Im about to swap out my 2.8 and I was wondering what the difference between goin to the 3.1 is? Can I use my same motor mounts and computer? How about the valve covers and intake? And if so what car is the best to get the 3.1 from?
Originally posted by Jncomutt: Im about to swap out my 2.8 and I was wondering what the difference between goin to the 3.1 is? Can I use my same motor mounts and computer? How about the valve covers and intake? And if so what car is the best to get the 3.1 from?
The 3.1 is a stroked 2.8; you can rebuild your 2.8 into a 3.1.
An example of a rebuild kit to do this can be found at http://www.engine-parts.com or you can put together your own parts list and do it.
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11:24 AM
avengador1 Member
Posts: 35467 From: Orlando, Florida Registered: Oct 2001
Seriously, The 2.8 can be built into a real barn burner. I've made two 3.1 and 3.2 build-ups.
But if you are trying to minimize expense the best option is a 3.4 swap. The block is virtually identical and you only need to make a few mods to get it to fit. Then bolt on all the Fiero accessories and you're tearing up the street at a fraction of the cost.
My 3.1 and 3.2 have ALL the bells and whistles: roller rockers, internally balanced, hyper pistons, polishing and a dab of porting, etc. No expense spared. And for this I get about 185-190 HP. Add a turbo and I'd be in the 245 range. More expense. The 3.4 gives you 180hp in stock trim and can be bought direct from GM or second hand for a couple hundred bucks!
The thing is, I'm planning on pickin up a junkyard 2.8 and throwin that baby in over the weekend. This is my daily driver, and I got rid of my other 2 drivable fieros to own this own. I already have a 4.9 conversion going on and am not looking for a major project with fabricating parts and redirecting all kinds of stuff with this one. I would like to just get the new block like suggested, but thats going to run over $1000 and I don't have that kinda change lying around.
One of my friends just asked what the difference was and suggested it to me. So I figured, why not take a quick look into it. I was thinking I can just take a 3.1 from like a cavalier or such and drop that in. Not really looking to make my blown 2.8 into anything more than it is now.. Thanks for the advice guys, guess another 2.8 is in the lineup..
My 3.1 and 3.2 have ALL the bells and whistles: roller rockers, internally balanced, hyper pistons, polishing and a dab of porting, etc. No expense spared. And for this I get about 185-190 HP. Add a turbo and I'd be in the 245 range. More expense. The 3.4 gives you 180hp in stock trim and can be bought direct from GM or second hand for a couple hundred bucks!
I believe I have seen some posts in the past about adding SBC v8 rods for a early 283-327. Am I crazy or is this something do-able?
I have a 85 2.8 I am working on now to build up for my hopefully turbocharged monster engine. Plan is to use the 3.1 crank but I was told you had to use the 3.1's rods and pistons from a 3.4 TDC or do I have this all backwards?????? I need the CR to stay BELOW 9.0 to 1 or as close to 8.5 as possible. I also plan on using the larger of the 2 GM cams. I beleieve its the same cam as the 3.4 crate motor.
Ideas?
Steven
------------------ 87 Fiero GT 14.9/ 89mph 94 Formula WS6 w/ NOS 12.4 /118mph 84 Fiero 2M4 T-top, Turbocharged and tons of extras! 87 Conquest TSi 406 SBC V8!
The V6 engines with the aluminum heads have dished pistons. You'll want them. If you have the crank from a 2.8, then you'll need pistons from an aluminum head 2.8. With the effort of a complete build up, why not go the extra (small) step and start with a 3.4?
To take a quick side note from building up a motor. If I took the 3.1 from like the 6000 or a cavalier, etc, will I be able to drop it right in the fiero?
Or is everything too different such as altenator, etc, for it to work?
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05:58 PM
Toddster Member
Posts: 20871 From: Roswell, Georgia Registered: May 2001
You can't just drop in a 3.1 or 3.4 or any other engine into a Fiero. You MUST keep your Fiero accessories and bolt them up to the new block. The intake, throttle body, water pump, belts and pulleys, a/c compressor, alt, etc. are all incompatible with both the Fiero Computer AND the physical dimentions of the engine bay. If you want a quick week-end engine swap then you need to start with a complete "Fiero" 2.8. Anything else will take several days more.
