This swap needs to look good without any engine covers… so first thing that needs to go is the LS4 intake… it is just ugly (and a restriction). Now while the LS2 intake isn’t as good as the LS6 one, it has very clean lines for use without any covers.

The problem is the LS2 intake will not fit the stock LS4 DoD valley cover without major clearance work (it fits just fine with some minor work when used with non-DoD valley covers - Archie’s swaps do this all the time). Even with the OPSU boss cut down about 1/2" in this picture, you can see the valley cover needs to come down another 3/8" to be able to fit... this is going to take some work.

First thing under the knife was the connector. Right behind the flange for the connector, I gently cut through the plastic and eventually was able to pry the end off exposing the 5 terminals:


Call me finicky... but I wanted to know the OEM wire colors for this connection so the new wires (recycled from other GM harnesses) can match.

New wires (about 24" in length - way too long) soldered to the appropriate terminals:

Heat shrink x2:



Now back to the OPSU - it will be relocated entirely. I had already cut it down about 1/2" and cut it down another 3/8" to expose the oil passage while still leaving material to drill a new oil passage.

New oil passage:

Then the top side of the OPSU boss was welded up to close up the passages. Here is a finished pic of the welded OPSU and the modified connector:



Sadly, the LS2 intake still isn't going to accept installation without modifying the intake.
Lower ribs flattened and the area of the connector and OPSU was cut open (this also give me room for the vent upgrade):


But now it can be installed w/o interference:


Patch panel fabricated to seal the hole:



This patch panel was glued in place inside and out.

Just because I thought they would look better, I cut the intake manifold bold bosses down about 1”

I have a sickness for stainless steel button heads and even at this shorter length, they just do not exist in the proper length/thread... so I made some using some other metric stainless steel button heads. Drilled the center, cut the OEM bolts the proper length, pressed them into the bottom of the button heads, weld then together, grind off the excess...



Even have button heads for the fuel rail and throttle body:


The last intake manifold modification was to bend the stock LS2 fuel rail so the fuel line will not cross over the valve cover (like the stock LS4) and then bent the original LS4 fuel line to go down the end of the head and exit down low away from the exhaust.

In this picture you can see where the OPSU was relocated - drilled/tapped the oil passage below the valley cover:


One last upgrade while the intake is off…
I plan to wail on this engine once installed and it might see some NO2 at some point, so I went ahead and installed the 4 corner vent setup from a 6.0L truck just to ensure cylinders 7&8 have the best chance for equal cooling.

It took some slight bending of the lines to route them around all the raised bosses and oil passages and I bent the exit tube to be vertical so it clears the intake. 2 bolt bosses for the DoD stuff under the cover needed cut down, but not far enough to touch the bolts. Some RTV should seal them back up. The bottom corner of the LS2 intake (the triangle part that rests between the heads and the valled cover) needed about 1/2" trimmed from it at the corner to clear the tube in the upper right hand corner of the picture. But now it fits!

[This message has been edited by fieroguru (edited 12-13-2010).]

The other significant beautification modification was to do something with the unsightly coil arrangement and collection of wires over the valve covers (valve covers are to be seen, not covered). After some disassembly and brainstorming, the LS4 coils fit together quite nicely when mounted with some off the shelf spacers from Lowes:

Then it was a matter of determining where on the engine this more compact coil pack could be positioned. Had I used headers, along the oil pan would have made them disappear all together, but since the LS7 manifolds do not have room for the plug wires to come from underneath, I settled on this area:

Some 1/8” scrap plate and a little fabrication and I had these:




The really nice part about the coils being in this location is all the harness connectors point down to the bellhousing area, so the harness will be mostly hidden from view.

Once the coils were off the valve covers, it was time to cut down the bosses, weld up the holes and smooth everything to get a nice clean look.

Here is good inspirational shot of the intake, coil and valve cover work so far. The stock LS4 fuel line will pass behind the front coil pack and disappear from view. The only wiring that will need to be on top of the intake will be for the injectors and those will be ran under the fuel rails out of sight as well.

