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Discussion Starter #1
There are 100's of pages of information that I've read through on the swap suggested in the titled of this new thread. I am however in a strict California SMOG area; Sacramento County. If I did not live in California I would have already started my swap but because I am here am a bit hesitant to start pouring money in places that might just leave me stuck with a trailer queen versus a rig I can drive to the trails. (No offence to trailer queens but I don't own a truck to pull a non-smogable jeep to the trail-head) The jeep I am getting ready to upgrade is an 89 YJ with 4.2L

I've read allot about the swapping of heads. A 4.0 Head on my 4.2 block is the direction I am leaning. (I tested my compression and all is in good shape). So keeping my 4.2 block seems like the more simple option for most gains.

As Long as I'm going to a 4.0 head, it is my understanding that I need to use the 4.0 intake and exhaust manifolds. As long as I'm switching manifolds I figure why not go Multipoint injection. Pulling a whole 91-94 XJ Motor with all injectors, the wiring, and computer is under 400 bucks and includes a 13 month warranty on ALL parts (Yeah even parts as small as the injectors). I have a large selection of XJ's to pull parts from; there are 3 pick 'n pulls within 25 miles of me. I also live just a few miles from a well know jeep yard J&W (But I'd have to be VERY VERY VERY VERY VERY desperate to even consider doing business with that place).

Anyhow my questions are not about the HOW to do this swap; I wouldn't do that to you guys... My question is how to get through doing this swap and passing smog in California.

I do plan to call a California Ref Station this week and also ask/pick their heads as to what I need to know. I do feel I should have advise on not being too honest with them. Bottom line my goal is NOT to be a gross polluter. In fact the setup I desire to swap to should be more “eco” friendly. More power, better MPG, and less pollution.

So who has gone through this swap within, California, where the smog laws apply?

California 4.2L with 4.0Head swap and Multipoint Fuel injection upgrades that have passed smog success stories, and how, is what I'm hoping for here. What extra tricks did you have to pull to pass?

Extra parts, extra cost, Clue to getting through the reffing processes more easy?

On another note I do have one NON-smog related question:
After running a 4.0 head and blocking some of the 4.2L neccesary water cooling to allow adaptation of installing the 4.0 head has anyone had heating issues over time? I Had a metalcloak rep telling me I'd be in for heat issues. So I'm looking to hear a few success stories from people that have ran the head swap for a couple years or so.
 

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Technically, the only CA legal smog options for the 4.2L are:


  • Carter BBD with full OEM factory setup in functioning order
  • Howell TBI (CA version)
  • Mopar MPFI (CA version)
  • Complete engine swap to a newer model engine (such as the 91-95 4.0L MPFI)

If it isn't OEM, it must have a CARB exemption and have a E.O.# for the part and the exempted vehicle. The 4.0L head swap is not CA legal, technically speaking, because the 4.0L head (and the associated MPFI) is not OEM equipment on the 4.2L and such parts don't have an exemption via a CARB EO#. The Mopar kit was specifically approved and has an E.O.# which makes it legal. Doesn't matter that the 4.0L head swap does the same job, the head swap isn't approved.

The tech who sees a straight six with MPFI will likely first ask you "where is your CARB sticker" for what appears to be a Mopar MPFI kit. No sticker, no pass. A smog ref whose knows his stuff will be able to tell when the engine block was made by checking the casting numbers, and will be able to tell for what displacement engine it is meant. The fuel injected straight 6 for the YJ didn't come out until 1991. The 4.2L engine casting numbers will give it away that the MPFI doesn't match with the engine block, so you couldn't pass it off as an engine swap to a 4.0L. Again, that is if the tech knows his stuff and is sticking to the book.

I had to pony up the cash for the Howell kit to keep my 4.2L. An engine swap to a 4.0L would have been too much to handle, and I kinda liked the idea of keeping the 4.2L.
 

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Man, I'm really glad I don't live in CA :facepalm:

I think here in TX, they just check tailpipe emissions with a sniffer (for pre-OBD2 vehicles). If you are under the factory emission specs, then you can swap in whatever engine you desire.
 

