Head size for a 598" engine...
 

Requirements:
Marine application
Naturally aspirated
Approx. 9.5-9.8 comp ratio
Single carb
Hydraulic roller cam
Power band must be good from 3000-5600rpm

I keep getting 101 different opinions as to what heads would be good enough for a 598" engine and I am sure I will get more by asking here. I would kinda like to see where the majority sits on this idea. I not looking to see how much torque I can make with a 598 incher, therefore I don't really need torque that rips your head off.
The torque that I have now with my 540's is enough. I don't really need more than what I already have, although I realize it may be somewhat unavoidable with a 598.

My 540's now make:

RPM Ft. Pounds of Torque:
3000 592
3500 598
4000 662
4500 694
5000 688
5500 651

I've been told I can run heads 320cc, 335cc, or 360cc. I'm sure they would ALL work okay, BUT I need only as about as much throttle response as what I already have. I know I will already bennefit from the BIGGER cubes from a 598 alone.

With the info I have given; any of you guys want to take a stab at it?

Thanks,
Mark

Dart 355 Pro 1's in case you missed it in the other post.

Only my opinion but I would think a very efficient 320 to 340 CC intake runner will give you very good throttle response and still flow plenty of air to support a 600" motor at 5600 RPM. If you were running solid rollers and planned on twisting 6000 to 6500 RPM 340 to 360 would probably work better.:cool:

Here is a way to look at it. You have 310 CC heads on your 540. Assuming about the same volumetric efficiency and similar RPM you can increase runner volume proportional to engine displacement for equal intake velocity.

540/310 = 598/x

X = 343.3 CC's

Probably not perfect, but better than shooting from the hip. If the baseline of your current 540 is performing the way you want it to it is probably a decent estimate.;)

Kaama,

I'm going to be using using the Dart Pro 1 355's on my 598. But I'll be using a Stage 4 Pro Charger also.

If you're not looking for every ounce you can get the 335's on a nat asp will work just fine.

DAVE

I think I remember that someone used a pair of Dart 360cc heads on a pair of 572 cubic inch engines that only had 8.6 comp ratio, hydraulic roller cam, single dominator and still made more torque/horsepower than my 540's @5200rpm! Perhaps the Dart Pro-1 CNC 355cc, Brodix CNC 355cc 2-Xtra, AFR CNC 357cc, Pro Topline 360 (CNC not available) heads might be the choice. All are within 355cc to 360cc. Perhaps these might be the size heads that will suit what I need. Thanks for all your input and all are guys I highly respect. Anyone else please feel free to chime in and/or add to anything said. Any/all input is appreciated! Thanks.

Mark/KAAMA

BTW, the reason why I don't need/want too much of a torquey engine is to be easier on the Bravo One drives if that is possible.

Mark your bored already????Its going to be a long winter.....leave things alone run it until it breaks then go bigger!!!

YES MARK ,PLEASE AT LEAST GET WHAT YOU'VE GOT TUNED UP AND RUNNING

YOU KNOW IF YOU ASK TEN PEOPLE YOU'LL GET 10 DIFFERENT ANSWERS !!!
THAT QUESTION WAS A BIG ,

DAVE BE CAREFUL WITH DECK THICKNESS ON PRO-ONES WITH A BLOWER ,THE BRODIX AND AIR FLOW RE. HEADS ALL ARE ABOUT
750 THICK ,IT REALLY HELPS

I got a call tonight from AFR telling me they were sending my heads out & I should have next friday. Once I get them I will take & have flowed. Will keep you informed of progress.

Thanks Bobby D. I didn't give that a real thought. Just assumed coming from Dart they would be ok.
Still, I should be ok as I'm using the Fel Pro Lock ring gasket and the additional two head bolts per side on the Dart Big M block.

I will bring it up for discussion with Dart however.

DAVE

I plan on running my 540's this next coming season just going to get them tuned up real good! ;)

But you never know---those 598's might make an appearance some day. Thanks guys.

Dave F, glad to see that you went with the BIG M block. I think Turbo Jack is too!

Kaama,

Thankyou for steering me in the right direction. Saved some money too. :)

Thanks
DAVE

Canfield 350's man!

LOL, 350ci heads!!!!!

I think thats the compression chamber on my 4.3!!!!

I cant imagine over 700 ft/lb!!!!

Okay, I'm going to stir the pot a little more here. I'll get a little more detailed. The heads I have now are Dart Pro-1 310cc aluminum heads w/2.30" intakes valves and 1.88" exhausts. Now then, by the way it sounds some from people that I have talked with that once ported, the Darts Pro-1's are pretty good. However right out of the box they aren't very good at all as JimV took them out of the box when I originally recieved them. Since then, he has fully ported the these same heads---this also included a chamber port. I have also been told by others that the Dart Pro-1's are NOT a very good head for supercharged applications because of their deck thickness. I don't need to worry about that because I plan to use the 598's in a naturally aspirated application anyway, so I should be fine there.

