Need help LQ4
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Teching In
Joined: Jun 2014
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Need help LQ4 Hi, everyone ... New to the form and i am a car enthusiast. My current project is my 86 chevy long bed c-10. I just bought a 2002 lq4 6.0 long block so oil pan and all. I wanna go through the whole engine and rebuild it. Looking to make around 430-500hp when done, natural aspirated and cheap as possible..... i know Ls and cheap dont mix. Plz lend your expertise and help a guy create a monster motor on a budget. Thanks
Actually LS and cheap do mix compared to getting the same power out of an old style SBC. You could do a standard rebuild and use arp rod bolts and cam change and not be to far off your number. If I were rebuilding the motor I buy new pistons with valve reliefs so you can bring the compression up and run a decent cam without having to worry about PTV clearance. I don't know what your budget is but a good set of heads would be on the top of my list.
In my experience, a machine shop will charge right around $900-1000 to disassemble, machine, and rebuild an LS with new rings and bearings.
The problem with an LQ4 in a performance application is the dished pistons. The volume of the dish reduces compression ratio, which will hinder power. You can find brand new Speed Pro flat top pistons for roughly $250 and bump up compression almost a full point.
The stock 317 castings also have a large chamber, which again, reduces the compression ratio. Since the engine will be disassembled and the heads will be off, I would sell the 317's and purchase a set of 799 or 243 castings. After selling the 317 heads, you may only be out $150-200 for the 799/243 heads.
Those two changes would bring your compression ratio up from about 9.4:1 to roughly 11.2:1 for less than $500 on top of a normal rebuild cost. The increase in compression will bump horsepower and more importantly torque, all across the RPM range to get a big heavy truck moving. With a decent set of 1-3/4" long tube headers and an appropriately spec'd cam, 430whp should be cake, even through a heavy truck trans and drivetrain, and still provide a good broad powerband.
The problem with an LQ4 in a performance application is the dished pistons. The volume of the dish reduces compression ratio, which will hinder power. You can find brand new Speed Pro flat top pistons for roughly $250 and bump up compression almost a full point.
The stock 317 castings also have a large chamber, which again, reduces the compression ratio. Since the engine will be disassembled and the heads will be off, I would sell the 317's and purchase a set of 799 or 243 castings. After selling the 317 heads, you may only be out $150-200 for the 799/243 heads.
Those two changes would bring your compression ratio up from about 9.4:1 to roughly 11.2:1 for less than $500 on top of a normal rebuild cost. The increase in compression will bump horsepower and more importantly torque, all across the RPM range to get a big heavy truck moving. With a decent set of 1-3/4" long tube headers and an appropriately spec'd cam, 430whp should be cake, even through a heavy truck trans and drivetrain, and still provide a good broad powerband.