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I was considering this too when I lived in CA. Swapping all the 4.0l head, fuel injection, and sensors/electronics over wouldn't be a problem. You can just get it inspected by whoever inspects them after install and say you swapped in a newer 4.0l engine. They couldn't tell the difference.
 

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Discussion Starter #5
Technically, the only CA legal smog options for the 4.2L are:


  • Carter BBD with full OEM factory setup in functioning order
  • Howell TBI (CA version)
  • Mopar MPFI (CA version)
  • Complete engine swap to a newer model engine (such as the 91-95 4.0L MPFI)


I had to pony up the cash for the Howell kit to keep my 4.2L. An engine swap to a 4.0L would have been too much to handle, and I kinda liked the idea of keeping the 4.2L.
Thanks for the detailed response. Ultimately, I think your spot on. The fully "legal" (because mainly they have c.a.r.b #s) Options are what you list. What is very sad is that I could pull a whole 4.0 motor with injectors and computer exc, exc, for about 200 dollars this weekend. But if am going to use the whole pulled motor I would end up feeling the need to rebuild it. IF I did not live in CA, I would just take the head, maybe have it remachined, and have basically a multipoint mopar system on my 4.2L for 1000 or less bucks. Plus some lucky guy gets a free 4.0 block.

Instead I'm stuck because I agree that while some refs might just see the 4.0 head and multipoint fuel injection and either assume, OR BELIEVE, when I tell them, its a full 4.0 motor swap. Its a gamble but only a gamble because I live in CA! ErRr

This Metalcloak guy I was talking to about it a couple days ago suggested each time I see a ref it could be costing me 200-300 bucks for my "gambling".

Anyone out there gone through the Reffing process?

I'd love to pick-up the whole motor for 200 bucks /w 13 month warrenty (50% off pick n' pull sale in sacramento) this weekend. (As is my 4.2L needs a new exhaust manifold. So staying with a 4.2L head costs me $150 for a new manifold and then at least 1200 for a howell TBI setup.

I guess I should be temped to just pop a full 4.0 motor, rebuild it, and do the full swap... I loose the .2 and add ALLOT of extra work but ditch the gamble the smog refs.

I'm googling now to see spec differences between a 4.2L Howell TBI versus 4.0L MPEFI.. I'm not aiming to build a power house here. I just want to have more kick that my 2.5L MY little 4 banger has done me well but it doesn't want to hold the weight of the extras I wanna carry; at least not on the highway.

Just because I do live in CA, I am reasonable enough to consider the pricey kits JUST because of the potential stress of the drawn out maybe over complicated reffing process. But the smartest thing I feel is like learning how to best make the smog laws work for me without shelling out the extra cash and using that cash for my Spring Over Axle upgrade!
 

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Discussion Starter #6
I was considering this too when I lived in CA. Swapping all the 4.0l head, fuel injection, and sensors/electronics over wouldn't be a problem. You can just get it inspected by whoever inspects them after install and say you swapped in a newer 4.0l engine. They couldn't tell the difference.
Man, I wanna believe that your right... I mean about a ref believing I did a full 4.0 swap. But its a hell of a gamble that they wouldn't run the numbers on my 4.2 block.

Wanna trade addresses? J/K But should would be nice to live in NV right now. lol
 

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Discussion Starter #7
Man, I'm really glad I don't live in CA :facepalm:

I think here in TX, they just check tailpipe emissions with a sniffer (for pre-OBD2 vehicles). If you are under the factory emission specs, then you can swap in whatever engine you desire.
Yeah your lucky. I wish they would be that simple here. I can assure you that my emissions will be less than the stock setup. In this case. California smog laws are NOT helping the environment. They are rather helping empty my pockets. MY goal is to build an efficient motor.

Hopefully this thread keeps on going until all us californians figure out a way to do the swap without becoming unsmoggable.

The must be a legal loop hole that helps a guy with fair intentions. I mean this is driving me crazy!
 

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Man, I wanna believe that your right... I mean about a ref believing I did a full 4.0 swap. But its a hell of a gamble that they wouldn't run the numbers on my 4.2 block.

