I'm curious what the differences are between the 87 and 88 2.5L 4 cylinder engines. Are they interchangeable at all? Would the 88 motor work in an 87 SE using the all the hardware from an 87 motor? I see that there are two seperate rebuild kits for each of those years. And what is with the engine codes? I see someone said that a "U" code engine from a Pontiac Grand Am will not work in a Fiero, yet the Tech IV in my 87 Fiero SE looks amazingly similar to the Tech IV in a 91 Pontiac Grand Am that I previously owned. Is there any sort of reference available telling what is easily swappable amongst these cars? I would love to swap the 140hp 2.3L DOHC/4 speed auto out of my wife's Pontiac Sunfire into my Fiero as I think it would really make it scream, but I think she'd get a little upset.

that I'm aware of there is no diferance externaly. Internal diferances would not suprise me at all. I'm pretty sure the ECM, TBI, etc, are all the same. the ECM may have diferant chips, but chips are easy to swap. Unless 88 did something like add an over head cam, the thing should interchange with an 87 for purposes of whole motor swapping.

There was another discussion called "2.5L in other cars" that covered some of the differences between 87 and 88 2.5 engines. The main change was that in 88 they went to a force balancer and internal oil filter (makes changing oil slightly more messy). Since the oil pan is different, maybe this is why there is a different gasket kit, I don't know.

Since we are sort of on the topic of 2.5 differences, I've been looking for a good used 2.5 for my 87 Fiero (the old motor passed away peacefully a couple weeks ago). I found a really nice 2.5 that's in a wrecked 86 Celebrity. Runs good, great compression in all cylinders, 40-45 lbs of oil pressure, etc. Their computer showed that it was a direct replacement for my Fiero. At another salvage yard, they showed me on their computer that 1987 2.5 motors were unique and not interchangeable with other years. When asked "why?" he was a little vague and muttered something about different manifolds and head. Anyone know about this or know a place where I can look this up in order to get a third opinion?

Batboy- in my experience with junk yard cross references, if there is one sensor or wire different, the books/computer will tell the parts guy that they are not interchangeable. I wish that I had a good answer for you on this one, but I dont. Maybe check what the differences are in rebuild kits for the motors would show what is not the same between the two. Good Luck

According to my Haynes manual, Pontiac switched from the 84-86 style 2.5 (92 hp, distributor, oil filter on side of block) to the 88 style (98 hp, distributorless ignition, balance shafts, oil filter in pan, new TBI unit and intake manifold) sometime during the 1987 model year.

So I'd say if your 87 had a distributor, the 86 Celeb motor ought to swap right in. If your 87 had the 88-style motor, it should still swap in, but you'll need the ECM and harnesses. I couldn't see a difference in the exhaust manifolds between my 84 and 88, so it should bolt right up to either head.

Chad dude, your comment got me on the right track, I think. My 87 2.5 engine does not have the force balancer or internal oil filter, but does have the "coil packs" rather than a distributor. That must be what makes them unique. Now I'm getting a difference of opinion on whether my Fiero external stuff will go onto the 86 2.5 motor. One person said that there is a place (a hole or something) near the crank where a sensor goes on the 87 that isn't on the 86. Maybe using the donor car's ECM like you said could be the best bet. Now I'm wonder if the wiring harness is the same and what all else needs to be done to swap the 86 engine in? Maybe I should keep looking for a 87 engine, might be easier in the long run. Why does GM have to make things so confusing?

I forgot about the slagging balancer..... god what a mess..... The 88+ motors with that item should still interchange into 87. Check the specific motor to be sure tho, as the balancer may not be in all post 87's, and frankly I'll take the balancer free motor. The ECM and the rest should be the same from 87 to 92-93 as far as I know.

If you change across the 86/87 line you will need the ECM, and Wiring, to go in either direction. The TBI connectors and other things are diferant in the 2 harnesses. The ECM's are completely diferant. For one thing the new ECM supports DIS.(You can't swap chips across the 86/87 boundry either.)

As far as I can tell, the DIS motors cannot be converted to distributors, and visversa. There appear to be some small diferances in the block. You would have to change cranks at the least.

You will also need other things like the throtle linkage I think. 87+ TBI linkage layout is differant.

As for the intake, yes, it's changed in 87 too.... the 700 TBI is completely diferant from the older one, and has diferant mountings.

Looks like Ogre's right (as usual?). It looks like the block casting is similar for DIS and non-DIS engines, but the cranks are different. Instead of a drive for the distributor, the DIS engines have a "notched reluctor ring" on the crank that is read by the DIS crank position sensor. So converting a DIS engine to distributor wouldn't be worth the effort.

When my 88's 2.5 finally goes to that graveyard in the sky, if I can't afford a 3800 or SB Chevy swap, I'll investigate swapping for the later 110-hp 2.5. 12 hp is 12 hp, after all. Plus, maybe it would pass as stock for autocross purposes. :-)

Okay, guys, so if I got this straight, the only real difference between the 87 and 88 2.5 motors is the addition of the force balancer in 88, necessitating the internal oil filter and different oil pan. I'm talking about a whole engine swap, anyhow, so that shouldn't really make difference, right? And the ECM, wiring harness, and all the sensors should still be the same and in the same places, correct?

Just a little more to chew on, I do not remember there being an internal oil filter on the Tech IV 2.5L in my 91 Grand Am, and I've changed the oil and filter in every car I've owned. The reason I bring this up is that I am assuming the force balancer became standard on all Tech IV 2.5Ls after 88 and anyone considering swapping a 88 or newer FWD Tech IV 2.5L into their Fiero might run into clearance problems with the external oil filter that was retained in the motors intended for use in FWD cars. Isn't that why Pontiac used the internal filter in the 88 4 cyl Fieros? On the upside, you might also be able to use a remote filter kit to relocate the external oil filter for easier, less messy oil changes. I will probably also investigate this possibility with the internal filter as the thought of changing that bugger does not enthuse me. At the very least, I would run synthetic oil and stretch out the time between oil changes.

On a somewhat different subject, and probably worthy of it's own thread, I may be able to eventually get a 91 Grand Am parts car with the Quad 4 engine really cheap. Has anyone here managed to swap one of these engines into a Fiero?

Yes, any 2.5 from 87-92/3 should drop in. The ECM is the same. there could be some small variations in sensors, but not anything you can't work around.

That I can tell...... the force ballancer was not used on all the cast iron 2.5's after 87. It was sort of an optional thing at GM.

The FWD version of the motor is the same as it is in Fiero except that all the brackets are differant. You could take one from a culass or 6000, and put it into Feiro by simply moving all the brackets, and changing the pully on the water pump. (Lets ignore year boundry for this example....) I saw a fiero motor in a cutlass recently. It's time consuming, not hard.

The oil filter on the nonbalancer should not be a problem unless the balancer motor has something below the intake I don't know about.

Which 2.5 engines were rated at 110 hp? I've given up on the pre-87 distributor engines since I have a 87 DIS engine car.

Boomer, ACE offers a kit for the Quad 4 for $1800. According to them, the 90-92 HO engines are the best to use. You must use the donor tranny as the engine will not bolt to the Fiero tranny. Apparently, they're kind of a dog with an auto, they recommend using the 5-speed. I had a friend with a Quad 4 in a Cutlass, he had all kinds of head problems. He finally got sick of it and sold the car after he spent a fortune trying to get it fixed. I think he went through two or three heads. Other people have had good luck with them. Here is the ACE URL:

http://www.americancustomeng.com/Quad-4.htm