598 Engine Advise
 

I pulled the engine out of my 27' V bottom due to high oil consumption and poor leakdown numbers. I knew it had a Merlin block and Brodix heads and not much else. It has a 1050 Dominator with a Dart intake. The Dart is a 4100 manifold with a 4500 adaptor.
The heads are BB2x with 345 intakes. Turns out it is a tall deck, 4.5 stroke with 4.6 bore. Full roller cam etc. A nice suprise to find out its a 598. Any good reccomendations as to cam, compression etc? I want a reliable pump gas, 91 octane engine. Thanks in advance.

Look into super victor 4500 or sv565 for starters. That intake is killing you.

What exhaust are you running on it?

It has Imco Powerflows.

Compression 10:1 conservative., cam I will be like a MT and lay low. You should spec out and see what's in it currently though. A particular grind I would hate to say without proven certainty. The heads ported? You wanting to go hyd or solid roller? What rpm you want to run at wfo? Another words what outdrive you have?

I would like to stay with a roller cam. Not sure what I want for a max Rpm. It was thinking 5400. I have the weak link here, its a Bravo One drive currently. I baby it.

Baby it... Say whaaaat.

As best that I can!!

I have the perfect intake for that motor SV632 Edelbrock powder coated black nice no corrosion $350 pretty much half price. As far as a camshaft goes if you want the motor to be happy and 850hp right around 6,000 rpm at 10.0:1 compression you need a 273-275 intake high 280's exhaust @.050 113lsa works great the more lift the better. That cam with those heads and intake will pull like a freight train to almost 6,000 rpm and be all done by 6,200-6,300 rpm.

my bob mandura cam he specked for my 598 was lot smaller than that , its for sale cheap brand new . in box id have to dig it out to give final specs .. 254 260 632 lift maybe not sure though

my bob mandura cam he specked for my 598 was lot smaller than that , its for sale cheap brand new . in box id have to dig it out to give final specs .. 254 260 632 lift maybe not sure though 10 to 1 , dart 345 s . dart block . close to same as you

What did the boat not do good before? Top speed? Anyone out there with same boat as yours to compare some numbers? Don't over cam it if you only want to spin it to 5400. What other parts you have in the motor? Crank Rods?

Think its to much camshaft for his exhaust would need a good header on it.

I don't. He has a head with a small csa. The larger cam will help carry the torque with the smaller head. Anything smaller than that I think he will end up with a turd.

Sounds like a nice cam for a 454

I tried several different cams in my 598, all solid rollers. It depends on what you're wanting to do with the boat, enjoy the day with the wife and kids or go to the shootouts and see if it stays together. You may be looking at more than just a cam change, valve springs, push rods, rockers, more detail may help.

Thanks for all of the advise. I have no issue with running it above 5400. The engine was just torn down on Friday. The engine builder said it had a Callies crank, good rods etc. It needs bored out a little and he will get custom pistons for it. I'm waiting until next week to get specifics of the cam and top end as well as the rest of the components will be cleaned up and checked for problems. The engine shop is well known for their marine engines and I will get their recommendations as to how to build it hopefully soon.

Hopefully they can go 4.610 and leave a little for the next time.

That is what the builder said he plans on doing.

If I had to bet I would say he might be off with his memory. Just a guess... Would be interesting to see what cam card says. I can't imagine cam that size in a 598 performance engine.

It would work well in your 555's... With a 4.5" stroke motor you really can't give the motor enough duration or lift. Best thing to do is just leave the intake valves out of the heads.

Hodup now. Let's try something like that in yours first. Should idle very nicely for you. Besides you'll never guess what I'm going with??? Might surprise you. :ernaehrung004: actually kinda close to something you mentioned in a thread a few weeks ago.

On a serious note I have a question for you BB. I realize stroke eats up duration but let's say for same stroke engine how much would .100 larger bore size difference make with same duration cam in regards to peak hp rpm? My gues would be minimal but what's your take on that? Maybe 100 rpm or slightly more? Just wondering.

It's not going to eat up the cam as much with the larger bore. The larger bore help helps the head move more air. Big stroke want a big valve you really can get a big enough valve in a 24 degree head. Then when you put a bigger valve in the head to support the motor now you end up with the valve to close to the bore. So what do you do? bore notch? Not going to happen when the bores are almost touching each other... So you move the cylinder head on the bore. If you want to get everything out of the combination that's how it's done and that is the difference between an engine builder and an engine assembler.

ill dig that card up .marine kenetics specked it .. I know nothing more than it didn't go in the engine .. lol probly why ..im going to hunt it down rite now

I have a nice combo for 598. If you have any questions send me a PM and I'll share specs.