[This message has been edited by fieroguru (edited 12-13-2010).]

When it came to the camshaft, there were a few options I considered:

1: Ditch all the DoD stuff and run any LS(x) cam I wanted… lots of work and cost to replace the lifters, oil pump, valley cover, etc, and the heads have to come off… which always leads to more upgrades. Downside/Upside is you lose DoD… but have an near endless selection of camshafts to pick from.

2: Stock LS4 cam (193/193 .283/.283 @ 114lsa – Non DoD lobes) with 1.80 or 1.85 rockers – this is the least expensive and simplest approach, but gains would be minimal (10-20hp). Several LS4 guys have done this on LS1 tech.

3: Stock G8 cam (197/207 .278/.282 – non DoD lobes) with 1.80 or 1.85 rockers. Slightly more expensive than the using the stock cam and requires a camshaft swap, but provides more duration vs. stock LS4 and was a factory DoD camshaft. Probably would result in a slight improvement vs. the stock cam and rockers, bust still very mild.

4: Go with a much larger DoD compatible aftermarket camshaft… this is the route I took. This camshaft was designed for DoD and comes with the springs, pushrods, chain tensioner… only downside is they would not tell me the specs. The one guy on LS1 tech who installed this cam and said it was big (peak power in the 6800-7000 range), probably too big, but if he could still get his 3400 lb automatic beast moving with the cam. It has also been installed in some 5.3 full size trucks… so I figured it would be OK in a 2900 lb fiero with manual transmission and a stump pulling gear ratios. This cam was advertized to provide a 54 hp increase on the 6.0L… so for better or worse I went big.

Since they would not tell me the specs… I just HAD to find out what they were, so an 18” degree wheel was added to my tool collection.


First order of business to degee the stock LS4 cam on cyl #1 (which is a DoD cylinder which might explain why my measurements are slightly different than the internet specs… I took a degree reading at .006, .050 and every .025 up to max lift up and down for intake and exhaust).
Stock LS4 camshaft specs: 197/197 .286/.286 @ 114LSA
Stock LS4 events @ .050 lobe lift:
IVO (BTDC): -18
IVC (ABDC): 35
EVO (BBDC): 31
EVC (ATDC): -14

I never confirmed the G8 stock specs… but here they are for comparison
Stock G8 DoD camshaft specs: 197/207 .278/.282
IVO (BTDC): -17
IVC (ABDC): 37
EVO (BBDC): 40
EVC (ATDC): -12

I did the same for my aftermarket camshaft and it was 224/231 .332/.338 @ 113 lsa but I also noticed it was really not what I was expecting. Here is an overlay of the two cams with the larger/wider lobes being the aftermarket one. As you can see everything was moved much later in the cycle.


So I spent quite a bit of time checking out other cams of the 224 to 230 duration, comparing where the valve events are for those camshafts and where mine were to figure out a better position in which to install the camshaft. A couple of the comparison cams are as follows:

MTI Stealth II 224/220 (everything at .050 lobe lift)
IVO (BTDC): -4
IVC (ABDC): 48
EVO (BBDC): 46
EVC (ATDC): -6

Comp Cams xer 224/230 (54-444-11 XER273HR)
IVO (BTDC): -1
IVC (ABDC): 45
EVO (BBDC): 50
EVC (ATDC): 0

After much thought and discussion with the other guy running this cam, I chose to install the came with the approximate valve events at .050” lobe lift:
IVO (BTDC): -3.5
IVC (ABDC): 47.5
EVO (BBDC): 46
EVC (ATDC): 5.5

This installed position places the new cam intake centerline right on top of the stock LS4's and pulls the IVO event back down to a more reasonable level for the 5.3 (it is still pretty high). This could be a major mistake, but only time will tell…

[This message has been edited by fieroguru (edited 01-03-2011).]

[This message has been edited by Will (edited 12-14-2010).]