Building power with the Jeep 4.0

[AgitatedPancake]

Let's cut and splice some cylinder heads.

This should be fun. It's just a personal project that I'm chipping away at on the back burner, so it'll be very slow but it has some pretty spicy potential. If it all works out I may make a handful as there have been some pretty interested people.

I've got a set of L83 (Gen V 5.3 LT truck motor) cylinder heads that I'm going to cut and splice onto a jeep 4.0 and stuff with boost.

The 4.0 is actually a surprising platform, as people are pretty comfortable stuffing 10+psi of boost into a completely stock still sealed long block and keep them alive with great success. With ARP head studs and forged pistons people push things closer to 20PSI and the 500HP ballpark. There have been a few 600hp builds, and the record as of now peaked above 800HP. But all of that is done with massively limiting reverse flow heads with the intake and exhaust on the same side. People run larger LS valves and port the heads for decent flow numbers, but the platform is essentially tapped out flow wise. So adapting a modern cross flow head will unlock the next level of potential for a 4.0, and I believe could help it break the 4 figure HP barrier or break parts trying.

Bore spacing:
4.0 - 4.38"
LS/LT - 4.4"

Bore diameter
4.0 - 3.875"
L83 - 3.78"

Lifter bore spacing:
4.0 - 2.02"
LS/LT - 2.2"

Jeep 4.0 stock head flow:
Intake - around 190-210 CFM depending on casting with 1.91" valve
Exhaust - around 140 CFM depending on casting with 1.5" valve

Jeep 4.0 average ported head flow:
Intake - 250-270 with 2.02" valves
Exhaust - 170-200 with 1.57" valves

L83 stock head flow:
Intake - 250 CFM wtih 1.928" valve
Exhaust - 180 CFM with 1.555" valve

L83 ported head flow:
Intake - 330 CFM wtih 1.928" valve
Exhaust - 210 CFM with 1.555" valve


They keep the valve size small to work with the small bore of the L83, with the extra 60 thou clearance to the bore in the 4.0, can't wait to see what it can do with bigger valves. But even before that, it's capable of more flow than the best ported 4.0 head out there that I'm aware of.

So the heads are getting lopped in the center and welded together, then I have to reposition one bank of head bolt holes to align the valves over the bores where I want them. Then a custom intake and exhaust, and turbo if I feel like getting wild. But the header is designed so it works well with NA builds as well.

 

[Will Scarlet]

This ought to be interesting. Good luck

 

[chaplinfj60]

wow i want to see you do this , very very interesting indeed.

 

[Ghetto Fab.]

Well this outta be good! Got to love CAD stuff! It sure is fun to play with!

Have you scanned a 4.0 yet?

 

[willis_racing]

I've seen a few blurbs online about people doing this for Ford 300s but not for a 4.0... definitely looking forward to this.

 

[chaplinfj60]

so how do you weld a head together, i get the out side is easy day, but how about the inside?

 

[gt1guy]

Is the plan to dry deck the block and heads? Or did you get really lucky and the water passages line up?

 

[Grendel]

In to read along.

 

[MigGunslinger]

I don't know shit about fuck but I have questions.

Are the head bolt patterns close enough like the bore centers or are bolt holes going to have to be filled in and re-drilled in the block or head/s? Same with water passages?

If this was a one off than the cutting and welding heads sounds like a plan, if the plan is to make 2 or more, whittling out ( 3d printing?) some molds for casting probably makes more sense, then you could get the valve geometry, bolt pattern, intake and exhaust port location and shape exactly where you want them.

I like the crossflow idea for more than just flow. Some nitwit at Chrysler decided that 2 catalytic converters needed to be 10" directly below the intake on the 4.0 which is neat.

Either way i'm posting in here so I get notified of updates.

 

[AgitatedPancake]

Glad to see you guys have the same interest I do! It's an experiment, but I have high confidence so we'll see how it ends up working out.

Ghetto - I haven't scanned a 4.0 block yet, but I do have a head gasket that I scanned for comparison, I'll attach a pic of that

Willis - same! People have definitely had fun with the Ford 300s and some other engines, but much less experimenting has been done for the 4.0 unfortunately.

GT1 - Actually most of the water jackets will line up reasonably with a little welding and reshaping. In the process of reworking the head bolts on the exhaust side I may end up having to fill and add back those ones, but it will have full water flow. In fact I haven't decided on this yet, but someone very familiar with 4.0s has been prodding me to add a water port to the back of the head so I can balance the cooling to the rear cylinders which the stock heads struggle with.

