Overlap is not your friend with a turbo because of the boost pressure and exhaust back pressures of a turbo motor, keep it to a minimum. The cam still sets the personality of the engine, whether it be a torque engine or high RPM. As far as lift goes, unless your making a killer engine, the turbo will push it in just fine.

This is why the racers only run 5:1 or even 6:1. All of this is great for a drag car, but because the static compression is lower, you will not have much bottom end torque either. So, since most of us don't drag race every place we go, a good compromise would be 8:1 or 8.5:1 compression. This way you don't loose too much bottom end for driveability, and if you don't run too much boost, say 10 to 15 PSI, you stay away from the gray effective compression area of 15:1 and up.

Valves: One interesting thing about heads we found with the turbo engines is that some people have taken and made both valves the same size. Rumor has it that they are different sizes to keep the vacuum signal high to keep the carb happy. Anyway, the one's that have made both valves 40mm are very fast and an interesting side effect is they say it takes longer to heat up the motor. They seem to run cooler.

Cam: On naturally aspirated engines that run high RPMs, usually there is a lot of overlap because the air doesn't start moving instantly. By opening both valves at the same time, it gives the intake a head start and helps to flush out the cylinder of the exhaust. The exhaust by now is a column of air that is already headed out the pipe and helps pull in the intake charge. On turbo cars, this valve overlap will allow the increased cylinder and exhaust pressure to flow backward into the intake.

Some turbo cam grinds also wait with opening the intake valve until the piston is already headed down. This is because on a boosted engine the exhaust back pressure can be as high as 30 PSI. The intake pressure under boost is only 15 PSI and will be blown backward. By waiting until the piston has started downward, the cylinder pressure drops and the trick is to open the intake valve just as the cylinder pressure is crossing 15 PSI (in this example).

Good high performance cams for naturally aspirated engines will have a intake and exhaust duration of say 270, 280, or 288, 298 etc. Notice the exhaust event is longer than the intake. On turbo grinds, it is always shorter, say 270, 260 (intake, exhaust), or 275, 255.

On turbo VW's, reports are coming in that the Engle 110 turbo grind has better bottom end than the Engle 120 turbo grind. The turbo grind 120 loses bottom end but trades it for top end RPMs.  This is all "Seat of the pants" scientific evaluations. Hopefully somebody out there has done some "Turbo" cam comparisons. I have used a regular Engle 120 and have had very good success although I would recommend a turbo grind if you are building a new turbo motor.

Engle 110: TCS-10 284 deg advertised .430 lift(in) 112 lobe center 276 deg advertised .420 lift(ex) 112 lobe
Turbo cam street/strip good idle-low compression.

Engle 120: TCS-20 294 deg advertised .435 lift(in) 112 lobe center 284 deg advertised .430 lift(ex) 112 lobe
Turbo Drag race only/large cc-low com

Rod Length:  What's the difference in the length of the rods and what effect does it have on an engine?  After doing a lot of research, here's what I found. First, a stock length rod will make good bottom end torque because of the thrust angle relationship to the crank. The piston speed is much faster for a given RPM compared to a longer rod. The long rod motor has 3 things going for it. First, the piston speed is slower because the thrust angles are less. Second, because the thrust angles are less, it can spin the crank faster. And third, the reason a long rod engine makes more horsepower than a short rod is because the piston is at the top of the cylinder longer, so the combustion pressures have more time to push on it. Just things to consider when building up an engine. Short rod = Good bottom end torque and mid range. Long rod = Good mid range, excellent high RPMs.

Oil: At full throttle, the turbo can spin at speeds upwards of 100,000 RPMs. At these speeds it's going to need a constant supply of oil to lubricate and cool the bearings. It will have a small supply line going into the top (1/8" pipe thread)  and a larger return line coming out the bottom (1/2" or 5/8"). You can supply the turbo with oil by adding a "T" fitting at the oil pressure sending unit on the engine (next to the distributor.)

Why the bigger return line? After the oil goes through the turbo bearings, it's going to get whipped into a frothy lather.  It's important that this large return line be allowed to gravity drain back into the case at a point above the oil level. This will allow some time for the oil and air to separate. You can return the oil into a valve cover, or into the old fuel pump hole. It never-ever "T"s back into the oil lines!!!

Oil Pressure: Wire the oil pressure sender to a loud horn. Something that's loud enough to overcome the noise of your eyeballs rattling at the top of that monster hill. With the higher RPMs, full flow, and bigger oil pump it is possible you could run out of oil at the top of a hill. Depending on your application, it may be necessary to increase your engines oil capacity through the use of a deep sump or dry sump. That decision is something you have to make yourself. I can say this though, your engine will run without oil for a certain period of time. (Don't test this though!) Because of the high rotational speeds of a turbo under boost, it will fail quicker than your co-pilot can say "What was that noise?"  so keep it oiled.

Oil Type: The science of oil and oil types is enough to fill a book so don't expect this paragraph to answer all questions for every engine application. You want to use an oil with an SE or SF classification. This classification has antiscuffing agents that turbochargers like. Watch out with multi-viscosity oils. The polymer additives in these oils do not like the heat of the turbo bearing very well. In a street car with a really hot turbo, these viscosity additives can aid in oil "coking" which means that after you shutdown the engine, the oil will bake itself into charred clumps in the turbo's bearing housing. In a buggy, the turbo will typically be exposed to open air so it will tend to stay cooler than it would be in a closed engine compartment so oil coking is not as much of a problem. Whenever possible avoid these multi-viscosity additives and use the proper straight grade oil (SAE 30, etc.) If your climate requires you to use a multi-viscosity oil, then use the smallest range of viscosity necessary. One more thing: It should go without saying that you should change your oil often.