Wanna trade addresses? J/K But should would be nice to live in NV right now. lol
You're close to Nevada haha, just ditch California before it becomes worse. You might have to get the Howell kit though.

Lucky for me I went to the pull yard and got all the sensors and throttle body off an older chevy 4.3l so I can put together my own kit. Cost me $150 for everything and it'll be another $200-300 for the adapter.
 

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Discussion Starter #9
You're close to Nevada haha, just ditch California before it becomes worse. You might have to get the Howell kit though.

Lucky for me I went to the pull yard and got all the sensors and throttle body off an older chevy 4.3l so I can put together my own kit. Cost me $150 for everything and it'll be another $200-300 for the adapter.
Yeah Howell looks like my best CA option (Unless I hear some more reffing success stories) But so far I've heard ZERO successful 4.0head on a 4.2L MPEFI, within CA, successful smog stories. I looked at a bunch more write ups on TBI's The GM kit your pulling is suppose to be more tunable than the howell not to mention a cheaper route for the pockets; still pretty much the same thing minus a CA c.a.r.b #.

I did also allot more reading up on Multi Point Injection VS. TBI for the 4.0/4.2. At least what I have read so far shows my desire of junk yard MPEFI has only minor gains over the TBI (concerning the fuel system). So while still not giving up on finding a more pocket book friendly option to the Smog laws of CA, I've got a side mission to find a 4.0 head that takes the 4.2 intake and exhaust. Maybe I'm just finding ways to make myself feel better.

If I have to shell out cash for the howell setup, to stay legal, then I've got to stick to my 4.2L head until I can find a 4.0 head that is setup for TBI. I'm sure these are out there? I'm guessing in the 90-95ish 4.0 wranglers.

Also researching what I can maybe do with my current 4.2L head to get closer to the performance of a 4.0HEAD Because yeah, CA will find a way to screw me on a head swap too. Last time I smogged my 2.5L they got down to the detail of making me change a perfectly good PCV Valve. I told them it was the right valve but they didn't care. I swapped it to match what they wanted but now its different than what the manual shows... Whatever though it got me through smog with my 2.5L

Sigh... I will be leaving CA and/or going pre-74 on my next build. Still hoping for some success stories though... Maybe someone out there has had, if not a successful junk yard MPI from a 4.0 head, a successful junkyard TBI swap pass through CA smog?
 

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Yeah Howell looks like my best CA option (Unless I hear some more reffing success stories) But so far I've heard ZERO successful 4.0head on a 4.2L MPEFI, within CA, successful smog stories. I looked at a bunch more write ups on TBI's The GM kit your pulling is suppose to be more tunable than the howell not to mention a cheaper route for the pockets; still pretty much the same thing minus a CA c.a.r.b #.

I did also allot more reading up on Multi Point Injection VS. TBI for the 4.0/4.2. At least what I have read so far shows my desire of junk yard MPEFI has only minor gains over the TBI (concerning the fuel system). So while still not giving up on finding a more pocket book friendly option to the Smog laws of CA, I've got a side mission to find a 4.0 head that takes the 4.2 intake and exhaust. Maybe I'm just finding ways to make myself feel better.

If I have to shell out cash for the howell setup, to stay legal, then I've got to stick to my 4.2L head until I can find a 4.0 head that is setup for TBI. I'm sure these are out there? I'm guessing in the 90-95ish 4.0 wranglers.

Also researching what I can maybe do with my current 4.2L head to get closer to the performance of a 4.0HEAD Because yeah, CA will find a way to screw me on a head swap too. Last time I smogged my 2.5L they got down to the detail of making me change a perfectly good PCV Valve. I told them it was the right valve but they didn't care. I swapped it to match what they wanted but now its different than what the manual shows... Whatever though it got me through smog with my 2.5L

Sigh... I will be leaving CA and/or going pre-74 on my next build. Still hoping for some success stories though... Maybe someone out there has had, if not a successful junk yard MPI from a 4.0 head, a successful junkyard TBI swap pass through CA smog?
The smog laws mostly work inversely for people with carbureted vehicles. Sure, a carb swap or fuel injection would lower emissions and increase fuel economy, but it's not stock so they won't allow it. You can however pay out the ass for California air resource board authorized crap. This actually is a good part of the reason I left Commiefornia. I have 2 old vehicles, my 89 wrangler and my 69 firebird.

