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Building an engine for boost. Ok, lemme just do a quick rundown of my thoughts when it comes to building an engine for boost.
Crank: Stock is fine, but recommended mods would be getting it knife edged and balanced. There are a few other processes out there (cyro-treatment, etc), but since I have only heard of a limited number of crank failures (mainly due to oiling issues), its not a concern. Aftermarket definately isn't worth the price unless the stroke can be changed.
Rods: Again, stockers are forged, so not a big issue. Shot-peening is always a good idea, but not a necessity. As far as rod bolts, ARP would be ideal, but I know people (Curtis Walker comes to mind) that are running high boost engines using stock bolts.
Pistons: Here is an area to concentrate on. Custom forged is the best way to go, especially for an engine that is going to see 8+psi of boost. Several companies make them for the engine, including Ross, JE and Mahle. Pistons will also allow you to slightly lower the CR of the engine allowing for increased reliability when it comes to higher boost levels.
Heads: For boosted applications, the more air you can get in, the better. When you have something helping to push the air into the combustion chamber, the flow path isn't a critical part of the equation. But, on the same note, you can't just take a die grinder to the ports and start removing as much material as possible. With high boost levels, you will still need to keep in mind the intergity of the heads under those boost levels. Get the walls too thin and there is a chance that the heads will fail. ARP bolts, or better yet, studs are a very good idea for boosted applications.
Cam: The stock cam is surprising good for boosted applications. There are certainly better grinds available for those wanting more power, especially for a target powerband.
Valvetrain: It has been said that the lighter the rotating mass, the better. Since the valvetrain is an integral part of the rotating mass, this is an area that can be massaged to work well with boost. Increased spring rates are a must, and the LS1/LS6 spring upgrade has been documented to work well. Lighter valves are a good idea . There are really no aftermarket lifters available, so you are pretty much stuck with the stock rollers. Lighter pushrods can also help, but aren't a major item to look into. The only time I would look into different pushrods would be if custom lengths needed to be ordered to match a cam grind. Different rockers have also been documented to work, such as the Crane Gold Race Rockers, although some modifications are required.
Manifolds: Unless you are mechanically inclined and have access to some major tools (metal cutters, benders, welder, etc..), and want to spend alot of time researching proper plenum tuning calculations and designs, you are pretty much stuck with the stock manifold and plenum. These can be ported out to allow for more flow, or even sent off to get Extrude Honed (clay with abrasive is pumped through to open up everything). There are significant improvements to be made when hand porting for those looking for more power.
Exhaust for a SC setup: When pushing huge amounts of air into the motor, you must have a good way to get the exhaust out of the motor, otherwise you are just holding the motor back. Headers. Period. It is not worth the time, money or effort to even touch the stock exhaust manifolds. There are just too many restrictions. Headers are available from S&S Headers and The Other Guys. Although the are designed for 99+ N-Bodies, they have been altered to fit several other body styles including Berettas and Monte Carlos. Then there is always custom. You will see better results from custom, but it again takes more time, effort and money, as well as a few special tools to get it done right.
Exhaust for a turbo setup: Headers are a waste on a turbocharged engine unless a custom exhaust is needed for mounting the turbocharger. The use of headers for a turbocharged motor will not provide performance improvments as they do a normally aspirated motor. The reason for this is that headers work by using the scavanging effect, and once an obstruction to normal exhaust gas flow that a turbo represents has been attached, the scavanging effect is no longer available.
Engine Management: This is probably the single most imprtant part of boost there is. If you can't accurately and precisely control what the engine is doing, you will be limiting the power potential of the engine. This can be easily seen with the aftermarket SC kits for the Grand Ams. The kits come with a slightly modified PCM to make some generic alterations to account for the boost. But it is far from ideal. Each car is different, and when you incorporate different modifications along with the boost, fuel and timing need to be changed to match. With a stock PCM, this just isn't possible. DHP has a controller that works with their OBD-II PCM which allows for some adjustment of the fuel and timing. This is a great way to do things, but it is limited to cars which DHP offers PCMs for. A standalone ECM is the best way to go, but with the current electronically controlled transmissions, you have to overcome that obstacle as well. There are some piggyback controllers that can provide some tuning abilities (such as the Perfect Power SMT-6), but again can only do so much.
Transmission Selection: The selection of fwd automatic transaxles is not too bad, but the stock 4T60-E is not something I would put behind a 60V6 motor boosted to any level I consider extreme (> 12 PSIG). Rebuilding the 4T60-E to withstand torque levels that can easily exceed 300 ft-lbs is extremely expensive, enough so in fact that swapping to a manual trans becomes quite desireable. Since using a manual trans also permits the use of an OBDI PCM loaded with modified TGP code, you will save yourself the grand or two you would have had to spend for an aftermarket engine management system, and therefore the trans swap pretty much pays for itself. The stock Getrag 282 5-spd is commonly used behind high performance small block V8 transplants, so it will likely withstand just about anything a turbocharged 60V6 can throw at it just fine. The use of a manual trans may also provide the clearance required to mount a turbocharger directly on the exhaust outlet when a 95' 3100 exhaust manifold is used on that side. This is something that should be explored further for the particlular platform involved, as the cost required to mount a turbocharger with this method can be easily be less than $50.
