem with the P22 is that it lists a single oil pan, flywheel, and timing chain cover part number for all years when we know with certainty that this isn't correct, so you must take what the factory parts manual says with a grain of salt. Do you know how to identify a later block externally? If not, the sealing flange along the top of the oil pan slopes downwards at the pulley end, where the later blocks have oil pan flanges that are flat. This still might be a red herring though because it may be possible to retro fit either stye pan to a different block provided you have the correct timing chain cover.

With the oil pan off the engine, you can easily tell if your crank is an internally or externally balanced crank by the existance (or lack) of the crankshaft position sensor disk that is on the internally balanced cranks (but not used):



I know I haven't definitively answered your questions, but perhaps with some of the info I've provided you can make a better informed decision regarding what you actually have.

(Edited for spelling)

[This message has been edited by Bloozberry (edited 02-27-2012).]

Yes, this information is very helpful. I will share this information with the shop when I speak with them. If they were sent an externally-balanced engine when they ordered an internally-balanced engine then they'll have to deal with the engine supplier. It does not appear from the picture that an '88 crank could be used in an '87-spec engine.

Thank you for your help.

Just to follow up on the excellent (and correct) information that Bloozberry already posted, a big remaining question is whether the pre-'88 blocks are machined to clear the central timing disc on the '88 crankshaft. All of the '88 and later internally-balanced 2.8, 3.1, and 3.4 blocks I've seen have a small boss cast into the rear (trunk) side of the block to mount a crankshaft position sensor; it's just not drilled out on the Fiero blocks. That should be an easy way to identify an '88 (internally balanced) block without having to pull the oil pan.

[This message has been edited by Marvin McInnis (edited 02-27-2012).]

Here's what Marvin's talking about:

Excellent info - thanks, gentlemen.

quote Originally posted by Bloozberry: Here's what Marvin's talking about:

Thanks for posting that. (Wow! That is a clean block!)

But the block could still have a pre 88 crank in it no matter what casting it is. You could pull the pan off the old engine to make sure that it really was internally balanced. Larry

[This message has been edited by trotterlg (edited 02-27-2012).]

The original flywheel was used. If the new engine is the same as the old, there wouldn't be a vibration problem.

However, the new engine is actually remanufactured, so it *might* have been fitted incorrectly with the crank for an externally-balanced engine.

[This message has been edited by LZeitgeist (edited 02-27-2012).]

Could also be that you have a very early 88 which may have had different parts in it, or it could have had a problem early in life that was fixed with different parts, or a new engine of an earlier year or parts. There are lots of things that could have been done to either engine or the parts that are in them. Could be that it is just missing and you think it is out of balance. I will be curious to find out what you discover. Larry

quote Originally posted by trotterlg: Could also be ...

There are lots of possibilities, but what really matters is verifying what he has and not speculating how it happened.

From a thread in the archives: https://www.fiero.nl/forum/A...120111-2-110752.html

quote The true facts / info on 2.8l fiero engines is the 85-87V6 had the same crankshaft and flywheel. (Externally balanced) The 88 has a different crank and flywheel. (Internally balanced) The pistons where about 3 ounces lighter and about 15 mm shorter. The 88V6 engine on fieros came with a newer style design injectors. The 85-86V6s engines have the same oil pan and timing cover. And those engines used the old "cork" 2 piece gasket design. The 87-88V6s share the same oil pan / and timing cover. They have the improved (one piece) rubber seal gasket. This is what those engines came from the factory, but now most V6 engines where probably rebuilt and used aftermarket / jobber parts (pistons, oversize bearings, cam, etc. But on all V6 engines, the fiero heads were the HO (hi-output) and used on all 85-88 fiero V6s.

If this is correct and the pistons are different, you can't just change the crank. Even if you do change the crank, the entire rotating assembly will have to be rebalanced because the pistons and crank are balanced together as a unit. So, IF you have an externally balanced engine, swapping the crank isn't an option.




And here's an externally balanced flywheel.