Here are the flow numbers from my heads from the full port:

Dart Pro-1 Aluminum 310cc @28" water on a "Super Flo" flow bench without a pipe on 4.50" cylinder.

Valve Lift CFM(Intake) CFM(Exhaust) % of Flow

.200" 149 130 87
.300" 225 171 76
.400" 295 206 68
.500" 348 256 73
.600" 380 286 75
.700" 394 300 76

I highly doubt I'll be using a cam much over .635" lift. I have discussed my heads with JimV and asked him how many CC's does he think they are now since he fully ported them? He said rough guess would be approximately 320cc's. Now then, I am wondering if I can use these heads on a 598" engine and perhaps spread the lobe seperation angle out on the cams to curb the torque numbers a little. Something like maybe 116* to 120* (lobe seps)even. I'm looking for anywhere from 700-725hp, but I'd like to keep the torque no higher than 700ft pounds if it is possible------but as I have said; that may not be possible or as easy as we think. 5400rpm is the RPM goal to run these engines with 5600rpm being the maximum.

Have you played on desktop dyno or similiar to get an idea for your hp and tq and rpm desires.

Yes, I have a "Desk Top Dyno" but it doesn't get into intake runner CC sizes. Some stuff I have compared from a real dyno sheet to a desk top dyno have been very accurate and other stuff not very close at all. But it is good for some reference points when making some other changes just to give you and idea of how much of a difference is between trying two different parts.

I'll play with my 'engine analysis' program. It is better than the desktop dyno. It allows for more input like head flow numbers, etc. What cam, intake manifold, exhaust?

Marty, I have the Stellings full length tubular headers. I think the primaries are something like 2-1/8" on the headers, with a 4.5" O.D. tailpipe (4.0" I.D. tailpipe), dry stack OPEN (no mufflers). I'll be using a single plane intake manifold something like a Dart or Brodix. For 598 cubes, I would probably use something like a 256*/260* or a 256*/262* or a 256*/264* @.050" hydraulic roller cam with something like .600"-.635" lift on 116*-120* lobes. Holley HP950 series carb. I would be using the longest rod possible with bore/stroke combination being 4.600"/4.500". Perhaps you can punch that in and see what it comes up with. Thanks :)

BTW Marty, I like a cam with slow/easy ramps speeds like the Crower cams have.

After playing around on the 'Engine Analysis' program and looking at all you numbers, I can come up with this:

Your 540 is pretty healthy now with 1.26hp/cid with 9.5CR, peak tq at 4500 but I would think that at 5500 rpm you haven't hit your peak hp. All this means that you have very good heads-what ever they are- and maybe a bit overcammed for your intended rpm range/goal.

Now with the 598 you can add 10% to your tq figures and I would think that your heads and cam would be pretty darn close to perfect. But your tq will be in the 750-765 range.

Change in CR from 9.5 to 9.8 is worth 15 tq and hp across the board.
Change from 1.7 to 1.6 rockers only lose 10 tq and hp but reduce lift by 0.030" which might really help the valve train/springs/lifters last longer.

Unless the 598's are free, I would keep the 540's. Why go to the tall deck for very little change. The 'EA' program has the Brodix BB-2 fully ported heads as about the best power producers.

I hope that helps a bit to confuse you some more.

Cobra- I was also noticing that. I was going to build a 572 this winter but as I ran the numbers on desktop I saw I was going to increase my low rpm HP & torque (bravo killers) & gaining very little on top end. Since I am not needing any more low rpm torque I decided it was waste to spend the money.

My AFR's are to be here friday, They shipped when they said they would first week of Oct.

Marty, thanks a million for checking into that for me. When comparing with your "engine analysis" program, I have sort of came to the same conclusion when comparing to my Desk Top Dyno---lots of torque down low with the 598 which is good, but is it really worth the small gain you get on top at about 5400-5600rpm??? Sounds like TurboJack has found the same thing. I also called Bobby Daniels' shop and they ran my flow numbers and found about the same thing. JimV felt the same way about the head size for a 598 as well. He felt the heads I have now would work well with a 598. But I think I may just stay with the 540's. It just doesn't sound like it's worth all the fuss going to tall decks and all the expense and aggrivation. I'm going to work on super tuning my engines and remove the hook from the hull of my boat and have the last 4 feet of it blueprinted. Then possibly going with some 2" IMCO's lowers or something. I think if I am going to find any speed it will be from the things I have just mentioned.

Thanks to everyone who has contributed to the input within this thread----you're help has just saved me some BIG $$$ and aggrivation and that makes me smile. :)

I left out one small item. I was working with stage 4 procharger. Motor being blown made the HP about the same but max was at a lower RPM. I guess if I went with a wilder cam I would get more HP but I figured I would just save the money. At least I will not have the kitchen remodeled now.