2.8 to 3.1 Swap - Newbies Forum

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2.8 to 3.1 Swap
Friday, June 30, 2017 4:14 PM
I know this topic has been hashed over and over so I apologize in advance...
I have a 89 Cavalier Z24 Convertible. The 2.8 is roached...I plan on buying a rebuilt Long Block. Should I replace the 2.8 or get the 3.1? I have read that all you need to do is put the 2.8 TB and the 2.8 EGR valve and the rest bolts up like money.. so my question is, will the intake/valve covers, and all that stuff transfer over to the 3.1? If buying the 3.1, what year 3.1 should I get?

Re: 2.8 to 3.1 Swap
Friday, June 30, 2017 11:30 PM
Not much help here but isnt the 2.8 a 4cyl? I kno the 3.1 from a 91 cav is a v6

ReD RaiN
Re: 2.8 to 3.1 Swap
Saturday, July 01, 2017 11:16 AM
The most I know about them is that both are 60* V-6s. I would imagine it would be a pretty straight forward swap.

Re: 2.8 to 3.1 Swap
Saturday, July 01, 2017 11:48 AM
2.2 is a 4 cylinder. 2.8 and the 3.1 are almost identical. I have herd that the 3.1 is just a stroked 2.8
Re: 2.8 to 3.1 Swap
Saturday, July 01, 2017 2:55 PM
I believe the exhaust manifolds might be different. You can get them off of another car, 90-94 Cavalier/Sunbird and maybe other models too, I don't know what all had these engines.
As for the year, just be sure it is a VIN code "T" 1990-1994 LHO. There is also a GM 3100 and it is a bit different. You do not want that, for a simple swap. You want the 3.1 LHO.
Re: 2.8 to 3.1 Swap
Saturday, July 01, 2017 10:11 PM
You can transfer everything with no problem, even the exhaust manifolds.
Re: 2.8 to 3.1 Swap
Sunday, July 02, 2017 12:04 PM
So everything from a 2.8 will bolt up to the 3.1 long block no problem?
Re: 2.8 to 3.1 Swap
Monday, July 03, 2017 2:59 PM
Yeah, everything will. All the brackets and mounts, etc. bolt right up. I wasn't sure about the exhaust manifolds, since my 88 (2.8) calls for a different gasket than my 92 and 94 (both 3.1) does.
If Frank says they'll work, then they will work. He is very knowledgeable about these cars/engines
Re: 2.8 to 3.1 Swap
Monday, August 07, 2017 6:00 PM
I got a 3.1 long block to replace the 2.8 motor in my 89. Will everything from the 2.8 mount up to the 3.1 long block? I just want to make sure I don't need a larger oil pan, or something crazy like that.
Thanks for all of your help,
Re: 2.8 to 3.1 Swap
Wednesday, February 28, 2018 1:51 PM
I made the swap and everything went perfect. Everything bolted up and the car runs great.
Re: 2.8 to 3.1 Swap
Friday, March 30, 2018 12:33 PM
Glad everything went smooth for you.

Re: 2.8 to 3.1 Swap
Sunday, May 13, 2018 12:51 PM
Hi Guys,
looks like I came to the right place, I am in the middle of swapping the 2.8 in an 89 z-24 ragtop 5 speed, with an NOS long block crate I picked up. Looks like everythiong is pretty much cut and dry am wondering a couple things:
[listive heard the flywheel may have balance issues when installed in the new 3.1, true or false.
Since this longblock spanned a few years and a couple different intake a FI offerings, is thewre an advantage to building it to a newer spec. even if it involves changing to a more recent FI type and computer to run it?
If you were in my shoes, how would you reasonably hot rod this new V6, keeping within the GM factory offering as far as FI systems?

Re: 2.8 to 3.1 Swap
Sunday, May 13, 2018 3:19 PM
Not sure about the FI. Visually, everything seems the same, but that really doesn't mean anything. If you can get all the parts for it, it might be worth putting it on it. May get a little more performance and better mileage too, but I don't really know.

As for the flywheel, it is the same. In fact it is the same for the 3400 (and other GM 60 V6 as well as the 4cyl engine). Just be careful and look it over very well. I got one that was poorly machined, returned it. I ended up getting a ZF and it is great. You can read about that here:
As well as the confirmation that the flywheel is the same for all of them (within years, of course). I assume your NOS block is an 89?

Good luck on your swap
Re: 2.8 to 3.1 Swap
Tuesday, May 15, 2018 10:16 AM
From what I understand the 3500 intake manifold is the best option. I'm not sure how injectors are for those setups, never dealt with one. I also know that the 2.8 heads flow terrible compared to the others. I'm not sure if 3400 or 3500 heads are better than 3.1s but I'm sure you could check. This forum may have all of that information for you.

"In Oldskool we trust"
Re: 2.8 to 3.1 Swap
Sunday, September 16, 2018 9:54 PM
As far as I know 2.8 , 3.1 , 3.4 , & 3.8 are from the same engine family I know the 3.4 l is the same and all the parts will fit , the 3.8 is newer and I not to sure about it .
Re: 2.8 to 3.1 Swap
Monday, September 17, 2018 4:29 AM
3800 is different yes. Mounting points are an issue. It's been done but requires custom upper and lower supports.

"In Oldskool we trust"
Re: 2.8 to 3.1 Swap
Friday, September 21, 2018 9:58 AM
I thought I commented on this. 2.8 and 3.1 are the exact same engines. Different bore, same crank, rods, heads, intakes. They are directly interchangeable. Only difference is the 3.1 has an electric egr which can be swapped. 3400 is almost a direct swap and gives you close to 80hp more and the 3500 is just a little more work. I have had 2 3400/3500 hybrid swapped 2nd gens.

On the inside my car looks like a fighter jet.
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