That is why I suggest the 3.4. Of all the other cheap alternatves it give the best bang for the buck and costs no more time in your coveralls. Fiero Owner Magazine had an article out there about what you need to do to make it fit right. Can't remember which issue but a web search will turn up something
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06:39 PM
Freshj Member
Posts: 1250 From: Holly, Michigan Registered: Nov 2001
As other's have mentioned, the difference between the 2.8 and the 3.1, essentially is the crank and pistons. ALL 60 DEGREE GM V6'S used the same connecting RODS. This includes the 3400 TDC. Don't fork out the cash for new ones just yet. If you want a good idea for a rebuild, install the 3.1 crank and 3.1 pistons (they are dished due to longer stroke), and use the neutrally balanced flywheel/flexplate as the 3.1 crank is internally balanced. I purchased a 3.1 crank kit (crankshaft and correctly sized main/rod bearings) last year for about $230 (this was a reman. crank). Sealed Power, Silvolite, and many others offers pistons at very reasonable prices for these engines. I believe a .060 overbore will yield real close to 3.2CID. And I want to say both the 60 degree engines and the stock 350 use 5.7" rods already, but someone might want to confirm that.
My whole plan is to take out the current 2.8, swap over all my accessories to the bare block that I will be buying, then putting it back in.
If the procedure is the same for bolting them all on the new 2.8 as it is for the 3.1/3.4 and it will mount in the bay the same, then thats what I was looking to do. Doesn't seem like I was quite that lucky though, or is it like that?
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07:08 PM
BV MotorSports Member
Posts: 4821 From: Oak Hill, WV Registered: May 2001
Thanks for the info. Yes the 60 deg V6 and SBC's do use the same 5.7 rods but I believe only the small journal 283-327 have the same size ends as the 60 deg v6. Can anyone verify this? Has anyone added ARP rod bolts to their v6 build up? Alot of people keep telling me the 60 deg v6 has a weak bottom end but I have beat my engine on many a track and it now has 116k miles on it and has excellent oil pressure.
So anyway... use a 3.1 crank, bearings, 3.1 pistons (to stay near the origianl 2.8 CR) and have my flywheel neutrally balanced. Hmm will I have to get a new harmonic balancer as well?
Thanks guys.
Steven Boy I love engine swaps!!!!!
------------------ 87 Fiero GT 14.9/ 89mph 94 Formula WS6 w/ NOS 12.4 /118mph 84 Fiero 2M4 T-top, Turbocharged and tons of extras! 87 Conquest TSi 406 SBC V8!
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10:58 PM
Jun 23rd, 2002
kslish Member
Posts: 1475 From: Womelsdorf, PA Registered: Apr 2000
Originally posted by Jncomutt: My whole plan is to take out the current 2.8, swap over all my accessories to the bare block that I will be buying, then putting it back in.
John, call Jim (Jen's Dad) and he will fill you in on all the details of bolting in a 3.4 (all the little stuff no one tells you after they tell you that you just need to drill the starter holes).
As for a 3.1L, you either have to be lucky enough to find a front wheel drive iron head motor, or have one built from a 2.8 block. The 3.1L iron head motors out of the Chevy Lumina/Pontiac TranSport/Olds Silhouette minivans will work (out of the first generation vans that have the huge windshield looks-like-a-Dustbuster styling). I also think some of the Pontiac 6000 STE's came with the iron head 3.1L. It's worth a shot if you can manage to come across one in a boneyard. 99% of what you'll probably find is the newer generation aluminum head motors which is what you don't want for ease of install.
Hmm, thanks ken. I'll see what I can find as far as that iron 3.1 goes. If no luck, I'll call about the 3.4. I'm really not in the mood for a month long build up tho. Just need something to drive. Hell, i'll throw my damn complete duke cradle in there for now if I have to, just need to get places!!
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02:20 PM
hotmechanic Member
Posts: 36 From: chicago illinios Registered: Jun 2002
if your looking for a 3.1 iron motor, look in the early 90's chevy lumina apv/pontiac transsport minivans. They use em in those. All the ones i have seen have throttle body...but looks like the 2.8 otherwise.
Yes, they are telling you correctly. The easiest route is to get the 3.1 with cast iron heads from an early 90's mini-van. All the other 3.1 engines from front wheel drive cars have aluminum heads and different pistons. The intake and fuel injection is completely different (won't interchange) and will require a different computer and wiring. Lots of headaches. The 3.1 with cast iron heads will just require you swapping the accessories over from the Fiero and is fairly straight forward. See the below link for more info about engine conversions. http://members.yourlink.net/dragon/parks/e-conv.htm
