rmbuilder

iamfaster,
The cam #132561/H-228/312-2S-14T 1.2, originally designed for the 400, 405, 420, 425 HP and 525SC-454 CU. IN. Merc engines, is a very different grind than the 139731/HR-288-2S-12 IG. The 561 flat tappet was used in both N/A and supercharged applications from the factory, but by today’s standards is not an optimum design. The specs on the Hyd-roller 731 may appear similar @.050 but are misleading in that respect. The adv durations are:
561) 298*/306* @.005
731) 288*/296* @.004
The 561 has 10* more adv duration than the 731
561) 228*/236* @.050
731) 226*/234* @.050
The 561 has only 2* more duration at .050. As you can see the more aggressive lobe is the 731 as the difference in duration from seat to .050 is 62*/62* compared to the 70*/70* even though the measurement is .004”/.005”
The most significant figure is the duration at .200”
561) 134*/143* @ .200”
731) 145*/154* @ .200”
The 731 has 11*/12* more duration at .200” (.340” valve lift) as the roller allows for a much more aggressive ramp. Overlap on the 561 is 74* compared to 68* for the 731. From a power and durability standpoint a correct roller designed around the parameters Chris mentioned is the best choice for your project. If you are keeping your max RPM to 5200 be aware more duration wont make more peak torque after a certain point, it will just raise the rpm that you make peak torque.
Bob

kevinr

well put rm, dead on

Griff

Don't plan on doing anything else to it. It was basically a top end freshening job and a cam change to add a little more HP. If I was going try and make a significant increase in HP, I would dump the 177 all together.
Actually, if I wanted to make 600+hp, I'd start over with a 540 and sell the 525SC complete.

RLW

I am with Griff on his recommendation. I had a 468 (told it was a 496) with a 250 blower. It was fun but I wanted simple horsepower. No extra whirlygigs etc. I went NA with a 540 CID. Not any more money than a 502. You can run the heads and carb you already own if on a budget.
Of course, just keep what you have and cam accordingly. Just don't expect more than it is capable of delivering.

KAAMA

Yep, you're right! I totally missed your 177 blower---sorry. Looks like you are getting some good advice from some of the others anyway.

iamfaster

thanks for the info...motors coming out tommorrow and meeting with builder this w-end.