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Ok were do you think the real bottle neck in upping the horse power of a mid 80's-mid 90's 330HP motor is?
1 the penutport heads?
2 the Stock merc exhaust
3 the cam
4 the compresion
5 all of the above

If you do one should you do them all? or is one less important? were talking making 1 HP per cubic inch.
Rag's

if you do a search "dynos's 330's on roids " you can see what I did....right at 500 hp now!!

well I had some of the parts from another motor....bought some used here on the board...hard to tell I think I had about 6k in two complete motors but I had one set of heads. Thats with new EMI exhaust.

I changed heads (to rect) and cam (comp cam) leaving the stock center rise manifolds and flat top pistons and went from 61-62mph to 67-68mph. Didn't have gps when the engines were 330hp, but am estimating low sixties based on how everyone was going past me. I have gps now and ended the year with a 69.6 max speed. I also did a little unshrouding of the valves (Kaama taught me :) ), which could have factored in. This year I am replace the qjets with 800cfm holleys and installing headers. Still will be running the flat top pistons with a calculated 8.4:1 comp ratio. I think the compression is going to be the bottle neck now and has been slowing me down. Just can't do it all at once on two engines ;)

Dave

You forgot none of the above.

1. the peanut port heads - these do no limit the power but the rpm you could make 1hp/ci with them but it would have to be a torquer at like 3500rpm or by supercharging

2. the stock exhaust wiil support 450hp but it would be easier to make this hp with better exhaust

3. cam - you cold prob make 450 hp with this cam with really good heads,headers, and a big bump in CR or by supercharging

4. compression - actually at 8:1 this is great for supercharging but you could also reach that 450hp with great heads/exhaust and a bigger cam

you could replace them all and have a well mannered combination or just do a couple to the extreme and almost reach your goal but have the manners comprimised or you could supercharge and leave everthing the same

My own opinion. Naturally aspirated 454 cu/in. Theres a limit to what you can get out of them for a boat (ie torque). Once its breathing well and has the right cam for the compression and rpm the only thing you can do beyond that is more compression, more cam and more rpm. If one of those 3 is not done, like not wanting to spend the money to turn 6000 rpm, then adding cubic inches is the answer. Ive seen some real radical 454's that ran well look like lawnmower engines once the owner went to 540's. This is all based on heavy v-hulls though and maybe cats or lighter boats are different.

Jafo would tell you guys to put in a pair of turbines. They do double-duty as really nice hairdryers.

Hmm, seems a small blower would eliminate all those bottleneck problems. I wonder what a 177 with 5psi at 4400 rpm would give for hp.
Anyone got desktop dyno?
Gary

A 177 would probably add 80-100hp and eventually add some holes into those cast pistons:eek:

and you would have to spin it up to the 4800-5000 range.