If you have a neutral balanced flywheel, it won't have that counterweight on it.

All this is pointing to swapping in the correct engine if you indeed got the wrong engine. If it's the correct engine, they need to either figure out if the engine is defective or they did something wrong during the install. Could valves be adjusted wrong? Crossed timing wires? Is there good compression? What kind of break-in procedure was done and what kind of lube was used? This goes back to the low zinc content oil we have today. If it was broken in with low zinc oil, the cam could be wiped out and you'll lose that cylinder. (compression check will verify) It's entirely possible to destroy a lobe on a brand new cam during break-in if the correct lube isn't used. It's happened to others on here with freshly rebuilt engines.

[This message has been edited by Formula88 (edited 02-28-2012).]

quote Originally posted by Formula88: ... what really matters is verifying what he has and not speculating how it happened

Exactly. External visual examination of the block will determine whether or not it has the boss for a crankshaft position sensor. Visual examination of the flywheel will determine whether it is neutrally balanced or not. Pulling the oil pan and looking for the timing disc will determine whether the crankshaft is neutrally balanced or not. If all three are consistent and indicate an internally-balanced engine, then that's probably what you have. It still doesn't confirm that the pistons are correct (or not), but verifying that would probably require a complete teardown.

I had never heard or read that the '88 pistons were different than in the earlier externally-balanced engines, but it's possible. On the other hand, the Pontiac 22P Parts Manual I have (Nov 1990 edition) lists the same V6 pistons (14094101-14094104) for all years '85-'88. (Caution -- The 22P manual is the most authoritative source we have, but it does contain errors.)

[This message has been edited by Marvin McInnis (edited 02-29-2012).]

Excellent info - thanks to all. I've directed the shop to this thread for the info within. Hopefully an obvious and correct solution will be made apparent to them soon.

Patrick, John, ... Sent PM.

quote Originally posted by LZeitgeist: The engine they ordered was matched to the numbers with the engine in the car. The original flywheel was used. I have owned the car for 160,000 miles and I have no reason to believe that the engine was not original. Since the vibration issues did not exist before the engine was swapped and the same flywheel was used, the vibration must be coming from the engine. It might not actually be a problem between internally and externally balanced engines but I'm trying to narrow down the possibilities. I am hoping they don't have to pull this engine out and put another one in but I paid for an '88 spec motor to replace my '88 spec motor and that's what I expect the job to be done with.

At the end of the day, I think the 1st sentence really says it all. I suspect the cash you laid out for this wasn't exactly pocket change. Nice of you & the forum folk to try to help figure it out but ultimately, the car should run like it has a nice rebuilt engine in it. I remember the earlier threads where you were looking for the option with the least risk and that's what you deserve.

OK, off the soap box.

Good advice above and agree that other things could be at work with the vibration problem. Curious, were the original rubber motor & trans mounts retained or were they switched to poly mounts?

Thanks,

Mark

------------------
86 SE V6 4 speed
86 SE V6 Auto
2008 G6 GT "Street" Coupe
2005 Buick 3.6 Rendezvous
2001 Olds Silhouette (AKA The Band Van)

Yes, it definitely is more than pocket change paying for this - in fact, the money I'm spending could have paid for a couple different ways of upgrading, but I wanted to retain the stock look and keep things simple for the shop chosen to do the work - 'custom' usually means more work + less success of perfection + more money.

Oh - forgot to add - the dogbone is a poly adjustable one, but the rest of the mounts are OEM (new), the same as they were with the old engine. No change there...

[This message has been edited by LZeitgeist (edited 02-29-2012).]

Just a comment on blocks.

When I built the turbo motor for my 88, I bought an 87 (external balance) core engine as I wanted to build it up and then swap it out so as not to be off the road for long. The engine I bought was getting a 3.1 internally balanced crank assembly. It fit with no problem and it already had the threaded hole in the side of the crankcase - I know, as I use it for my knock sensor.

Note that the earlier (than 87) blocks may not be drilled.