I read on one of the Canadian forums (forgot which one) that GM started using internally balanced 2.8L engines in mid to late '87. If this is true, and since I just got an '87 engine without a flywheel/flexplate, is there any way to tell which engine I have without disassembling it? With disassembling it? I'd hate to put the wrong flywheel on and damage the engine.

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88 Formula Yellow 5-Speed T-Top
88 Formula White 5-Speed

First of all, welcome to the forum. Second of all, I believe that all internally balanced crankshafts for the 2.8 V6 had a big metal disc in the middle with little notches cut in it, which is used for the crankshaft sensor on cars with DIS. If your crankshaft does not have the big disc in the middle, then it should be externally balanced.

It won't damage the engine if used in just a short time. It will make the engine vibrate like an old Harley.

quote Originally posted by Blacktree: I believe that all internally balanced crankshafts for the 2.8 V6 had a big metal disc in the middle with little notches cut in it, which is used for the crankshaft sensor on cars with DIS.

The '88 V6 doesn't have DIS, and so it doesn't have the crankshaft sensor or sensor wheel on the crankshaft... so you won't be able to tell using this approach... sorry Blacktree! Unfortunately I don't have more light to shed on this yet, but I've got both engines on stands in the shop right now so I'll try to see what other differences there may be to help you figure it out. I'll post later today if someone else doesn't beat me to it.

Actually, the '88 Fiero V6 does have the trigger wheel on the crankshaft. It just isn't used. And if you look on the side of the engine block, there's also a mounting spot for the crank position sensor. But the holes aren't drilled out.

Blacktree, perhaps that's true on some '88's, but definitely not all of them. I overhauled two '88's recently and neither had the trigger wheel so it's not a reliable indicator.

N3YT: I had a look to see if there were listed differences between the internally balanced engines and externally balanced ones in the illustrated parts manual called the "P Book". Unfortunately, it doesn't show different part numbers for either the flywheel, damper, crankshaft, nor oil pan, but that's clearly wrong so clearly the info isn't reliable when it comes to those specific engine parts.

Nevertheless, it is quite likely that the oil pan design was changed as a result of internally balancing the engine, so you might have a look to see which design you have. The '85 to '87's (if I recall correctly) all have the front of the oil pan angled downwards at about 45 degrees where it meets up with the timing chain cover. The '88's on the other hand have a different timing chain cover so the oil pan seals up to the bottom of the block in the front rather than to the chain cover. This may be the key to figuring out which engine you have.

[This message has been edited by Bloozberry (edited 08-12-2010).]

sombody asked this before and i forgot to look as i have both in my garage...BUT 88 and newer V-6's are internally balanced and 87 and older are externally balanced. So that being said, 87 and older should have the big "harmonic ballancer" on the front behind the crank pulley......right? I'll have to try and remember to look when i get home and maybe even post a picture.

My '86 2.8L harmonic balancer and '95 3.4L harmonic balancer are the same size even though the '86 is externally balanced and the '95 is neutrally balanced.

Everything I've read states the Fiero changed from externally balanced to neutrally balanced in 1988.

(BTW - http://60degreev6.com/ has been shut down with an acerbic message from the owner. Sure had lots of good info.)

My 88 crank had the disc in the middle of the crank. No timing notches were cut however.
It also had an undrilled boss on the right (trunk) side of the block, where the sensor would be mounted.

I've never noticed the differences in the harmonic dampers.

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Raydar
88 4.9 Formula IMSA Fasback..........................88 3.4 coupe - going...going...

Read Nealz Nuze! Praise the Lowered!

quote Originally posted by Hudini: My '86 2.8L harmonic balancer and '95 3.4L harmonic balancer are the same size even though the '86 is externally balanced and the '95 is neutrally balanced.

The balancer is neutral for both internal and external balanced engines. It is only the flywheel/flexplate that differs.

That is consistent with the '85 engine and '88 engine I have on stands here too. Both balancers are identical. However one was an auto and the other a manual so I can't compare the flywheels.

quote Originally posted by Bloozberry: Blacktree, perhaps that's true on some '88's, but definitely not all of them. I overhauled two '88's recently and neither had the trigger wheel so it's not a reliable indicator.

That's very interesting. I'm assuming you checked to be sure they weren't earlier (externally balanced) engines swapped in? For example, the '87 Fiero V6 has the same oil pan and timing cover as the '88, but is externally balanced.

[This message has been edited by Blacktree (edited 08-13-2010).]

