Ok i know some about valvetrains but have never worked with a turbo valvetrain. From what ive gathered a 236/230 cam .005 duration 114LS is looking like a good cam for my 383 single 75mm turbo. If anyone has any input on cam please give me info. Im in this to learn. Im aiming for a free flowing efficient street strip car, hp between 500-600.

Now Im looking for a valvetrain kit if possible with matching valves, springs,and rocker arms for my car. It has a lt1 heads with stock valve size on the engine now. Not looking to get much bigger valves really. I figure with forced induction it wont make as much of a difference. But Im not sure about what ratio rockers i should use? either 1.5s or 1.6s?

I know there are different types of valves made of different materials what kinda valve do you boosted guys run? anyone tried the "filled" valves? Or are standard valves ok? A knowledge base for this would be sweet of if you guys could post some of your setups that run and flow well ide gladly appreciate it.

 

Not sure about the cam choice, need more info on the whole engine combo and use. One thing to consider with springs is the intakes will need a little more than what the cam recommends (unless they are specing #'s with boost in mind). If you have an intake valve with about 3 square inches of area on the back of the valve, 15 psi will make about 45 lbs of force trying to open the valve. This will make 145 lbs on the set act like 100 lbs. You don't need any more over the nose force on them, but more seat pressure to cancel it out. Valves can go into early float with boost from this.

 

So the intake springs should b tighter? Ive heard from someone it may be helpful to have two dif rocker sizes like 1.5 on intake while 1.6 on exh? The motor is a 383 stroked crank single turbo probably push around 12psi. mid 8s on the compression ratio.

 

I like to have the intake have more seat force without going more over the nose force on a forced induction engine. You'll want at least enough seat pressure to get what you need for the PSI running, whether or not that makes more over the nose pressure will depend on what valve spring are available. A roller cam will not have a problem dealing with high over the nose pressures, so it wont be too big of a deal. A flat tappet cam might have issues if you have too much.

Rocker ratio depends on a lot of things. Yes, some engines work better with mixed ratios on the rockers. Really depends on the cam and head flow #'s. IMO mixing rockers is a way to make something less than optimal work a little better.

 

is there any typical brand of valvetrain that is known for good quality for price?

 

I could see that being true in a supercharged application, but with a turbo, you should have exhaust pressure equal or greater than intake pressure. So the net force on the intake valve before it opens would be zero, or even closing, right? And after it closes, the pressures on each side would be very similar as well, so from a intake pressure point of view, I would think turbocharged spring forces could be similar to NA (assuming equal rpm limits).

 

what heads are you using? roller cam? For roller cam there are some good dual springs that will fit in most head spring pockets as they are 1.27-1.29" in diameter. I have AFR heads with their 8019 springs, shimmed to 170lbs on the intake, 166 exhaust. I ran that on my n/a motor and never had a valve float problem over 6500rpm. I plan on using that same setup for a cam that will peak near 5800-6000 rpm or so with very similar motor to yours, a 383 single turbo with around a 75-80mm turbo, not sure yet, and up to 14-15 lbs but most likely 10-12 on the street since it should give me my power goals. I dont think it will have valve float problems with that pressure and boost but we'll see

 

Im running the stock aluminum lt1 heads. portd a little over. just for better flow. idk bout the cam yet. if itll b roller or not. i was not sure which would be better. i always figured roller would b good for the turbo rpms but ive seen some people use other types....idk. wht are your preferences on cams for turbos? i was thinking bout asking comp cam or crane for their input.if u have an good info on roller or solid ide love to hear it.

 

small block cams in general i prefer a roller. Street cars more hydraulic roller, race/strip cars solid roller. Solids you have to adjust the valve train often and if you drive alot on a street car that can be a pain in the ass.

Hydraulics you can get better cam lobes and run higher pressure springs and not worry about wiping out the cam lobes. I'd go hydraulic roller since your using LT1 motor. Its already hydraulic roller so keep it that way.

For springs you can look at Patriot Extreme Gold springs. They are a nice spring, with stiff pressures. Shim them up abit for a lower installed height and you'll have plenty of pressure. At 1.80" i believe they are good to .650 lift. I'd shim them to 1.75 or so and that should be somewhere around 170-175 lbs on the seat. Should handle most cam lobes with that boost i would think.