Need advice on this Crane 502 Cam
 

I'm planning on doing a mild HP upgrade to my 502 MPI's this winter: Revolution manifolds w/ spacers between the mfld & riser (current Merc mflds are set up w 3" spacers), Arizona Speed's super flow flame arrestor, remap ECU's, pocket port the heads and all new roller valve train (Crane rockers, lifters, rods and springs) w/ the Crane #168731. If anyone wants to weigh in w/ any general advice, have at it, but here's my question: should I be concerned about reversion? The 168731 cam is supposedly more or less the HP500 factory cam (Duration 226/236, .587/.610 lift, 69 deg. of overlap). I can't find the LSA spec -does anyone know it? Are HP500's prone to reversion? Guy I bought the boat from told me the blocks were replaced by Merc due to the origional 502 MPI cam being prone to reversion which is why it has the spacers and resonators in the exh. hoses. I've had no problem but of course have a lot milder cam (211/221 dur, .512 lift)

I'd go with the 168741 instead. It's a little bigger and louder exhaust noise if that won't be an issue. I used the 168731 and I wish I had gone with the 741. The 741 is about the same as what is used in the Merc 525's N.A.

Thanks, but I'm not planning on spending the $ for larger valves and fuel system upgrades, so I've probably got a little more cam than I can use in the 731-

Its a good choice. I used one in my 525SC.

It will make just as much power up to 5000rpms as the 741. The 741 will make more in higher rpm ranges.

Ive used the RM exhaust with milder cams w/o any reversion problems but i think you might be pushing it with that much duration. I would chose a milder cam or a longer riser exhaust. Gotta agree w/ Griff on the 741. good luck.

BTW, lobe separation is 112. You could get it custom ground on 114 to better help prevent reversion.

I'm redoing an HP 500, and I think I'm going to use the 731 also.

What is the effect on performance of 112 versus 114 lobe seperation?

Nothing you will ever notice with ~500hp or less.....:D To really simplfy it, the 112 should have a "peakier" TQ and HP curve, shifted slightly higher in the rpm band.....as Griff suggested, I'd go with the 741 on a 114 as well......:circle:

This is the cam I will use when I up the anti on my 502Mag MPI.

The 500 EFI cam specs as follows:
292*/298* @ .004"
230*/236* @ .050"
.352"/.359" Lobe
.598"/.610" Valve
114* LSA
109* ICL

With the 114°LSA, you will have a better idle with an EFI engine. On a carb engine it probably would not matter.