I want a built shortblock but....

BGTV8 · 08-13-2010, 02:49 AM

Generically speaking, an NA engine makes its power because of 2 things, increased compression (requires full-race fuel) to increase torque. but there is little point going beyond 12.5:1 because of the exotic fuels required, and increased revs to shift the torque up the rev curve and therefore increase HP.

The former requires stronger pistons. gas-flowed heads (inlet and exhaust) and better head clamping to withstand a bigger "bang" which means more torque, and the latter requires a stronger crank/rods/fasteners and possibly block to decelerate and accelerate the piston as they rotate thru top and bottom dead centre and hold everything in the proper spot so the engine does not self-destruct.

"If" the heads will flow enough air at elevated rpm's, then you can consider 120-150bhp/litre if everything is radical (re-engineered oiling system to support elevated rev's, big-port heads, cams to match the objectives, port matched inlet and exhaust, improved coolling ot handle additional heat rejection, blah, blah).

The real question is "what are you after" - a dyno pull number, a car you can still drive on the street, a race car ????

I have been racing sports cars for 40 years ... and an NA big-power engine is always a compromise - in terms of ulitmate driveability, absolute levels of power and the reliability that goes with it ..... so the first thing is to establish exactly what you are looking for.

Then you can figure out the next step.

Most s/c will increase torque of a std engine by 50%, dead easy and simple. If you don;t drive it at WOT all the time, it will probably live for a while

Most Turbo systems that do not drop the compression will give infinitely adjustable torque for a relatively short time before detonation or a melted piston turns the engine to custard.

A fully engineered turbo installation can offer a heap, but they are expensive if not OEM engineered, as you are sometimes forced to do the engineering R&D yourself, and by fully engineered, I mean crank, pistons, rods, bearing package, heads and head gaskets, electronics to manage detonation risk etc).

Have fun - you are talking about ground breaking .... with NA

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08-13-2010, 02:49 AM	#17 (permalink)
BGTV8 A True Z Fanatic Join Date: Dec 2009 Location: 03350 Australia Posts: 1,515 Drives: 09 Nissan 370Z M6 Rep Power: 39974	Generically speaking, an NA engine makes its power because of 2 things, increased compression (requires full-race fuel) to increase torque. but there is little point going beyond 12.5:1 because of the exotic fuels required, and increased revs to shift the torque up the rev curve and therefore increase HP. The former requires stronger pistons. gas-flowed heads (inlet and exhaust) and better head clamping to withstand a bigger "bang" which means more torque, and the latter requires a stronger crank/rods/fasteners and possibly block to decelerate and accelerate the piston as they rotate thru top and bottom dead centre and hold everything in the proper spot so the engine does not self-destruct. "If" the heads will flow enough air at elevated rpm's, then you can consider 120-150bhp/litre if everything is radical (re-engineered oiling system to support elevated rev's, big-port heads, cams to match the objectives, port matched inlet and exhaust, improved coolling ot handle additional heat rejection, blah, blah). The real question is "what are you after" - a dyno pull number, a car you can still drive on the street, a race car ???? I have been racing sports cars for 40 years ... and an NA big-power engine is always a compromise - in terms of ulitmate driveability, absolute levels of power and the reliability that goes with it ..... so the first thing is to establish exactly what you are looking for. Then you can figure out the next step. Most s/c will increase torque of a std engine by 50%, dead easy and simple. If you don;t drive it at WOT all the time, it will probably live for a while Most Turbo systems that do not drop the compression will give infinitely adjustable torque for a relatively short time before detonation or a melted piston turns the engine to custard. A fully engineered turbo installation can offer a heap, but they are expensive if not OEM engineered, as you are sometimes forced to do the engineering R&D yourself, and by fully engineered, I mean crank, pistons, rods, bearing package, heads and head gaskets, electronics to manage detonation risk etc). Have fun - you are talking about ground breaking .... with NA