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First I'm going to divide this into sections.
1) Why?
2) Wiring
3) Motor install
4) Exhaust

1) Why
I started out this build with a $500 85 Camaro intended to become a drift car. The original 2.8 ran really well, with the exception that the oil pump pickup fell off and I would lose oil pressure if I used the brakes anything but gradually. Fixing the problem would mean pulling the motor. If I didn't have to fix the pickup, I probably would have kept the 2.8 and turbo'd it. I also needed a 5-speed swap to make the car driftable. So my reasons...
- I got the motor cheap and they are very strong/reliable motors
- This one has a cam and makes more HP than any factory 3rd Gen V8 with room for more
- I knew I could make the swap happen for little cost

Forgive the dirty engine bay haha. This car sat for 3+ years before I bought it.

2) Wiring
I pretty much finished the wiring harness with the motor out of the car. There were many ways I could have approached wiring the swap; pretty much any other way would have been easier than what I did . I just wanted the most possible options moving forward. In the planning stages, I identified 4 different ways to go. A) Is mostly only a good option if you're starting with an 85-89 model.

A) '7165 ECM running $12P
This is probably the simplest approach, with a good amount of tuning options. $12P is a custom code that has a lot of features. Google for more info. The best part about the '7165 is that it's only about 6 wires IIRC of re-pinning away from the stock ECM. From there, the IAC, TPS, and ignition pigtails would have to be switched over, the MAF wiring would be modified into MAP sensor wiring, add a knock sensor pigtail and the 3500's injector harness would be spliced in (or modify the stock injector harness as necessary). I might be forgetting a couple steps, but you get the idea. Pretty basic stuff. Harness would probably have to be de-loomed to get some sensor pigtails to their respective locations on the new engine.

B) Snag a 90-92 '7730 Harness
I was at a local Pick'n'Pull and stumbled upon a '91 Firebird 3.1/auto car, so I pulled the whole engine harness (and to my surprise they only charged me $18 for it ) along with the ECM and a couple other accessories. If you're starting with a 90-92 car, having this harness means you already have a great ECM with lots of potential. Like using a '7165, you'd still need to swap the ignition wiring pigtails for the DIS equivalents, change around the injector wiring as necessary, and some sensor locations would be different, however the IAC/TPS pigtails would already be the right ones. Note: If starting with an 85-89 car, the 90-92 bulkhead plugs have different pinouts. Using a 90-92 harness would require splicing in the C100 and C207/C221 plugs from your original harness, and doing some re-arranging of the 90-92 harness as necessary for that change.

C) Use a 93-95 3.4 F-body PCM (What I did, essentially)
I like the fact that this PCM is fairly simple to wire in, and CHEAP to tune (cheaper than the above choices) yet has a lot of features that are only otherwise available from OBDII PCMs. Like SFI, dual O2 sensors, etc... Simplest way to wire in this PCM would be very similar to an LT1 harness merge, i.e. get a whole 3.4 harness, mount the PCM in the engine bay somewhere or drill a new hole in the firewall to feed the extra wires through, and splice in the C100/C207 plugs from your stock harness. If you wanted to use a 4L60E with the engine, this PCM can control one.

Personally, I wanted the cleanest possible install, so, after doing the research, I found I could use the 3.1/auto '7730 harness, delete the EGR and auto wires, and have enough wires leftover coming through the fender grommet to wire in the extra 24x crank sensor, cam sensor, individual injector wires, and second O2 sensor that the PCM uses. I did not delete any of the A/C stuff from the harness; I'm probably going to install A/C back into the car at some point. I also took the opportunity to upgrade to the stock 3500's heated O2 sensors and spliced in the pigtails for those.

I went even further, to keep my options open, just in case the 3.4 PCM for whatever reason couldn't do everything I needed ('7730 has sooooo much more tuning support), and spliced all the PCM wires into the existing '7730 wires so that, if I ever need/want to, I just unplug one computer and plug the other in, and use a jumper injector mini-harness to convert the injector harness from SFI mode to batch-fire mode.

Some pics of the process:







All the wiring goes through the fender grommet, with the PCM sitting out of sight in the stock ECM location, the T5 reverse light wires come through the auto's shifter cable grommet. I like that the harness is layed out like factory and is 100% removable without any cutting.

D) Wire in an OBDII 3400 PCM
Probably the most complex option. Benefit is a more modern engine management system, ability to use a MAF sensor (engines using MAF sensors in my experience generally run a bit smoother all around, more of a modern feel), and more comprehensive trouble codes. Cost of tuning is higher than any other option. I have no idea if these PCMs can control a 4L60E but if it's essentially the same as a 4T60E then they probably can.

