It sounds like from everyone's experiences there is no inexpensive horsepower to be had for the 6.2 MPIs. This doesn't make sense as 320 h.p. from 377 cubic inches in not much in this day and age. Yet all I see advertised is stainless headers for about 3k each (times two for the Fountain 29') or Whipples for 7k each. Has anyone tried S/R torquer heads from World Products? They claim up to 30 h.p. or different cams? One would think getting 1 h.p. per cubic inch would still result in a pretty mild tune. So far having the props labbed is the only half-way inexpensive way to add performance. Is there someone out there getting some good results without breaking the bank?

Mercury gets 400hp from that same platform
http://www.mercuryvidz.com/mercury/m...vo-400-hp.html

http://www.mercurymarine.com/media/m...6_Scorpion.pdf

HTRDLNCN,

Sifting through the info you sent shows the 80 h.p. increase comes from different heads, exhaust, 1:60 ratio roller rockers, a different intake and throttle body, 6 additional cubic inches (377 V 383) and a requirement for 91 octane fuel. I'm going to look into the RHS iron heads. It seems the 1:60 ratio rockers hit the guides on the stock heads. I'm curious as to how the RSR heads compare to the World Products S/R Torquers. Sometimes a single change can make a huge difference. I was hoping someone on the forum had played with their 6.2 MPI and found some affordable "magic."

I think the main difference between the 320 hp and the 400 hp 6.2 is the compression ratio. Almost 10 to 1, stock 6.2s have a good crank but cast pistons. Plus any build you will need to do the intake, injectors and map the ECM which may not be possible. I may repower next winter with the 400 hp. Then sell my existing engines.

I've messed with them quite a bit. The intake is the killer on the stock 6.2. It's designed for low rpm torque. The Merc 383's have the Scorpion intake which is a tunnel ram design, which is why it can pull the rpm. Also, keep in mind the 320 hp is a prop shaft rating. I've dynod stock 6.2s at 340-350 hp at the crankshaft. Unless you change the intake and throttle body, bigger heads won't help. The stock Vortec heads flow really well up to .500 lift anyway.

Bob Lloyd
Full Throttle Marine

Bob do you remember what we used for the cam in my 6.2?

Bob did a complete rebuild on my 6.2 last winter and it is night and day different than before!!!
Thing pulls and pulls and pulls!!!! Love it!
http://www.youtube.com/watch?v=FOL6r...e_gdata_player
http://www.youtube.com/watch?v=F2EyXQStnjE

I had 2 of these 6.2's in my 2003 29ft Baja Outlaw.. Very under powered boat. Always consistant at 65 mph..but that's it. I installed 2 sets of Stainless marine exhaust with no change in performance but had a nicer sound. I was told the only thing that would waken up the 6.2 is a wipple charger..
Too much work and not enough room to work in...

I've been running the S/R torquers on my present 406 sbc. supercharged with a 177 they have pretty thick deck surfaces which help with head gasket sealing and have induction hardened seats generous port volume just need a good pocket port and gasket match. jmo

Glad to see she is running great. Really sounds good. Love that video of your Donzi making a pass. Sure is a lot of power for an 18 footer. That has to be a blast!

Remind me again the peak HP and at what rpm?

Bob, I appreciate your input and experience "messing" with the 6.2MPIs. Sounds like the stock heads are the GM performance heads and the stock roller cam is 214/220 with .452/.465 lift, as you said a good combination. Realizing that the stock intake will not flow above the current recommending operating range of 4800-5200 I am curious if the World Products S/R Torquer heads or the RHS iron heads - both with 170 intake runners and 2.02/1.60 valve size, alone with a slightly bigger Crane cam - 216/224º and 509/528 lift might not make more power in the 3000-5200 r.p.m. range. I need an affordable combo as I have to do this twice (twins). I would consider a 40-50 h.p. gain per engine a success. Thoughts?