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 !

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 ?

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

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...)