Mig - the bank of head bolts on the intake side will work, though I have to relocate the bolt holes on the exhaust side. The plan there is to actually have the heads cut by waterjet including the bolt hole modifications, followed up by welding new bosses in. This first one is a welded one-off for myself, though I am gauging interest in the idea of creating more. It's a very slippery slope though, and doing anything billet or custom cast would have to be justified by an expectation to sell a reasonable amount. Getting some sand molds 3d printed and having a head cast is actually somewhat reasonable from what I've gathered. But the expense of having someone fixture that rough casting in a CNC large enough for an I6 head and prove out a brand new program to finish machine them for only a couple would make them very expensive unless I pumped the quantities up. I agree on the ross flow idea 110%, it's not like these 4.0s are known for boiling the fuel in the fuel rails or anything. Getting the IATs down will be a great bonus to all of this for sure!

4.0 head gasket against a chopped head -

 

[Grendel]

You have an L83 head listed there... are you going direct injection too?

 

[SLOWPOKE693]

This is gonna be so awesome!

Subscribed...

 

[AgitatedPancake]

I wish I could use the direct injection. I don't have a convenient way to create the insane fuel pressures needed for the direct injection system unfortunately as those engines have a high pressure pump running off a fuel pump lobe on the camshaft.

Hell yeah Slowpoke

 

[Byro]

Can’t believe how well the 4.0 head gasket lines up right out of the box.

This is gonna be bitchin.

 

[wvracer821]

I always look forward to seeing your work. I can’t wait to see this unfold.

 

[RSWORDS]

I wish I could use the direct injection. I don't have a convenient way to create the insane fuel pressures needed for the direct injection system unfortunately as those engines have a high pressure pump running off a fuel pump lobe on the camshaft.

Hell yeah Slowpoke

What pressure does the DI require?

 

[AgitatedPancake]

What pressure does the DI require?

2,000-3,000 psi

https://www.motortrend.com/how-to/understanding-lt-direct-injection-fuel-system-swapping/


Byro, right man. There's some serious potential here. I'm really curious to see if the massive valves in the L86/LT1 would fit the 4.0 bores, but I don't have my hopes up too high because they come stock on a 4.060" bore

Thanks WV, appreciated and I'm pretty excited to see what this unlocks as well!

 

[89yjon]

Definitely keep us updated with more pics as you go. Good Luck!

 

[gt1guy]

How close do the lifters line up with the rockers?

 

[AgitatedPancake]

Will do 89

gt, The lifter bore spacing is actually really close between the two. The push rods will be leaned a bit further toward the outside of the block, but should be completely manageable

 

[AgitatedPancake]

So I'm in the middle of a pretty interesting comparison. My path is set on using the L83 heads I already have inthis first version, but I'm also doing background research to see the absolute maximum performance that can be squeezed out of this configuration.

There are two distinctly different Gen V heads out there:
L83 head .......-5.3L with 3.75" bore and smaller valves (1.928" intake, 1.556" exhaust) that are closer together
L86/LT1 head - 6.2L with 4.060 bore and larger valves (2.120" intake, 1.6" exhaust) spaced around .100" further apart

Max flow for an L83 ported with stock valves is around 315 CFM, Max flow for an L86/LT1 ported with stock valves is about 360 CFM. (both of these in comparison to the highest flowing ported 4.0 heads in existence around 305 CFM). Nobody drops larger valves into L83 heads, because you get far more bang for the buck just swapping to a bigger long block. So all of the support out there is for the big heads.

So the questions are
1) How big of a valve can you squeeze into the L83 head? What will it flow?
-Well, I bought a pair of the huge L86/LT1 valves, and just dropped them in the L83 head Yesterday. Honestly, way closer to fitting than I expected, but just a tiny bit too large. It looks like with some new seats in the head, I can probably run the full size LT1 exhaust valve, and cut the intake from 2.120" down to around 2.06-2.08 and make it work. Then some port cleanup and reshaping the combustion chamber a bit for the bigger bore and bigger valves, I bet this head could push 340+ CFM.