Crank: Stock is fine, but recommended mods would be getting it knife edged and balanced. There are a few other processes out there (cyro-treatment, etc), but since I have only heard of a limited number of crank failures (mainly due to oiling issues), its not a concern. Aftermarket definately isn't worth the price unless the stroke can be changed.
Rods: Again, stockers are forged, so not a big issue. Shot-peening is always a good idea, but not a necessity. As far as rod bolts, ARP would be ideal, but I know people (Curtis Walker comes to mind) that are running high boost engines using stock bolts.
Pistons: Here is an area to concentrate on. Custom forged is the best way to go, especially for an engine that is going to see 8+psi of boost. Several companies make them for the engine, including Ross, JE and Mahle. Pistons will also allow you to slightly lower the CR of the engine allowing for increased reliability when it comes to higher boost levels.
Heads: For boosted applications, the more air you can get in, the better. When you have something helping to push the air into the combustion chamber, the flow path isn't a critical part of the equation. But, on the same note, you can't just take a die grinder to the ports and start removing as much material as possible. With high boost levels, you will still need to keep in mind the intergity of the heads under those boost levels. Get the walls too thin and there is a chance that the heads will fail. ARP bolts, or better yet, studs are a very good idea for boosted applications.
Cam: The stock cam is surprising good for boosted applications. There are certainly better grinds available for those wanting more power, especially for a target powerband.
Valvetrain: It has been said that the lighter the rotating mass, the better. Since the valvetrain is an integral part of the rotating mass, this is an area that can be massaged to work well with boost. Increased spring rates are a must, and the LS1/LS6 spring upgrade has been documented to work well. Lighter valves are a good idea . There are really no aftermarket lifters available, so you are pretty much stuck with the stock rollers. Lighter pushrods can also help, but aren't a major item to look into. The only time I would look into different pushrods would be if custom lengths needed to be ordered to match a cam grind. Different rockers have also been documented to work, such as the Crane Gold Race Rockers, although some modifications are required.
Manifolds: Unless you are mechanically inclined and have access to some major tools (metal cutters, benders, welder, etc..), and want to spend alot of time researching proper plenum tuning calculations and designs, you are pretty much stuck with the stock manifold and plenum. These can be ported out to allow for more flow, or even sent off to get Extrude Honed (clay with abrasive is pumped through to open up everything). There are significant improvements to be made when hand porting for those looking for more power.
Exhaust for a SC setup: When pushing huge amounts of air into the motor, you must have a good way to get the exhaust out of the motor, otherwise you are just holding the motor back. Headers. Period. It is not worth the time, money or effort to even touch the stock exhaust manifolds. There are just too many restrictions. Headers are available from S&S Headers and The Other Guys. Although the are designed for 99+ N-Bodies, they have been altered to fit several other body styles including Berettas and Monte Carlos. Then there is always custom. You will see better results from custom, but it again takes more time, effort and money, as well as a few special tools to get it done right.
Exhaust for a turbo setup: Headers are a waste on a turbocharged engine unless a custom exhaust is needed for mounting the turbocharger. The use of headers for a turbocharged motor will not provide performance improvments as they do a normally aspirated motor. The reason for this is that headers work by using the scavanging effect, and once an obstruction to normal exhaust gas flow that a turbo represents has been attached, the scavanging effect is no longer available.
Engine Management: This is probably the single most imprtant part of boost there is. If you can't accurately and precisely control what the engine is doing, you will be limiting the power potential of the engine. This can be easily seen with the aftermarket SC kits for the Grand Ams. The kits come with a slightly modified PCM to make some generic alterations to account for the boost. But it is far from ideal. Each car is different, and when you incorporate different modifications along with the boost, fuel and timing need to be changed to match. With a stock PCM, this just isn't possible. DHP has a controller that works with their OBD-II PCM which allows for some adjustment of the fuel and timing. This is a great way to do things, but it is limited to cars which DHP offers PCMs for. A standalone ECM is the best way to go, but with the current electronically controlled transmissions, you have to overcome that obstacle as well. There are some piggyback controllers that can provide some tuning abilities (such as the Perfect Power SMT-6), but again can only do so much.
Transmission Selection: The selection of fwd automatic transaxles is not too bad, but the stock 4T60-E is not something I would put behind a 60V6 motor boosted to any level I consider extreme (> 12 PSIG). Rebuilding the 4T60-E to withstand torque levels that can easily exceed 300 ft-lbs is extremely expensive, enough so in fact that swapping to a manual trans becomes quite desireable. Since using a manual trans also permits the use of an OBDI PCM loaded with modified TGP code, you will save yourself the grand or two you would have had to spend for an aftermarket engine management system, and therefore the trans swap pretty much pays for itself. The stock Getrag 282 5-spd is commonly used behind high performance small block V8 transplants, so it will likely withstand just about anything a turbocharged 60V6 can throw at it just fine. The use of a manual trans may also provide the clearance required to mount a turbocharger directly on the exhaust outlet when a 95' 3100 exhaust manifold is used on that side. This is something that should be explored further for the particlular platform involved, as the cost required to mount a turbocharger with this method can be easily be less than $50.
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