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Building power with the Jeep 4.0

Good notes. Actually that brings up one of the reasons I'm looking at different solutions than your average 4.0 stroker parts is to use more readily available parts, which are also cheaper per performance. Though if there is some wait time, that's alright by me as this is still a nice slow build.

I'm actually pretty heavy into research on Chevy smallblock / LS rods and pistons. There are sweet H beam rod options (instead of just a few I beams available for jeeps), and (almost?) all the chevy stuff run 7/16" rod bolts versus the jeeps which are stuck at 3/8"

Jeep rod journals are 2.095", and chevy are 2.100", so you can run chevy rods, and just turn your crank down to 2.090 with .010 under rod bearings, or 2.080 and .020 under rod bearings depending on condition. The chevy big end is narrower so you do have to set it up to be a piston-guided rod, but people have gotten really comfortable with that in recent decades from what I've gathered.

Then we have a 3.875" stock bore, so 3.903", 3.905", 3.913" chevy pistons are a perfect oversized fit with various piston pin heights available.

a 6.125" chevy rod with a 1.331" piston pin height gives you .0465" deck clearance
a 6.200" chevy rod with a 1.300" piston pin height gives you .0025" deck clearance
a 6.300" chevy rod with a 1.215" piston pin height gives you a -.0125" deck height (proud of the deck by that much)

I'd rather have a tighter quench than the top offering (even though that's a somewhat common setup), but the piston doesn't need any crazy dish to keep the compression reasonable. The bottom two are sweet on the quench, but need a pretty hefty dish to keep the static CR under 10:1. But most of those are in stock at Summit (or have a shipping date within a month), while a few are 2 months + out like you mentioned
 
6.125" is the most common LS rod length, and that is a valid point. Though I'm a little less concerned about rod ratio than I used to be because they use that same rod length for various different stroke length cranks, so availability is a big aspect. Which surprised me, as there were less to choose from but the price for 6.2" and 6.3" rods wasn't much different.

I could shave the deck to tune the quench, but on this build in particular I'm trying to keep as much material as I can in all highly stressed areas. So I'm going with the smallest bore the block will clean up to, and will probably have the deck measured and skimmed if necessary but a minimum of material removed. Ideally with where this build is going, the first point of failure is going to be pushing the head gasket out so I want the deck as rigid as I can get it haha. I've considered "fire rings" or "hoops" or the other handful of names people use for them, but think I'm going to try with MLS head gaskets and head studs first.
 
Alright, this thing is seriously looking like the cherry on top, best case scenario. Original American Motors rod and main bearings mean this has never been turned and rebuilt. Confirmed with a micrometer, stock journal sizes. The mains aren't too bad but they'll probably get a .010 under grind. The rod bearings were a little beat up (probably the end of the motor), so the rod journals are imperfect. But I'm really hoping it can clean up with a .005 downsize to fit .010 chevy rod bearings so it has a few rebuilds left in it. I'm going to get the rotating assembly balanced and possibly nitrided to give it the best chances of survival. Not fully sold on the coating yet, more research needed

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You don't need to weld the whole thing. Yes more is better, but anything more than the deck thickness is just a bonus. Deck on that is probably 5/8-3/4".
 
Yep that's basically the plan, a deep v so I can get material as deep into that area as possible, and multiple passes to build it up. The other challenging area is rebuilding the head bolt hole just above your arrow, but I think it's doable. I''m using the offcuts as my test run, so I've already sanded a taper into those and lined them up on the block. See what kind of mess I can make out of them :laughing:
 
AgitatedPancake said:
Yep that's basically the plan, a deep v so I can get material as deep into that area as possible, and multiple passes to build it up. The other challenging area is rebuilding the head bolt hole just above your arrow, but I think it's doable. I''m using the offcuts as my test run, so I've already sanded a taper into those and lined them up on the block. See what kind of mess I can make out of them :laughing:
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Why not just weld up the hole completely then re-drill it?
 
AgitatedPancake said:
I'm going to get the rotating assembly balanced and possibly nitrided to give it the best chances of survival. Not fully sold on the coating yet, more research needed
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just get this one running. Build a second engine with all of blings after you find out what work or don't work on the first (experimental) engine.
 
Yes, getting the section between the head bolt holes and the water jacket sealed up will be the hardest part. I would take the outer wall off and weld the thing solid like stated above. Don't you have to move the holes slightly anyways?
 
TrailTamer said:
just get this one running. Build a second engine with all of blings after you find out what work or don't work on the first (experimental) engine.
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Meh full confidence, go big or go home :lmao:. Good or bad, excitement is guaranteed lol. Realistically the short block isn't fully experimental, just going down a less common path for these engines (but common on other platforms). The head is definitely experimental, but I'm expecting the short block to stick around even if changes need to be made up top fingers crossed

bdkw1 said:
Yes, getting the section between the head bolt holes and the water jacket sealed up will be the hardest part. I would take the outer wall off and weld the thing solid like stated above. Don't you have to move the holes slightly anyways?
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Yeah those inner walls are the ones for sure. I've augered the front accessible side of the head bolt holes out so I can get the tungsten all the way into that back wall thickness, then I'll just build up material to rebuild the bolt holes in the new location
 
AgitatedPancake said:
Ideally with where this build is going, the first point of failure is going to be pushing the head gasket out so I want the deck as rigid as I can get it haha. I've considered "fire rings" or "hoops" or the other handful of names people use for them, but think I'm going to try with MLS head gaskets and head studs first
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Homemade MLS head gasket? a head gasket intended for Jeep 4.0 or LS?

