merc 525sc head + cam upgrade!!
 

I want to gain 100 hp with my 525sc stock engine.

Does he have anyone that he can suggest a good aluminum head that i can fit on this engine???

I want to mach the smaller 177 blower pulley (2,850'') and a good cam like Crane 731 or bether (anny cam suggest???) with a new aluminum head without chiller (no space for it).

What about the Eldebrock Performer rpm marine head????

Here are the spec:

Heavy-duty, 1.89" Inconel exhaust valves provide added durability for marine applications
Hard anodized black to protect the aluminum in the harsh marine environment
Sold with valves only to allow for valve spring choices
Match with an Edelbrock Performer RPM manifold, Performer Series 750 cfm marine carb and Performer RPM cam for proven performance
Smaller-than-stock 11/32" valve stems promote excellent flow and lighter valve weight



Combustion chamber volume 118cc
Intake runner volume 315cc
Exhaust runner volume 110cc
Intake valve diameter 2.25"
Exhaust valve diameter 1.89"
Valve stem diameter 11/32"
Valve guides Manganese bronze
Deck thickness 9/16"
Valve spring diameter Springs Not Included
Valve spring maximum lift Springs Not Included
Rocker stud 7/16"
Guideplate Hardened steel
Pushrod diameter 3/8"
Valve angle 26°
Exhaust port location Stock
Spark plug fitment 14mm x 3/4 reach, gasket seat
Made In USA


Does it is possible to get this aprox 100 hp with that upgrade More boost, aluminum head and cam upgrade???

I run the 177s on 454s with 9.5:1 compression, 731 cam and edelbrock rect heads, 1050 dom carbs. I run around 6psi with the 3.25" pulleys. I estimate the combo in the 625-650 hp range. Works nice. The higher compression crutches up the 177 blower which is a bit small for a 454.

What is your timing with 9:5 comp and 6lb of boost?
Also do you run with a chiller?

Im running a hyd roller cam, 8# pulley, crane gold roller rockers and a 1050 domain. id guess im in the high 500hp range. I don't think a 750 will be enough carb

I run with the same carb... do you have chiller with 8lb of boost?

Call Bob Madara at Marine Kinetics http://www.marinekineticsonline.com/

He has a good package for these engines. Should be able to get the power increase your looking for and he grinds his own cams...very knowledgeable guy.

I X2 Bob Madara! If you want an aluminum head go with the AFR 265 Oval or maybe the 290 Oval. They are both MUCH better than the Edelbrock heads. Either way call Bob he'll set you up with the right cam and head for your combo and goals. Here is his number 585-654-8583

No chiller, 30* all in with V6 tbolt modules, 11.8 afr wide open. Aluminum heads help.

The AFR heads do seem to be very good. The stock intake is rectangle port on a 525sc. Blue Thunder, I am curious what exhaust temps are running with 30 degrees total timing on your boat. I had some 2.85 splined pulleys that were for the Merc 177 blower and I didnt like the way they fit the shaft, so I changed the shaft out to the automotive one and it uses a keyway so you can get pulleys from summit or Jegs.

Good call on rec port intake. The AFR's the I mentioned won't work for that application. Either way give Bob a call, he'll make sure you do it right the first time.

I have already the 2,85 pulley that can make more boost than waht i have run this summer. But with new aluminum head with more flow i think it can affect the # of boost to the down size that is what i need to know or calculate to know if the hp gain will be good...

I will try to contact Bob...

To make sure what i do with that.

No way to pyro the exhaust. I started at 28* and worked up till no improvement than backed back down 1*. 30* is pretty common in supercharged apps. I didn't dyno the engines.

The reason I ask is, when I got my boat it was totally stock and it had the timing backed off to 30 or so deg total. The leakdown test indicated burned exhaust valves @ 144 hours.

The 177 is great on a mild 454. however, in my opinion, once you add some healty cams, good flowing heads, you will be limited.

You are correct that you will probably loose boost psi with the new heads/cam. however, you will make more power. I would consider a upgrade to a 250 or 256 blower. They work great on a modified 454. You will be able to make 7lbs of boost, but to do that after the mods, you will be overdriving the daylights out of the 177. The blower shop makes a really nice 250 sized blower. Used B&M 250 blowers are around cheap. Run a dominator if you are staying single carb. Most guys will tell you that you dont need that big of a carb, etc, etc. Roots blowers are hard to overcarb, and love unrestricted airflow above them. how come a 250 blower will normally make more power with twin 750 holleys over a single dominator? Don't get caught up in that going to a smaller 800-850 single carb talk. Run a big carb and tune it right. Merc knew what they were doing with the single dominator on a 177. its not a blow thru or N/A engine.

I would think a proper cam swap, intercooler, and 250 blower, you can probably run 8-9 lbs of boost, and make some really nice power, even with your stock heads. Install some headstuds, MLS headgaskets, and go. If you boat in freshwater, lose the water thermostats, and keep them cold.

