So how do you think this 496 will run?
 

I posted this for opinions before, which was mostly negative. But, now I'm looking for ideas on how it will run before it's first voyage tonight. He listened to his engine builder and not the marine pros.

Single engine 26 foot sleekcraft
The motor started out as a 365 mag motor, upgraded to eagle 496 ratator.
compression 10.5-1
ported rectangle steel heads (really opened up!)
single plane intake
850 holley carb
full MSD ignition
CMI tube top headers
stock 454 (330) oil cooler

The cam they recommended was as follows
Hydrolic roller
610/610 lift
230/242 duration
112 center

Looking for running characteristics, not just that it won't work.

It doesent look too bad on paper but who "really opened the heads"?

"compression 10.5-1"
On steel heads? Detonation, lots of detonation.

"ported rectangle steel heads (really opened up!)"
Hogging them out does not always help, opening them up and decreasing velocity without significantly increasing airflow might hurt.

It will probably run like a Raped Ape........For an hour at least
My $0.02

to much compression....93 all the time, water injection, etc..or keep timing way back..

It should make good power, but not sure how well it will hold up from a durability perspective. Looks like it was built to make its power on the top end of the RPM range, probably from 5000 - 6200 RPM, especially if the heads were hogged out. Those rectangle port heads are huge x wide to begin with. I think it will be a little soggy on the bottom end and mid range, and start to come to life around 4500 RPM.

That 10.5:1 CR with iron heads is what really worries me. Hopefully he went with quality forged pistons, good rods and a good steel forged crank. Best to run 93 octane with a boatload of octane booster, or add some 103 octane racing gas. Otherwise, I would worry that detonation is going to pound the bearings right out of that motor, and he will be doing this over again shortly.

Also, if he plans to run that motor hard all the time with that small cooler, he better invest in an oil temperature gauge to let him know when a Chernobyl like meltdown is imminent. :eek:

The heads were a "we have these, let's try them"
Not right for a boat aplication in my opinion, but not my boat.

He gets away with the oil cooler since we have a lot of no wake areas to slow down and let the oil cool.

Wow.....well the guys on here may not always say it in the nicest way, but I consider this site the most valuable high performance resource available on the web....hands down.


That set up may work in a street or pro street car, but imagine that car towing a trailer up hill, in first gear, at 4000-5500 rpms all day. Then ad a 80 gallon fuel tank in a moisture rich environment where fuel degrades quickly.

4bus,
I like the friendly way you put things.

Just got off the boat actually.
It plaines out ok, sounds like a pro stock at idle.
Seemed lazy in the midrange to me and was breaking up some at 4700 so far.

the issue I see with running is you are never going to get to where the engine needs RPM wise with those heads/cam/intake....sometimes less is better...

Make sure it is jetted a little rich and timed around 34-35 degrees. Do not run a thermostat and use premium fuel only.