Blower Engine Build Up Questions
01-17-2003, 12:17 PM
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Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
Blower Engine Build Up Questions
I'll be using a roots style blower. I'd like to be around 450 to 500 horsepower.
I'm going to find a 350 to rebuild it. Above and beyond what I'd do for a normal rebuild, what steps should I take so that I can handle a moderate amount of boost?
Can I use a stock crank? What pistons, rods and so on would you suggest?
I'll be running around 9 pounds of boost or so.
I'm going to find a 350 to rebuild it. Above and beyond what I'd do for a normal rebuild, what steps should I take so that I can handle a moderate amount of boost?
Can I use a stock crank? What pistons, rods and so on would you suggest?
I'll be running around 9 pounds of boost or so.
Last edited by gruveb; 01-17-2003 at 12:20 PM.
01-17-2003, 11:09 PM
#2
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I'd upgrade to forged pistons before I went with a forged crank, if I had to choose. If money were no object then obviously.....
I'm running cheap KB hypereutectics on my latest itteration roots-blown 383. And a cast crank and stock rods. They should handle 500 HP no problem as long as I stay out of detonation.
Remember that you're building the motor to handle increased TORQUE, not high RPMs if you're using a blower. A lumpy-lump cam is not required and a blower-specific cam is preferred- the spec will be quite different from a N/A engine application. Do some research before you choose
High compression is out. And not at all required to make big power. 9:1 max, maybe a little more with aluminum heads if you plan on running pump gas.
Keep the bottom end specs on the tight side. No massive rod or main bearing clearances. Tight clearances with standard weight oil will handle high torque better than loose clearances with thick oil will.
Watch your piston-to-wall clearance and piston ring end gap specs as they will typically be looser on a blower motor than a N/A motor to compensate for all the extra heat thrown at the top of the piston in a blower application.
Make sure you have a GOOD flowing exhaust. The blower helps the air get in but the exhaust is still running like it would on a N/A engine. Heads that flow good on the exhaust side are a good start. Headers, free flowing duals, etc.
BIG carb on top of that blower. The roots blower still draws air though the carb just like a N/A engine does- boost only happens downsream below the blower lobes. If you were building a 450 HP N/A engine what size carb would you use? Use at least that on top of the blower.
I'm running cheap KB hypereutectics on my latest itteration roots-blown 383. And a cast crank and stock rods. They should handle 500 HP no problem as long as I stay out of detonation.
Remember that you're building the motor to handle increased TORQUE, not high RPMs if you're using a blower. A lumpy-lump cam is not required and a blower-specific cam is preferred- the spec will be quite different from a N/A engine application. Do some research before you choose
High compression is out. And not at all required to make big power. 9:1 max, maybe a little more with aluminum heads if you plan on running pump gas.
Keep the bottom end specs on the tight side. No massive rod or main bearing clearances. Tight clearances with standard weight oil will handle high torque better than loose clearances with thick oil will.
Watch your piston-to-wall clearance and piston ring end gap specs as they will typically be looser on a blower motor than a N/A motor to compensate for all the extra heat thrown at the top of the piston in a blower application.
Make sure you have a GOOD flowing exhaust. The blower helps the air get in but the exhaust is still running like it would on a N/A engine. Heads that flow good on the exhaust side are a good start. Headers, free flowing duals, etc.
BIG carb on top of that blower. The roots blower still draws air though the carb just like a N/A engine does- boost only happens downsream below the blower lobes. If you were building a 450 HP N/A engine what size carb would you use? Use at least that on top of the blower.
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