By removing first base, I was left with a
significant gap in the intake tract. This was remidied with a 18"
long section of 4" PVC pipe, painted semi-gloss black for that classy "I
shop at only the best hardware stores" look. A rubber pipe coupler
hooks up the PVC pipe to the mass air-flow sensor. On the other end
of the MAF sensor sits a K&N cone filter, sitting in the location of
the stock airbox. If I used this car during the winter (which I don't),
I'd probably run the stock airbox during the wet months. The K&N
gets dirty enough during the summer, and I just think that the stock airbox
is a better choice for messy conditions.
So, there's some power to be had with a cam swap. This isn't the easiest of all tasks (I certainly wouldn't call it a bolt-on), and some other pieces of the puzzle need to be in place before this swap lives up to its potential (as I found when I did my cam swap before making any significant exhaust modifications). You'll also need to swap out the stock valve springs, at the very least, since the stock valve springs can cause valve float as low as 5000 RPM with the stock cam. Adding cam lift will only make the problem worse.
First, I selected the cam. I went with GM's ZZ3 cam (GM part # 10185071). This cam is for a standard roller-lifter small-block Chevy, and so it needs to be modified to fit in an LT1. The pilot hole in the front of the cam needs to be drilled out to 12 mm diameter, 26 mm deep. You'll also need to replace the dowel pin with a longer one (GM part # 10214485).
For valve springs, I choose Crane 10309 springs. These springs fit the spring pockets on the stock iron heads with no machining. They provide two advantages over the stock springs, both necessary for a cam swap: 1) the greatly-increased seat and open pressures prevent valve float (I've rev'd my engine over 6000 RPM without problems); and 2) the spring retainers included with the spring kit prevent valve-guide clearance problems (the stock retainers will hit the valve seals at about 0.480" of valve lift, while these provide adequate clearance for 0.520" or so of valve lift). Don't attempt a cam swap without these (or similar) springs!
I picked a split 1.5/1.6 set of Crane Gold roller rockers. Since the ZZ3 cam is a "split profile" cam, meant for use on older small blocks that have terrible exhaust-port flow, it has a lot more lift on the exhaust than on the intake. By using a 1.6 ratio rocker on the intake, and the 1.5 rocker on the exhaust, I balanced out the profile of the cam.
Installing the cam isn't difficult, but it's no picnic. Either use the Helms service manual, or else you can follow this cam-swap guide. This link also provides info for swapping the heads, so don't get carried away and remove the heads if you're not replacing them. Also note that it's for a '94 F-body LT1, which uses some different parts than the B-body LT1s. Make sure to use the appropriate parts numbers for gaskets, seals, and so on (your local parts-counter guy should be able to set you up with the necessary Fel-Pro gaskets for the swap).
Once you've completed the mechanical portion of the swap, you'll probably need to re-program the PCM to take advantage of the new cam. Although I use LT1_edit to program my PCM from a PC (you can check out my PCM programming page for more info), there's quite a few professional options for PCM programming. Generally speaking, you'll want to raise the redline and shift points to take advantage of the new upper-end power, raise the idle, advance the timing at lower engine speeds and MAP readings, and lean out the WOT enrichment if it hasn't already been done in a previous program.
You can check out some dyno results here. They're outdated, as I've upgraded the exhaust and PCM programming since this session. I'll try to get a final dyno run before the 350 gets replaced.
If I did the swap again, I'd probably use a GM/Crane "845" cam (GM part # 12370845) or the Comp Cam "CC304" (part # 07-304-8). Both of these cams don't require any machine work (they're true drop-ins). They're a bit bigger than the ZZ3 cam, but certainly won't affect low-end power or part-throttle drivability. Either one is probably worth about 5 HP over the ZZ3 on the top end, too, but just the fact that they're drop-in parts puts them at the top of my list. You could also go with the LT4 HOT cam. This cam is probably about as wild as you really want to run on a daily-driven B-body with the stock displacement, but that doesn't mean it's the biggest cam you can run - some F-body guys really like the Comp Cam "CC306" (part # 07-306-8). Just be warned that as the cam size increases, you really need to pay attention to gearing and torque convertor choices. Installing a big cam (like the HOT cam) into a B-body with 3:08:1 rear gears and the stock TC will result in a big disappointment.
I'm currently in the process of building up a 396 for my car. Here's the bill of materials so far:
- Block and assorted parts from a 1994 Camaro
Z28
- Milidon splayed 4-bolt main caps
- Cola 3.875" forged 4340 crank, one-piece
rear main
- Eagle H-beam 6" rods
- JE/SRP pistons, 4.030" bore
- LT4 heads and intake
- Cam - to be determined (I'd like to try
the CC305, CC306, and CC503)
There's a lot of details to be determined
yet, and I'll continue to update the BOM and provide some insight into
my parts selection as things progress.
Questions? Comments? Insults? Send 'em to eric@bryantperformance.com!
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