2.9 to 4.0 swap

[grumpy old man]

New to forum but you seem to have information on the above.

Building an 89 Bronco II for my granddaughter. All is well, runs great she loves it but unfortunately I live in California and cannot get it past smog. Bypassing that problem I am now considering a 4.0 SOHC late enough to have the OBDII so I can get rid of the OBDI. It will need to be instlled correctly in order to pass the smog gestapo, but that just means that everything is working as it did in its original home. My real question is will it bolt to the current A4LD? If not is there a bellhousing for the A4 that will work? I did rebuild the trans so swapping out a bellhousing is not a problem.

The other question which I should have addressed earlier is will the A4 handle the SOHC or should I look for a 4WD donor vehicle?

Thanks in advance for any info you can supply
Dwight















PAST

 

[lil_Blue_Ford]

So, there’s arguments. I’m not sure about commiefornia, but Federal emissions standards say a swap of like year or newer is legal.

Realistically, most average mechanics anymore aren’t really going to know the difference between a 2.9 and a 4.0 OHV, and realistically, a 4.0 OHV is a bored and stroked 2.9, so if it was me, I might try the 4.0 OHV swap and not say anything. If asked, say it’s a bored and stroked motor.

The 4.0 OHV in an 89 can be made to look entirely stock, just use a 90-92 donor if you can find one. It’s mostly bolt in at that point. I had to splice a couple wires on the drivers side of the engine bay, but I built adapter harnesses. It looks like it belongs in my Choptop.

My 88 the swap is a bit more involved and I don’t intend to use that B2 the same as the Choptop, so in that I’m just going to give the 2.9 some upgrades and see how that goes.

I will say that hands down the best thing that I’ve done for an auto trans RBV was a shift kit and valve body mods. I did almost hardcore in my 92 Ranger and the difference was night and day. With a limited slip and 4.0 OHV, once I did the transmission work (tedious but not difficult), it would smoke the rear tires with too much throttle. 1,000,000x better than stock A4LD slop.

 

[fastpakr]

I'm all for the 4.0 OHV swap, but the SOHC is a whole different can of worms. Avoid that - you're jumping into OBD2, physical space issues, etc.

That said - do you know WHY you're not passing the smog testing now?

 

[grumpy old man]

Commiefornia states it perfectly

I installed my first shift kit in the early 60's. Did an overhaul on a cast iron cruiseomatic and had the typical soft 1-2 shift. Heard about transmission research (now known as transgo) and got a shift kit. Took a lazy cruiso and made it shift like a torqueflight. That was back in the day when Gil Younger actually answered the phone. From that day to this I have not done a transmission without a shift kit. The one that is in my 89 has very positive shifts without being harsh.

Getting back to my original question about using a 4.0 SOHC. I am more interested in junking the OBDI than anything else. I have been working on this abomination off and on for 4 months now. and have figured out that it may not be repairable. It is a very early 89 and has things in the system that Ford does not admit to. The most notable being a 2Kohm resister that is located in a branch circuit about ten inches from the O2 ground wire. that resistor failed and threw the thing pig fat. I removed the entire wiring loom twice before I found that. I have chased a dozen things on this thing, and think it may be passable now but it keeps throwing a code 41 after about 15-20 miles of driving. I am in possession of a breakout box and an original 89 emissions manual which interestingly has no information about fixing a 41 and damn little information on the O2 circuit.

This is the main reason I am interested in installing an OBDII engine. I have seen conflicting information about the SOHC bolting up to the 2.9 transmission. I am not diametrically opposed to using engine trans and transfer case out of the later vehicle, but if the SOHC will bolt to the existing trans it will eliminate possible driveshaft problems and who knows what else. Not that I can't deal with those things but at my age the less time spent on a creeper the better.

 

[grumpy old man]

I'm all for the 4.0 OHV swap, but the SOHC is a whole different can of worms. Avoid that - you're jumping into OBD2, physical space issues, etc.

That said - do you know WHY you're not passing the smog testing now?