An extra thing I did was wire in a cruise control module from an Oldsmobile Intrigue. I made the cruise control harness separate, just like factory, and also a removable harness. When I was building this harness I decided I wanted to keep CCP after all (had deleted it from the engine harness), so under the dash I spliced the CCP purge wire into one of the wires that goes to the factory cruise module, then on the other side of the dash I'll integrate that wire into the C207. Another wire originally used for the cruise module will be used for the clutch anticipate switch wire (although this is optional in my experience).

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3) Motor Install

Transmission Mounting
If you have a T5, chances are you have a dual starter pocket bellhousing. Some very slight grinding is required to clear the driver's side starter. You will also need an '88+ flywheel. An F-body flywheel can be used, however the diameter is larger than the FWD ring gear size that the 3500 normally uses, so in this case a 9/16" shim is required for correct starter engagement. The alternative is to use an 88+ FWD flywheel (like from a Cavalier 3.1 or S10 2.2) and space the clutch fork pivot pin out a bit to compensate for the shallower flywheel depth. Clutch spline engagement is still just fine. Your stock clutch will work with either flywheel, but may or may not hold the power. Not all clutches are made equal. My setup is a little different but works great...









If you have an auto, again, you need an 88+ flex plate. I'm not an expert in this area, but I believe other than the flex plate, and possible starter shim (see above), the auto should bolt right up.

The dust shield for either transmission will need a new opening for the driver's side starter.

Timing Cover
First off you'll need a timing cover from an 87+ RWD 2.8, 3.1, or 3.4. Note: If running the 3.4 PCM, you NEED a 3.4 timing cover and harmonic balancer in order to have a 24x crank sensor. Bolting the RWD cover on requires 3 modifications. There's an extra water passage near the water pump inlet that needs to be plugged. And also the upper 'tab' on the timing cover needs to be cut off. You'll understand why later when you flip the upper intake. Also, 3 water pump mounting holes need to be drilled out for larger bolts (also on the water pump). Sorry that I don't have any pictures of this.

Pulleys
Your stock harmonic balancer and crank pulley will bolt on. If you're not starting with an 87+ car, you will need an 87+ water pump, crank pulley, and water pump pulley (really, the whole serpentine setup). I'm not actually sure how much of a stock 87+ serpentine system will bolt to the 3500 heads/block or what modification would be needed to do so. I'm currently running a very simple setup shown below.



Power Steering
The power steering pump is mounted with a modified 87+ bracket. A non-serpentine pump can be used but you will still need the 6-rib pulley for it. You can see below that one hole is slotted and another is enlarged a bit. The bracket also needed to be clearanced a little on the back to clear a protrusion on the 3500 block.





Alternator
The alternator is from an 88-94 Cavalier application and is mounted with a stud/spacer from one of the bolt holes in the head, and with a turnbuckle (the tensioner in this scheme) as the other mounting point. The turnbuckle mounts to one of the vacant bolt holes on the power steering pump behind the pulley.



Crank Trigger
Since the 3500 has a 58x crank sensor, it needs an external or aftermarket internal crank trigger to run on a tuneable factory PCM. Mine is modeled after the BCC external trigger, but I cut my notches on the outer ring of the crank pulley. You can buy the BCC RWD trigger or attempt to make your own. There are various diagrams available showing where to make the notches in relation to the sensor mount.



Intake manifolds
The upper and lower intake manifolds need to be flipped for an F-body swap. There is simply no room for a rear mounted t-stat housing. Doing this is very straightforward. Valve covers come off, intakes come off, rocker arms come out enough to remove the pushrods, old gaskets come off, new gaskets go on, and everything goes back on but with the intakes reversed. With one exception, of course .

In the FWD application, the pipe that runs along the top of the lower intake serves to feed a heater core bypass passage. I re-purposed this pipe to use as one of the heater core lines (the one that doesn't come from the water pump). I then took the opening in the lower intake that is used for a heater core line outlet in FWD application and tapped it to 1/2" NPT (the hole is already the perfect size for that tap). You can mount a 3-wire CTS in this hole with a 1/2 - 3/8 NPT reducer or plug it and mount the sensor elsewhere. I drilled/tapped the stock CTS sensor location in the rear of the passenger's side head to 3/8" NPT and installed the CTS there for a bit of a cleaner look, but both locations work fine.

K-Member
The k-member will need to be notched or replaced with a tubular version to clear the 3500's structrual oil pan. I wanted to have as much extra room as possible, so I cut the center of the stock k-member completely out, then boxed it back in and welded a bar across.

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Motor Mounts
To make the motor mounts, I decided on solid steel for simplicity and strength. With a stock/mild cam you honestly can't really feel many vibrations, with a more radical cam, vibrations increase a bit. I made plates to fit both the k-member and engine, then moved the engine/trans assembly into place, bolted the transmission in, and got the height set appropriately. I then tacked bars between the two plates and removed them again to fully weld.





