mopower

Anybody here change the carbed HP500 cam from the 721 to the 731? Are you happy and what were the results?

BajaRunner

Just changed mine to 731's. Im doing the sea test tommorrow to see how it performs. I also ported the heads, bumped the compression, and raised the rev limiter.

Griff

Not exactly what you are asking for, buy I changed my stock flat tappet 525sc cam to a 731 and am pretty happy with the results. I have much better response in the 3500-4500rpm area and picked up about 100rpms on top.
I really doubt that you see enough of a difference between the 721 and 731 to make it worth the work of cam swap, if thats all you are doing. If you have it apart anyway and are doing other stuff, then I'd switch it or even go to the 741.

mopower

Griff,
The engines going together and have no cam yet , so its a toss up.

US1 Fountain

Put the 741 cam in my HP465 motor (same thing as the HP500, but with dual plane intake) and loved it.

benspeed

I think your "toss up" should be between 731 and 741, not 721 and 731. I use a cam very similar to the 741 in a comp cams grind and have had no complaints. The power is good and with carb tuned right drivability is good too. Just my opinion though.