The primary reason is that I have a very early California 89. It appears to be a rare bird. I have been communicating with someone that was a driveability specialist when this thing was new. I have found things in this car he has never heard of and that do not appear in any ford information. The most notable thing was a 22Kohm resistor in the O2 ground wire that went out and threw the thing pig fat. I have chased a dozen other things and believe it might pass now but after 15-20 mi of driving it will throw a code 41. I took it out for a drive with the break out box in it and did not shut it off when I got home. I probed every system and found them all well within spec listed in my 89 emissions manual. My Granddaughter is going to school a thousand miles away and right now I would be more inclined to trust a used car salesman turned politician than to trust the bronco that far away from home.

I have read many code 41 horror stories and interestingly I can find no code 41 information in my genuine Ford emissions manual and damn little information on the O2 circuit.

As for physically inserting the SOHC into the existing hole I have spent a lifetime of inserting engines into places they do not belong. And as for the OBD2 as long as I have an intact donor vehicle and transfer everything as designed the Cal emissions gestapo will OK it. To the best of my knowledge they did not make a 4.0 OHV OBD2 but if they did obviously that would be an easier swap. I am just looking for a reliable car that I trust to take care of my granddaughter a thousand miles away

 

[fastpakr]

You can definitely get an obd2 4.0 OHV. 95-96 Explorer, and 95-98ish? Ranger. Might be more year ranges than that, but at least those. Mazda B series too.

 

[rusty ol ranger]

41 system lean....means ECM is going to dump fuel to compensate.

Im assuming youve checked for vacuum leaks, exhaust leaks, etc etc?

Personally id stay the course with whats already there rathed then rip into it and maybe end up further behind then what you started.

 

[grumpy old man]

I am well aware of what the code is stating. Problem is that it is running rich and showing lean. I have been all over this thing for going on 4 months off and on and am convinced that the permanent answer is to go to an OBD2. If it throws an OBD2 code away from home there are probably a dozen people within a reasonable drive capable of working on it. OBD1 not so.

Still haven't heard if the cammer will bolt to my trans. just trying to keep my options open.

 

[Josh P]

OBD II engine swap in California would require the donor engine and donor transmission to be swapped in to be considered a legal swap. Also if you do it, pick a year newer than 2000 as a donor cause anything older than that gets the obd port test and has to be ran on the rollers. Newer than 2000 is just the port test.

 

[rusty ol ranger]

I am well aware of what the code is stating. Problem is that it is running rich and showing lean. I have been all over this thing for going on 4 months off and on and am convinced that the permanent answer is to go to an OBD2. If it throws an OBD2 code away from home there are probably a dozen people within a reasonable drive capable of working on it. OBD1 not so.

Still haven't heard if the cammer will bolt to my trans. just trying to keep my options open.

It will bolt to it. One hole is different.

However a non 4.0 A4LD is weak at best behind a 2.9...an SOHC would probably grenade it pretty fast.

Also...yes...if the O2 is telling the ECM its lean the engines going to run rich. The ECM is trying to compensate for the lean condition that its (more then likely) being fooled into believing is there.

@RonD can explain it better then i can.

It could even be a bad ECM.

 

[grumpy old man]

Josh, Thanks for that information, I now know that I need a 4WD donor vehicle which limits my options somewhat but better to find out now.

The question is why is it calling lean? I have replaced everything including the ECM. I have checked and replaced everything except the intake air sensor. I have had the wire loom out and on the bench twice, the last time I checked every circuit through the loom including all the in loom connectors. That is how I found the resistor that ford hid in the loom for unknown reasons, and before you ask yes it had to be a factory install because it was run about 10 inches up and back through a branch circuit to hide it. The splice to put the resistor in was very professional and the heavy glue infused shrink sleeve actually had the resistor values printed on it. Plus the ground wire was 20 inches longer than it would have needed to be if they had run it straight with no connectors. I and others have concluded that this was a very early Cal car with modifications for unknown reasons, (likely having to do with the initial Cal smog testing) . Therefore the Ford publications covering the 89 model year are useless as they show nothing about the odd things I have found. Hence the desire to swap to an OBD2. If it malfunctions 1000 miles from home what do you think the chances would be of finding a mechanic around OSU that even knows what an OBD1 is let alone one that is probably one of a handful of early Cal manufacture?

