On 500 EFI's:

Question #1: Anyone have any experience with upgrading the pistons to a 10:1 compression? Did you have to reprogram the computers etc....

Question #2: Also, anyone have any experience in adding a larger camshaft? Same question -- what else did you have to do to make it run right?

Call me if it's too much to type:

Thanks,
Joe
713-222-7667 Office
832-277-3661 Mobile
[email protected]

I would keep the stock pistons and add a blower. No boat is complete with out one.


Look out adding to much compression. If I remember correctly when you add more compression and a larger cam you will lose your low end tork that is necessary for good cruse speed. Also if you add to large of a cam you have to watch out for reversion. An Hp500 has a good cam to start with. Hopefully someone with more experience on this subject will jump in. good luck

Paul

Changing pistons, unless you already have the engines out to rebuild, will cost thousands. The stock pistons are good quality forgings. No need to replace. Several companies make aftermarket heads with smaller chambers that also breathe better. You could get your compression that way. Along with a Crane 741 cam you should be in the low 600hp range. You will need to reprogram the computer and upgade the fuel system to insure supply.

PatriYacht, Please check your PM

Please keep the comments coming.... I'm talking with my engine builders (Owens Racing) this Friday and making a final decision as to add the new cam or not.

Yes, I'm already planning on having to re-program the computers w/ the 10:1 pistons.

All of your feedback is appreciated.

For the money you will spend, you could just add a Whipple and gain 200hp easy.

Thanks, John. The piston's are the same price as stock and the cams are only around $300 each.... not too expensive. Either way, I'd have to get the computers re-mapped, and that's also only around $300 each.

I bought EFI's mainly because I didn't want the maintance and did want the ability to run them hard. No interest in blowers (but all my friends also keep trying to talkk me into them!!! ).

Joe,
Something to consider. When you raise your static compression ration to 10:1, with the stock cam, you will elevate your cylinder pressures to the point you run the risk of detonation. You can lower cylinder pressure by increasing duration, which will give a later intake closing point, bleeding off some the additional pressure, in the process increasing cylinder fill time. These are all pluses for making power but there is a trade off. More duration=more overlap=greater chance of reversion. You can reduce the overlap by increasing LSA, but the wider lobe sep will alter the power band. The changes needed to make your combination work are all related.
Bob

Thanks rmbuilder,

It looks like I'm going to bore to 509's, add the 10:1 pistons (which will be more like 9.75:1), have the motors dyno'd and computers remapped from that dyno. I hear the Louisiana gang do the mapping. They have been successful duplicating this set-up on the 500 EFI's.

Great information, rmbuilder, thanks! I'll keep everyone posted.

Do you know who really does the mapping in Louisiana?