You're not going to find a 4.0l head to work for your exhaust application. The 4.2l exhaust manifold has a pre heater hose part on it required for passing smog, you can't use a 4.2l pipe on a 4.0l head. Maybe an older renix 4.0l engine has the pipe with the heater hose part on it?

Your best option for making a 4.2l head perform like a 4.0l head is to have it ported and polished. That's the route I went with when I had my blocked bored and all the machining for my rebuild. My borla manifold really helped too and it does have the pre heater hose part on it.

A full swap would probably be your cheapest route. You can probably find a complete 4.0l for around $500 and it is an easy swap. I didn't do this because I love the offroad ability of the 4.2l.
 

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Discussion Starter #11
You're not going to find a 4.0l head to work for your exhaust application. The 4.2l exhaust manifold has a pre heater hose part on it required for passing smog, you can't use a 4.2l pipe on a 4.0l head. Maybe an older renix 4.0l engine has the pipe with the heater hose part on it?

Your best option for making a 4.2l head perform like a 4.0l head is to have it ported and polished. That's the route I went with when I had my blocked bored and all the machining for my rebuild. My borla manifold really helped too and it does have the pre heater hose part on it.

A full swap would probably be your cheapest route. You can probably find a complete 4.0l for around $500 and it is an easy swap. I didn't do this because I love the off road ability of the 4.2l.
Thanks for the bold statment of "You will not find a 4.0Head that takes my required 4.2L exhaust." At least I can drop the hope of finding a compatible head and drop the cash on the new exhaust manifold.

I have a rebuilt carter carb (which I hear even new sucks). But maybe I'll just go ahead and pop that on there to pass smog and consider going the junkyard TBI route after. (OF COURSE I MUST be just joking about a junk yard tbi since it would be illegal) It would get me going right away without dropping 1,300 on a howell or 2500 on a mopar.

I kinda do agree the full motor swap COULD still end up being the cheapest route but I'm stubborn; If I'm swapping a whole new motor in I would have to at minimum bore it some, consider a different crankshaft, and remachine the head. Thus making my cheapest option no longer my cheapest option.

You mention you like the idea of having the 4.2L versus 4.0 for its off-road ability. I'm new to the 4.2L, other than hearing the stock carter sucks, and that the 4.2L does great with a 4.0 head, and that its very dependable; I know nothing else about it.

What is it you like about the 4.2L. In other words I suppose its time I start focusing on the benefits of having it as I give up hope for now of an affordable swap.

I'm also a novice when it comes to customizing heads. I'll start googling my options and also google up some info on the borla manifold. But meanwhile I'm eagerly look back at the forum for the info that is keeping me afloat rather than just in tears... LOL

Thanks everyone.

***
FOR ALL WHO LIVE IN CALIFORNIA; IF YOU FIND THIS THREAD 10 YEARS FROM NOW. AND HAVE HOPE THERE IS A SMOG LEGAL OPTION FOR THE UPGRADE I FIRST SUGGESTED: If there is still the above run-on sentence, typed in annoying caps; Give up, or more to another state :). Or please prove me wrong cause maybe I still live in CA and still want a 4.0 head and cheaper MPFI.

I'm still a little reluctant but and pretty darn sure its in my (and most 4.2L YJ folks) current best interest to move the topic to making the best out of 4.2L head and TBI.

I stick to using TBI versus a CARB because of MPG increase hopes and because I live at 200 feet above sea level but 90% of my wheeling occurs between 6500-9500' above sea level.
 

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I like the 4.2l because of the low end torque, a 4.0l you'd be higher in the rpm range to deliver the same torque a 4.2 puts out. The 4.2l sucks for highway/freeway performance though.

My 4.2 is heavily modified as you should see in my signature, so I get the best of both highway and offroad
 
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