Also, with a bravo and that much cubes I would let it spin some RPM to help it live. 5400 is going to kill it quickly IMHO and I think 5800-6000K is more where it should be.

https://youtu.be/u-5P0vw1UqQ https://youtu.be/Zjxja9AYp00 https://youtu.be/n9cQRzU9jdA

Mine is 110 LSA, Solid roller - 257* .7314 lift intake, 266* .7149 lift exhaust
I run it at 6400 RPM

Thanks for all of the advise. My builder called today. Thought I should either change heads from the BB-2X of do some work on them as they are stock. I'm having them go ahead and work my existing heads, new valves, springs etc. the are boring it to 4.61". Thats all I got today.

Is that lift with 1.7's or 1.8's. I'm assuming 1.7's but thought I'd ask.

I am running Jessel shaft rockers ( stock ratio)

I am running AFR 357 CNC'd heads.
8.6 to 1 ratio JE pistons ( plan on adding a M4 Procharger eventually.
Crower crank, Lunati rods, Big M block, Edelbrock sequential port EFI intake with the Holley 2000 CFM - Hp system.
Idles smooth and has so much torque it is unreal. Accelerates like it's tail got stepped on.

That's good to know. I'm glad to know the static compression for time being didn't hurt you from the way it sounds. That's awesome. I suppose that's where the cubic inch comes into play. Btw I like the stepped on a tail term. Pretty funny... Never heard that one before. I like it. Hah. So your leaning toward procharger vs SC. Elaborate when you get a chance. Just curious as what made up your mind on.

Looks like I will be getting new heads. It was recommended to use Dart Pro 1 345 heads or Brodix BB-2 Xtra 365 heads. Any preferences or thoughts?

If you want a nice package deal. I have a brand new set of AFR CNC'd heads with custom valve job assembled ready to bolt on. Make you a killer deal with a SV 632 Intake. With the right cam it would go over 900hp on a 10:1 598. PM me if interested. Heads are Hard Annodized with Inconel Valves.

What size runners on a 598 combo you suggest? My thought on dart 365's would be to much. You thinking a 335-345 with the sv-632. Would be a fun build to say the least.

Going by runner volume isn't the way to do it. Really need to know the cross sectional area of the port different heads have different CSA's the volume or CC's is just the volume and means nothing to the motor. A motor like this 598 over 6,000 rpm is going to want a cross sectional area around 3.5sq in. Based off of the CSA of the port Cubic Inch you can figure out the rpm Choke point of the motor. It's ok to go a little bigger on CSA but not too big. It's all about air speed in the motor.

How do you figure they would be too much?

GM saw fit to put 325cc rectangle port heads on 427s and 454s (for some reason). You've got 30% more displacement.

My builder likes the Dart 345 head. Says it his go to head for this size engine.

Very true but GM didn't design them for marine applications that most often run under 6,000 rpm. Just an example but look at many of the 540 marine builds that are making great power with 305-315 cnc heads. Velocity is huge and by getting it with the proper size runner vs CI is the name of the game. Some choose to go larger runner just for good flow numbers but pay for it in the long run. I'd rather start with a smaller runner and maximize velocity while achieving right runner size when done. That's where my head guy comes into play. We dyno'd several 572's marine engines downstate years ago and rarely went over 335 runners with dart heads and were typically for the lighter boats and cats. The single engine heavier boat applications would get the 325's/330's. Exception for race boats turning 7,000-7,500 different story. There are other factors involved absolutely. Supercharged engines will easily sustain a little more runner size also. Best thing to do is trust your builder and make sure he is marine savvy. Back in the late 80's early 90's some of the best engine builders in Michigan anyway made some huge mistakes from cams to heads. They learned in a hurry though drag racing and offshore were two entirely different breeds.

My head guy (valako) is adamant with 320's for my 565 builds. Or has even suggested starting with 310's but would ultimately end near 320 after porting. Engine builders and head guys all have the same goal just some go different routes but ultimately can end up with near same results in the end. Regardless trust your builder and don't go seeking advice from others or you'll be all messed up. Lol... Btw I know I used 572's as example but still believe 345's the way to go. The velocity should be ideal with that runner size and cubic inch.

The cnc Bb2 xtra will make right around 800 hp at 9:1 compression and good cam. There used to be a problem with the machine work on the Pro 1s, they ate valve guides they may have fixed it by now.

Mercury also used them on 454s.

Most builders go too conservative IMO. The engine won't be as sensitive to the intake, carb and cam combo when you've got huge velocity from putting average size heads on a huge engine. I'm sure they will run great but you probably left power on the table and they'll be dead after 5500.