Upping rev limit

[menostig]

Hi, anyone got any idea would it take to up my engine's limit from 5600rpm to 6800rpm ? This factory built and final balanced engine revs very freely, it so swift and smooth to the redline that it's a real shame to end the fun early. It's also supposedly very tunable.

The ZZ4 engine spec is as follows:
- Low profile dual plane manifold
- Lightweight alloy cylinder heads with raised D exh. Ports;
- Low friction hydraulic tappets;
- Undercut & rolled fillet LT4 nodular iron crankshaft;
- Forged steel shot-peened pink con rods;
- LT1 flat top pistons;
- HE1 distributor (vacuum advance) and 12-3/4” auto flex plate;
- 750 Holley carburettor;
- Mild steel exhaust
- BHP 360 @ 5250 rpm; Torque 405ft/lbs at 3500 rpm;

Given this spec, what's limiting the safe rpm, and is improving things necessarily an engine out job ?
Also any idea of costs ?

cheers
Roger

[Boosted LS1]

Check the rod bolts are top quality and not stock. That's where any weakness will be. All rods these days are forged and the pinks aren't at the cutting edge of technology, well not since the 70'ies or whenever. Does the engine feel like it wants to rev higher and produce power at the same time? If so you should be able to buzz up there for short bursts as it is. Next on the agenda would be some steel rods, billet of course and a rebalance plus a cam change. You could go billet titanium rods for $4k. If it were my project it would get a turbo.

Boosted.

[peterpsg]

AFAIK, the main limiting factors on the rev range of a SBC are almost all valve train related...

You'd probably want to consider some of the following...

Needle Roller Rockers - either shaft mounted or stud's with a girdle (I'm getting one installed pretty soon...), these will help track the cam better (and with less friction) at high revs, and WONT suffer from some of the problems hydralics have (like not closing/opening when they should!!!)

Better springs (2 or 3 coils or 2 with a shim), possibly even consider oil spray cooling if you really want to rev it, since the spring pressure in SBC is very high to counteract all the mass in the system (pushrods, rockers, locks, etc etc), this means that the springs also heat up a lot, and the faster they rev, the hotter they get, until they get so hot that they lose their 'temper' and then the $hit hits the fan... so keeping them cool is a good idea...

Titanium valves, locks & retainers - to reduce the mass of the system, hence reducing the spring pressure/rates required.

CF pushrods if you're really feeling keen...

Single plane manifold - you'll want the better breathing at the higher end, though you'll lose a bit of bottem end torque/smoothness.

Possibly a better ignition system to ensure a good spark at the higher revs...

I'm sure one of the US guys of UK engine builder types will fill us in on all the goodies, as these are just things I've mostly read about in several of the Chevy books I read prior to getting my GTR.

If you've ever read about Kurt Dobsons GTR, they had some kind of mental setup that would let them rev to 10k!!!
I'd hate to see the price tag though, I think they spent >US$65 on the engine alone...

[B1 ECC]

The camshaft, you would need to change the profile from your ZZ4, the heads would probably support more power and RPM as would the botom end, however, the following needs consideration any power produced over 6000 rpm increases the engine mortality rate by 40% but eh!