Sorry for the confusion... you were right all along Blacktree. I had a closer look at the '88 crank photos I took a while back because this wasn't sitting well with me. When I compared it to earlier pictures of my '86 crank, sure enough, the '88 crank does indeed have the trigger wheel. What threw me was that I was looking for a trigger wheel with teeth, and the teeth weren't cut on either '88 crank. You have to look closely at the photos to tell which is which, but the '86 crank has a small counter-weight between the connecting rods for #3 and #4 cylinder. It's no where near the diameter of the other larger counter-weights on the crank. Whereas on the internally balanced crank used on the '88's (and maybe some '87's), that same counter-weight (or trigger wheel) is much larger and thicker. It's roughly the same diameter as the larger counter-weights on the crank by comparison.

1986 V6 Crankshaft - Externally Balanced



1988 V6 Crankshaft - Internally Balanced



That should clear that boo-boo up, but it still doesn't help the OP to determine which flywheel he needs unless he can find the boss for the trigger sensor or pulls the pan. Does anyone have a picture of the sensor boss?

The photos are exactly what I need. Just to be safe, I can crack the pan and take a look. For future reference, I thoroughly examined the paper illustrated parts manual (much more comprehensive than the online version I've seen) and the only 2.8L engine parts with different part #'s between the '87 & '88 are:
Crankshaft
Flywheel
Exhaust crossover pipe
Oil pressure sensor/switch-Fuel pump
EGR valve adapter tube
Intake manifold bolts/studs?
O2 sensor
Oil filter

You guys seem to be good at thinking outside the box; has anyone tried to have an externally balanced crankshaft rebalanced neutral i.e. have a crankshaft balance shop balance the crankshaft to use a neutrally balanced flywheel?

Thanks for all the help.

quote Originally posted by N3YT: You guys seem to be good at thinking outside the box; has anyone tried to have an externally balanced crankshaft rebalanced neutral i.e. have a crankshaft balance shop balance the crankshaft to use a neutrally balanced flywheel? Thanks for all the help.

You would probably have to add weight to the crankshaft to do that -- not grind off weight.


Edit:

[This message has been edited by TopNotch (edited 08-16-2010).]

quote Originally posted by Blacktree: Actually, the '88 Fiero V6 does have the trigger wheel on the crankshaft. It just isn't used. And if you look on the side of the engine block, there's also a mounting spot for the crank position sensor. But the holes aren't drilled out.

Hmm....that might mean that to change an 88 to DIS, you (theoretically) would drill out the crank sensor hole, add the sensor, and then could be in business?)

(EDIT) I see that the 88 might not have the notches cut. Can anyone who has recently been in their 88's engine confirm or deny this? I'm thinking of doing the 7730 and DIS change, and it'd be very nice to 'just' drill out the hole, add the sensor and coil pack, and have DIS....

[This message has been edited by dsnover (edited 10-08-2010).]

It is my understanding that some 88 cranks have the DIS notches, and some don't. Which means that you'll have to look at yours to be sure.

quote Originally posted by TopNotch: It is my understanding that some 88 cranks have the DIS notches, and some don't. Which means that you'll have to look at yours to be sure.

Probably related to whatever they had in the parts bin at the time. I can't imagine, though, that they would normally put the same crankshafts through different manufacturing process, so it's probably more related to build date. I'll have to pull the pan, I guess.....

If your 2.8 doesn't have the notches cut for the DIS timing, you could swap in a crankshaft from a FWD 2.8 (i.e. with DIS). Granted, that would probably involve dropping the cradle. But the DIS conversion on an '88 Fiero V6 is definitely "do-able".

quote Originally posted by N3YT: I read on one of the Canadian forums (forgot which one) that GM started using internally balanced 2.8L engines in mid to late '87. If this is true, and since I just got an '87 engine without a flywheel/flexplate, is there any way to tell which engine I have without disassembling it? With disassembling it? I'd hate to put the wrong flywheel on and damage the engine.

I have a late 87 2.8 on my engine stand. Where it gets a little confusing is that mid 87 the engine plant started putting out the 88 style engine block but with externally balanced crank shafts. This threw me off at first because I didn't realize this combination was around. It uses the "new" style oil pan and gasket so the gasket set for the 87 doesn't work for the oil pan and timing cover. So, if you have a block that looks like an 88 block but is an 87, the only way you can really tell what you have is to open it up and look at the crank.

Arn

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.

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fierogt28

88 GT, loaded, 5-speed

As another data point, I can confirm that the 3.1 crankshafts are internally balanced, that they all have the central timing wheel. and that all I've ever seen had the timing notches. Based on my personal experience, I would highly recommend that anyone replacing an '88 (i.e. internally balanced) Fiero 2.8 crankshaft consider replacing it with a new 3.1 crankshaft and pistons; the cylinder bore and everything else remains the same. The price will be about the same, 2.8 vs. 3.1.