632 1000 hp crate! Ready or not?
 

Just got 2 of those nice engines!
what are the marine engine builders comments on that engine in a boat?
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If you run dry exhaust, yes

Holy cow ! Congrats.
subscribing.

I thought there had to be some clearances opened up on them being they weren’t built for marine use.

There was a guy on here years ago that ran some GM 572 Crate motors but I can’t remember how he made out.

Here is one of the threads on the crate 572/ 620 hp.

https://www.offshoreonly.com/forums/general-boating-discussion/106336-so-we-went-boating-today-5.html

Btw: the exhaust ports are not standard location, did you plan on bigger $$$ exhaust ?

agreed, maybe 20k to build dry exhaust that's water cooled. Stainless Marine will love you.

repost so link shows

Put that ***** in a COPO Camaro and go spank some Mustang, Dodge A$$.........:lolhit:.not in a boat.......:angry-smiley-038:

From Raylar years back



#11

Raylar , 03-03-2012 12:51 PM
Registered
All good points and sugesstions.
As for clearances we like to use on stock GM shortblocks are slightly different than for aftermarket specialty products we can use in a block. For the stock GM type crankshafts and rods we use what we call the 2.5 sizing or .0025" on rods and .0025" on mains. The GM type crate engines can be anywhere between .001" and .003" Piston clearances and ring gaps will vary based on forged (4032 alloy) and hypereutectic cast pistons. Ring gaps can vary all over the board depending on who assembled them. We like to see .024" or so on top ring and .022" - .028" on second ring depending on piston type and induction system. On long blocks valve guide clearances should be checked and brought to normal .001"-.0015" intakes and .0015" -.00175" for exhausts. Also should check installed spring heights and verify good valve seat face to valve seat patterns and seal. There are obviously a lot of clearances that can be checked and set properly and it will depend on the original builders base part qualities, specifications, machining processes, measurements and attention to detail during block prep and assembly.

Would I take most of the better crate bbc engines I have seen properly fitted and cammed and put them in a mild 300- 420HP replacement use in more pleasure/performance hulls and run them at 4000-5000rpms in lake and river enviroments with most usage at idle and cruise rpms- YOU BET!.

Would I take some of these same crate bbc's and put them in higher speed performance boats in bigger water and ocean wave enviroments and run them with 450-550HP levels at 5000-5800 rpms for moderate sustained near WOT runs, poker runs or long up the lake blasts - HELL NO!

Best Regards,
Ray @

Did you get build sheets with them regarding bearing clearances? In theory...these are hand built engines so kinda depends on how it was built really. I'm no builder like some on this board but to totally throw out the idea without having that info seems kinda silly to me....Congrats btw! Bada$$ hardware sitting there! :riding:

I would think cooling system would be important as closed keeps block temps more stable.

RUFSTR had one... They had talked to GM about marine use. it's Not even close. Id be surprised if it gets on plane without 2 speed trans or a ton of prop slip. Its also not even remotely tuned for it..so youre back to running dry exhaust with an 02 sensor and leaving it in closed loop (bad plan) or having it properly tuned. Too much compression for a pump gas marine engine as well. Knock sensors will be going nuts, and knock is very hard to quantify in a boat. The whole thing is a bad plan in a boat.
Still a deeply impressive engine though.

nice experience backed comments! The fact that it MAY not last years and years does not surprise me
but what DOES impress me is the fact you say it might not even get on plane even with 1000 hp!!!
marine engines seems to really need a complete different recipe then street cars!

Johnny,

Rod angle aside, wouldn't a cam swap, properly clearanced bearings and marine appropriate exhaust pretty much solve the issue?

Thanks. Brad.

I would rather have a boat engine in a boat.

Piston to wall clearance, bearing clearance, ring gap, compression ratio, cam, efi mapping, the potential list goes on and on. By the time you're done you'd been better off starting from scratch.

Johnny,

Gotcha. I guess I didn't realize the list of differences was so extensive. I knew about bearing clearances and cam (and obviously the ECM tune along with it), but I didn't realize piston clearances and ring gap would be all that different. I guess that's why someone else is rebuilding my 496, huh? :ernaehrung004:

Carry on.

Thanks. Brad.

Thye might be fine, they might not. 1000hp makes a lot of heat, Im sure there's a decent amount of clearance. BUT. 1000hp with 5+ gears (and coasting) makes way, way, way less heat than a boat that's essentially in 4th gear going up hill all day. You also have to add clearance for cold water marine application and the possibility of no stat. You can run a much tighter piston to wall if you warm the block up too.
It comes down to application. Somebody will bolt this in a 22 donzi or something else that is small and will basically be uncontrolable and get away with it. Anything that could handle sustained WOT pulls and you'll turn it into junk.
Perfect example. GM rates the Gen6 502 block at 700hp. 700SCIs live at wot all day. I have a Stage 4 (850ish hp) 700 in my shop right now out of a 42 fountain that had a massive cylinder wall failure. It would have been fine in a smaller lighter boat. a 42 Fountain with M6 drives? Nah. Happily, we didnt build it lol.

Johnny,

If you HAD built it, it would have been right and wouldn't have failed.

Thanks. Brad.

I think it would work and perform great.

Not sure how long it would last though.

6800rpm redline would let you run a pretty low pitch prop that should work for planing off.

My first concern would be if the valvetrain could live, then if there is enough bearing clearance. Pump gas could be questionable too.

There’s been a couple boats with 1000hp NA big blocks that ran hard. I forgot the screen names, one had a light 41’ Apache that ran 110+ and the other a skater 32B that ran 160mph.

You have some good advice here. Crate motors are built for a car that will experience full throttle for seconds at a time. Marine engines are under heavy load for hours at a time. Odds are high the engines will not live for all the reasons listed on the posts.

I understand this with tolerances on large BBs with cast iron blocks.
What about the LS3-6.2, which has an aluminum block and 80 hp/liter, close cooling sistem? Is it also dangerous to leave automotive tolerances there between the piston and the cylinder?
So far I have done about 200 hours, of which about 15% wot-6,000 rpm, the rest mostly at 4,500 to 5,000 rpm, but a reall comment from the "old saylors" on this forum would be very welcome.

Engines are prescribed beating tolerances. Marine engines, specifically the harder working specimens, need to be on the larger side of those tolerances.

Purpose build high performance marine engines pretty much need to be on their bearing specs.

Your 4500-5000 rpm is on the high end of a cruise rpm. Hard to say how your bearings are making out. You never really know unless you open them up and check/adjust etc. That is the point.

For what is supposed to be a hand built GM crate engine, I would expect a build sheet with bearing clearances.

If it lived 200hrs so far, I would think you are good.

Cut the oil filter open(if you haven't) and check if there is any metal on the next change.

I have to apologize.
The total is a little over 20 hours plus cca 10-15 hours slow drive and not 200 hours. I will look at what is in the cpu memory.