2.8 to 3.1

[MBaz84]

Hi,
I've got a 1986 Jeep Cherokee with a 2.8L in it. I recently had one of the crankshaft bearings fail and it ruined the crank and one of the connecting rods. I'm also going to replace rings while I am this far into it and was considering changing it over to a 3.1L. Unless I am mistaken all this would entail is new pistons and a new crank (which already needs replaced). I was wanting to know if that would be all I would need to do and if so maybe get some tips on things to look for.
Thanks in advance.

[sharkey]

did the bearing spin in the block??? if it did, you may aswell just pick up a core shortblock. if thats the case, try to find a 3.4l from a 93-95 camaro. all your top end would bolt right on to it.

you are correct, all you would need to build a 3.1l from your 2.8l is a 3.1l crank and 3.1l pistons for a camaro 3.1l. the pistons for a fwd 3.1l would net you around 7.1:1 compression.

[ForcedFirebird]

If you are going to rebuild, might as well stroke it.

ARI has rods for $17 IIRC, google them.

I have some .030 over hyper pistons for a 3.1 if you need a bore, but if the cyl walls look good, just hone them.

You can get a reground performance cam from Delta cams for around $100 with lifters for hyd flat tappets too (while you are in there).

[forcecop]

I have the same vehicle. My engine is also getting ready to fail on me. Depending on what your vehicle is being used for, you may want to consider a 3.4. It will a direct swap with the current engine. I'm (most likely) going to get a crate 3.4 and swap out my 2.8.
For the moment, I have two extra 2.8 blocks, so I will rebuild one until I have the money for the crate.

[MBaz84]

Alright, I've been looking more into doing this swap and have become worried about whether or not the 3.1L crankshaft will work in my 2.8L block.

The casting # I have been able to find on the side of the block is 14072061. There is also a 262 on the top. I was reading somewhere that compatible blocks should have a 459T or something along those lines on the side of the block. Thanks for any help.

[ForcedFirebird]

There are two different sized main journals, and 1986 was the dividing line. ARI engines have the small journal crank with the 3.1 stroke (stroker kits), so you should be able to convert it to 3.1 either way. I am unable to tell you the proper casting numbers, though .

[geoffinbc]

If you do have a small main block or a 2 piece seal block you are better off ditching it. Small journal cranks are prone to breaking and 2 piece seals leak. I would never invest anything in a small journal block. If I had to I would use a 2 piece rear main seal block but I would try and avoid it.

[ForcedFirebird]

If you do have a small main block or a 2 piece seal block you are better off ditching it. Small journal cranks are prone to breaking and 2 piece seals leak. I would never invest anything in a small journal block. If I had to I would use a 2 piece rear main seal block but I would try and avoid it.

^^^QFT

[MBaz84]

It's the large journal crank.

[sharkey]

if its the large journal crank with a 1 pc rear main seal, then the 3.1l crank will drop right into it.

[ForcedFirebird]

if its the large journal crank with a 1 pc rear main seal, then the 3.1l crank will drop right into it.

Yep, go for it

Also if you can find some, the MPFI heads have bigger valves than the earlier versions.

[jeep2.8]

Hi, I have an old jeep with the same engine.
I am looking at possibilities of converting this engine to EFI, preferably to MPFI. Is there a possibility of changing just the intake manifold and leaving the cast iron heads in place?
Thanks a lot in advance.

[ForcedFirebird]

Hi, I have an old jeep with the same engine.
I am looking at possibilities of converting this engine to EFI, preferably to MPFI. Is there a possibility of changing just the intake manifold and leaving the cast iron heads in place?
Thanks a lot in advance.

Yep, but the heads from a MPFI engine has larger valves to benefit from. MPFI RWD Camaros and Firebirds have what you are looking for. (IIRC 1987-1992)

[jeep2.8]

Are there any other problems regarding to conversion to EFI?
Namely:
o should i use computer from donor car or buy an aftermarket one?
o should i rather use donor heads as it may give different flow parameters and work better with donor computer
o is there enough clearance between hood and 'new' tbi stuff?
o what gas pump to buy (current 2.8 has mechanical)?
o would I be able to use existing water pump & chain cover, what else needs to be replaced?
o I guess the distributor can be left where it currently is?

Again, thanks a lot in advance!

[geoffinbc]

You could use either the TBI stuff from an S-10 or the MPFI stuff from a Camaro. I personally would use the TBI unit from an S-10. It is a very reliable system, easy to maintain and work on if needed. It will also bolt in place of your current carb manifold and all vacuum lines hoses and other small brackets will bolt back in the same place. There is really zero power difference between TBI and MPFI in the older models. The MPFI systems may have a 1MPG advantage but on a heavy rig like yours I highly doubt you would see it.