Inliners International Forums General Discussion Hi Performance 250 engine speed limits

I've searched the forums here for information regarding effective engine speed limits for a street based 250. Most recommendations revolve around accepting the typical 5000-5500 rpm limit, and maximizing low end power. While I understand this approach, I'm after a little something different, as my project will see considerable street time, but will also see limited track duty at out local dragstrip, as well as autocross/parking lot racing type events. A bit of extra engine speed helps in these arenas; I'd like to be able to go to 6000 or maybe 6200 if possible. I'm already planning on an ATI harmonic damper, as well as lighter pistons and 6" rods. What else, in terms of the bottom end, is typically done to make these engines more robust at 6K? Crank counterweight modifications? Is there any new flywheel technology out there (the car is going to be a stick)? Any and all advice is welcome.

TQ

Spend a lot of time designing a good oil pan system with baffles and scraper. An optimum pan for drag racing isn't going to be an optimum pan for turning. Be wary of losing oil pressure on decells and hi-G turns.

An Accu-Sump system and a good oil pressure gauge and an idiot light are all wise additions.

Is there anything off the shelf available? If not, I can certainly machine up some rails and weld up an aluminum pan, but companies like Canton, Moroso, Billet Fab, and Stef's can make them cheaper than I can. Any recommendations?

The Accusump is a good idea. Ive used them on a number of customers' projects with good luck. This car is going to primarily be a street car, but I want it to do everything "reasonably" well. You're right about the oil pans, They're always a compromise.

With a good damper, are the 250's good to 6000, or does the crank itself need work?

Crower made a billet crank and cam for my blown 292 and I think we are setting the rev limiter to 6000 rpm.

Unless you have a lot of cam and head work you won't get much use of high RPM. 6,000 is certainly a moderate number for the 3.53" stroke.

the stronger and longer rods, lighter pistons (pistons probably have a modern ring pack configuration), quality damper I think 6,000rpm will be fairly comfortable

In your opinion, how much cam is “a lot of cam”? I’m planning on either hydraulic roller or solid roller, neighborhood of .550-.575lift with duration in the mid 220 to 230 degree range at .050”. In terms of the cylinder head, I’m going to divide the intake port (this is going to be port injected EFI), and I plan on brazing up the roof so that I can raise it, and fill the floor. The engine will be turbocharged, and I plan on building a nice header and fabricated intake manifold. With these modifications, I should be able to get the port to where it needs to be to stay quiet and not choke. If there’s something I’m missing, please let me know! If this engine platform isn’t going to cut it, I can build something else. But, I really like taking the road less traveled, and learning in the process.

When ever you divide the intake ports it gets really restricted.

Need to port the roof of the port as wide as possible to get some of the flow back, just make sure you leave enough surface to for a gasket to seal ( like a triangle port shape ) (wide up top narrower at the bottom) but it is still severely restricted.
The cam specs you posted is not too much cam, just make sure it is grind for a turbo in mind.

MBHD