Rad Hoses
Onto the rad hoses; since you're using a RWD timing cover, you can re-use your stock lower rad hose and one of the heater core lines. I cut the heater core hard line bracket so that the stock line/hose remained the same while removing the now-unused hard line. I re-purposed the hard line-heater core hose to go to the pipe coming off of the lower intake. For the upper rad hose, you can use the stock 3500 t-stat housing, or BCC makes a front-facing housing. The BCC housing would work well with the stock upper rad hose, but I just used the 3500's housing. It had an extra nipple on it, so I removed the nipple and tapped the hole to 1/8" NPT (hole was the perfect size) and re-purposed the 3500's coolant bleeder for the task of plugging the hole. The bleeder is probably mounted too low in relation to the rad to be useful, but who knows . I'm not sure where the upper rad hose came from, but it was a perfect fit after trimming an inch or two of one end down.





Fuel Lines
I used a 3400 fuel rail for this swap. A 3500 rail could be used, but I'm not going to get into the specifics. I also re-used the stock fuel lines, just with adapter fittings. Russell makes fittings that connect to the 3400 quick disconnect lines, and also fittings that connect to the O-ring fittings on the stock fuel lines. I used these and two -6 female unions to connect everything. I heated and bent the rail's lines to route under the alternator.

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Throttle Body and Cable
The 3500 normally uses a cable throttle body, so I made my own adapter for an LX5 65mm throttle body (the Oldsmobile Intrigue 3.5L DOHC engine). I also grabbed the throttle cable throttle cable bracket, cruise cable, and cruise module from the same car.









The Intrigue throttle cable hooks up to the pedal like stock. The fit in the firewall opening isn't perfect, but it works pretty well.

Misc
Using a 3400 coil pack is necessary for any factory ECM/PCM. Since the 3500's upper intake bosses are spaced differently than the 3400 ones, I just cut off the bottom mounts and used the two upper holes only. The 3500 coil bracket can also be re-drilled for the 3400 coils if you want to use all 4 mounting points.

The brake booster hose hooks up pretty much like stock; the fitting on the upper intake is a bit big but the stock hose will stretch over or alternatively you could get a 3/8 NPT fitting with the right nipple size.



PCV can either be used like stock, but in my case I'm going to slash-cut into the exhaust so I hooked up hoses to the openings in the valve cover. One of the valve covers I drilled/tapped to 1/2" NPT to mount a nipple fitting in.

I chose not to install EGR but it could be achieved with some custom fab.

I also chose in this case to use the stock CAI. I cut up a 3" 90* coupler and some aluminum pipe to make this happen.

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4) Exhaust

There are a few different ways the exhaust can be approached. You could even use your factory V6 manifolds with a modified y-pipe even though they would be a HUGE restriction. The only way you're going to get the most ideal exhaust is with custom headers, since the 3500 has D-ports and there are no direct-fit D-port V6 headers available. However, there are a few other options that, though not perfect, are probably sufficient for most people. Note: To use ANY iron head manifolds/headers, the lower holes must be slotted to accommodate the change in port spacing

2x 3500 Front Manifolds
These fit, and are actually not too terrible for fitment. The driver's side is a perfect fit, however, the passenger's side would need a pretty tight bend to clear the k-member. I believe it's doable, but definitely tight. These manifolds have D-ports and I believe flow reasonably well, and at the very least, you shouldn't lose any power from stock by using them.





Pacesetter Headers
I didn't take any pics but these are another somewhat viable option. In this case the passenger's side is a perfect fit, but the driver's side almost points right at the oil pan and the y-pipe would probably need to be completely re-worked. They also come extremely close to the starter. It would probably be ok if the header was wrapped. Like with the 3500 manifolds, you could probably use the driver's side with some well-planned bends.

OBX S10 2.8 Headers
My friend had them on his S10 and they look great, being stainless steel, and are pretty cheap. They are a mid-length header and clear the driver's side starter just fine. I'm not 100% sure that they will fit in an F-body, but judging by the pics I have of the fitment in the S10, I think they will, along with the y-pipe. Note: With my friend's S10, he had to weld a flex-pipe into the y-pipe to get it to fit. Also, the emissions hook-ups are totally wrong for an F-body

Hooker 2.8 Long Tube Headers
Probably the best for fitment but the primary tube size is definitely on the small side. They are also very rare since they were discontinued in the early 90s as far as I can tell. In my case, the motor sits a bit lower than stock, so the passenger's side gave me some fitment issues, but I was able to bend it enough to fit. The driver's side has lots of clearance. I wasn't terribly impressed with the flange quality either and had to use 2.8 exhaust gaskets to have any hope of sealing. I added O2 bungs and it's what I currently have on the car. The plan is to get some proper D-port flanges and model the Hooker long tubes with 1 3/4" pipe in the near future. At the very least I can use these to build the rest of the exhaust and run the engine.







As It Sits Today





And of course the start-up vid.. just forgive the cell phone mic for not picking up the deep LOUD exhaust note correctly