Build a Catera Performance V6 - 240 to 250 HP

UPDATE: 04-22-2015

While visiting the Omega Owners Forum (OOF) site I stumbled upon an engine upgrade for the Catera. In a nutshell it means pulling the 3.0L from your Catera and replacing it with the 3.2L V6 from the 2003-2004 Cadillac CTS after rebuilding it with the cylinderheads off the Saab 2.5L V6 and the fuel delivery system off the Catera's 3.0L V6. The 3.2L engine obviously has 200 CCs more than our 3.0L but less well known is that its compression ratio is lower. Replacing the 3.2L heads with the 2.5L heads, and their smaller combustion chambers, raises compression, and thus makes more power. More "Squeeze" equals more "Bang". There are a few other parts involved but these are all stock GM and will fit without altering since the 3.2, 3.0, and 2.5 are basically the same engine. The 3.2L engine was used in the Omega so it'll slip into the Catera without fuss. This eliminates the cutting and welding needed to fit other engines. This modified V6 also utilizes the Catera's stock wiring harness and ECU for a basically plug & play project. Not exactly easy or cheap, but short of the GM 3800 V6, or 5.7 LS1 V8 swaps, and turbo pipe dreams, this is a way to potentially add 40 to 50 horsepower to the GM 54 Degree V6.

Here comes the nuts & bolts.

According to Marks DTM Calib of OOF, we use a 3.2L (LA3) V6 as the core long-block (with the 3.0L's oil pan), swap a pair of 1993-1998 Saab 900 2.5 liter V6 heads onto it (using the 3.2L's head gaskets), and the 3.2L's exhaust manifolds (they're formed steel rather than cast iron, and are internally wider). The "front pipe" from the Catera (the length of exhaust pipe between the manifold and the catalytic converter), must be modified to match the CTS manifold with some grinding of their flanges. The stock 3.2L has a 10.0:1 compression ratio and produces approx. 220 HP. Replacing its heads with those  from the 1993-1998 Saab 900 2.5L (B258I) V6 will raise the ratio to approx.10.8:1.
[notes 1,2,3]


---------3.2L Long Block-------------2.5L Heads with "G" Camshafts--

Per Zirk of OOF, if we want more top end HP we must swap the 2.5L's intake and exhaust camshafts with 4 intake ("G") camshafts from the 3.2L and/or 3.0L engines (both motors use the same "G" intake camshafts). If we want more low to midrange torque we must use the "A" exhaust cams from the 3.0L (L81). Either way we should use the exhaust valves from either the 3.0L or 3.2L (sodium filled for better heat transfer). The "J" exhaust camshafts from the low compression 3.2L will reduce both power & torque in this higher compression "Frankenengine". Throw those "J" sticks in the dumpster. Some British Police's Omegas used the 4x"G" cam mod for an approx. 18HP boost. Not sure how much more torque we can expect from the 2x"G"/2x"A" setup but with the increased compression from the 2.5L heads' smaller combustion chambers there should be a noticable increase over the 3.2L's 218 lb/ft. To make the most of the new cams and increased compression, the 2.5L's heads must be ported slighty to mimic the contours of the 3.2L/3.0L head's exhaust passages so to match their airflow specs.
[note 4]


left port opened -------------------- middle port almost done -------------- right port original shape

Next we use the Catera 3.0L's fuel delivery setup (injectors, fuel rails) and the 3.8 Bar Fuel Pressure Regulator from the CTS. That combination makes for finer fuel atomization and an improved flame-front. The Catera's stock ECU and sensors will work fine with this hodgepodge engine and though it should be safe to use regular grade gas, I suggest mid to high grade gas. It will protect the pistons by preventing pre-detonation.
[note 5]


