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general turbo questions


ToddK

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I need to learn up on general turbo stuff. Anybody have some sites that I can go to and gain some basic turbo info. Here is my situation. I have been building Rover V8 motors for years. The cylinder heads are the limiting factor. My most recent motor started out as a 4.6 liter. I offset ground the crank to bring it to 4.9. Used forged pistons, chevy 6 inch rods, solid lifter cam, roller rockers, larger valves and ported the cylinder heads. This only netted me around 300 at the wheels. I have built much less expensive 4.0 liter motors and gotten around 280 at the wheels. It would seem that I have hit the ceiling with these heads. I was figuring that I could overcome alot of the cylinder head deficiencies with a turbo. I want 400 at the rear wheels out of a 4.0 liter motor. Seems easy enough with what I've seen on other motors. My budget will be around 10K for this one. I need to know where to spend the money in conjunction with the limited amount of aftermarket parts available for these motors.

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Guest Anonymous

or your camshaft could be the limiting factor.. or the heads.. or both... you would need to post the flow numbers for the heads, the camshaft specs, the rocker ratios, and the dyno charts for anyone to make a sugestion.

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Trust me, it's the heads. The last cam was huge. It used solid lifters, had a .544 lift, a 258 duration at .050" and was cut on a 106+4. Anything bigger, and the car would not be driveable. I am not looking for specific advice on building a motor. I need to know where to look so I can learn more about turbos. Give me a map and I'll get there.

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Guest Anonymous
Trust me, it's the heads. The last cam was huge. It used solid lifters, had a .544 lift, a 258 duration at .050" and was cut on a 106+4. Anything bigger, and the car would not be driveable. I am not looking for specific advice on building a motor. I need to know where to look so I can learn more about turbos. Give me a map and I'll get there.

Since you know the answer why ask the question. Sure the camshaft you quoted is aggressive. That isn't always the problem.

My most recent motor started out as a 4.6 liter. I offset ground the crank to bring it to 4.9. Used forged pistons, chevy 6 inch rods, solid lifter cam, roller rockers, larger valves and ported the cylinder heads. This only netted me around 300 at the wheels. I have built much less expensive 4.0 liter motors and gotten around 280 at the wheels.

All that work.. to make a 4.9L. You actually lowered the VE of the engine. ie. Backed up. If you can do that to a 4.0 and make 280 and all that other stuff to make 300. You've got a problem with whoever is the engine builder. Either your cam is to aggressive for your cylinder head port, your not turning the RPM needed or something is wrong. I would certainly hope by making the engine 25% higher in displacement you would increase the power by more than 10%.

You should speak to whoever ported those heads and get the flow numbers for them. I expect you don't have enough CFM to make that cam work and your torque curve is lame.

hy35 hx35 hx40 holsets would be a cheap but reliable turbo for a 4/4.9L engine. will make the power you desire.

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