high RPM use

[Guest Nic-Rebel450CA]

I have a couple questions about parts for high RPM use.

 

*I would like to get opinions on using cast or forged cranks. Which is better for high RPM use? In a couple books I have read, they indicate that cast cranks may be better because they wear better than forged cranks. One book also mentions that SCAT makes cast cranks at a good price with a special setup to make them balanced better.

*What parts should be considered for the valve-train for high RPM use?

*Any recommendations on main bearings? (brand, etc)

*Any recommendations on connecting rods? (brand, etc)

*What about a dry-sump setup? I have read that oil splashing on the crank can significanly lower HP at higher RPMs, I was thinking that a dry-sump setup might be a good idea (especially since that is what is used on high RPM race cars such as CART, if I am not mistaken). I know dry-sump setups are expensive, but how expensive? Any recommended sources for setups and/or resources?

 

As a note, I plan to run the engine for about 15,000 - 20,000 miles between rebuilds/swaps. Whatever heads I use will be kept when I swap out the engine for a new short-block so the valvetrain must be able to last.

[Mike C]

Small block chevy never had cast rods. Until recent times, all were forged but newer ones are powdered metal. They have a good reputation for strength, but are more difficult to rebuild because they are "cracked". Cast cranks break at a lower RPM than a steel crank bends. The SCAT cast steel (vs. cast iron GM) cranks are better than stock, but are cheaper than a steel crank for a reason.

 

What displacement?(bore and stroke) Occasional (drag racing) or continuous high RPM operation? How high? What's the bore and stroke? How light are the pistons? HOw much money are you going to spend on lightweight valvetrain components? What style camshaft?

 

Carillo rods are the cat's meow. The Manley forged H-beams are better $ wise. Oliver makes a fine rod. There are others. Clevite 77 tri-metal bearings are time-tested. For sustained high rpm operation, you should seriously consider shaft mount rockers. Look to NASCAR for a model.

 

Use mushroom flat tappet lifters instead of rollers, shaft mount rockers, the lightest most expensive valves and retainers you can afford, Same goes for piston and ring assembly. NASCAR may be dinosaur racing, but those 358" motors turn 9000 rpm +/- for hours at a time. BLock integrity becomes an issue. Bowtie block or a partial fill with Blokhard. Studded bottom end is mandatory. Get the stroke short and the bore large. The large bore mandates a lightweight piston to keep weight down. Reduced reciprocating weight and piston speed will help it live a long time. 3.25" stroke and a 4.125" bore is a good model for high rpm and high flow small block.

 

JMO