Thanks to all for the responses at least I now have enough information to determine my plan of attack. Since there are OHV's with an OBD2 I just need to figure out how much work I want to go through. At least I have until end of summer to complete it. Wish me luck.

Oh just as a point of no particular interest my daily driver is a '63 Pontiac Catalina with an LT engine and 6L80 trans out of a '15 Silverado. This ain't my first rodeo. Hardest install ever did but well worth it.

 

[lil_Blue_Ford]

The OBD2 equipped 4.0 OHV was 95-00 for the Ranger and 95-01 for the Explorer, but some of the 98-01 Explorers got the OHV and some got the SOHC for the 4.0, it was a really weird transition.

The OHV would largely bolt right in. SOHC requires modifications because it’s wider by a lot, not sure what headaches that could cause for fit.

It’s a good point that OBD2 equipped vehicles are a little more serviceable now days. Most places don’t have any ability to pull codes or do diagnostics on the older stuff. Generally speaking, the older stuff is technically simpler to fix, but modern shops have forgotten about how to work on them. Going to OBD2 you will have to use the 4R or 5R transmission out of the donor because there’s more electrical controls for the transmission which is an improved A4LD basically. Not sure about length, but you should be able to use the Bronco II transfer case on any of those transmissions. Don’t forget to change the tire size in the computer if you do the OBD2 swap because that affects everything. You will need to use a later rear axle (ABS/speed sensor in the later rear axle that OBD2 uses) and you’ll have to change the gauge cluster plus block off the old speedo sensor in the transfer case unless you use a newer t-case.

 

[grumpy old man]

Good stuff to know going in. I will be using a complete donor car so I am sure to have all the necessary widgetts to complete the swap. My inclination is to use the cammer but that is what I would want if I was driving it. My granddaughter doesn't need the HP and would not know what to do with it if she had it so logically I should go with the OHV which probably has more bottom end torque anyway. For reasons I have not tried to figure out cam in block engines generally have better bottom end than cam in head. One of lifes mysteries. Tire size is the original bronco 215/75/15

I have an acquaintance in the midwest who tunes via the net so I will need to contact Andy to see if he can dial this thing in when I am done.

If I have a complete donor truck, that should solve the speed sensor issue. I would want to change both ends because having two different gear ratios would not be good if that is a possibility.

Also the newer donor truck should have anti lock. The current Bronco does not and she will be driving in snow at college. Front disc rear drum. Possibly adding that?

She will probably be driving this for many years to come so doing all I can for safety and longivity is a necessity.

Thanks for all the info. If you think of anything else please send it my way. The more I know going in the less I need to figure out in process.

My mind often follows very strange paths and It just occurred to me, what about lifting up the existing body and rolling the new chassis under it? I have done stranger things.

 

[RobbieD]

Just adding of couple of thoughts, as food for thought.

Also the newer donor truck should have anti lock. The current Bronco does not and she will be driving in snow at college. Front disc rear drum. Possibly adding that?

If your donor truck is a '93 or '94 Explorer it'll have 4 wheel ABS that could possibly be swapped into the B2. I don't know of anybody that has done that, though.

She will probably be driving this for many years to come so doing all I can for safety and longivity is a necessity.

While the cammer 4.0 is better horsepower, it also has the timing chains which are expensive when they need replacement. The OHV 4.0, while not as powerful and more of an old-school motor, will be kinder to a driver who won't be their own mechanic.


Good luck with getting it fixed up how you want. B2's are a blast to drive; your daughter is lucky that you're fixing her up right.

 

[grumpy old man]

That is the crux of the matter. trhe truck runs and drives great it is just the d... OBD1 and not smogging.

Don't know what stage of life you are in but I have found that you will do things for a really sweet granddaughter that you would not for a minute consider doing for any one else including yourself! A good cam change will probably find some untapped horsepower.

She has loved the Bronco II since she was in grade school. You got to help a kid that loves old cars don't you?