------3.2L vs 3.0L Fuel Rails---------------3.5Bar Fuel Regulator------

If you want to take this a step or two further there are large bore twin throttle bodies available from The UK, or go crazy and chuck the entire GM intake assembly altogether, and install 6 individual throttle bodies with air-horns and foam air filters. If you still have money left over there are aftermarket performance camshafts, a lightened balance pulley (quicker revs), an uprated 4 bar Fuel Pressure Regulator, honest to God tubular headers, and even a cooler rated thermostat to help deal with the additional heat generated. There maybe more if you check some German sites and understand the lingo. In the meantime, follow the links below.
http://www.courtenaysport.co.uk/v6-tuning/info_21.html
http://www.jenvey.co.uk/products2/throttle-body-kits/opel-vx-v6-sfs42-throttle-body-kit-ckvx06
http://shop.friedrich-motorsport.de/shopware.php?sViewport=cat&sCategory=1438


--Twin Throttlebodies----Six Throttlebodies & Horns--------Tube Headers---

At this point you could convert to an external oil cooler to avoid problems with the internal cooler leaking, pop in a new thermostat w/gasket, replace the camcover gaskets, switch to Saab aluminum camcovers, convert to a spin-on oil filter, move the HBV to an more accessible location, and replace the Timing & Serpentine Belts as well as their Tensioners. Finally, reinstall the ancillary equipment (Alternator, AC, PS, intake stacks & plenum, etc,).

Summary: After all this we end up with a 200cc displacement increase, a stronger crankshaft, a higher compression ratio, the best camshafts, the most efficient exhaust valves, the best fuel delivery set-up, freer flowing "factory headers", and an increase in horsepower anywhere from 20 to 30HP over the 220 HP of the stock 3.2L V6 plus approx. 20 lbs/ft more torque, all with stock GM parts. Sounds easier than swapping in an SC3800 V6 or an LS1 V8, doesn't it? True, not as powerful than either of those two but with them you'd have to do lots of custom fabrication, modification, and maybe install a stronger transmission and differential.

While the fruit of this project won't resemble the highly modified GM LA3/X32XE V6 engine pictured below in this Lotus Exige racecar I include it here to illustrate the potential in the lump under our Cateras' hoods. It started out as an Opel V6 just like our Cateras have. If its builders were willing to spend the time, effort, and money it must have taken to create this tuned engine then there must be hidden power in our V6 somewhere. All we have to do is have a little faith.

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NOTE 1:
Placing the 3.0L heads on the 3.2L block will raise the compression, but not to the 10.8:1 ratio. I would guess to approx. 10.4:1.

NOTE 2:
Placing the 3.2L heads on the 3.0L block will lower the compression below 10.0:1. I would guess to approx. 9.5:1.

NOTE 3:
Placing the 2.5L cylinderheads on the 3.0L will raise the ratio above its stock 10.8:1 and could lead to predetonation (pinging) and damage (holing) the pistons, even if using high octane gasoline.
DO NOT DO IT!

NOTE 4:
All 3.0L Catera V6s have "G" intake cams and "A" exhaust cams. All 3.2L CTS V6s have "G" intake cams and "J" exhaust cams. Using "G" intake cams as exhaust cams instead of "A"s or "J"s will increase HP at the top of the RPM range at the expense of some bottom end torque. Using the "A" cams as exhaust cams will create more bottom end torque with a slight reduction of HP at redline. Using "J" cams will decrease both HP and Torque and aren't recommended.

NOTE 5:
The 2.5/3.0 had a 3bar and the 3.2 had a 3.8 bar Fuel Pressure Regulator. Upping the fuel pressure might not give you extra HP, but it will give you better fuel atomization for a more efficient burn, and if you were struggling to fuel it when floored it could help there.

NOTE 6:
I cannot guarantee this engine will pass emissions testing. If that is a requirement in your state it may fail.

REMEMBER: These mods are based on OOF experience with the European versions of the GM 54 degree V6 engines. As far as they know they are mechanically identical to the engines available here, the differences being largely the electronics. I'm confident these mods will work, but as always, try these mods at your own risk.

The stock L81/X30XE 3.0L V6:
Cylinder bore 86mm  
Piston stroke 85mm
200 BHP - 199 lb/ft Torque
Organic fiber head gaskets
Cast iron exhaust manifold

The stock LA3/Y32SE 3.2L V6:
Larger Bore - 87.5mm
Longer stroke - 88mm
220 BHP - 218 lb/ft Torque
Steel mutlilayer head gaskets
Forged steel crank (stronger)
Larger diameter exhaust manifolds (formed steel)