Paul Spotts responds:First off, it is not recommended to just have a crank polished. This is a common mistake, as without knowing what the clearances of the engine are, you may have increased them too much, causing oil pressure to be low and unwanted flex or movement of the crankshaft. The 400 engines are more forgiving, so you may be OK. The big word is "may." It is best to align the saddles, then check the sizes with the bearings installed to see where you are clearance-wise. Polishing is not an accurate way to make a journal round because you're relying on the shape you're polishing. There is no substitute for machining. In other words, the crank should have been cut.
It sounds like you used cast replacement pistons. I do not like those in a performance application. They are strictly for stock replacement use and they lower compression. You should have used forged units or even hypereutectic ones.
The cam you selected is a good choice, but I doubt it will work well with the 8:1 compression you most likely have. You should change the heads or change the cam-depending on the ramp design. Contact Lunati and ask the company if your cam will work with 8:1 compression in a Pontiac 400.
Three-tube headers are not as good as four-tube. They are a low-cost-fits-all replacement and will rob you of some power, compared to four-tube units.
If the cam is sufficient for low compression and you're street-driving the car, I would recommend 3.55 gears with 27/28-inch tall tires. Again, consult with the cam manufacturer on gearing. Steeper gears like 3.73s or 3.90s will be quicker, but less streetable for highway use.
Fourth-Gen V-6 Advice
Thank you for a great magazine. I've subscribed for four years now, and you've done nothing but improve. I own a '79 Firebird project car with a 400 motor, but you already cover plenty of options and ideas for that entire era.
My daily driver is a '96 Firebird with a 3.8L Gen II V-6 (231 cid). I've found almost no aftermarket items for this engine. The car is in the shop now for some basic 200,000-mile upkeep. I'm also having the Eibach spring kit and Bilstein struts/shocks installed and I have 17-inch C6 Corvette-style rims on the car.
I was really interested in the prototype supercharged V-6 article you had, but that would be prohibitively expensive. Can you recommend any upgrades to increase horse-power/performance? I am not opposed to a cam swap as long as it will still work with the computer. Thanks for the help and for your dedication to Pontiacs.
B. T. Raulerson
Bryceville, FL
Ray Bohacz responds:The Buick-produced 3800 V-6 in your Firebird is an excellent engine with a reputation for extreme longevity, even if exposed to only minimal service intervals. Thus, I am sure that it has many more miles left in it if it remains stock.
Cylinder pressure creates horsepower, and if you are looking to step up the output of the V-6, the combustion pressure (not to be confused with the compression ratio) will be increased. The higher pressure will impact the piston ring package and bearing life, especially those on the connecting rods.
I would not invest in a supercharger for an engine with 200,000 miles on the internal components. I would also think twice about tearing into it for a cam swap or cylinder head porting, both of which would satisfy your desire for more power. Instead, I would look to make superficial improvements to the intake and exhaust airflow path with a low-restriction air filter/box and an after-cat exhaust. SLP (www.slponline.com) has a Cold Air Induction Package to fit your V-6 Bird under PN 21013 for about $300 and Flowmaster (www.flowmastermufflers.com) has an after-cat system under model number 17357 for just under $500. Other manufacturers offer similar products.