Can I do it with what I have?

[bmjudd]

I have a 258 WITH 20k miles on it. I was given a '90 Cherokee with everything there, just body damage.

I have been told that between the 2 I have all I need for a very basic stroker. I was planning on the 4.0 head swap to get EFI but if I have what I need for a stroker than why not. It has to be on the very cheap.

[SilverXJ]

Are you planning on doing the 4.0L head w/ EFI and the stroker? If you have all the parts that is the way I would go.

[gradon]

It's almost ashame to tear into a 20K motor--have you tried selling it(you might be able to get good money--$1000+ if you find the right guy)? If you do tear into it, I would expect the crank and rods to be in tip-top shape(still check em out).

[bmjudd]

Are you planning on doing the 4.0L head w/ EFI and the stroker? If you have all the parts that is the way I would go.

What I would like to do is maximize as much power gain as I can with what I have with little financial burden. Right now I have a 1990 4.0 complete stock engine in the complete vehicle and a stock 258 with 20K miles on the block in the jeep now with valve issues. My original plan was to do the 4.0 head to the 258 block. I understand this requires a CPS harmonic balancer. Then I was told I could take parts out of the 258 and really amp up the 4.0.

What ever I do, even if it is to jut stuff the 4.0 into the Scrambler, I want to do this this spring and summer. I would like as much power gain as I can get without having to sleep in the thing for being locked out of the house.

Is there a good thread here for this? I could not find it.

[Cheromaniac]

The 258 with a 4.0 head and EFI is a good torquey combo but I think those Jeepers who did this still craved for more power. I'd say take the crank/rods from that 258 and transplant them into the 4.0 with new pistons to make a stroker. Just take a look at my "recipes" and see which one fits closest to your needs and budget.

[bikedude189]

on the very cheap, as you said, just take the 258 crank and rods and put them in the 4.0. no other new parts, no machine work, nothin. just take it all apart and make sure its clean and good to go, then have the 4.0 pistons pressed onto them (make sure they are in the same order...) then re assemble everything into the 4.0 block and go. you will probably need a crank snout spacer if you have one of the 258 engines where the snout is longer. i made mine .55" probably take it down a bit once i actually measure everything ...

so long as the 4.0 is in good shape don't have anything machined, the pistons/valves and everything else have worn into each other, so make sure everything stays in the same order it came out, especially the valvetrain and camshaft/lifters.

you might want to think about changing main bearings since they will be going on a new crankshaft...

good luck!

[SilverXJ]

on the very cheap, as you said, just take the 258 crank and rods and put them in the 4.0. no other new parts, no machine work, nothin.

Bad idea right there. Good luck getting the pistons off the rods with out breaking a piston, the piston will be pulled further down in the bore than it was with the original wear pattern.

[bikedude189]

Bad idea right there. Good luck getting the pistons off the rods with out breaking a piston, the piston will be pulled further down in the bore than it was with the original wear pattern.

ok, so he will have to have the rods swapped over at the shop and the cylinders honed (can do himself). but unless there is excessive wear in the 4.0 it wont hurt to pull them down farther. it just goes to the original bore size, not like it gets smaller with wear.

only thing he has to be careful of is wear wise, is if there is a ridge at the top...

[SilverXJ]

ok, so he will have to have the rods swapped over at the shop

Even a machine shop won't guarantee that a piston won't be broken in the process.

and the cylinders honed (can do himself). but unless there is excessive wear in the 4.0 it wont hurt to pull them down farther.

Its a 1990 4.0L. He didn't state the miles, but I doubt it is low, which means that there is a ridge at the top and a lot of wear up there, which he cannot remove with a hone. How do you size a piston ring for a tapered bore?

it just goes to the original bore size, not like it gets smaller with wear.

ok.. so you have a larger bore at the top of the cylinder and less at the bottom.

If he just swaps parts over as you suggested he will have a very short lived stroker. At the minimum he will need a re bore and larger pistons. Why go through the effort of cleaning everything up, using new gaskets, bearings, etc only to skimp on the bore and hone and new pistons.

[bmjudd]

Thanks guys for the replies. Sorry for the stall in reply. Jeep got set to the back burner.

The 4.0 to 258 head swap with efi is the first choice as it appears to be the easiest and cheapest. The 4.0 has around 160,000 miles on it. The block of the 258 has 10,000. I suspect that the only real problem with it is bad valve seals as I foul the 2 and 5 cylinders all the time and it loads up and belches blue smoke at idle or fast deceleration as when coming off the interstate.

I figure that I could pull the 4.0 head, clean it up and have a nice HP gain. Then I could dress the 4.0 block over time if I wanted to stroke later.

With the XJ in the pasture I have lots to pick from. This is a tight finance year and so i have to be frugal, but I am tired of not driving my Scrambler.

[jbxx]

I did an HO head on my 258 wi a Howell TB EFI.
I am quite happy with the results.
As was said earlier, I am addicted now and am building a full on stroker.
Enough is never enough.
If finances dictate, do a bit at a time.
J.B

[Don H Jr]

BM: YOU DO REALIZE that the 1990 4.0 head IS NOT AN HO, right? That started in 91. So you won't have the good flowing head with the raised intake ports.
don jr