Difference btwn cams??
 

Can some one explain in simple terms "cams for idiots", what is the difference between the crane 132561(stock 525s) and the 139731. Would there be much perf. gain with the 731?

468
weiand 177(5lbs)
8.5:1
Dart Eagle Iron 310cc
full hydrolic
1050 dom
max HP r's at aprox 5200
Want aprox 625hp

Want durability and minimal chance for water reversion.

Re: Difference btwn cams??
 

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Re: Difference btwn cams??
 

cam will be hyd Roller

Re: Difference btwn cams??
 

iamfaster,

With your engine being only 468cid and using a 310cc sized head, then I would suggest using the smaller cam of the two. Simply because a 310cc head is too large for a 468cid marine application. Also, I highly doubt you will see 625hp from a naturally aspirated 468cid engine.

I once had a pair of 468cid engines in my 32' A/T that made about 600hp @5500rpm on the dyno. However, these engines had 9.5 comp ratio with Merlin oval port heads with 2.30" intake valves. The heads were professionaly ported as well in the bowl/pocket areas, and used Dart single plane intakes, and MECHANICAL/SOLID roller cams.

Re: Difference btwn cams??
 

The stock 525sc cam #132561 is NOT a roller cam. Its a flat tappet hydraulic.

The 731 should make 20-30 more hp. As I said in one of your other posts, I did the switch on a stock 525sc. I saw 50-100rpm increase and more torque from 3800-5200rpms.

Re: Difference btwn cams??
 

Without an intercooler, I doubt you will ever see more than about 575-600hp. The 177 blower just gets too hot to move enough air to make that HP.

I'm at 7lbs of boost w/o a cooler and I'm probably around 550-570hp.

Re: Difference btwn cams??
 

Kamma, I am using my existing 177 weiand blower.

Griff, Yes, the stock cam is a hyd tappet, but i want to go with the Hyd roller. Is that #168731??? The flat tap 731 is part#139731. Which one did u use? We will also be bumping the Comp to aprox 8.5:1.

need some help understanding the specs when comparing the stock cam to the hyd roller. #168731. Have a longer duration? taller exaust and intake? Crane rep recommended 741. But thought that it may be more than i need.

I will finally be meeting with builder this week to spec. I appreciate yours and others advice last couple weeks.

Re: Difference btwn cams??
 

I'm pretty sure #139731 is for a Gen IV and V engines and the #168731 is for Gen VI engines. They have the same specs and are both hyd rollers. I have a Gen V engine and used the 139731.
This has been discussed before about the 731 vs the 741. That info is largely what I based my decision on. The general concensus was that the 731 is a better cam for a SC'd 454 and the 741 was too big. The 741 would have to be run at too high of an rpm on a 454 to make it real power. The 731 will make more torque in lower and midrange cruise and make more power than the 741 unless you are at 5500+rpms. The 741 would the better choice for a 502-540ci.

Re: Difference btwn cams??
 

Griff, Do you plan on new heads or porting? Would that help compliment your cam for more top end as well as mid?

Re: Difference btwn cams??
 

Cams are a little more difficult then, which one will make more power? There are to many variables that have to be known before an educated selection of a camshaft can be made. Just because a cam may be bigger then another doesn't mean it will make more power under the curve. Sure it will more then likely make more peak power but if that power occurs at 6K and you are propped to make max power at 5500, then the cam is worthless.

The cam is derived from the combination to be run; ie bore, stroke, rod length, compression and cylinder head flow and cross section numbers. In your case the added blower will change everything. An OEM headed blown 454 will take a much different cam then a Merlin Headed 454 due to the fact the airflow is much greater on the merlins.

Chris

Re: Difference btwn cams??
 

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

Re: Difference btwn cams??
 

well put rm, dead on

Re: Difference btwn cams??
 

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.

Re: Difference btwn cams??
 

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.

Re: Difference btwn cams??
 

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. :)

Re: Difference btwn cams??
 

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