800 HP? Easy. Stock 502 short block, AFR heads, GOOD head gaskets and a Whipple with Intercooler. 800 hp very easy on 91 octane. Talk to Dustin, I'm sure he can help.



Darrell.

I Have A 598 With Dart Cnc Heads That Jim Valako Did Up For Me This Spring. It's Got A Solid Lift Cam .264/.270 @.050 .730 Lift Dart Tunnel Ram 2 850 Holleys Oliver Rods Lunati Crank Jesel Shaft Rockers Comp Belt Drive It Made 830 Hp At 6300 Rpm And 783 Tq At 5300 Rpm It Runs Very Good And Its For Sale

The best you can figure, pushing the envelop, is 1.2HP per Cubic Inch on pump gas without a blower. You need to look at the HP at 5200RPM. You can rev it up but you will not run it that hard so that is the usable HP. Mercury rates them @ 5200RPM normally. What is the HP at 5200RPM? That would be a start to a comparision to a Mercury rated HP.

A 598 will only give you about 720HP@ 5200RPM on pump gas. Any body can give you a dyno number but if someone give you a dyno number of 800 HP @5200RPM, then if they stuck a HP 500 on it they would have a 560HP plus motor.

The bigger engines require much faster cam timing that is very hard on the valve train. They greater the valve timing the more compression is needed to overcome the cylinder loss. Not on pump gas any longer. Also does not idle well.

Remember that HP is not the thing, its how much torque you can make & how well you can achieve the torque curve after 4400 RPM.

I get tired of hearing all those big HP numbers, they are sales gimmicks. MY 2 cents

You were doing fine 'till you got to here.
The torque absorption curve is hull dependant. Hp and torque cross each other at 5250rpm and hp is a calculation of torque vs rpm except on an eddy current dyno. Obviously you want the torque curve to maintain or even keep rising, depending on the rpm band you want to run. Before you start spouting that high horsepower numbers are a sales gimick, you might want to know what you are talking about. ;)

I do, however, agree that there is alot of dyno's that give high numbers and don't prove themselves in the real world. :)

You may get tired of hearing these big HP numbers...but many are real, and in many cases very usable...technology has come a long ways in the past few yrs...let alone the past 15 yrs. Many engines are regularly pushing 11:1 CR on Pump gas, non fuel infected, and living long healtly lives...but everything better be right, especially the cam....:ernaehrung004: 5200 rpm is for very conservative (read...warrenty) power...6k is no big deal and can be done with a hydralic roller with ease..1.5 to 1.6hp per CI is very dooable NA...RELIABLY on pump gas with solid roller...:nhl_fight:

Both the last two have points, I push the engines with compression and they have to be right. We agree with that. Everytime I do one for a friend they burn it up with stupidity. A 11/1 Solid roller cam motor is not something that the average person can put in his boat and run turn key. That is more of a drag motor that will suck in a boat at idle. They also come with little or no warranty.

JD
I think 1.5 or 1.6 HP is on the high side. I have never seen a 502 advertised at 753 to 803 Marine HP. Most all those engines are 600HP. 600/502 = 1.2HP

Richard, I have never seen a torque curve from anybodies dyno that was rising at 5250. Most all I see start falling off at 4500. I agree hull has a lot to do with it but with the stuff i did, if you propped the boat at 5400 rpm, any switch to more RPM only gave more RPM and not much speed difference.

Agreed on 502's, I'm talking larger CI engines ~600"ish they do it regularly..850-900HP+ is pretty easy to do these days with; ~10:1, Good CNC head, and pretty mild solid roller...low to mid 6k.....

Even stock power can be broken quickly in the hands of idiots...:hitfan::drink:

here is a Steve Schmidt motor...with single quad, wet sump...
http://www.steveschmidtmarineengines...ne-engine.html

The new 18 degree ovals from Dart seem to be the way to go now...I'm trying to talk my buddy into a set who's running Dart 355 CNC heads on 598" solid roller motor. ~65 trouble free hours and already throwing down 900+HP. I'd love to see what he can pick up...

I'd go bigger Cu. In., mild cam, blown-low boost....but my opinion is biased.. ;)

If the proposed boat is light, then I would go smaller cu. in., compression, NA with higher RPM's.

Unless things have changed, their engines are assembled with less-than-premium internals. The price looks good bit the Eagle (IIRC) crank & rods don't exactly inspire confidence. I've seen more than a few of their warranty returns and build detail is lacking as well.

There's alot more to building a high-performance engine than just buying all the right parts. I can go to the grocery store and buy all the elements for a fabulous gourmet meal. That doesn't mean it will be near to edible after I'm done with it. One of the bigest barriers is machine work. Even if you really know what you're doing, if the machine or tooling isn't 100% there, you're going to have a tough time getting 200 or 300 hours out of an engine.

FWIW- I wouldn't do anything that one of the big-names doesn't do. Merc, Sterling, etc. all have to live with the engines they build. While the big-inch motors sound good on paper, getting long, reliable service might not happen. Everything from high rod angles to aggressive cams are overly stressful on hardware. You'll likely end up with an idle higher than what you want which isn't fun for dockside maneuvering and also exhaust reversion issues that put uou into noisy dry pipes. They only cost less if you factor in everything- from lifespan to aggravation. I'd call every reputable builder and inquire what they're doing in the 800HP range. You might come to like the sound of one of their price quotes in the process.

I have 598 na 750hp motors and mine fall off at 5400 and make peak tq at 4500 to 4800. They are great around the dock and have been trouble free for the 40 hrs I have put on them so far. As far as pricing, if you build a 598 with all the best components, it will cost more in most cases, than putting a blower on an existing semi stock 502 or 540. The way I looked at it was this: I used the best parts, builder and combination that I could find. If I want to step it up later for more power, I already have the best parts and foundation already there. I have a more HP capable platform than I will ever use or be able to afford for that matter. As they set, they do make an insane amount of power not to have a huffer on them that is for sure. The boat runs faster than the last pair of blower motors I had in it. It is not for everybody, but I could not be happier with mine.....plus 600 inches just sounds different than the 502 mills.....if you get in a pekker contest.....you can't beat playing the cubic inch card!!:D