Big Cubic Inch Engine Opinions ?
 

Here in the wonderful state of Michigan, it's now bench racing season.............

We started talking about big block combos (naturally aspirated). I thought a 4.600 bore x 4.25 stroke would be a good combo (565 CI). Anyways, my friend keeps tryin to convince me that if you're going that big, you might as well build at least a 600 CI.

My question..............is anyone running any naturally aspirated engines over the 600 cubic inch mark, and if so, what kind of power are you making, rpms do you spin, and how reliable are these big engines ?

Or how big are you guys running reliably ?

I won't be doin anything right now, and realize anything I do will be chewin up & spitting out bravos, but just thought I'd ask.

Thanks,
RJ

Going with a 4.600 bore...you might have 1 oversize left in the block.
And going with a longer throw crank, 4.5+...your cylinders and pistons will wear quicker.
I like the 4.500 bore with a 4.500 crank...hense 572CI
So it depends if your in the mood to toss the blocks at every rebuild lasting 200hrs or so.
Im not an engine builder but this is my opinon.

There is reliability in cubic inches with a naturally aspirated engine. You don't have to build them as radical to make good power in the usable RPM ranges for a marine engine. I'm only running 540 cubes naturally aspirated. Next time I'll build a minimum of 598's (4.500" stroke X 4.600 bore). With those kinds of cubes at 3000rpm I would probably be able to maintain a cruising speed of something like 55-60mph or more in my 32'A/T---those kind of RPM's are practically nothing for an engine with those kind of cubes. I prefer naturally aspirated engines and big cubes vs any kind of blower on any size engine. Supercharged engines make awesome power and the torque comes in like gang busters, therefore they're harder on parts and drives, more complicated, more moving parts and more maintenance. I guess it comes down to how much SMACK you're willing to lay down. Just my .02

Hey RJ,
Don't you have some work to do !?!?

Plus what are you doing talking motors...Don't you have a house that you have to finish
building ?!?!? You won't have any spare money for years !:D

I agree with the fact that blower motors are a *****... mine are.
Im giving it a thought of going NA myself...All I would need is new heads, intakes and 1050's.

Back4more,
Why are your blower motors a ***** ? Just curious. Myself personally have never liked them. Now I'm doing research for my next boat purchase (28-30 w/single) and want to make around 800hp and I don't think an N/A motor will be too reliable.
I currently have a 675hp N/A 540 and have had some reliablity problems in the past..mostly
valvetrain (lifters)

Great topic
KAMMA please keep us informed. My next boat is going to be another AT and my thoughts are exactly yours. Big CUBES for reliable power. Id like a 32 to run 90+, I hope I dont have to wait for a step!

Kaama,

$$$$$$$$ is what it always comes down too - lol.

Right now I'm running 355's in a 31 scarab and going in the low 70's. But eventually, I'd like to get into the high 500 cubic inch range, and get into the 90 mph range.

I was thinkin a set of 582s or so would be a good combo - 4.600 bore x 4.375 stroke with a 6.7, or 6.800 rod.

Heck, if I had the $$$$$$$$$ I'd build one of those 1050, 91 octane naturally aspirated 565s (I think the key is the new oval port big chiefs).


I just mentioned the 565 because I noticed a lot of engine builders are using this combo now. Sonny Leonard, Rehere Morrison, etc. Maybe something to do with the big bore / short stroke ?

Little by little
 

I know.............the house is gonna keep me from doin that (for now). Like I said, just bench racin for now :D

But I figure this gives me a little time to think

dont listen anybody!!!!
always bigger is better....
(I have 510's now ,will have 632's soon...)

A guy I know had a big 600++ CU motor in his 30 foot V. He was not happy and ended up with a HP500 W/Whipple. He is super happy and has had no problems.

He thought the NA big cubic inch did feel fast and was a dog.

Just someone's experiance.


Mike

I got a chance to test drive Fred Inman's test mule with a single 708 (out of the mid-west I believe). Impressive torque for an NA motor. If I remember correctly it only ran about 5400 or so rpm...

What the heck ?
 

Might as well go with the 700 CI then - lol :D

The only issue will be the fact that you need a supertalldeck 11.625 block, and an oddball crank (cause of the bore spacing)

Actually, that's a pretty heavy combo, and I don't know if it would fit if you didn't have staggered engines. Heck that big you may beed big chiefs, or big brodies to flow enough......that just adds to the problem.

Oh well........you can always dream big

I run a 632" Merlin in my Carrera cat. 4.75" stroke / 4.60 bore. The only real issues I've had have been valvetrain related. (You have to run big duration and big lift to really make the power NA)

The motor makes 820 Ft/# of TQ at 5000 and 900HP at 6700 on 93 octane. 10.5:1 CR on tunnel ram with fully ported Dart 360 heads. After a couple of lifter failures I've gone to the Schubeck "radius lifters" in hopes of more durability. (basically a solid flat tappet that is "radiused" to run on a roller cam lobe) The jury is still out on these but I hear Comp Cams is in heavy development of their own design and Pro stock cars will be running them next year.

What you're friends are saying is basically true, bigger is better (to a point) 632" is about as big as you can practically go without getting into basically custom made parts. I would start with a 622" (4.56" bore) to leave room for addnl bores if they're ever needed.

If you want I can give you a run-down on the major parts in my motor and dyno sheets, I don't know where you live but around here you can duplicate my motor for around $18k using all high end parts.

Big Cubes
 

MakDaddy, I can relate to your situation. I bought a new boat on October 24th and ran in the Sarasota poker run on Oct. 26th and the boat now has 10 hrs on it and going into hibernation. When it awakens in the spring, I will have 2 new whipple EFI's awaiting the new 500's. I will probably run it another 10 or 20 hrs. before surgery. As far as the large cubes, I believe it is better to use the whipples w/intercoolers, and run about 5 lbs of boost which should deliver about 650 to 675, very reliable horsepower on pump gas. I have friends who have the whipples with no problems and making outrageous horsepower. The quad rotor on a 540 is making over 1000 horsepower with racing fuel. Outstanding

Big Cubes
 

Catmando, If only I had a magic lamp. That power would be awesome in any boat and twins is even better. I bought a 390 Velocity.

Cool............pump or race gas ?

Lets see, 565" on a 4.25" crank, 4.600 bore, .025" left. Custom pistons anyway.. Merlin block measures out at 11.665" deck. Very long rods! Flat tappet cam, .904 Shubeck lifters. Jury is still out! The drive had major drag due to broken bearing wedged beteen race and lower pinion gear. Going to outdrive school now! Next summer maybe! And maybe a set of those big chiefs!!

Dick

Ambusher,

You're going to hear a lot of opinions here, but I'm not so sure I would limit my search to an IMCO SC drive. I was thinking of the IMCO SC's myself, but lately I haven't always heard of good things with these IMCO SC's. I've been looking into a couple other drive shops that I have heard about and you might want to check them out as well. BilletMarine.com and MaxMachineWorx.com are two other companies that I would check before settling on IMCO. Right now Billet Marine has a modified Bravo One drive that is supposed to handle 1400hp and Max Machine Worx has one that is close to that figure as well. Just throwing out more options. I would say at least check them out first before making a decision on whose drive to buy. Just my .02

BTW, love your avitar---how true it is!

Mr Gadgets................the block you're referring to is a "super tall deck"

Typical Blockls are 9.800, or 10.200 (tall deck)



;)