correct its the B&M version of the 256...I know still a little on the small side but gotta use what I can afford for now lol

thanks for all the input guys!! think I have a direction to go now

Stewart

didn't catch that . I just saw the 525sc part. I Agree, the 256 will work better than the 177.

I had both 177s and 250 on my 454s . The 250s at 7psi with no chiller were still screaming pretty hard around 10,000 rpm blower speed, but it was a nice little power upgrade to the 177. I had the single carb version of the 250, with a dominator. With that setup, the front cylinders were substantially leaner than the rears.

Sounds like a nice package over a stock 525sc , good luck

Thanks!! I plan to go dual carb on it...found a dual carb plate for it and going to run whatever carb came stock on a 900SC...have a pair of those laying around so might as well put them to good use!! theyre holleys 800 cfm maybe?? need to go through them and once this project is done start the jetting process...running an innovative wideband on both sides so should hopefully make things a little easier

Stewart

the 900sc came with twin dominator carbs. The 800sc , had twin 700 cfm if I recall

must have been an 800 then because I know theyre not dominators

Contrary to what most think, MLS are not the ONLY gasket that requires a specific RA finish. And you do not need as smooth of a finish when dealing with cast iron heads, as you do aluminum, with either MLS or Composition style gaskets. This is right from Federal Mogul

Imo, a 250 blower, dart heads, you may be in the 700hp, or even more range, out of a 454 engine. Pretty sure Felpro will tell you , at that power level, you should be looking at MLS. ESPECIALLY, if you were using an aluminum head. Its not just about whether the gasket will seal on a dyno pull. It comes down to service life. Theres a reason OEM's are using MLS gaskets these days, even on lower power engines. A good example was the 575sci engines. Gaskets sealed great...for a little while. Then by 200 hours, they were failing. The common fix was installing some Cometics.

a head gasket must conform to thermal expansion, and expansion from cylinder pressures. A MLS gasket acts like a spring, and can conform to these changes over and over. I would not look to save 100 bucks on gaskets on
A supercharged marine engine.
Head Gaskets and Fasteners - Engine Builder Magazine

when i posted my thoughts about the perma torque gasket being all the head gasket he would need it was from practical experiance,i don,t always pay attention to what should work but rather relied on what has worked for years.if he is having block&heads machined then by all means the mls would be fine.i will add that a lot of the mercury marine head gaskets problems were not caused from the gasket but rather from the junk gm head bolts they started using around the time the gen 5 engines came out.

i agree their is a reason the oem are using mls gaskets,they design the engines to go 300+thousand miles without even a head removal,part of that is very mild camshaft,s that don,t kill the valve springs.that equates to many thousands of running hours.question,what is the normal valve spring life on a mercury racing hp 500 efi or a hp 525 efi engine?hint,hundreds,not thousands.

I know quite a few boaters, and pretty rare that I see anyone running 700+HP supercharged engines, that go 300 hours without a head being yanked off for some reason, to really see how things are holding up at that point. Half the time guys with custom built engines are barely making it past the 50 hour mark before something melts down.

Being that he is using iron heads, and an iron block, he should have no issues running a MLS gasket without the need for a super fine RA finish. Fel-Pro recommends a finish of 60 to 100 Ra for cast iron cylinder heads and blocks, and 50 to 60 Ra for aluminum .My advice isn't something I am making up. Its recommendations and data right from the gasket manufacturers. Could you run a cast crank with a 2 bolt main , sure, know guys who have. Would I recommend a friend to go that route, nah.

Mercury Racing's updated gasket for the failure prone 575sci head gasket, is part #27-811546A04 . That is a Cometic MLS gasket. Used on a 575HP supercharged marine engine with cast iron heads. This is the gasket you will get from mercury if you order a HG for a 575sci. It replaces the old part # 811546A03