Offshoreonly.com - upgrading a 509

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with a blower i dont think you need a high dollar, high flowing heads, you just need an affordable aluminum to help with detonation

Quote:

Originally Posted by 5050 (Post 2390811)

with a blower i dont think you need a high dollar, high flowing heads, you just need an affordable aluminum to help with detonation

Good heads make power , I have a buddy with a 454 4.250 crank making it a 496, 250 blower dart 360 aluminum heads making 699hp on the dyno:cool.-smiley-027:

The Canfield cyl head is a great head for the money , about 2500.00 a pair complete with siv dudy valves tit retainers & springs Beware not all complete heads are sold with good marine grade parts . Make sure that your short tail pipes are not causing water injest. or more cam will make things worst.

Quote:

Originally Posted by Griff (Post 2390312)

Yes, its a roller cam. As far as heads, I'm no expert. I have read the merlins really are not very good w/o some porting work. You get what you pay for. I would probably go with some AFR's. The Edlebrock Marine heads are pretty decent too and a good bang for the buck. The are what merc uses on the 525EFI. A friend made about 800hp with them on a whippled engine.

Are you really saying that Merc uses Edelbrock heads on factory built 525EFI's?

Quote:

Originally Posted by Alex (Post 2391759)

Are you really saying that Merc uses Edelbrock heads on factory built 525EFI's?

Yes, that is what is on 525EFI's. Not sure how or if they are modified.

http://www.offshoreonly.com/forums/s...ight=edlebrock

mercury used Edelbrock on the 525efi ,they work well if you only run your motor to 5200 rpm.

What limits the rpm? Runner size, flow numbers ...? And what about the oval ports, even lower in rpm?

Quote:

Originally Posted by hoozeyurdaddy (Post 2388344)

I'm looking for suggestions on upgrading a 509, It's going to need a bore due to minor watermarks in the cyl's, It's running a 256 blower w/superchiller and 6psi boost, 2 750 holley's built by nickerson, 525sc cam, flat tappet w/roller rockers, 502 bowtie heads rec. port, thinking about alum. heads and cam upgrade, but water ingestions seems to be a problem, It was disassembled for a blown head gasket between #5&7.
what is a good alum. head that will perform well but not break the bank, this boat gets run about 10 hours a year.
Thanks
Larry

you probably already know this but you are right as far as buying an aluminum head on a budget, so you wont have to worry about detonation. there is gonna be heads that flow more, that are more expensive which would be the right idea for nat. aspirated motor. with a blower you just create more boost to get your flow so dont waste your money on an overly expensive set of heads just make sure you get high quality valves, springs ect. just my opinion
i would suggest edelbrock or procomp

ARP makes stud kits for just about everything.