I have a stock 1998 502 Mag. The engine is out of the boat as a result of some transom work. I am installing a Vortec supercharger and was wondering if a crane 731 cam would do anything for me. The cam that is in the motor right now is the stock cam? Dose anyone know what the stock cam is? Can I use the Crane 731 on a ECM / fuel injected engine with the Vortec supercharger? Is this a good combination? I am also thinking about going with a good set of roller rockers if I do a new cam. Should I go with 1.6 or 1.7 roller rockers? What is the difference between a $125 set of roller rockers and a $450 set?

Thats a good choice for a cam upgrade, if you can find one. Crane is out of business. You would need new valve springs to match the cam and new roller lifters. You would also need a custom tune for the ecm.
The $450 rockers will last, the others???? Stock ratio is 1.7.

Ya, I know I have to retune the ECM, but since I have to do it for the supercharger I might as well add the cam at the same time, right? It saves having to program it twice. Do you know, is the MSD Ignition system worth the $$'s? Would I have to reprogram the ECM if I add the MSD later?

I know I have the distributer, coil, MSD 6m controller and the rev-limiter. Should I go ahead and put it on?

You could have the ECM reprogramed or you could replace it with a aftermarket computer and harness. Doing a upgrade is expensive if you do it correctly. I have a post called "Roller Cam Upgrade" check it out if interested. I just upgraded to a Marine DUI distributer with computer controled timing.

It's a big cam, and will require top end rebuilds much more frequently. If I were you, I'd stick with the stock, or close to stock cam and call it a day. you will already gain so much power with the Vortech it really will make life easier to let things be.

Yes you are right. the Crane 731 is a big cam. I just spoke to Summit on the phone and the tech sait that the 731 is best suited for 4,000 to 7,200 RMP. This sounds awful high, Is he right? I am not sure if I have the RPM's for that. I was thinking I would run about 5,600 range?

I think the guy at Summit must have been either smoking somthing or looking at the wrong cam. If you want to do it right call RMbuilder and he will put you on the right track. It will cost a little more money but he uses the best components.

The 731 cam runs out of power at 5600 on the dyno in a 502 it made 517hp at 5570 rpm. A buddy of mine has two hp500 EFI's cams with 63 hrs on them $200.00 each plus shipping. They are not the crane 731 they are from Mercury Racing. Let me know.

Joby

The 731 cam is a very good cam. Will run well and make good power. I ran one for 3 seasons.

I ran a 468 with a 731 cam for 5 seasons and a little over 350 hours. I would be running it again this year if I hadn't overheated the engine when I threw a belt from the water pump. Wasn't paying attention to the guage and didnt have an alarm.