I'm running twin 500 efi's with 215 reliable hours. Looking for more hp without supercharging... don't want to compromise reliability.

Thanks for any suggestions.

Aluminum heads at least, cam, computer remap by some experienced. Thats what I would do if I didn't supercharge mine.

Any idea on hp gains to be had from this?

A good 25 to 50 hp I have read here, depending on the cam.

You can buy the heads with new valves and springs already installed. Your close to the hours of replacing the springs anyways.

Try a search and you'll find alot on this engine.

How about making them 540's.

Tyler did mine this winter. Replaced heads with Darts, his cam design, MSD ignition, redid my carbs (he prefers EFIs) and I dynoed at 585 per side. Carder

Thanks - gives me some direction... now I have to find the right shop to handle the job.

Use a shop who has doen the work before. Ask the shop for referenses, and call the customers to see how it went. For a job like that, I would insist on a dyno tuned finished product.

Totally agree with Jeff...you can't tell how youv'e changed the dynamics of the engine without the dyno sorting it all out. Carder

I also have 200 hours on our 2000 Slingshot with 500EFI's. E-mailed Crockett and talked to Joe @ Hustler this week, still waiting for a reply from Tyler but have heard of good things from his shop. I would like to see the motors in the 600-700 horsepower range. Are there any advantages to N/A vs. supercharged, i would also like to see engine life of 300-500 hour range.
Thanks Steve