2) Will the valves in the LT1 head clear the bore of a 4.0? With the cylinder wall shrouding the valve, what will it flow?
-The 4.0 starts with a 3.875" bore, I had someone roughly measure outside of valve to outside of valve at appx 3.865". The heads are 12 degree IIRC, and the valves are slightly canted toward the center of the bore. So while the slight cant helps valve clearance as you open to more lift, the 12 degree means it would scrape stock cylinder walls. So the bores need to be punched out to 3.9-3.92 (which is common) and/or slightly smaller valves (or valve reliefs in the cylinder walls). I have a junk LT1 head on the way from someone so I can get that one scanned up and analyzed in more detail, but that would be for a later build.

Stock L83 valves:

Left cyl L83 valves, right cyl LT1 valves

Stock LT1 valves in an L83 head (still factory seats, just resting in there). Probably .015-.020" between them

The point at which they contact due to being canted toward each other. They're over .200" out of the seats which means they'd theoretically clear even using a cam with serious overlap, but that doesn't account for wobble in the guide and stem flex so I want like .030 clearance between them at this point

L86/LT1 valve part numbers:

 

[JohnnyJ]

This isn't what I was expecting, very exciting concept.

Any thought on upgrading to 58x/4x crank & cam triggers? This would unlock the use of many more modern software packages.

 

[CarterKraft]

I wish I could use the direct injection. I don't have a convenient way to create the insane fuel pressures needed for the direct injection system unfortunately as those engines have a high pressure pump running off a fuel pump lobe on the camshaft.

Hell yeah Slowpoke

Could you not belt drive like the diesel pumps

 

[Weasel]

well this is beyond cool. Working with Bishop at all on this?

 

[AgitatedPancake]

This isn't what I was expecting, very exciting concept.

Any thought on upgrading to 58x/4x crank & cam triggers? This would unlock the use of many more modern software packages.

Possibly, though initially I'll probably be running it on the OEM OBD2. I believe I've seen someone machine notches into a stock balancer hub to accomplish it, and then adapting cam pulses is probably pretty doable. Even though the last few years of 4.0 had coil on plug, the cam sensor was just the lower half of a distributor with an integrated sensor as the blocks were still configured for distributors. I believe that's what Newcomer did in the 800+ HP max power run

Could you not belt drive like the diesel pumps

That may be a possibility, I just haven't invested much time analyzing the DI pumping system beyond the stock config yet. Funny though, one of the downsides of this setup is that it's going to require a full custom cam due to flipping the valve arrangement around on a few cylinders, so it's going to be expensive. The upside though, I've jokingly considered having them put an LT-style fuel pump lobe on the cam between the lifters on #1 or #2 because why not. You would just have to punch a hole through the side of the block and weld/braze on a mounting bracket for an LT style pump to ride on that lobe just like it's intended on the V8s

well this is beyond cool. Working with Bishop at all on this?

Unfortunately I'm not sure I know Bishop, but I could always use another person to bounce ideas off of haha

 

[Weasel]

Russ Pottenger -
Bishop-Buehl Racing
1 626-967-1000
West Covina, CA

He's sorta the go to for strokers and 4.0L mods. He's been stuffing LS stuffin them for a bit.

 

[AgitatedPancake]

Ohhhhh my bad I didn't know that's who you were talking about, yeah I'm definitely planning to speak with him and probably build the forged stroker bottom end with his parts and recommendations. I actually want to talk with him about the cams as well, see if he would have any interest in being a part of the sourcing process, or at minimum make some recommendations as I work with the manufacturers. I've spoken with Comp directly and it doesn't seem like it'll be a huge issue besides price, but I definitely want to shop around

 

[gt1guy]

If you're planing to run boost, do you really need the biggest valves possible in the heads?

 

[AgitatedPancake]

If you're planing to run boost, do you really need the biggest valves possible in the heads?

Yes and no. You can make a lot of power with a restrictive head by stuffing it with boost as plenty of 4.0s shows, but the less efficient the setup is, the harder you have to work the engine including more boost and more heat. Less boost needed also means you can stretch a smaller turbo further, so you can keep spool times down. But the other aspect is while I'm personally planning to boost, I've been giving consideration to every potential use including NA if I do build a handful of these after thrashing the test mule. That's actually why I configured the header the way I did too, the header dump is positioned nicely to an NA downpipe in the XJ/ZJ/WJ chassis w/ some engine mount modification.

But the reality is if I produce a few beyond the first one, I'm expecting the average customer to be someone who wants more performance than can be had with a full tilt 4.0 head build, so I can't leave too much performance on the table

 

[AgitatedPancake]

Wastegate location and a DBW throttle body model because it's the first I came across, everything still needs a ton of refinement but who doesn't like renders