TBI or Carb? '86 2.5L to 3.4L upgrade

[FigurativeGarbage]

I'm doing the '86 2.5L swap to a 3.4L from a '94 Camaro. For background and pictures, I've linked my VIN thread.

 

To summarize, I bought this truck over the summer for mild fun and home projects. The idle was getting rough until it stopped working five weeks ago. I approached a neighbor who is pretty good with cars and we found rainwater in the tank (such that it wouldn't even light when poured in the street). He's been toying with the TBI and thinks the problem might be the ECU. I'm sure an injector cleaning wouldn't hurt.

 

I explained why 3.5Ls are a standard option over a 4L and....he happened to have a 3.5L mid-90s Camaro engine in his work area. He's willing to do the swap and says we should ditch the TBI for a simpler carb system.

 

Should we do a TBI or carb? And which parts should I look for?

 

I have read a few threads on this swap and I'll have to review them again to get my shopping list for wire harness, oil pan, etc. I have also read some threads on this subject, but not for this specific swap (correct me if I'm wrong).

 

After this, there's plenty of things to do. Neighbor said he's also willing to fix the ugly wiring. I'd look into taking out the busted AC, fixing the stereo, installing dome lights, fix the doors, maybe redo the aftermarket fan.

 

 

[JeepcoMJ]

Use the mpfi from the f body.

[gogmorgo]

x2 on the fuel injection from the camarobird. Carb swaps are for people who would rather spend a bunch of time screwing around to keep the thing running after the fact than spend a little more time on the initial install to get a better product that'll run better with less screwing around.

[FigurativeGarbage]

Thanks, JeepcoMJ. Agree gogmorgo. I don't want to mess with the carb in bad weather. I'm a novice, but I assume replacing the MAP, ECU, etc. all from the Camaro. Right now, my list includes:

1. oil pan
2. wiring harness
3. fuel system (looking into the MPFI parts)
4. exhaust manifold
5. flywheel (I may just machine the existing flywheel).

I know I need to get more, but only so much sticks in my mind if I note something.

[FigurativeGarbage]

I ordered upper/lower manifolds and an oil pan tonight. What do I do for ECU programing if I don't have a VIN? I'm looking at sellers like this: 1994 1995 Camaro 3.4L Auto. 16184737 Engine computer Programmed to your VIN ECM | eBay

[Gojira94]

The PCM choices from 93-95 are: 16172693, 16184164, 16184737, 16196397.  Which one do you have? FlashHack for L32 can be used to retrieve the calibration and programming the PCM with any of these. You'll need an ALDL cable to connect to it. 94 should still be a 12 pin OBD-I interface. The shortcomings of the L32 right now at least is the lack of widely known/ supported definition files, which show the hex code in the PCM in human readable form in an editor like TunerPro RT. There is a well-known datastream definition for it which would allow you to datalog/ observe powertrain data. There are definition files out there on gearhead-efi.com and I can certainly assist you in getting what you need to edit the calibration if it's necessary.

 

What transmission are you planning to run with this combo? That might really only be the thing you need to change, i.e. turn off auto trans features if running a manual. If engine and trans are from the same car and you can make it fit, you'd really not need to change the calibration much, if at all.

 

EDIT: I see you said "flywheel." so it's manual of some sort...

[Big_Mark]

22 hours ago, gogmorgo said:

x2 on the fuel injection from the camarobird. Carb swaps are for people who would rather spend a bunch of time screwing around to keep the thing running after the fact than spend a little more time on the initial install to get a better product that'll run better with less screwing around.

Where's the "like" button when you need one!  

I agree go with Fuel injection, unless you like screwing around with gas, float bowls, etc.

If you plan on doing any off-roading, definitely go with Fuel injection (any kind), with carbs there is typically one off camber angle that will cause the carb to flood until you get past it (Holley 2BBl, Weber 2 BBL do this) with Fuel injection it just works, even upside down (at least temporarily)
If you do go carb a Rochester carb is better for offroading than Weber/Holley, for whatever reasons they flood less, and I've seen em running upside down as well (though for a shorter period that the fuel injected engines)

[Big_Mark]

21 hours ago, FigurativeGarbage said:

Thanks, JeepcoMJ. Agree gogmorgo. I don't want to mess with the carb in bad weather. I'm a novice, but I assume replacing the MAP, ECU, etc. all from the Camaro. Right now, my list includes:

1. oil pan
2. wiring harness
3. fuel system (looking into the MPFI parts)
4. exhaust manifold
5. flywheel (I may just machine the existing flywheel).

I know I need to get more, but only so much sticks in my mind if I note something.

When swapping motors I suggest grabbing the entire Engine harness and computer along with the engine (same with the transmission if it's an automatic). Ultimately you "just" connect the harness back to the engine, computer, power and ground, then vroom vroom! No programming needed; it will just work as it did in its old home.