I used Isky's Groove-O-Matic. It works nice. I can lend it to you if you'll be interested to try it out.

Groove-O-Matic Tool [200GRM] - $430.00 : ISKY Racing Cams, Do It Right

ISKY Racing Cams Groove-O-Matic Tool [200GRM] - Groove-O-Matic Tool Full-Size V8 With 3 3/4 -4 3/8 Cyl. Bores Incl. Copper Wire/Complete Instructions
iskycams.com iskycams.com
 
TrailTamer said:
Homemade MLS head gasket? a head gasket intended for Jeep 4.0 or LS?

I used Isky's Groove-O-Matic. It works nice. I can lend it to you if you'll be interested to try it out.

Groove-O-Matic Tool [200GRM] - $430.00 : ISKY Racing Cams, Do It Right

ISKY Racing Cams Groove-O-Matic Tool [200GRM] - Groove-O-Matic Tool Full-Size V8 With 3 3/4 -4 3/8 Cyl. Bores Incl. Copper Wire/Complete Instructions
iskycams.com iskycams.com
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MLS jeep gasket. I actually have a spare kicking around that I think will probably end up on this build, mid-.040's compressed thickness iirc. Paired with 1/2" ARP studs should have some decent clamping force. Very interesting on the groove-o-matic as well, that is a tempting offer!
For you and those who have run orings/hoops of some sort, what did you do for the "rest" of the head gasket for the water passages? Soft copper? MLS? I hear to run a sealant either way to make sure the water passages still seal with the reduced clamping force out there, any other notes/considerations?
 
Hmm interesting. The consensus seems to agree - that if you're keeping MLS you want to run copper for the oring material, protruding around .009" from the deck. The MLS is hard so it needs the soft rings, then people running composite gaskets go with a harder steel oring material (same groove for either option though).

I've seen that hylomar referenced a few times as well, interesting stuff. Looks like a solid fit for the water passages where flex and distortion may occur.

TrailTamer I may take you up on that offer with your groove-o-matic haha
 
A little scanning, put the crank in the block with a mockup rod part file so I can look at what kind of room there is for a girdle. I also just heard the beefier main caps on the 4.2 I just picked up may be nodular vs grey cast iron, that's very interesting as I am looking at the various ways to ensure they won't be a failure point

Engine Assembly - Jeep 4.0 - Render 13.JPG
 
Yeah, my '98 XJ actually came with one too. Nice little bonus to find putting it together for the first time. But with how long and narrow the actual tangs out to each bolt are, seems like they would still allow a lot of flex. I'm fussing around with the idea of going from the bolts outward for reinforcement of each row of bolts separately. Then some sort of windage tray that bolts between them to make a stronger 3 piece (but simple bent plate) assembly. Or something along those lines, currently just exploring the idea. Worst case I just end up with one of those late model ones though
 
rockyota83 said:
i was thinking the exact same thing as you, that thing isnt adding much strength but i thought it might be good visually for ideas
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Honestly much appreciated, I miss a lot lol, so I really appreciate regular back and forths just to even think out my own train of thought further.

In fact an amusing thought I had was adding the outward girdle sections I was describing in conjunction with one of those stock girdles double stacked for the ultimate strength (though redundant if I add that windage tray). I bet longer studs exist from some other application if the stacked height gets too tall, still looking for a good ARP catalog that lists by specs instead of by application
 
Boooooooo, NERDS! I want a video of a 4.0 making 2jz like noises! :flipoff2:

Seriously though, more power to you, lots of shit over my head. Hopefully you figure out how to get rich of some of your out of the box ideas. :usa:
 
YotaAtieToo said:
Boooooooo, NERDS! I want a video of a 4.0 making 2jz like noises! :flipoff2:

Seriously though, more power to you, lots of shit over my head. Hopefully you figure out how to get rich of some of your out of the box ideas. :usa:
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Nerding is what I do :flipoff2:

The reality is this will never be a truly profitable endeavor. I think it can potentially break even while advancing 4.0s to the next level, but it won't be some market miracle as much as we wish there was that kind of interest. But definitely a hell of a ride along the way. Realistically I want this thing to comfortably run for the long run in the ~600hp range, but I know I'm going to be tempted to see if this platform can break that 4 digit HP barrier on a dyno "just because" :grinpimp:.

And I want to be clear here - I'm not an engine guy. But I am methodical, good at research, and like doing things that haven't been explored. I'm confident I can get the bearings, rods, and pistons to survive. The failure point of the crank, block, and this wild head are anyones guess haha:beer:
 
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