Why don't you tell us all WHY a 509 with a 240* cam won't make 700hp? We deal with customers who have over cammed, over headed, piss poor combinations that don't make power every day. Typical internet builds like the ones you posted links to. It's all too common and unfortunate when people spend a bunch of good money and follow really bad advice on trying to make good, usable power. The 509 that made 709hp had no port work done, no vac pump, no crank trigger, no trick carb, and had a hyd. roller. Funny thing is, we did the first pulls with the customer's 850 Demon vac. secondary carb and the best it did was 652 hp and 641 tq. The customer was pretty impressed, even at that, till I bolted the 850 DP and a 1" spacer on. Just a carb and spacer were worth over 50hp, and no one would have known the difference had we not tried.
So again, instead of just repeating something can't be done, just because YOU say so, tell us WHY.

If you want to read about a bbc that made a little over 700 hp (900+) with a 240 @ 50 cam, you can go to web site with some fairly sharp people talking engine combos (yellow bullet). Look up a thread about "My 565" of Engine Masters experience".

For the record, I see Foxwell and Staub in the mix on that site but I don't see any famous engine marine designers over there. I also see head designers, NASCAR engine builders, Pro Stock engine teams, cam designers, spintron experts, as well as plenty of drag car guys. On a site with some heavy engine talent they seem to contribute quite well. It baffles me with this site's level of knowledge that we don't listen and learn a little better. For the record if Scott would have made that math error on yellow bullet several guys would have caught that and corrected it within 30 seconds (led by Stan Weis math expert). Maybe Scott didn't make a mistake and was testing us over here?

Gee, the just typical BS response I thought I'd get. I hate to tell you, but you don't have to get paid for building engines to have been there done that. Not even getting into the boats, how many engines do you think we built in 9 years of racing? How many do you think we had spares of? I have no idea how many or if any motors you have ever built, for your own stuff, but I will bet that it was no where near that number. Not to mention that to keep up in racing the tech changes most times during the season which means even more tear downs. You ever pull the heads on a motor in the dark at midnight in a mud field?

So yea no, I'm not an engine builder.

So you just described straub and foxwell. because straub can't use a screwdriver, nor can he "rig boats, prop boats, set up x dimensions, tuning, , and so on" Neither does foxwell. straub sells parts Ask him to use a wrench and he's done. and in foxwell own name dropping "biography" note that he has listed ONE jet boat. Thats it. ONE. If you want to call a jet boat offshore, you need to get back on Google!

Because there are maybe 3 people here that know what it means and even less that care. This is NOT a drag race forum where 1 HP is the difference between winning and going home.

I didn't intend to turn into a negative, I just asked a question, for my own knowledge. I have neither bashed nor cheered either side in this.
Another question, same 540 with 315s will it be a turd, have less power, or an unusable power band?

And yet, you still cant answer why you are advising the 315 heads are the way to go, over the 305s , and what kind of gains will be seen

You keep reverting to how this isnt a car forum......well, many of the guys on those forums have built a good amount of offshore engines as well. You think alex haxby, dean gellner, richie zul, paul phaff, or many others, have never built a drag racing engine? And because they have, should we discredit their advice on a marine engine build ?

Darrin morgan and curtis boggs posts on those forums, should we ignore the cylinder head advice they give , because they dont normally deal with 600hp 509s with silent thunder exhaust?

Mike jones has a bunch of offshore engine builders that use his camshafts, and he posts on those sites. Should we discredit his valvetrain knowledge ?

Let me ask you. Offshoreexcursions 572 that made 750hp at 5900 with a 240ish straub cam, on an independent dyno, how does that stack up to your superb 637hp 509ci build ? Looks to me, he was making more hp per ci than your build. Was your engine dynoed with your silent thunder wet exhaust at that 637hp, or was that with dyno headers ? Do you have a dyno sheet on yours to post up, since you seem to enjoy discussing correction factors on others builds ..

Still same as us, yes I have pulled many engines part the night before going racin and such, hence my boats name is quickchange.... You don't know me, I don't know you, but neither are professional builders and advice is just opinions. Simple as that...

I can't explain it to you because you, just like foxwell don't understand how airflow on a MARINE engine works.

But hey, the Holley chart says that a 502 only needs a 600-650 cfm carb. Try that on a BOAT and tell me how it works for you

What about a 540 with 325's?