 

Notice "just" is bold and highlighted, you will need to figure out fuel delivery (as you noted) as well as ignition on/off. But otherwise yeah the donor harness should do the job and for $300-$700 less than some aftermarket harness that may or may not work when you get it, and you will still need to hook it up as described.

 

When I put the 5.0 in my Scrambler It took a minute to wrap my head around the major systems that run independently of each other.

 

Comanche System that remain/can remain stock:

1. Lighting

2. wipers

3. Ignition

4. Fuel system power

 

Non stock Systems:

1. Engine/computer

2. Transmission computer (if using modern Automatic)

 

Dassit!

The new system will overlap in places with the old system (fuel system power/Ignition)

but other than that, you will need to keep them separated in your head.

 

Hope this helps

 

P.S. keep that donor vehicle around until your new one is up and running, if you have a donor vehicle that is.

[FigurativeGarbage]

It's a manual. I heard manuals can accept computers and engines from automatic donor vehicles, but not vice versa. Correct me if I'm wrong.

 

I found an automatic 94 Camaro in a junkyard near me today. I'll have to see if I can get ahold of them. Used 1994 Chevrolet Camaro Air And Fuel Throttle Body Throttle Va (hollanderstores.com). Maybe I bought the manifolds and oil pan too soon if I can get it cheaper from them, but I like idea of getting the harness, ECU, etc from one vehicle. I think that might solve the ECU VIN issue if it comes straight from the junkyard rather than refurbished like some of the ebay sellers?

[Gojira94]

In a "plug and play" situation with no modification, a manual trans PCM would be missing a lot of the auto trans parameters, though the tables would be there. There is a Flag set for auto trans that causes all those tables/ flags/ scalars to be read with a 60* 4L60E from 94-on. Speedo calibration and gear ratios would be the worst of your tuning. The pulses per mile in the VSS has a table to figure it against the gear ratios of the transmission, this is true for both auto and manual, and they are different from each other. To use a factory HO speedo, which works off a VSS, could be made to work, though not sure how to approach it without some thought and research.

 

Also, the PCMs aren't locked so VIN isn't important. Though it can be easily read from the PCM and changed.

[gogmorgo]

Does the HO speedometer even go through the ECU? It just reads off the tail shaft of the transfer case, or trans for 2wd, so there’s no gear calculation necessary. It also can only be recalibrated by changing the speedometer gears. None of the other instruments in the cluster are reading ECU data either. 

[Gojira94]

14 hours ago, gogmorgo said:

Does the HO speedometer even go through the ECU? It just reads off the tail shaft of the transfer case, or trans for 2wd, so there’s no gear calculation necessary. It also can only be recalibrated by changing the speedometer gears. None of the other instruments in the cluster are reading ECU data either. 

 

You're right, I got ahead of myself. 91-92 VSS is 2 pins and takes a changeable gear in the t-case or tailshaft housing. 1994 4L60E and GM's T5 read teeth on a gear that's part of the output shaft. A GM T5 would be the prospect of replacing the case entirely to use for 4WD or finding one from an old CJ. And the T5 is probably no better than the AX5 in terms of strength. Though they were offered to fit a 4.2 from 82-86 on the CJs, not recommended. There are AX-15 bellhousing adapters available for GM V6s. But given that the L32 is 160 hp @ 4,600 rpm and 200 lb.ft. torque @ 3600 rpm, and the cost and complexity of using it, makes getting the 4.0 rebuilt finding a used 4.0 or even rebuilding the 2.5 probably a more cost effective answer. 

[FigurativeGarbage]

Does the exhaust header and y-pipe come from the 3.4L camaro? Cuz that's what I did (new, wasn't cheap).

 

However,@JeepcoMJ said: 

The parts you will be saving from the original 2.8 will be:

1.  Exhaust manifolds and y pipe...(continued)

 

I'm on my big yearly stay-cation until January 2nd, so I'm trying to get as much of this sorted as I have time for it. I have ordered my fuel rail, ordered an engine harness at a nearby scrape yard today (I'll pull out the automatic wiring), ordered fuel pump. Have sensors, have the motor, have upper manifold, have flashed ECU.

 

Still need air intake, flywheel, 2.8L oil pan, oil pressure cut-off switch?, water pump?, alternator?, valve covers?

[Gojira94]

Do you have any pics of what you're working with so far? This is an example of the 93-95 F-Body L32 V6:

 

[Gojira94]

These things took a CS-130 130mm case alternator. Aftermarket has higher output options than stock btw. A little pricey but I have a comparable PowerMaster CS-130 unit on my 92 C1500: https://www.summitracing.com/parts/pwm-48114

[FigurativeGarbage]

I've been learning a lot and trying to move this along each week. I'm attaching many photos, but the big question is the last one: I don't know if the engine mounts are the same as a 2.8L. I can order those cheap or get rubber Brown Dog mounts for like $200 with the bolts, but I can't seem to find the frame mounts. I have heard the mounts are the same between the 2.5L and the 2.8L.