Cost wise, a pair of heads will cost you at least 2-2500 bucks for a decent set. In my opinion, if you were on a budget, the larger blower with more boost and chiller would net bigger power gains. Although your heads are iron, your static compression is really low with the stock pistons. GM square port heads aren't as bad as some guys make them out to be, especially on a blower app. You can make some power with them. If I remember right, the stock cam is pretty decent for a blower motor. It's ground on a 114LSA. A upgrade to a Roller cam would net some gains, but not necessary.

My boat has built up 454's with dart alum heads, custom roller cams, 250's blowers, and some other goodies. 7lbs of boost, single dominator, 84mph on gps. Same boat, same drives, ran 70-72 with 500EFI mercs (not my boat but another old 38 Fever). have no idea what mine dyno at, but they run great and been together for about 6 seasons. Best i could get out of the boat with the 177's at 5psi, was 77mph. Bolting on the 250's and 7psi, got me 84mph. Leakdown tested yesterday, 6-9% leakage. Not bad.

Just so you know what you are starting with:

Carb: Holley Dominator: Jetted 98 all four corners. 6.5 High FLow Power Valves (not standard ones) Front and Rear
SC: 177 CID
Heads: CHevy Iron Rectangle Ports 2.19, 1.88 valves
Compression: 7.5:1 (yup!)
Cam: Merc 400 / 420 / 425 / 525SC
Crane Part#132561 Grind # H-228/312-2S-14 T1.2
Duration at .004” : 298, 306
Duration at .050”: 228, 236
Lift with 1.7 rocker: .530”, .551”
LSA 114LSA
ICL 109 ATDC , ECL 119 BTDC

Quick heads up on 525SC:
T-Bolt Module does not reach total timing until 4200 or so rpm. One the two 525SC's I tweaked real timing was few degrees different than stated on module, so use your gun to set total correctly, again at or just over 4200rpm :o Always go further to see when timing advance stops to make sure you got there. Total specs should be on the flame arrestor, I believe somewhere around 36 degrees?.

Plugs are Delco MR41T's

Thanks for the engine info spec.
The total timing should be at 35 deg.

So......my vote is:

Good cylinder head. AFR 305 if want aluminum and RHS if you want cast iron. With 7.5:1 going aluminum for detonation control is really a non issue.

Cam change: guaranteed. Hydraulic roller to get these BBC heads flowing some air.

Back to cyl head: I'd strongly recommend looking into a reduced CC combustion chamber to help give you some more compression.

AS Blue Thunder stated (and BTW, his boats hauls with his 177cid fed 454 based engines but I advise you not to drive like him. LOL. :evilb:) compression will be your friend to help make up for the lack of air the 177cids will provide in comparison to the bigger blowers.

If i will go with aluminum head at what comp ratio can i go without having problem at 5-6 psi boost?? 8:1 8:5 ???

Now with the stock setup i ran it at 5.5 psi the upper pulley is 3.368 in dia and lower 7 in dia i have fond a 2.850 in dia that i have not trying, the boat is now stored for the winter:(

I know with bether head flow i will drop my boost but i dont want to run it below 5 psi with the 2.850 in dia pulley.
So i need to calculate that point. I need to know the stock head flow to make any comparison of hp gain and boost lost....

I did this one 4 or 5 years ago and it's still runnin strong. Stock 525sc cam, carb, blower, stock pulley made about 4.5 lbs. Edelbrock RPM heads and compression bumped to 8.5. A little more boost and a bit more rpm and you'd be close to where you want to be. There's a bunch of different ways to do it and they're almost all relatively cheap and easy.

http://www.offshoreonly.com/forums/a...blem-525sc.jpg

What's you talkin bout willis :cool-smiley-011:

9.3:1 with the right tune and setup at 6psi and 93 octane will give you a good margin of error. Mine were as high as 9.6:1 last year with 6.2psi but I did end up breaking a crank. But that was a engine builder issue not setup or detonation I'm pretty sure. My engine builder can be a real putz at times. :lolhit:

I am afraid to go more than 8.5:1 at 5-6 psi...... It will give an effective comp ratio of around 13.0:1 it is little higher with 92 fuel.

Are you in high altitude???

No, close to seas level on the chesepeake. I don't think your dynamic compression estimate is right but don't have my chart with me at work. From memory my setup at 6psi and 9.5 was 13.4:1. With my 4.8psi pulleys it was mid 12:1s I have engines tore down now and there is no signs on the piston tops of detonation on the 9.6:1 engine. There is a broken crank though but that is a different story.

Hey Dave, I didnt know you broke a crank. Rough.

I am sure that you will have it back together for next season ready for another shot at the old single engine Kryptonite :party-smiley-004:

Dave's (Blue Thunder) boat hauls some serious ass.:drink:

I actually just got done putting the smackdown on a green activator and it broke. Pretty ugly. New block and all needed. I start assembling next week on the new block so it will definately be go time come spring. I wanted to get a couple imco shorties over the winter but that may have to wait. That was going to be my secret weapon for you come spring.. :angry-smiley-038:

Did someone know the stock 525sc rod length??

I will probably do a piston ring refresh so i think i need this info to get the right stuff....

should be a 6.135 rod.