Follow along as we get the 4.6L 3V engine installated in our Fox Body Fairmont! We ran into a few issues with headers. Read this article to see our solution!
Part 2 of the 3v 4.6 Fox project is concentrating on getting the motor in the car. As a group here at 50resto, this is our 4th effort at a 4.6 swap into a fox body, so we knew what we were getting into, for the most part. The difference here is the 3-valve. The exhaust bolt pattern is unique on the 3 valve, so header choices are nill. To my knowledge, no one makes headers for this application. Companies like KOOKS headers will pretty much build you whatever you want, but that can get expensive, and we're working on a budget.
My first attempt at an installation was with the Ford Racing 2005-2009 Mustang GT shorty headers that came on the motor.
I attempted the first installation with a stock k-member out of a 2004 Mustang GT, because the used tubular k-member I purchased from a buddy hadn't shown up yet. I used our urethane 4.6 motor mounts, installed the k-member in place of my 79's stock straight-six k-member and crossed my fingers. The engine fell right into place. It was as if it were made to be there. Score!....Or so I thought. Further inspection revealed that the header's collectors pointed directly at the firewall. This was a real bummer, because everything fit so well otherwise.
Back to the drawing board!
Since I knew I had to change headers, I started scouring the forums. My search yielded a company called Logan Motorsports. Although they haven't done any fox-body 3v swaps, they had done some SN95 swaps by manufacturing adaptors to bolt 2v headers to a 3v. The port spacing is exact. The only difference between the 2v and 3v headers is the bolt pattern. This looked like a good option. I knew from prior experience, aside from a little firewall interference, that SN95 headers would fit a fox.
I gave it a shot. I ordered the adaptors, and purchased a set of MAC Industrial plated longtubes for a 96-04 Mustang. I bolted them to the motor, along with the spacers. They fit the engine perfectly and looked awesome.
The k-member I bought second-hand had also shown up, so, I crossed my fingers that this would be my final installation.
I removed the previously installed stock 4.6 k-member and lowered the motor in place with the headers and bellhousing on. My plan was to get the motor in position, then bolt the k-member underneath it. I didn't want to damage the engine compartment by wrestling the longtubes in place with the k-member in the way. After a lot of blastpheming, it went in...sort of. The headers were hitting the k-member on both sides, and preventing the motor from sitting down in the mounts completely. I also had clearance problems between the framerails, causing the right header to sit against the frame rail, and the left header to sit against the brake lines.
This wouldn't work. The adaptors, combined with the design of the used k-member of unknown brand caused major trouble. Back to the drawing board, again.
I had a couple of different options at this point. My first was to pull the long tubes, and install a set of 2v shorties. Ford Racing's 2v shorties allow tons of engine bay clearance. My second option was to try another k-member, hoping that clearance would be better than the one I had. The third option would be to try and have a header built. Option 4 would be to try a different brand of 2v longtubes and see if any offer more clearance.
Option 1 didn't sound too good to me, as this will be a race car for all intents and purposes, and I didn't want to suffer the power loss (although minor) of switching to shorties.
Option 3 meant mega dollars and weeks of delay, so that was out.
Option 4 meant a lot more trial and error, as well as additional cost from buying multiple sets of headers, hoping that one would fit.
Option 2 was the choice. I would try another k-member and see if clearance would be better. Since the stock 2004 k-member was just laying there, I thought I'd try it first. If it worked, I could see what other clearance issues I had, and make an assessment on keeping the MAC headers.
So that's what I did. I removed the offending k-member, and re-installed the stock one that fit so well with the 3v shorties. Guess what? The motor fell right in to place. I still had some clearance issues on the passenger side frame rail, and at the bottom of the firewall where it meets the floor pan, but those were issues I had experienced on prior 4v 4.6 installs, and I was able to work with that with the motor in the car.
All in all, the motor fits the engine compartment very well, and it looks awesome. If this were strictly a street car, I would have opted for the 2v Ford Racing shorties and suffered the small power loss in order to gain more engine compartment clearance. I am certain that I'm going to have some extra NVH from the longtubes touching the framrail. Otherwise, things look good, and I can move forward on wiring, fuel system, and transmission.
For now, I'm going to leave the stock k-member in the car. Part of this project was to show you how inexpensively this can be done, and the stock k-member is certainly inexpensive. You can pick one up for almost nothing. I will also be able to tell you first-hand how much a tubular k-member and coil-overs can benefit, as I will perform that swap after the car has been sorted out and to the track a few times.
The headers presented problems due to the long-tube design, coupled with the 1/2" thick adaptors from Logan Motorsports. The adaptors did a great job of adapting the MAC 4.6 2v long-tube headers, and they offered additional bellhousing and starter clearance, but the added thickness of the spacers caused the right header to contact the frame rail.
In addition to this, the header contacted the lower portion of the firewall on the right side, due to the 79-93 firewall's limited clearance compared to newer, SN-95 Mustangs.
After some thought, I elected to install Maximum Motorsports' 1/2" k-member spacers. My thought was that lowering the engine would provide additional clearance at the firewall, as well as increase much-needed hood clearance, as I plan to run a stock hood.
Installing the spacers was a breeze. I simply hooked the engine hoist to the engine, removed the k-member bolts, and lowered the engine. While it was below the frame rails, I clearanced the passenger side header tube that was contacting the frame rail, and slightly dinged the firewall. I then raised the motor back up, at the same time sandwiching the Maximum Motorsports spacers between the k-member and the frame rail. This will raise the body over the k-member slightly. Ride height adjustments will be made with the coil overs, so I won't be hurting the car's stance.
Once everything was bolted back up, I found I'd gained the firewall and frame rail clearance I needed, at the same time, earning much-needed hood clearance. A quick test fit of the hood showed me that only slight trimming of the forward hood brace would be needed, but no holes or removal of the brace is going to be required. Remember, my car is a 79 model. 83-93 Mustangs have thinner hood bracing. Installation of a stock 83-93 hood with the k-member spacers should require no modifications.
Other accomplishments from the last blog include installing the 96-04 adjustable clutch cable kit with an 82-93 Mustang clutch pedal assembly, and installation of the manual brake conversion with custom-bent lines.
I then bolted on a SVE radiator/fan kit, Mustang Fuel Pressure Regulator, and I restored and installed the factory headlight wiring.
Next, I will be installing the Ford Racing harness and controls package, as well as installing the fuel pump and plumbing the fuel system. Stay tuned! It's getting close!!