1. current engine bay after removing the engine. Two engine pans resting on the side.
2. old 2.5L
3. New 3.4L side (from 1994 camaro)
4. 3.4L rear
5. 3.4L after cleaning and painting
6. 3.4L oil pan next to the 2.8L engine pan I bought. 3.4L oil pan won't clear the differential, while the 2.8L won't mount to the engine because the timing cover is different (flat instead of rounded (see the blue gasket in prior pic)). I may have to buy another one from ebay for $130 (asking price is $172).
7. New engine with aluminum valve covers (will clean and paint later), intake manifold.
8. Interior after ripping out carpet and bench seat. I'll eventually go with Lizardskin paint, but I need this driving first.
9. Driver's engine mounts (original 2.5L).

I need the PS pump, alternator, starter, and brackets, which I can either order new, or strip from my neighbor's S10.

[FigurativeGarbage]

Here's the passenger-side mount. It is different from the 2.8L mount, as the 2.8L mounts appear to be interchangeable (same on both sides).

[The86manche]

15 hours ago, FigurativeGarbage said:

Here's the passenger-side mount. It is different from the 2.8L mount, as the 2.8L mounts appear to be interchangeable (same on both sides).

The rubber engine mounts are the same. And by the looks of it need to be replaced. The metal ones off a 2.8 will also work though I can't say if they are the same as s10 mounts. Might be better snagging them off an mj 2.8

[Pete M]

do you need the rubber mount?  or the metal bracket that holds it to the frame?  I've got a set of MJ 2.8 brackets in that empty shell of a truck.

[FigurativeGarbage]

I think I should definitely get new mounts based on the condition of the current mounts.

 

Rubber dog sells two different mounts for the 2.5L and the 2.8. Here's the 2.8L 

And here's the 2.5L  You can see the passenger mount bolts just a bit differently, although I'm not sure why.

 

Currently I have the 2.5L frames/brackets, but will they put the mounts in the correct position for the 3.4L? If possible, could I see and/or buy the 2.5 frames? Otherwise, Brown Dog thinks I might need to custom fabricate frames.

 

[FigurativeGarbage]

The 2.8L frame brackets look the same as the 2.5L brackets. From this decent thread: '86 Comanche Long bed, Slow build... | Expedition Portal

 

[FigurativeGarbage]

I bit the bullet and got the Camaro oil pan custom cut to clear the differential. Got some aluminum valve covers from the neighbor and painted them rustoleum red. Replaced the rear main seal and need to replace a few studs (stripped or missing) from the hardware store tonight. New flywheel bolts come in tomorrow, then I can install the 2.8L S10 neutrally balanced flywheel I have and a 2.8L clutch kit from M-PACT. I was worried it wouldn't mount to the 2.5L 4 speed transmission, but it appears to be fine....

 

Engine is on the hoist and otherwise ready to see how it aligns with the existing mounts. I'll need engine-side brackets, hopefully picked from 2.8L Comanches in a junkyard an hour away.

[FigurativeGarbage]

Got the flywheel on, replaced the rear main seal, clutch, release bearing, and slave cylinder (old one pictured below...). The hydraulic line was stuck/mangled, so that will need to be replaced too. With much difficulty, my neighbor helped me get the engine connected to the transmission. The custom oil pan was still difficult to maneuver around the differential and sway bar.

 

I ordered Brown Dog mounts for a 2.5L two days ago. My plan is to mockup some cardboard engine brackets for a weld shop to fabricate. Then order accessories, accessory brackets, replace missing transmission bolts, exhaust, air intake, delete the charcoal filter.....then wiring and world peace.

 

[eaglescout526]

You should probably start a build thread on this at this point. Doesn’t seem like much of questions here and just more documentation of your swap. 

[Greentoy]

On 2/22/2023 at 11:15 AM, FigurativeGarbage said:

I bit the bullet and got the Camaro oil pan custom cut to clear the differential. Got some aluminum valve covers from the neighbor and painted them rustoleum red. Replaced the rear main seal and need to replace a few studs (stripped or missing) from the hardware store tonight. New flywheel bolts come in tomorrow, then I can install the 2.8L S10 neutrally balanced flywheel I have and a 2.8L clutch kit from M-PACT. I was worried it wouldn't mount to the 2.5L 4 speed transmission, but it appears to be fine....

 

Engine is on the hoist and otherwise ready to see how it aligns with the existing mounts. I'll need engine-side brackets, hopefully picked from 2.8L Comanches in a junkyard an hour away.

We're in the middle of this swap in an 85 XJ. Was your modification to the oil pan absolutely necessary? I ask because our plan is to lift the xj about 3 " and I wonder if that will give adequate clearance for the pan. Thoughts?